[libvirt PATCH v2 06/13] util: extract storage file probe code into virtstoragefileprobe.c

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This code is not directly relevant to virStorageSource so move it to
separate file.

Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
---
 po/POTFILES.in                        |   1 +
 src/libvirt_private.syms              |   6 +-
 src/qemu/qemu_driver.c                |   1 +
 src/storage/storage_backend_gluster.c |   1 +
 src/storage/storage_util.c            |   1 +
 src/util/meson.build                  |   1 +
 src/util/virstoragefile.c             | 939 +------------------------
 src/util/virstoragefile.h             |  11 -
 src/util/virstoragefileprobe.c        | 967 ++++++++++++++++++++++++++
 src/util/virstoragefileprobe.h        |  44 ++
 10 files changed, 1026 insertions(+), 946 deletions(-)
 create mode 100644 src/util/virstoragefileprobe.c
 create mode 100644 src/util/virstoragefileprobe.h

diff --git a/po/POTFILES.in b/po/POTFILES.in
index e9fc3991f1..19eb15ada0 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -306,6 +306,7 @@
 @SRCDIR@src/util/virstorageencryption.c
 @SRCDIR@src/util/virstoragefile.c
 @SRCDIR@src/util/virstoragefilebackend.c
+@SRCDIR@src/util/virstoragefileprobe.c
 @SRCDIR@src/util/virstring.c
 @SRCDIR@src/util/virsysinfo.c
 @SRCDIR@src/util/virsystemd.c
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 84b650cb86..2dfc7e32d5 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3148,7 +3148,6 @@ virStorageFileInit;
 virStorageFileInitAs;
 virStorageFileParseBackingStoreStr;
 virStorageFileParseChainIndex;
-virStorageFileProbeFormat;
 virStorageFileRead;
 virStorageFileReportBrokenChain;
 virStorageFileStat;
@@ -3212,6 +3211,11 @@ virStorageTypeToString;
 virStorageFileBackendRegister;
 
 
+# util/virstoragefileprobe.h
+virStorageFileProbeFormat;
+virStorageFileProbeGetMetadata;
+
+
 # util/virstring.h
 virSkipSpaces;
 virSkipSpacesAndBackslash;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 027617deef..34a8fbe233 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -83,6 +83,7 @@
 #include "domain_nwfilter.h"
 #include "virhook.h"
 #include "virstoragefile.h"
+#include "virstoragefileprobe.h"
 #include "virfile.h"
 #include "virfdstream.h"
 #include "configmake.h"
diff --git a/src/storage/storage_backend_gluster.c b/src/storage/storage_backend_gluster.c
index 6c99c270da..205a707a17 100644
--- a/src/storage/storage_backend_gluster.c
+++ b/src/storage/storage_backend_gluster.c
@@ -28,6 +28,7 @@
 #include "viralloc.h"
 #include "virerror.h"
 #include "virlog.h"
+#include "virstoragefileprobe.h"
 #include "virstring.h"
 #include "viruri.h"
 #include "storage_util.h"
diff --git a/src/storage/storage_util.c b/src/storage/storage_util.c
index 2e2c7dc68a..4117127d65 100644
--- a/src/storage/storage_util.c
+++ b/src/storage/storage_util.c
@@ -62,6 +62,7 @@
 #include "vircrypto.h"
 #include "viruuid.h"
 #include "virstoragefile.h"
+#include "virstoragefileprobe.h"
 #include "storage_util.h"
 #include "virlog.h"
 #include "virfile.h"
diff --git a/src/util/meson.build b/src/util/meson.build
index 395e70fd38..9fb270fadd 100644
--- a/src/util/meson.build
+++ b/src/util/meson.build
@@ -91,6 +91,7 @@ util_sources = [
   'virstorageencryption.c',
   'virstoragefile.c',
   'virstoragefilebackend.c',
+  'virstoragefileprobe.c',
   'virstring.c',
   'virsysinfo.c',
   'virsystemd.c',
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 13a86f34e5..98a3222d09 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -22,8 +22,6 @@
 #include <config.h>
 #include "virstoragefile.h"
 
-#include <unistd.h>
-#include <fcntl.h>
 #include "viralloc.h"
 #include "virxml.h"
 #include "viruuid.h"
@@ -32,13 +30,13 @@
 #include "virfile.h"
 #include "vircommand.h"
 #include "virhash.h"
-#include "virendian.h"
 #include "virstring.h"
 #include "viruri.h"
 #include "virbuffer.h"
 #include "virjson.h"
 #include "virstorageencryption.h"
 #include "virstoragefilebackend.h"
+#include "virstoragefileprobe.h"
 #include "virsecret.h"
 #include "virutil.h"
 
@@ -113,650 +111,6 @@ VIR_ENUM_IMPL(virStorageAuth,
               "none", "chap", "ceph",
 );
 
-enum lv_endian {
-    LV_LITTLE_ENDIAN = 1, /* 1234 */
-    LV_BIG_ENDIAN         /* 4321 */
-};
-
-enum {
-    BACKING_STORE_OK,
-    BACKING_STORE_INVALID,
-    BACKING_STORE_ERROR,
-};
-
-#define FILE_TYPE_VERSIONS_LAST 3
-
-struct FileEncryptionInfo {
-    int format; /* Encryption format to assign */
-
-    int magicOffset; /* Byte offset of the magic */
-    const char *magic; /* Optional string of magic */
-
-    enum lv_endian endian; /* Endianness of file format */
-
-    int versionOffset;    /* Byte offset from start of file
-                           * where we find version number,
-                           * -1 to always fail the version test,
-                           * -2 to always pass the version test */
-    int versionSize;      /* Size in bytes of version data (0, 2, or 4) */
-    int versionNumbers[FILE_TYPE_VERSIONS_LAST];
-                          /* Version numbers to validate. Zeroes are ignored. */
-
-    int modeOffset; /* Byte offset of the format native encryption mode */
-    char modeValue; /* Value expected at offset */
-
-    int payloadOffset; /* start offset of the volume data (in 512 byte sectors) */
-};
-
-struct FileTypeInfo {
-    int magicOffset;    /* Byte offset of the magic */
-    const char *magic;  /* Optional string of file magic
-                         * to check at head of file */
-    enum lv_endian endian; /* Endianness of file format */
-
-    int versionOffset;    /* Byte offset from start of file
-                           * where we find version number,
-                           * -1 to always fail the version test,
-                           * -2 to always pass the version test */
-    int versionSize;      /* Size in bytes of version data (0, 2, or 4) */
-    int versionNumbers[FILE_TYPE_VERSIONS_LAST];
-                          /* Version numbers to validate. Zeroes are ignored. */
-    int sizeOffset;       /* Byte offset from start of file
-                           * where we find capacity info,
-                           * -1 to use st_size as capacity */
-    int sizeBytes;        /* Number of bytes for size field */
-    int sizeMultiplier;   /* A scaling factor if size is not in bytes */
-                          /* Store a COW base image path (possibly relative),
-                           * or NULL if there is no COW base image, to RES;
-                           * return BACKING_STORE_* */
-    const struct FileEncryptionInfo *cryptInfo; /* Encryption info */
-    int (*getBackingStore)(char **res, int *format,
-                           const char *buf, size_t buf_size);
-    int (*getFeatures)(virBitmapPtr *features, int format,
-                       char *buf, ssize_t len);
-};
-
-
-static int cowGetBackingStore(char **, int *,
-                              const char *, size_t);
-static int qcowXGetBackingStore(char **, int *,
-                                const char *, size_t);
-static int qcow2GetFeatures(virBitmapPtr *features, int format,
-                            char *buf, ssize_t len);
-static int vmdk4GetBackingStore(char **, int *,
-                                const char *, size_t);
-static int
-qedGetBackingStore(char **, int *, const char *, size_t);
-
-#define QCOWX_HDR_VERSION (4)
-#define QCOWX_HDR_BACKING_FILE_OFFSET (QCOWX_HDR_VERSION+4)
-#define QCOWX_HDR_BACKING_FILE_SIZE (QCOWX_HDR_BACKING_FILE_OFFSET+8)
-#define QCOWX_HDR_IMAGE_SIZE (QCOWX_HDR_BACKING_FILE_SIZE+4+4)
-
-#define QCOW1_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8+1+1+2)
-#define QCOW2_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8)
-
-#define QCOW1_HDR_TOTAL_SIZE (QCOW1_HDR_CRYPT+4+8)
-#define QCOW2_HDR_TOTAL_SIZE (QCOW2_HDR_CRYPT+4+4+8+8+4+4+8)
-
-#define QCOW2_HDR_EXTENSION_END 0
-#define QCOW2_HDR_EXTENSION_BACKING_FORMAT 0xE2792ACA
-
-#define QCOW2v3_HDR_FEATURES_INCOMPATIBLE (QCOW2_HDR_TOTAL_SIZE)
-#define QCOW2v3_HDR_FEATURES_COMPATIBLE (QCOW2v3_HDR_FEATURES_INCOMPATIBLE+8)
-#define QCOW2v3_HDR_FEATURES_AUTOCLEAR (QCOW2v3_HDR_FEATURES_COMPATIBLE+8)
-
-/* The location of the header size [4 bytes] */
-#define QCOW2v3_HDR_SIZE       (QCOW2_HDR_TOTAL_SIZE+8+8+8+4)
-
-#define QED_HDR_FEATURES_OFFSET (4+4+4+4)
-#define QED_HDR_IMAGE_SIZE (QED_HDR_FEATURES_OFFSET+8+8+8+8)
-#define QED_HDR_BACKING_FILE_OFFSET (QED_HDR_IMAGE_SIZE+8)
-#define QED_HDR_BACKING_FILE_SIZE (QED_HDR_BACKING_FILE_OFFSET+4)
-#define QED_F_BACKING_FILE 0x01
-#define QED_F_BACKING_FORMAT_NO_PROBE 0x04
-
-#define PLOOP_IMAGE_SIZE_OFFSET 36
-#define PLOOP_SIZE_MULTIPLIER 512
-
-#define LUKS_HDR_MAGIC_LEN 6
-#define LUKS_HDR_VERSION_LEN 2
-#define LUKS_HDR_CIPHER_NAME_LEN 32
-#define LUKS_HDR_CIPHER_MODE_LEN 32
-#define LUKS_HDR_HASH_SPEC_LEN 32
-#define LUKS_HDR_PAYLOAD_LEN 4
-
-/* Format described by qemu commit id '3e308f20e' */
-#define LUKS_HDR_VERSION_OFFSET LUKS_HDR_MAGIC_LEN
-#define LUKS_HDR_PAYLOAD_OFFSET (LUKS_HDR_MAGIC_LEN+\
-                                 LUKS_HDR_VERSION_LEN+\
-                                 LUKS_HDR_CIPHER_NAME_LEN+\
-                                 LUKS_HDR_CIPHER_MODE_LEN+\
-                                 LUKS_HDR_HASH_SPEC_LEN)
-
-static struct FileEncryptionInfo const luksEncryptionInfo[] = {
-    {
-        .format = VIR_STORAGE_ENCRYPTION_FORMAT_LUKS,
-
-        /* Magic is 'L','U','K','S', 0xBA, 0xBE */
-        .magicOffset = 0,
-        .magic = "\x4c\x55\x4b\x53\xba\xbe",
-        .endian = LV_BIG_ENDIAN,
-
-        .versionOffset  = LUKS_HDR_VERSION_OFFSET,
-        .versionSize = LUKS_HDR_VERSION_LEN,
-        .versionNumbers = {1},
-
-        .modeOffset = -1,
-        .modeValue = -1,
-
-        .payloadOffset = LUKS_HDR_PAYLOAD_OFFSET,
-    },
-    { 0 }
-};
-
-static struct FileEncryptionInfo const qcow1EncryptionInfo[] = {
-    {
-        .format = VIR_STORAGE_ENCRYPTION_FORMAT_QCOW,
-
-        .magicOffset = 0,
-        .magic = NULL,
-        .endian = LV_BIG_ENDIAN,
-
-        .versionOffset  = -1,
-        .versionSize = 0,
-        .versionNumbers = {},
-
-        .modeOffset = QCOW1_HDR_CRYPT,
-        .modeValue = 1,
-
-        .payloadOffset = -1,
-    },
-    { 0 }
-};
-
-static struct FileEncryptionInfo const qcow2EncryptionInfo[] = {
-    {
-        .format = VIR_STORAGE_ENCRYPTION_FORMAT_QCOW,
-
-        .magicOffset = 0,
-        .magic = NULL,
-        .endian = LV_BIG_ENDIAN,
-
-        .versionOffset  = -1,
-        .versionSize = 0,
-        .versionNumbers = {},
-
-        .modeOffset = QCOW2_HDR_CRYPT,
-        .modeValue = 1,
-
-        .payloadOffset = -1,
-    },
-    {
-        .format = VIR_STORAGE_ENCRYPTION_FORMAT_LUKS,
-
-        .magicOffset = 0,
-        .magic = NULL,
-        .endian = LV_BIG_ENDIAN,
-
-        .versionOffset  = -1,
-        .versionSize = 0,
-        .versionNumbers = {},
-
-        .modeOffset = QCOW2_HDR_CRYPT,
-        .modeValue = 2,
-
-        .payloadOffset = -1,
-    },
-    { 0 }
-};
-
-static struct FileTypeInfo const fileTypeInfo[] = {
-    [VIR_STORAGE_FILE_NONE] = { 0, NULL, LV_LITTLE_ENDIAN,
-                                -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
-    [VIR_STORAGE_FILE_RAW] = { 0, NULL, LV_LITTLE_ENDIAN,
-                               -1, 0, {0}, 0, 0, 0,
-                               luksEncryptionInfo,
-                               NULL, NULL },
-    [VIR_STORAGE_FILE_DIR] = { 0, NULL, LV_LITTLE_ENDIAN,
-                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
-    [VIR_STORAGE_FILE_BOCHS] = {
-        /*"Bochs Virtual HD Image", */ /* Untested */
-        0, NULL,
-        LV_LITTLE_ENDIAN, 64, 4, {0x20000},
-        32+16+16+4+4+4+4+4, 8, 1, NULL, NULL, NULL
-    },
-    [VIR_STORAGE_FILE_CLOOP] = {
-        /* #!/bin/sh
-           #V2.0 Format
-           modprobe cloop file=$0 && mount -r -t iso9660 /dev/cloop $1
-        */ /* Untested */
-        0, NULL,
-        LV_LITTLE_ENDIAN, -1, 0, {0},
-        -1, 0, 0, NULL, NULL, NULL
-    },
-    [VIR_STORAGE_FILE_DMG] = {
-        /* XXX QEMU says there's no magic for dmg,
-         * /usr/share/misc/magic lists double magic (both offsets
-         * would have to match) but then disables that check. */
-        0, NULL,
-        0, -1, 0, {0},
-        -1, 0, 0, NULL, NULL, NULL
-    },
-    [VIR_STORAGE_FILE_ISO] = {
-        32769, "CD001",
-        LV_LITTLE_ENDIAN, -2, 0, {0},
-        -1, 0, 0, NULL, NULL, NULL
-    },
-    [VIR_STORAGE_FILE_VPC] = {
-        0, "conectix",
-        LV_BIG_ENDIAN, 12, 4, {0x10000},
-        8 + 4 + 4 + 8 + 4 + 4 + 2 + 2 + 4, 8, 1, NULL, NULL, NULL
-    },
-    /* TODO: add getBackingStore function */
-    [VIR_STORAGE_FILE_VDI] = {
-        64, "\x7f\x10\xda\xbe",
-        LV_LITTLE_ENDIAN, 68, 4, {0x00010001},
-        64 + 5 * 4 + 256 + 7 * 4, 8, 1, NULL, NULL, NULL},
-
-    /* Not direct file formats, but used for various drivers */
-    [VIR_STORAGE_FILE_FAT] = { 0, NULL, LV_LITTLE_ENDIAN,
-                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
-    [VIR_STORAGE_FILE_VHD] = { 0, NULL, LV_LITTLE_ENDIAN,
-                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
-    [VIR_STORAGE_FILE_PLOOP] = { 0, "WithouFreSpacExt", LV_LITTLE_ENDIAN,
-                                 -2, 0, {0}, PLOOP_IMAGE_SIZE_OFFSET, 0,
-                                 PLOOP_SIZE_MULTIPLIER, NULL, NULL, NULL },
-
-    /* All formats with a backing store probe below here */
-    [VIR_STORAGE_FILE_COW] = {
-        0, "OOOM",
-        LV_BIG_ENDIAN, 4, 4, {2},
-        4+4+1024+4, 8, 1, NULL, cowGetBackingStore, NULL
-    },
-    [VIR_STORAGE_FILE_QCOW] = {
-        0, "QFI",
-        LV_BIG_ENDIAN, 4, 4, {1},
-        QCOWX_HDR_IMAGE_SIZE, 8, 1,
-        qcow1EncryptionInfo,
-        qcowXGetBackingStore, NULL
-    },
-    [VIR_STORAGE_FILE_QCOW2] = {
-        0, "QFI",
-        LV_BIG_ENDIAN, 4, 4, {2, 3},
-        QCOWX_HDR_IMAGE_SIZE, 8, 1,
-        qcow2EncryptionInfo,
-        qcowXGetBackingStore,
-        qcow2GetFeatures
-    },
-    [VIR_STORAGE_FILE_QED] = {
-        /* https://wiki.qemu.org/Features/QED */
-        0, "QED",
-        LV_LITTLE_ENDIAN, -2, 0, {0},
-        QED_HDR_IMAGE_SIZE, 8, 1, NULL, qedGetBackingStore, NULL
-    },
-    [VIR_STORAGE_FILE_VMDK] = {
-        0, "KDMV",
-        LV_LITTLE_ENDIAN, 4, 4, {1, 2, 3},
-        4+4+4, 8, 512, NULL, vmdk4GetBackingStore, NULL
-    },
-};
-G_STATIC_ASSERT(G_N_ELEMENTS(fileTypeInfo) == VIR_STORAGE_FILE_LAST);
-
-
-/* qcow2 compatible features in the order they appear on-disk */
-enum qcow2CompatibleFeature {
-    QCOW2_COMPATIBLE_FEATURE_LAZY_REFCOUNTS = 0,
-
-    QCOW2_COMPATIBLE_FEATURE_LAST
-};
-
-/* conversion to virStorageFileFeature */
-static const int qcow2CompatibleFeatureArray[] = {
-    VIR_STORAGE_FILE_FEATURE_LAZY_REFCOUNTS,
-};
-G_STATIC_ASSERT(G_N_ELEMENTS(qcow2CompatibleFeatureArray) ==
-       QCOW2_COMPATIBLE_FEATURE_LAST);
-
-static int
-cowGetBackingStore(char **res,
-                   int *format,
-                   const char *buf,
-                   size_t buf_size)
-{
-#define COW_FILENAME_MAXLEN 1024
-    *res = NULL;
-    *format = VIR_STORAGE_FILE_AUTO;
-
-    if (buf_size < 4+4+ COW_FILENAME_MAXLEN)
-        return BACKING_STORE_INVALID;
-    if (buf[4+4] == '\0') { /* cow_header_v2.backing_file[0] */
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-
-    *res = g_strndup((const char *)buf + 4 + 4, COW_FILENAME_MAXLEN);
-    return BACKING_STORE_OK;
-}
-
-
-static int
-qcow2GetExtensions(const char *buf,
-                   size_t buf_size,
-                   int *backingFormat)
-{
-    size_t offset;
-    size_t extension_start;
-    size_t extension_end;
-    int version = virReadBufInt32BE(buf + QCOWX_HDR_VERSION);
-
-    if (version < 2) {
-        /* QCow1 doesn't have the extensions capability
-         * used to store backing format */
-        return 0;
-    }
-
-    if (version == 2)
-        extension_start = QCOW2_HDR_TOTAL_SIZE;
-    else
-        extension_start = virReadBufInt32BE(buf + QCOW2v3_HDR_SIZE);
-
-    /*
-     * Traditionally QCow2 files had a layout of
-     *
-     * [header]
-     * [backingStoreName]
-     *
-     * Although the backingStoreName typically followed
-     * the header immediately, this was not required by
-     * the format. By specifying a higher byte offset for
-     * the backing file offset in the header, it was
-     * possible to leave space between the header and
-     * start of backingStore.
-     *
-     * This hack is now used to store extensions to the
-     * qcow2 format:
-     *
-     * [header]
-     * [extensions]
-     * [backingStoreName]
-     *
-     * Thus the file region to search for extensions is
-     * between the end of the header (QCOW2_HDR_TOTAL_SIZE)
-     * and the start of the backingStoreName (offset)
-     *
-     * for qcow2 v3 images, the length of the header
-     * is stored at QCOW2v3_HDR_SIZE
-     */
-    extension_end = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
-    if (extension_end > buf_size)
-        return -1;
-
-    /*
-     * The extensions take format of
-     *
-     * int32: magic
-     * int32: length
-     * byte[length]: payload
-     *
-     * Unknown extensions can be ignored by skipping
-     * over "length" bytes in the data stream.
-     */
-    offset = extension_start;
-    while (offset < (buf_size-8) &&
-           offset < (extension_end-8)) {
-        unsigned int magic = virReadBufInt32BE(buf + offset);
-        unsigned int len = virReadBufInt32BE(buf + offset + 4);
-
-        offset += 8;
-
-        if ((offset + len) < offset)
-            break;
-
-        if ((offset + len) > buf_size)
-            break;
-
-        switch (magic) {
-        case QCOW2_HDR_EXTENSION_BACKING_FORMAT: {
-            g_autofree char *tmp = NULL;
-            if (!backingFormat)
-                break;
-
-            tmp = g_new0(char, len + 1);
-            memcpy(tmp, buf + offset, len);
-            tmp[len] = '\0';
-
-            *backingFormat = virStorageFileFormatTypeFromString(tmp);
-            if (*backingFormat <= VIR_STORAGE_FILE_NONE)
-                return -1;
-            break;
-        }
-
-        case QCOW2_HDR_EXTENSION_END:
-            return 0;
-        }
-
-        offset += len;
-    }
-
-    return 0;
-}
-
-
-static int
-qcowXGetBackingStore(char **res,
-                     int *format,
-                     const char *buf,
-                     size_t buf_size)
-{
-    unsigned long long offset;
-    unsigned int size;
-
-    *res = NULL;
-    *format = VIR_STORAGE_FILE_AUTO;
-
-    if (buf_size < QCOWX_HDR_BACKING_FILE_OFFSET+8+4)
-        return BACKING_STORE_INVALID;
-
-    offset = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
-    if (offset > buf_size)
-        return BACKING_STORE_INVALID;
-
-    if (offset == 0) {
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-
-    size = virReadBufInt32BE(buf + QCOWX_HDR_BACKING_FILE_SIZE);
-    if (size == 0) {
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-    if (size > 1023)
-        return BACKING_STORE_INVALID;
-    if (offset + size > buf_size || offset + size < offset)
-        return BACKING_STORE_INVALID;
-    *res = g_new0(char, size + 1);
-    memcpy(*res, buf + offset, size);
-    (*res)[size] = '\0';
-
-    if (qcow2GetExtensions(buf, buf_size, format) < 0)
-        return BACKING_STORE_INVALID;
-
-    return BACKING_STORE_OK;
-}
-
-
-static int
-vmdk4GetBackingStore(char **res,
-                     int *format,
-                     const char *buf,
-                     size_t buf_size)
-{
-    static const char prefix[] = "parentFileNameHint=\"";
-    char *start, *end;
-    size_t len;
-    g_autofree char *desc = NULL;
-
-    desc = g_new0(char, VIR_STORAGE_MAX_HEADER);
-
-    *res = NULL;
-    /*
-     * Technically this should have been VMDK, since
-     * VMDK spec / VMware impl only support VMDK backed
-     * by VMDK. QEMU isn't following this though and
-     * does probing on VMDK backing files, hence we set
-     * AUTO
-     */
-    *format = VIR_STORAGE_FILE_AUTO;
-
-    if (buf_size <= 0x200)
-        return BACKING_STORE_INVALID;
-
-    len = buf_size - 0x200;
-    if (len > VIR_STORAGE_MAX_HEADER)
-        len = VIR_STORAGE_MAX_HEADER;
-    memcpy(desc, buf + 0x200, len);
-    desc[len] = '\0';
-    start = strstr(desc, prefix);
-    if (start == NULL) {
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-    start += strlen(prefix);
-    end = strchr(start, '"');
-    if (end == NULL)
-        return BACKING_STORE_INVALID;
-
-    if (end == start) {
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-    *end = '\0';
-    *res = g_strdup(start);
-
-    return BACKING_STORE_OK;
-}
-
-static int
-qedGetBackingStore(char **res,
-                   int *format,
-                   const char *buf,
-                   size_t buf_size)
-{
-    unsigned long long flags;
-    unsigned long offset, size;
-
-    *res = NULL;
-    /* Check if this image has a backing file */
-    if (buf_size < QED_HDR_FEATURES_OFFSET+8)
-        return BACKING_STORE_INVALID;
-    flags = virReadBufInt64LE(buf + QED_HDR_FEATURES_OFFSET);
-    if (!(flags & QED_F_BACKING_FILE)) {
-        *format = VIR_STORAGE_FILE_NONE;
-        return BACKING_STORE_OK;
-    }
-
-    /* Parse the backing file */
-    if (buf_size < QED_HDR_BACKING_FILE_OFFSET+8)
-        return BACKING_STORE_INVALID;
-    offset = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_OFFSET);
-    if (offset > buf_size)
-        return BACKING_STORE_INVALID;
-    size = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_SIZE);
-    if (size == 0)
-        return BACKING_STORE_OK;
-    if (offset + size > buf_size || offset + size < offset)
-        return BACKING_STORE_INVALID;
-    *res = g_new0(char, size + 1);
-    memcpy(*res, buf + offset, size);
-    (*res)[size] = '\0';
-
-    if (flags & QED_F_BACKING_FORMAT_NO_PROBE)
-        *format = VIR_STORAGE_FILE_RAW;
-    else
-        *format = VIR_STORAGE_FILE_AUTO_SAFE;
-
-    return BACKING_STORE_OK;
-}
-
-
-static bool
-virStorageFileMatchesMagic(int magicOffset,
-                           const char *magic,
-                           char *buf,
-                           size_t buflen)
-{
-    int mlen;
-
-    if (magic == NULL)
-        return false;
-
-    /* Validate magic data */
-    mlen = strlen(magic);
-    if (magicOffset + mlen > buflen)
-        return false;
-
-    if (memcmp(buf + magicOffset, magic, mlen) != 0)
-        return false;
-
-    return true;
-}
-
-
-static bool
-virStorageFileMatchesVersion(int versionOffset,
-                             int versionSize,
-                             const int *versionNumbers,
-                             int endian,
-                             char *buf,
-                             size_t buflen)
-{
-    int version;
-    size_t i;
-
-    /* Validate version number info */
-    if (versionOffset == -1)
-        return false;
-
-    /* -2 == non-versioned file format, so trivially match */
-    if (versionOffset == -2)
-        return true;
-
-    /* A positive versionOffset, requires using a valid versionSize */
-    if (versionSize != 2 && versionSize != 4)
-        return false;
-
-    if ((versionOffset + versionSize) > buflen)
-        return false;
-
-    if (endian == LV_LITTLE_ENDIAN) {
-        if (versionSize == 4)
-            version = virReadBufInt32LE(buf +
-                                        versionOffset);
-        else
-            version = virReadBufInt16LE(buf +
-                                        versionOffset);
-    } else {
-        if (versionSize == 4)
-            version = virReadBufInt32BE(buf +
-                                        versionOffset);
-        else
-            version = virReadBufInt16BE(buf +
-                                        versionOffset);
-    }
-
-    for (i = 0;
-         i < FILE_TYPE_VERSIONS_LAST && versionNumbers[i];
-         i++) {
-        VIR_DEBUG("Compare detected version %d vs one of the expected versions %d",
-                  version, versionNumbers[i]);
-        if (version == versionNumbers[i])
-            return true;
-    }
-
-    return false;
-}
 
 bool
 virStorageIsFile(const char *backing)
@@ -792,289 +146,6 @@ virStorageIsRelative(const char *backing)
 }
 
 
-static int
-virStorageFileProbeFormatFromBuf(const char *path,
-                                 char *buf,
-                                 size_t buflen)
-{
-    int format = VIR_STORAGE_FILE_RAW;
-    size_t i;
-    int possibleFormat = VIR_STORAGE_FILE_RAW;
-    VIR_DEBUG("path=%s, buf=%p, buflen=%zu", path, buf, buflen);
-
-    /* First check file magic */
-    for (i = 0; i < VIR_STORAGE_FILE_LAST; i++) {
-        if (virStorageFileMatchesMagic(fileTypeInfo[i].magicOffset,
-                                       fileTypeInfo[i].magic,
-                                       buf, buflen)) {
-            if (!virStorageFileMatchesVersion(fileTypeInfo[i].versionOffset,
-                                              fileTypeInfo[i].versionSize,
-                                              fileTypeInfo[i].versionNumbers,
-                                              fileTypeInfo[i].endian,
-                                              buf, buflen)) {
-                possibleFormat = i;
-                continue;
-            }
-            format = i;
-            goto cleanup;
-        }
-    }
-
-    if (possibleFormat != VIR_STORAGE_FILE_RAW)
-        VIR_WARN("File %s matches %s magic, but version is wrong. "
-                 "Please report new version to libvir-list@xxxxxxxxxx",
-                 path, virStorageFileFormatTypeToString(possibleFormat));
-
- cleanup:
-    VIR_DEBUG("format=%d", format);
-    return format;
-}
-
-
-static int
-qcow2GetFeatures(virBitmapPtr *features,
-                 int format,
-                 char *buf,
-                 ssize_t len)
-{
-    int version = -1;
-    virBitmapPtr feat = NULL;
-    uint64_t bits;
-    size_t i;
-
-    version = virReadBufInt32BE(buf + fileTypeInfo[format].versionOffset);
-
-    if (version == 2)
-        return 0;
-
-    if (len < QCOW2v3_HDR_SIZE)
-        return -1;
-
-    feat = virBitmapNew(VIR_STORAGE_FILE_FEATURE_LAST);
-
-    /* todo: check for incompatible or autoclear features? */
-    bits = virReadBufInt64BE(buf + QCOW2v3_HDR_FEATURES_COMPATIBLE);
-    for (i = 0; i < QCOW2_COMPATIBLE_FEATURE_LAST; i++) {
-        if (bits & ((uint64_t) 1 << i))
-            ignore_value(virBitmapSetBit(feat, qcow2CompatibleFeatureArray[i]));
-    }
-
-    *features = feat;
-    return 0;
-}
-
-
-static bool
-virStorageFileHasEncryptionFormat(const struct FileEncryptionInfo *info,
-                                  char *buf,
-                                  size_t len)
-{
-    if (!info->magic && info->modeOffset == -1)
-        return false; /* Shouldn't happen - expect at least one */
-
-    if (info->magic) {
-        if (!virStorageFileMatchesMagic(info->magicOffset,
-                                        info->magic,
-                                        buf, len))
-            return false;
-
-        if (info->versionOffset != -1 &&
-            !virStorageFileMatchesVersion(info->versionOffset,
-                                          info->versionSize,
-                                          info->versionNumbers,
-                                          info->endian,
-                                          buf, len))
-            return false;
-
-        return true;
-    } else if (info->modeOffset != -1) {
-        int crypt_format;
-
-        if (info->modeOffset >= len)
-            return false;
-
-        crypt_format = virReadBufInt32BE(buf + info->modeOffset);
-        if (crypt_format != info->modeValue)
-            return false;
-
-        return true;
-    } else {
-        return false;
-    }
-}
-
-
-static int
-virStorageFileGetEncryptionPayloadOffset(const struct FileEncryptionInfo *info,
-                                         char *buf)
-{
-    int payload_offset = -1;
-
-    if (info->payloadOffset != -1) {
-        if (info->endian == LV_LITTLE_ENDIAN)
-            payload_offset = virReadBufInt32LE(buf + info->payloadOffset);
-        else
-            payload_offset = virReadBufInt32BE(buf + info->payloadOffset);
-    }
-
-    return payload_offset;
-}
-
-
-/* Given a header in BUF with length LEN, as parsed from the storage file
- * assuming it has the given FORMAT, populate information into META
- * with information about the file and its backing store. Return format
- * of the backing store as BACKING_FORMAT. PATH and FORMAT have to be
- * pre-populated in META.
- *
- * Note that this function may be called repeatedly on @meta, so it must
- * clean up any existing allocated memory which would be overwritten.
- */
-static int
-virStorageFileGetMetadataInternal(virStorageSourcePtr meta,
-                                  char *buf,
-                                  size_t len)
-{
-    int format;
-    size_t i;
-
-    VIR_DEBUG("path=%s, buf=%p, len=%zu, meta->format=%d",
-              meta->path, buf, len, meta->format);
-
-    if (meta->format == VIR_STORAGE_FILE_AUTO)
-        meta->format = virStorageFileProbeFormatFromBuf(meta->path, buf, len);
-
-    if (meta->format <= VIR_STORAGE_FILE_NONE ||
-        meta->format >= VIR_STORAGE_FILE_LAST) {
-        virReportSystemError(EINVAL, _("unknown storage file meta->format %d"),
-                             meta->format);
-        return -1;
-    }
-
-    if (fileTypeInfo[meta->format].cryptInfo != NULL) {
-        for (i = 0; fileTypeInfo[meta->format].cryptInfo[i].format != 0; i++) {
-            if (virStorageFileHasEncryptionFormat(&fileTypeInfo[meta->format].cryptInfo[i],
-                                                  buf, len)) {
-                int expt_fmt = fileTypeInfo[meta->format].cryptInfo[i].format;
-                if (!meta->encryption) {
-                    meta->encryption = g_new0(virStorageEncryption, 1);
-                    meta->encryption->format = expt_fmt;
-                } else {
-                    if (meta->encryption->format != expt_fmt) {
-                        virReportError(VIR_ERR_XML_ERROR,
-                                       _("encryption format %d doesn't match "
-                                         "expected format %d"),
-                                       meta->encryption->format, expt_fmt);
-                        return -1;
-                    }
-                }
-                meta->encryption->payload_offset =
-                    virStorageFileGetEncryptionPayloadOffset(&fileTypeInfo[meta->format].cryptInfo[i], buf);
-            }
-        }
-    }
-
-    /* XXX we should consider moving virStorageBackendUpdateVolInfo
-     * code into this method, for non-magic files
-     */
-    if (!fileTypeInfo[meta->format].magic)
-        return 0;
-
-    /* Optionally extract capacity from file */
-    if (fileTypeInfo[meta->format].sizeOffset != -1) {
-        if ((fileTypeInfo[meta->format].sizeOffset + 8) > len)
-            return 0;
-
-        if (fileTypeInfo[meta->format].endian == LV_LITTLE_ENDIAN)
-            meta->capacity = virReadBufInt64LE(buf +
-                                               fileTypeInfo[meta->format].sizeOffset);
-        else
-            meta->capacity = virReadBufInt64BE(buf +
-                                               fileTypeInfo[meta->format].sizeOffset);
-        /* Avoid unlikely, but theoretically possible overflow */
-        if (meta->capacity > (ULLONG_MAX /
-                              fileTypeInfo[meta->format].sizeMultiplier))
-            return 0;
-        meta->capacity *= fileTypeInfo[meta->format].sizeMultiplier;
-    }
-
-    VIR_FREE(meta->backingStoreRaw);
-    if (fileTypeInfo[meta->format].getBackingStore != NULL) {
-        int store = fileTypeInfo[meta->format].getBackingStore(&meta->backingStoreRaw,
-                                                               &format,
-                                                               buf, len);
-        meta->backingStoreRawFormat = format;
-
-        if (store == BACKING_STORE_INVALID)
-            return 0;
-
-        if (store == BACKING_STORE_ERROR)
-            return -1;
-    }
-
-    virBitmapFree(meta->features);
-    meta->features = NULL;
-    if (fileTypeInfo[meta->format].getFeatures != NULL &&
-        fileTypeInfo[meta->format].getFeatures(&meta->features, meta->format, buf, len) < 0)
-        return -1;
-
-    VIR_FREE(meta->compat);
-    if (meta->format == VIR_STORAGE_FILE_QCOW2 && meta->features)
-        meta->compat = g_strdup("1.1");
-
-    return 0;
-}
-
-
-/**
- * virStorageFileProbeFormat:
- *
- * Probe for the format of 'path', returning the detected
- * disk format.
- *
- * Callers are advised never to trust the returned 'format'
- * unless it is listed as VIR_STORAGE_FILE_RAW, since a
- * malicious guest can turn a raw file into any other non-raw
- * format at will.
- *
- * Best option: Don't use this function
- */
-int
-virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid)
-{
-    struct stat sb;
-    ssize_t len = VIR_STORAGE_MAX_HEADER;
-    VIR_AUTOCLOSE fd = -1;
-    g_autofree char *header = NULL;
-
-    if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) {
-        virReportSystemError(-fd, _("Failed to open file '%s'"), path);
-        return -1;
-    }
-
-    if (fstat(fd, &sb) < 0) {
-        virReportSystemError(errno, _("cannot stat file '%s'"), path);
-        return -1;
-    }
-
-    /* No header to probe for directories */
-    if (S_ISDIR(sb.st_mode))
-        return VIR_STORAGE_FILE_DIR;
-
-    if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
-        virReportSystemError(errno, _("cannot set to start of '%s'"), path);
-        return -1;
-    }
-
-    if ((len = virFileReadHeaderFD(fd, len, &header)) < 0) {
-        virReportSystemError(errno, _("cannot read header '%s'"), path);
-        return -1;
-    }
-
-    return virStorageFileProbeFormatFromBuf(path, header, len);
-}
-
-
 static virStorageSourcePtr
 virStorageFileMetadataNew(const char *path,
                           int format)
@@ -1123,7 +194,7 @@ virStorageFileGetMetadataFromBuf(const char *path,
     if (!(ret = virStorageFileMetadataNew(path, format)))
         return NULL;
 
-    if (virStorageFileGetMetadataInternal(ret, buf, len) < 0) {
+    if (virStorageFileProbeGetMetadata(ret, buf, len) < 0) {
         virObjectUnref(ret);
         return NULL;
     }
@@ -1183,7 +254,7 @@ virStorageFileGetMetadataFromFD(const char *path,
         return NULL;
     }
 
-    if (virStorageFileGetMetadataInternal(meta, buf, len) < 0)
+    if (virStorageFileProbeGetMetadata(meta, buf, len) < 0)
         return NULL;
 
     if (S_ISREG(sb.st_mode))
@@ -5149,7 +4220,7 @@ virStorageFileGetMetadataRecurse(virStorageSourcePtr src,
                                                    &buf, &headerLen, cycle) < 0)
         return -1;
 
-    if (virStorageFileGetMetadataInternal(src, buf, headerLen) < 0)
+    if (virStorageFileProbeGetMetadata(src, buf, headerLen) < 0)
         return -1;
 
     /* If we probed the format we MUST ensure that nothing else than the current
@@ -5292,7 +4363,7 @@ virStorageFileGetBackingStoreStr(virStorageSourcePtr src,
     if (!(tmp = virStorageSourceCopy(src, false)))
         return -1;
 
-    if (virStorageFileGetMetadataInternal(tmp, buf, headerLen) < 0)
+    if (virStorageFileProbeGetMetadata(tmp, buf, headerLen) < 0)
         return -1;
 
     *backing = g_steal_pointer(&tmp->backingStoreRaw);
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index 46da6a8a18..27ac6a493f 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -31,15 +31,6 @@
 #include "virenum.h"
 #include "virpci.h"
 
-/* Minimum header size required to probe all known formats with
- * virStorageFileProbeFormat, or obtain metadata from a known format.
- * Rounded to multiple of 512 (ISO has a 5-byte magic at offset
- * 32769).  Some formats can be probed with fewer bytes.  Although
- * some formats theoretically permit metadata that can rely on offsets
- * beyond this size, in practice that doesn't matter.  */
-#define VIR_STORAGE_MAX_HEADER 0x8200
-
-
 /* Types of disk backends (host resource).  Comparable to the public
  * virStorageVolType, except we have an undetermined state, don't have
  * a netdir type, and add a volume type for reference through a
@@ -401,8 +392,6 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC(virStorageSource, virObjectUnref);
 # define DEV_BSIZE 512
 #endif
 
-int virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid);
-
 virStorageSourcePtr virStorageFileGetMetadataFromFD(const char *path,
                                                     int fd,
                                                     int format);
diff --git a/src/util/virstoragefileprobe.c b/src/util/virstoragefileprobe.c
new file mode 100644
index 0000000000..bca098cd35
--- /dev/null
+++ b/src/util/virstoragefileprobe.c
@@ -0,0 +1,967 @@
+/*
+ * virstoragefileprobe.c: file utility functions for FS storage backend
+ *
+ * Copyright (C) 2007-2017 Red Hat, Inc.
+ * Copyright (C) 2007-2008 Daniel P. Berrange
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "internal.h"
+#include "viralloc.h"
+#include "virbitmap.h"
+#include "virendian.h"
+#include "virfile.h"
+#include "virlog.h"
+#include "virstoragefile.h"
+#include "virstoragefileprobe.h"
+
+#define VIR_FROM_THIS VIR_FROM_STORAGE
+
+VIR_LOG_INIT("util.storagefileprobe");
+
+enum lv_endian {
+    LV_LITTLE_ENDIAN = 1, /* 1234 */
+    LV_BIG_ENDIAN         /* 4321 */
+};
+
+enum {
+    BACKING_STORE_OK,
+    BACKING_STORE_INVALID,
+    BACKING_STORE_ERROR,
+};
+
+#define FILE_TYPE_VERSIONS_LAST 3
+
+struct FileEncryptionInfo {
+    int format; /* Encryption format to assign */
+
+    int magicOffset; /* Byte offset of the magic */
+    const char *magic; /* Optional string of magic */
+
+    enum lv_endian endian; /* Endianness of file format */
+
+    int versionOffset;    /* Byte offset from start of file
+                           * where we find version number,
+                           * -1 to always fail the version test,
+                           * -2 to always pass the version test */
+    int versionSize;      /* Size in bytes of version data (0, 2, or 4) */
+    int versionNumbers[FILE_TYPE_VERSIONS_LAST];
+                          /* Version numbers to validate. Zeroes are ignored. */
+
+    int modeOffset; /* Byte offset of the format native encryption mode */
+    char modeValue; /* Value expected at offset */
+
+    int payloadOffset; /* start offset of the volume data (in 512 byte sectors) */
+};
+
+struct FileTypeInfo {
+    int magicOffset;    /* Byte offset of the magic */
+    const char *magic;  /* Optional string of file magic
+                         * to check at head of file */
+    enum lv_endian endian; /* Endianness of file format */
+
+    int versionOffset;    /* Byte offset from start of file
+                           * where we find version number,
+                           * -1 to always fail the version test,
+                           * -2 to always pass the version test */
+    int versionSize;      /* Size in bytes of version data (0, 2, or 4) */
+    int versionNumbers[FILE_TYPE_VERSIONS_LAST];
+                          /* Version numbers to validate. Zeroes are ignored. */
+    int sizeOffset;       /* Byte offset from start of file
+                           * where we find capacity info,
+                           * -1 to use st_size as capacity */
+    int sizeBytes;        /* Number of bytes for size field */
+    int sizeMultiplier;   /* A scaling factor if size is not in bytes */
+                          /* Store a COW base image path (possibly relative),
+                           * or NULL if there is no COW base image, to RES;
+                           * return BACKING_STORE_* */
+    const struct FileEncryptionInfo *cryptInfo; /* Encryption info */
+    int (*getBackingStore)(char **res, int *format,
+                           const char *buf, size_t buf_size);
+    int (*getFeatures)(virBitmapPtr *features, int format,
+                       char *buf, ssize_t len);
+};
+
+
+static int cowGetBackingStore(char **, int *,
+                              const char *, size_t);
+static int qcowXGetBackingStore(char **, int *,
+                                const char *, size_t);
+static int qcow2GetFeatures(virBitmapPtr *features, int format,
+                            char *buf, ssize_t len);
+static int vmdk4GetBackingStore(char **, int *,
+                                const char *, size_t);
+static int
+qedGetBackingStore(char **, int *, const char *, size_t);
+
+#define QCOWX_HDR_VERSION (4)
+#define QCOWX_HDR_BACKING_FILE_OFFSET (QCOWX_HDR_VERSION+4)
+#define QCOWX_HDR_BACKING_FILE_SIZE (QCOWX_HDR_BACKING_FILE_OFFSET+8)
+#define QCOWX_HDR_IMAGE_SIZE (QCOWX_HDR_BACKING_FILE_SIZE+4+4)
+
+#define QCOW1_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8+1+1+2)
+#define QCOW2_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8)
+
+#define QCOW1_HDR_TOTAL_SIZE (QCOW1_HDR_CRYPT+4+8)
+#define QCOW2_HDR_TOTAL_SIZE (QCOW2_HDR_CRYPT+4+4+8+8+4+4+8)
+
+#define QCOW2_HDR_EXTENSION_END 0
+#define QCOW2_HDR_EXTENSION_BACKING_FORMAT 0xE2792ACA
+
+#define QCOW2v3_HDR_FEATURES_INCOMPATIBLE (QCOW2_HDR_TOTAL_SIZE)
+#define QCOW2v3_HDR_FEATURES_COMPATIBLE (QCOW2v3_HDR_FEATURES_INCOMPATIBLE+8)
+#define QCOW2v3_HDR_FEATURES_AUTOCLEAR (QCOW2v3_HDR_FEATURES_COMPATIBLE+8)
+
+/* The location of the header size [4 bytes] */
+#define QCOW2v3_HDR_SIZE       (QCOW2_HDR_TOTAL_SIZE+8+8+8+4)
+
+#define QED_HDR_FEATURES_OFFSET (4+4+4+4)
+#define QED_HDR_IMAGE_SIZE (QED_HDR_FEATURES_OFFSET+8+8+8+8)
+#define QED_HDR_BACKING_FILE_OFFSET (QED_HDR_IMAGE_SIZE+8)
+#define QED_HDR_BACKING_FILE_SIZE (QED_HDR_BACKING_FILE_OFFSET+4)
+#define QED_F_BACKING_FILE 0x01
+#define QED_F_BACKING_FORMAT_NO_PROBE 0x04
+
+#define PLOOP_IMAGE_SIZE_OFFSET 36
+#define PLOOP_SIZE_MULTIPLIER 512
+
+#define LUKS_HDR_MAGIC_LEN 6
+#define LUKS_HDR_VERSION_LEN 2
+#define LUKS_HDR_CIPHER_NAME_LEN 32
+#define LUKS_HDR_CIPHER_MODE_LEN 32
+#define LUKS_HDR_HASH_SPEC_LEN 32
+#define LUKS_HDR_PAYLOAD_LEN 4
+
+/* Format described by qemu commit id '3e308f20e' */
+#define LUKS_HDR_VERSION_OFFSET LUKS_HDR_MAGIC_LEN
+#define LUKS_HDR_PAYLOAD_OFFSET (LUKS_HDR_MAGIC_LEN+\
+                                 LUKS_HDR_VERSION_LEN+\
+                                 LUKS_HDR_CIPHER_NAME_LEN+\
+                                 LUKS_HDR_CIPHER_MODE_LEN+\
+                                 LUKS_HDR_HASH_SPEC_LEN)
+
+static struct FileEncryptionInfo const luksEncryptionInfo[] = {
+    {
+        .format = VIR_STORAGE_ENCRYPTION_FORMAT_LUKS,
+
+        /* Magic is 'L','U','K','S', 0xBA, 0xBE */
+        .magicOffset = 0,
+        .magic = "\x4c\x55\x4b\x53\xba\xbe",
+        .endian = LV_BIG_ENDIAN,
+
+        .versionOffset  = LUKS_HDR_VERSION_OFFSET,
+        .versionSize = LUKS_HDR_VERSION_LEN,
+        .versionNumbers = {1},
+
+        .modeOffset = -1,
+        .modeValue = -1,
+
+        .payloadOffset = LUKS_HDR_PAYLOAD_OFFSET,
+    },
+    { 0 }
+};
+
+static struct FileEncryptionInfo const qcow1EncryptionInfo[] = {
+    {
+        .format = VIR_STORAGE_ENCRYPTION_FORMAT_QCOW,
+
+        .magicOffset = 0,
+        .magic = NULL,
+        .endian = LV_BIG_ENDIAN,
+
+        .versionOffset  = -1,
+        .versionSize = 0,
+        .versionNumbers = {},
+
+        .modeOffset = QCOW1_HDR_CRYPT,
+        .modeValue = 1,
+
+        .payloadOffset = -1,
+    },
+    { 0 }
+};
+
+static struct FileEncryptionInfo const qcow2EncryptionInfo[] = {
+    {
+        .format = VIR_STORAGE_ENCRYPTION_FORMAT_QCOW,
+
+        .magicOffset = 0,
+        .magic = NULL,
+        .endian = LV_BIG_ENDIAN,
+
+        .versionOffset  = -1,
+        .versionSize = 0,
+        .versionNumbers = {},
+
+        .modeOffset = QCOW2_HDR_CRYPT,
+        .modeValue = 1,
+
+        .payloadOffset = -1,
+    },
+    {
+        .format = VIR_STORAGE_ENCRYPTION_FORMAT_LUKS,
+
+        .magicOffset = 0,
+        .magic = NULL,
+        .endian = LV_BIG_ENDIAN,
+
+        .versionOffset  = -1,
+        .versionSize = 0,
+        .versionNumbers = {},
+
+        .modeOffset = QCOW2_HDR_CRYPT,
+        .modeValue = 2,
+
+        .payloadOffset = -1,
+    },
+    { 0 }
+};
+
+static struct FileTypeInfo const fileTypeInfo[] = {
+    [VIR_STORAGE_FILE_NONE] = { 0, NULL, LV_LITTLE_ENDIAN,
+                                -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
+    [VIR_STORAGE_FILE_RAW] = { 0, NULL, LV_LITTLE_ENDIAN,
+                               -1, 0, {0}, 0, 0, 0,
+                               luksEncryptionInfo,
+                               NULL, NULL },
+    [VIR_STORAGE_FILE_DIR] = { 0, NULL, LV_LITTLE_ENDIAN,
+                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
+    [VIR_STORAGE_FILE_BOCHS] = {
+        /*"Bochs Virtual HD Image", */ /* Untested */
+        0, NULL,
+        LV_LITTLE_ENDIAN, 64, 4, {0x20000},
+        32+16+16+4+4+4+4+4, 8, 1, NULL, NULL, NULL
+    },
+    [VIR_STORAGE_FILE_CLOOP] = {
+        /* #!/bin/sh
+           #V2.0 Format
+           modprobe cloop file=$0 && mount -r -t iso9660 /dev/cloop $1
+        */ /* Untested */
+        0, NULL,
+        LV_LITTLE_ENDIAN, -1, 0, {0},
+        -1, 0, 0, NULL, NULL, NULL
+    },
+    [VIR_STORAGE_FILE_DMG] = {
+        /* XXX QEMU says there's no magic for dmg,
+         * /usr/share/misc/magic lists double magic (both offsets
+         * would have to match) but then disables that check. */
+        0, NULL,
+        0, -1, 0, {0},
+        -1, 0, 0, NULL, NULL, NULL
+    },
+    [VIR_STORAGE_FILE_ISO] = {
+        32769, "CD001",
+        LV_LITTLE_ENDIAN, -2, 0, {0},
+        -1, 0, 0, NULL, NULL, NULL
+    },
+    [VIR_STORAGE_FILE_VPC] = {
+        0, "conectix",
+        LV_BIG_ENDIAN, 12, 4, {0x10000},
+        8 + 4 + 4 + 8 + 4 + 4 + 2 + 2 + 4, 8, 1, NULL, NULL, NULL
+    },
+    /* TODO: add getBackingStore function */
+    [VIR_STORAGE_FILE_VDI] = {
+        64, "\x7f\x10\xda\xbe",
+        LV_LITTLE_ENDIAN, 68, 4, {0x00010001},
+        64 + 5 * 4 + 256 + 7 * 4, 8, 1, NULL, NULL, NULL},
+
+    /* Not direct file formats, but used for various drivers */
+    [VIR_STORAGE_FILE_FAT] = { 0, NULL, LV_LITTLE_ENDIAN,
+                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
+    [VIR_STORAGE_FILE_VHD] = { 0, NULL, LV_LITTLE_ENDIAN,
+                               -1, 0, {0}, 0, 0, 0, NULL, NULL, NULL },
+    [VIR_STORAGE_FILE_PLOOP] = { 0, "WithouFreSpacExt", LV_LITTLE_ENDIAN,
+                                 -2, 0, {0}, PLOOP_IMAGE_SIZE_OFFSET, 0,
+                                 PLOOP_SIZE_MULTIPLIER, NULL, NULL, NULL },
+
+    /* All formats with a backing store probe below here */
+    [VIR_STORAGE_FILE_COW] = {
+        0, "OOOM",
+        LV_BIG_ENDIAN, 4, 4, {2},
+        4+4+1024+4, 8, 1, NULL, cowGetBackingStore, NULL
+    },
+    [VIR_STORAGE_FILE_QCOW] = {
+        0, "QFI",
+        LV_BIG_ENDIAN, 4, 4, {1},
+        QCOWX_HDR_IMAGE_SIZE, 8, 1,
+        qcow1EncryptionInfo,
+        qcowXGetBackingStore, NULL
+    },
+    [VIR_STORAGE_FILE_QCOW2] = {
+        0, "QFI",
+        LV_BIG_ENDIAN, 4, 4, {2, 3},
+        QCOWX_HDR_IMAGE_SIZE, 8, 1,
+        qcow2EncryptionInfo,
+        qcowXGetBackingStore,
+        qcow2GetFeatures
+    },
+    [VIR_STORAGE_FILE_QED] = {
+        /* https://wiki.qemu.org/Features/QED */
+        0, "QED",
+        LV_LITTLE_ENDIAN, -2, 0, {0},
+        QED_HDR_IMAGE_SIZE, 8, 1, NULL, qedGetBackingStore, NULL
+    },
+    [VIR_STORAGE_FILE_VMDK] = {
+        0, "KDMV",
+        LV_LITTLE_ENDIAN, 4, 4, {1, 2, 3},
+        4+4+4, 8, 512, NULL, vmdk4GetBackingStore, NULL
+    },
+};
+G_STATIC_ASSERT(G_N_ELEMENTS(fileTypeInfo) == VIR_STORAGE_FILE_LAST);
+
+
+/* qcow2 compatible features in the order they appear on-disk */
+enum qcow2CompatibleFeature {
+    QCOW2_COMPATIBLE_FEATURE_LAZY_REFCOUNTS = 0,
+
+    QCOW2_COMPATIBLE_FEATURE_LAST
+};
+
+/* conversion to virStorageFileFeature */
+static const int qcow2CompatibleFeatureArray[] = {
+    VIR_STORAGE_FILE_FEATURE_LAZY_REFCOUNTS,
+};
+G_STATIC_ASSERT(G_N_ELEMENTS(qcow2CompatibleFeatureArray) ==
+       QCOW2_COMPATIBLE_FEATURE_LAST);
+
+static int
+cowGetBackingStore(char **res,
+                   int *format,
+                   const char *buf,
+                   size_t buf_size)
+{
+#define COW_FILENAME_MAXLEN 1024
+    *res = NULL;
+    *format = VIR_STORAGE_FILE_AUTO;
+
+    if (buf_size < 4+4+ COW_FILENAME_MAXLEN)
+        return BACKING_STORE_INVALID;
+    if (buf[4+4] == '\0') { /* cow_header_v2.backing_file[0] */
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+
+    *res = g_strndup((const char *)buf + 4 + 4, COW_FILENAME_MAXLEN);
+    return BACKING_STORE_OK;
+}
+
+
+static int
+qcow2GetExtensions(const char *buf,
+                   size_t buf_size,
+                   int *backingFormat)
+{
+    size_t offset;
+    size_t extension_start;
+    size_t extension_end;
+    int version = virReadBufInt32BE(buf + QCOWX_HDR_VERSION);
+
+    if (version < 2) {
+        /* QCow1 doesn't have the extensions capability
+         * used to store backing format */
+        return 0;
+    }
+
+    if (version == 2)
+        extension_start = QCOW2_HDR_TOTAL_SIZE;
+    else
+        extension_start = virReadBufInt32BE(buf + QCOW2v3_HDR_SIZE);
+
+    /*
+     * Traditionally QCow2 files had a layout of
+     *
+     * [header]
+     * [backingStoreName]
+     *
+     * Although the backingStoreName typically followed
+     * the header immediately, this was not required by
+     * the format. By specifying a higher byte offset for
+     * the backing file offset in the header, it was
+     * possible to leave space between the header and
+     * start of backingStore.
+     *
+     * This hack is now used to store extensions to the
+     * qcow2 format:
+     *
+     * [header]
+     * [extensions]
+     * [backingStoreName]
+     *
+     * Thus the file region to search for extensions is
+     * between the end of the header (QCOW2_HDR_TOTAL_SIZE)
+     * and the start of the backingStoreName (offset)
+     *
+     * for qcow2 v3 images, the length of the header
+     * is stored at QCOW2v3_HDR_SIZE
+     */
+    extension_end = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
+    if (extension_end > buf_size)
+        return -1;
+
+    /*
+     * The extensions take format of
+     *
+     * int32: magic
+     * int32: length
+     * byte[length]: payload
+     *
+     * Unknown extensions can be ignored by skipping
+     * over "length" bytes in the data stream.
+     */
+    offset = extension_start;
+    while (offset < (buf_size-8) &&
+           offset < (extension_end-8)) {
+        unsigned int magic = virReadBufInt32BE(buf + offset);
+        unsigned int len = virReadBufInt32BE(buf + offset + 4);
+
+        offset += 8;
+
+        if ((offset + len) < offset)
+            break;
+
+        if ((offset + len) > buf_size)
+            break;
+
+        switch (magic) {
+        case QCOW2_HDR_EXTENSION_BACKING_FORMAT: {
+            g_autofree char *tmp = NULL;
+            if (!backingFormat)
+                break;
+
+            tmp = g_new0(char, len + 1);
+            memcpy(tmp, buf + offset, len);
+            tmp[len] = '\0';
+
+            *backingFormat = virStorageFileFormatTypeFromString(tmp);
+            if (*backingFormat <= VIR_STORAGE_FILE_NONE)
+                return -1;
+            break;
+        }
+
+        case QCOW2_HDR_EXTENSION_END:
+            return 0;
+        }
+
+        offset += len;
+    }
+
+    return 0;
+}
+
+
+static int
+qcowXGetBackingStore(char **res,
+                     int *format,
+                     const char *buf,
+                     size_t buf_size)
+{
+    unsigned long long offset;
+    unsigned int size;
+
+    *res = NULL;
+    *format = VIR_STORAGE_FILE_AUTO;
+
+    if (buf_size < QCOWX_HDR_BACKING_FILE_OFFSET+8+4)
+        return BACKING_STORE_INVALID;
+
+    offset = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
+    if (offset > buf_size)
+        return BACKING_STORE_INVALID;
+
+    if (offset == 0) {
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+
+    size = virReadBufInt32BE(buf + QCOWX_HDR_BACKING_FILE_SIZE);
+    if (size == 0) {
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+    if (size > 1023)
+        return BACKING_STORE_INVALID;
+    if (offset + size > buf_size || offset + size < offset)
+        return BACKING_STORE_INVALID;
+    *res = g_new0(char, size + 1);
+    memcpy(*res, buf + offset, size);
+    (*res)[size] = '\0';
+
+    if (qcow2GetExtensions(buf, buf_size, format) < 0)
+        return BACKING_STORE_INVALID;
+
+    return BACKING_STORE_OK;
+}
+
+
+static int
+vmdk4GetBackingStore(char **res,
+                     int *format,
+                     const char *buf,
+                     size_t buf_size)
+{
+    static const char prefix[] = "parentFileNameHint=\"";
+    char *start, *end;
+    size_t len;
+    g_autofree char *desc = NULL;
+
+    desc = g_new0(char, VIR_STORAGE_MAX_HEADER);
+
+    *res = NULL;
+    /*
+     * Technically this should have been VMDK, since
+     * VMDK spec / VMware impl only support VMDK backed
+     * by VMDK. QEMU isn't following this though and
+     * does probing on VMDK backing files, hence we set
+     * AUTO
+     */
+    *format = VIR_STORAGE_FILE_AUTO;
+
+    if (buf_size <= 0x200)
+        return BACKING_STORE_INVALID;
+
+    len = buf_size - 0x200;
+    if (len > VIR_STORAGE_MAX_HEADER)
+        len = VIR_STORAGE_MAX_HEADER;
+    memcpy(desc, buf + 0x200, len);
+    desc[len] = '\0';
+    start = strstr(desc, prefix);
+    if (start == NULL) {
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+    start += strlen(prefix);
+    end = strchr(start, '"');
+    if (end == NULL)
+        return BACKING_STORE_INVALID;
+
+    if (end == start) {
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+    *end = '\0';
+    *res = g_strdup(start);
+
+    return BACKING_STORE_OK;
+}
+
+static int
+qedGetBackingStore(char **res,
+                   int *format,
+                   const char *buf,
+                   size_t buf_size)
+{
+    unsigned long long flags;
+    unsigned long offset, size;
+
+    *res = NULL;
+    /* Check if this image has a backing file */
+    if (buf_size < QED_HDR_FEATURES_OFFSET+8)
+        return BACKING_STORE_INVALID;
+    flags = virReadBufInt64LE(buf + QED_HDR_FEATURES_OFFSET);
+    if (!(flags & QED_F_BACKING_FILE)) {
+        *format = VIR_STORAGE_FILE_NONE;
+        return BACKING_STORE_OK;
+    }
+
+    /* Parse the backing file */
+    if (buf_size < QED_HDR_BACKING_FILE_OFFSET+8)
+        return BACKING_STORE_INVALID;
+    offset = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_OFFSET);
+    if (offset > buf_size)
+        return BACKING_STORE_INVALID;
+    size = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_SIZE);
+    if (size == 0)
+        return BACKING_STORE_OK;
+    if (offset + size > buf_size || offset + size < offset)
+        return BACKING_STORE_INVALID;
+    *res = g_new0(char, size + 1);
+    memcpy(*res, buf + offset, size);
+    (*res)[size] = '\0';
+
+    if (flags & QED_F_BACKING_FORMAT_NO_PROBE)
+        *format = VIR_STORAGE_FILE_RAW;
+    else
+        *format = VIR_STORAGE_FILE_AUTO_SAFE;
+
+    return BACKING_STORE_OK;
+}
+
+
+static bool
+virStorageFileMatchesMagic(int magicOffset,
+                           const char *magic,
+                           char *buf,
+                           size_t buflen)
+{
+    int mlen;
+
+    if (magic == NULL)
+        return false;
+
+    /* Validate magic data */
+    mlen = strlen(magic);
+    if (magicOffset + mlen > buflen)
+        return false;
+
+    if (memcmp(buf + magicOffset, magic, mlen) != 0)
+        return false;
+
+    return true;
+}
+
+
+static bool
+virStorageFileMatchesVersion(int versionOffset,
+                             int versionSize,
+                             const int *versionNumbers,
+                             int endian,
+                             char *buf,
+                             size_t buflen)
+{
+    int version;
+    size_t i;
+
+    /* Validate version number info */
+    if (versionOffset == -1)
+        return false;
+
+    /* -2 == non-versioned file format, so trivially match */
+    if (versionOffset == -2)
+        return true;
+
+    /* A positive versionOffset, requires using a valid versionSize */
+    if (versionSize != 2 && versionSize != 4)
+        return false;
+
+    if ((versionOffset + versionSize) > buflen)
+        return false;
+
+    if (endian == LV_LITTLE_ENDIAN) {
+        if (versionSize == 4)
+            version = virReadBufInt32LE(buf +
+                                        versionOffset);
+        else
+            version = virReadBufInt16LE(buf +
+                                        versionOffset);
+    } else {
+        if (versionSize == 4)
+            version = virReadBufInt32BE(buf +
+                                        versionOffset);
+        else
+            version = virReadBufInt16BE(buf +
+                                        versionOffset);
+    }
+
+    for (i = 0;
+         i < FILE_TYPE_VERSIONS_LAST && versionNumbers[i];
+         i++) {
+        VIR_DEBUG("Compare detected version %d vs one of the expected versions %d",
+                  version, versionNumbers[i]);
+        if (version == versionNumbers[i])
+            return true;
+    }
+
+    return false;
+}
+
+
+static int
+virStorageFileProbeFormatFromBuf(const char *path,
+                                 char *buf,
+                                 size_t buflen)
+{
+    int format = VIR_STORAGE_FILE_RAW;
+    size_t i;
+    int possibleFormat = VIR_STORAGE_FILE_RAW;
+    VIR_DEBUG("path=%s, buf=%p, buflen=%zu", path, buf, buflen);
+
+    /* First check file magic */
+    for (i = 0; i < VIR_STORAGE_FILE_LAST; i++) {
+        if (virStorageFileMatchesMagic(fileTypeInfo[i].magicOffset,
+                                       fileTypeInfo[i].magic,
+                                       buf, buflen)) {
+            if (!virStorageFileMatchesVersion(fileTypeInfo[i].versionOffset,
+                                              fileTypeInfo[i].versionSize,
+                                              fileTypeInfo[i].versionNumbers,
+                                              fileTypeInfo[i].endian,
+                                              buf, buflen)) {
+                possibleFormat = i;
+                continue;
+            }
+            format = i;
+            goto cleanup;
+        }
+    }
+
+    if (possibleFormat != VIR_STORAGE_FILE_RAW)
+        VIR_WARN("File %s matches %s magic, but version is wrong. "
+                 "Please report new version to libvir-list@xxxxxxxxxx",
+                 path, virStorageFileFormatTypeToString(possibleFormat));
+
+ cleanup:
+    VIR_DEBUG("format=%d", format);
+    return format;
+}
+
+
+static int
+qcow2GetFeatures(virBitmapPtr *features,
+                 int format,
+                 char *buf,
+                 ssize_t len)
+{
+    int version = -1;
+    virBitmapPtr feat = NULL;
+    uint64_t bits;
+    size_t i;
+
+    version = virReadBufInt32BE(buf + fileTypeInfo[format].versionOffset);
+
+    if (version == 2)
+        return 0;
+
+    if (len < QCOW2v3_HDR_SIZE)
+        return -1;
+
+    feat = virBitmapNew(VIR_STORAGE_FILE_FEATURE_LAST);
+
+    /* todo: check for incompatible or autoclear features? */
+    bits = virReadBufInt64BE(buf + QCOW2v3_HDR_FEATURES_COMPATIBLE);
+    for (i = 0; i < QCOW2_COMPATIBLE_FEATURE_LAST; i++) {
+        if (bits & ((uint64_t) 1 << i))
+            ignore_value(virBitmapSetBit(feat, qcow2CompatibleFeatureArray[i]));
+    }
+
+    *features = feat;
+    return 0;
+}
+
+
+static bool
+virStorageFileHasEncryptionFormat(const struct FileEncryptionInfo *info,
+                                  char *buf,
+                                  size_t len)
+{
+    if (!info->magic && info->modeOffset == -1)
+        return false; /* Shouldn't happen - expect at least one */
+
+    if (info->magic) {
+        if (!virStorageFileMatchesMagic(info->magicOffset,
+                                        info->magic,
+                                        buf, len))
+            return false;
+
+        if (info->versionOffset != -1 &&
+            !virStorageFileMatchesVersion(info->versionOffset,
+                                          info->versionSize,
+                                          info->versionNumbers,
+                                          info->endian,
+                                          buf, len))
+            return false;
+
+        return true;
+    } else if (info->modeOffset != -1) {
+        int crypt_format;
+
+        if (info->modeOffset >= len)
+            return false;
+
+        crypt_format = virReadBufInt32BE(buf + info->modeOffset);
+        if (crypt_format != info->modeValue)
+            return false;
+
+        return true;
+    } else {
+        return false;
+    }
+}
+
+
+static int
+virStorageFileGetEncryptionPayloadOffset(const struct FileEncryptionInfo *info,
+                                         char *buf)
+{
+    int payload_offset = -1;
+
+    if (info->payloadOffset != -1) {
+        if (info->endian == LV_LITTLE_ENDIAN)
+            payload_offset = virReadBufInt32LE(buf + info->payloadOffset);
+        else
+            payload_offset = virReadBufInt32BE(buf + info->payloadOffset);
+    }
+
+    return payload_offset;
+}
+
+
+/* Given a header in BUF with length LEN, as parsed from the storage file
+ * assuming it has the given FORMAT, populate information into META
+ * with information about the file and its backing store. Return format
+ * of the backing store as BACKING_FORMAT. PATH and FORMAT have to be
+ * pre-populated in META.
+ *
+ * Note that this function may be called repeatedly on @meta, so it must
+ * clean up any existing allocated memory which would be overwritten.
+ */
+int
+virStorageFileProbeGetMetadata(virStorageSourcePtr meta,
+                               char *buf,
+                               size_t len)
+{
+    int format;
+    size_t i;
+
+    VIR_DEBUG("path=%s, buf=%p, len=%zu, meta->format=%d",
+              meta->path, buf, len, meta->format);
+
+    if (meta->format == VIR_STORAGE_FILE_AUTO)
+        meta->format = virStorageFileProbeFormatFromBuf(meta->path, buf, len);
+
+    if (meta->format <= VIR_STORAGE_FILE_NONE ||
+        meta->format >= VIR_STORAGE_FILE_LAST) {
+        virReportSystemError(EINVAL, _("unknown storage file meta->format %d"),
+                             meta->format);
+        return -1;
+    }
+
+    if (fileTypeInfo[meta->format].cryptInfo != NULL) {
+        for (i = 0; fileTypeInfo[meta->format].cryptInfo[i].format != 0; i++) {
+            if (virStorageFileHasEncryptionFormat(&fileTypeInfo[meta->format].cryptInfo[i],
+                                                  buf, len)) {
+                int expt_fmt = fileTypeInfo[meta->format].cryptInfo[i].format;
+                if (!meta->encryption) {
+                    meta->encryption = g_new0(virStorageEncryption, 1);
+                    meta->encryption->format = expt_fmt;
+                } else {
+                    if (meta->encryption->format != expt_fmt) {
+                        virReportError(VIR_ERR_XML_ERROR,
+                                       _("encryption format %d doesn't match "
+                                         "expected format %d"),
+                                       meta->encryption->format, expt_fmt);
+                        return -1;
+                    }
+                }
+                meta->encryption->payload_offset =
+                    virStorageFileGetEncryptionPayloadOffset(&fileTypeInfo[meta->format].cryptInfo[i], buf);
+            }
+        }
+    }
+
+    /* XXX we should consider moving virStorageBackendUpdateVolInfo
+     * code into this method, for non-magic files
+     */
+    if (!fileTypeInfo[meta->format].magic)
+        return 0;
+
+    /* Optionally extract capacity from file */
+    if (fileTypeInfo[meta->format].sizeOffset != -1) {
+        if ((fileTypeInfo[meta->format].sizeOffset + 8) > len)
+            return 0;
+
+        if (fileTypeInfo[meta->format].endian == LV_LITTLE_ENDIAN)
+            meta->capacity = virReadBufInt64LE(buf +
+                                               fileTypeInfo[meta->format].sizeOffset);
+        else
+            meta->capacity = virReadBufInt64BE(buf +
+                                               fileTypeInfo[meta->format].sizeOffset);
+        /* Avoid unlikely, but theoretically possible overflow */
+        if (meta->capacity > (ULLONG_MAX /
+                              fileTypeInfo[meta->format].sizeMultiplier))
+            return 0;
+        meta->capacity *= fileTypeInfo[meta->format].sizeMultiplier;
+    }
+
+    VIR_FREE(meta->backingStoreRaw);
+    if (fileTypeInfo[meta->format].getBackingStore != NULL) {
+        int store = fileTypeInfo[meta->format].getBackingStore(&meta->backingStoreRaw,
+                                                               &format,
+                                                               buf, len);
+        meta->backingStoreRawFormat = format;
+
+        if (store == BACKING_STORE_INVALID)
+            return 0;
+
+        if (store == BACKING_STORE_ERROR)
+            return -1;
+    }
+
+    virBitmapFree(meta->features);
+    meta->features = NULL;
+    if (fileTypeInfo[meta->format].getFeatures != NULL &&
+        fileTypeInfo[meta->format].getFeatures(&meta->features, meta->format, buf, len) < 0)
+        return -1;
+
+    VIR_FREE(meta->compat);
+    if (meta->format == VIR_STORAGE_FILE_QCOW2 && meta->features)
+        meta->compat = g_strdup("1.1");
+
+    return 0;
+}
+
+
+/**
+ * virStorageFileProbeFormat:
+ *
+ * Probe for the format of 'path', returning the detected
+ * disk format.
+ *
+ * Callers are advised never to trust the returned 'format'
+ * unless it is listed as VIR_STORAGE_FILE_RAW, since a
+ * malicious guest can turn a raw file into any other non-raw
+ * format at will.
+ *
+ * Best option: Don't use this function
+ */
+int
+virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid)
+{
+    struct stat sb;
+    ssize_t len = VIR_STORAGE_MAX_HEADER;
+    VIR_AUTOCLOSE fd = -1;
+    g_autofree char *header = NULL;
+
+    if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) {
+        virReportSystemError(-fd, _("Failed to open file '%s'"), path);
+        return -1;
+    }
+
+    if (fstat(fd, &sb) < 0) {
+        virReportSystemError(errno, _("cannot stat file '%s'"), path);
+        return -1;
+    }
+
+    /* No header to probe for directories */
+    if (S_ISDIR(sb.st_mode))
+        return VIR_STORAGE_FILE_DIR;
+
+    if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
+        virReportSystemError(errno, _("cannot set to start of '%s'"), path);
+        return -1;
+    }
+
+    if ((len = virFileReadHeaderFD(fd, len, &header)) < 0) {
+        virReportSystemError(errno, _("cannot read header '%s'"), path);
+        return -1;
+    }
+
+    return virStorageFileProbeFormatFromBuf(path, header, len);
+}
diff --git a/src/util/virstoragefileprobe.h b/src/util/virstoragefileprobe.h
new file mode 100644
index 0000000000..2b94a4ae51
--- /dev/null
+++ b/src/util/virstoragefileprobe.h
@@ -0,0 +1,44 @@
+/*
+ * virstoragefileprobe.h: file utility functions for FS storage backend
+ *
+ * Copyright (C) 2007-2009, 2012-2016 Red Hat, Inc.
+ * Copyright (C) 2007-2008 Daniel P. Berrange
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <sys/stat.h>
+
+#include "virstoragefile.h"
+
+/* Minimum header size required to probe all known formats with
+ * virStorageFileProbeFormat, or obtain metadata from a known format.
+ * Rounded to multiple of 512 (ISO has a 5-byte magic at offset
+ * 32769).  Some formats can be probed with fewer bytes.  Although
+ * some formats theoretically permit metadata that can rely on offsets
+ * beyond this size, in practice that doesn't matter.  */
+#define VIR_STORAGE_MAX_HEADER 0x8200
+
+int
+virStorageFileProbeGetMetadata(virStorageSourcePtr meta,
+                               char *buf,
+                               size_t len);
+
+int
+virStorageFileProbeFormat(const char *path,
+                          uid_t uid,
+                          gid_t gid);
-- 
2.29.2





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