From: Matthew Garrett <mjg59@xxxxxxxxxx>
Some filesystems may be able to provide hashes in an out of band manner,
and allowing them to do so is a performance win. This is especially true
of FUSE-based filesystems where otherwise we recalculate the hash on
every measurement. Make use of this if policy says we should, but provide
a parameter to force recalculation rather than trusting the filesystem.
Signed-off-by: Matthew Garrett <mjg59@xxxxxxxxxx>
---
Documentation/ABI/testing/ima_policy | 5 +++-
.../admin-guide/kernel-parameters.txt | 5 ++++
security/integrity/ima/ima.h | 3 ++-
security/integrity/ima/ima_api.c | 5 +++-
security/integrity/ima/ima_crypto.c | 23 ++++++++++++++++++-
security/integrity/ima/ima_policy.c | 8 ++++++-
security/integrity/ima/ima_template_lib.c | 2 +-
security/integrity/integrity.h | 1 +
8 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 09a5def7e28a..6a517282068d 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -24,7 +24,8 @@ Description:
[euid=] [fowner=] [fsname=] [subtype=]]
lsm: [[subj_user=] [subj_role=] [subj_type=]
[obj_user=] [obj_role=] [obj_type=]]
- option: [[appraise_type=]] [permit_directio]
+ option: [[appraise_type=] [permit_directio]
+ [trust_vfs]]
base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
@@ -41,6 +42,8 @@ Description:
lsm: are LSM specific
option: appraise_type:= [imasig]
pcr:= decimal value
+ permit_directio:= allow directio accesses
+ trust_vfs:= trust VFS-provided hash values
default policy:
# PROC_SUPER_MAGIC
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 52e6fbb042cc..cc9302b79409 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1658,6 +1658,11 @@
different crypto accelerators. This option can be used
to achieve best performance for particular HW.
+ ima.force_hash= [IMA] Force hash calculation in IMA
+ Format: <bool>
+ Always calculate hashes rather than trusting the
+ filesystem to provide them to us.
+
init= [KNL]
Format: <full_path>
Run specified binary instead of /sbin/init as init
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d213e835c498..cdaffe6c8a8d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -133,7 +133,8 @@ int ima_fs_init(void);
int ima_add_template_entry(struct ima_template_entry *entry, int violation,
const char *op, struct inode *inode,
const unsigned char *filename);
-int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash);
+int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash,
+ bool trust_vfs);
int ima_calc_buffer_hash(const void *buf, loff_t len,
struct ima_digest_data *hash);
int ima_calc_field_array_hash(struct ima_field_data *field_data,
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index c7505fb122d4..0def9cf43549 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -206,6 +206,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
int length;
void *tmpbuf;
u64 i_version;
+ bool trust_vfs;
struct {
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
@@ -225,10 +226,12 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
/* Initialize hash digest to 0's in case of failure */
memset(&hash.digest, 0, sizeof(hash.digest));
+ trust_vfs = iint->flags & IMA_TRUST_VFS;
+
if (buf)
result = ima_calc_buffer_hash(buf, size, &hash.hdr);
else
- result = ima_calc_file_hash(file, &hash.hdr);
+ result = ima_calc_file_hash(file, &hash.hdr, trust_vfs);
if (result && result != -EBADF && result != -EINVAL)
goto out;
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index a32878e10ebc..1c83d23d21a6 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -32,6 +32,10 @@ static unsigned long ima_ahash_minsize;
module_param_named(ahash_minsize, ima_ahash_minsize, ulong, 0644);
MODULE_PARM_DESC(ahash_minsize, "Minimum file size for ahash use");
+static bool ima_force_hash;
+module_param_named(force_hash, ima_force_hash, bool_enable_only, 0644);
+MODULE_PARM_DESC(force_hash, "Always calculate hashes");
+
/* default is 0 - 1 page. */
static int ima_maxorder;
static unsigned int ima_bufsize = PAGE_SIZE;
@@ -401,11 +405,14 @@ static int ima_calc_file_shash(struct file *file, struct ima_digest_data *hash)
* shash for the hash calculation. If ahash fails, it falls back to using
* shash.
*/
-int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
+int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash,
+ bool trust_vfs)
{
loff_t i_size;
int rc;
struct file *f = file;
+ struct dentry *dentry = file_dentry(file);
+ struct inode *inode = d_backing_inode(dentry);
bool new_file_instance = false, modified_flags = false;
/*
@@ -418,6 +425,20 @@ int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
return -EINVAL;
}
+ /*
+ * If policy says we should trust VFS-provided hashes, and
+ * we're not configured to force hashing, and if the
+ * filesystem is trusted, ask the VFS if it can obtain the
+ * hash without us having to calculate it ourself.
+ */
+ if (trust_vfs && !ima_force_hash &&
+ !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER)) {
+ hash->length = hash_digest_size[hash->algo];
+ rc = vfs_get_hash(file, hash->algo, hash->digest, hash->length);
+ if (!rc)
+ return 0;
+ }
+
/* Open a new file instance in O_RDONLY if we cannot read */
if (!(file->f_mode & FMODE_READ)) {
int flags = file->f_flags & ~(O_WRONLY | O_APPEND |
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index bb4e265823a7..c293cbc6c578 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -681,7 +681,7 @@ enum {
Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt,
Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
Opt_appraise_type, Opt_permit_directio,
- Opt_pcr, Opt_err
+ Opt_pcr, Opt_trust_vfs, Opt_err
};
static const match_table_t policy_tokens = {
@@ -716,6 +716,7 @@ static const match_table_t policy_tokens = {
{Opt_appraise_type, "appraise_type=%s"},
{Opt_permit_directio, "permit_directio"},
{Opt_pcr, "pcr=%s"},
+ {Opt_trust_vfs, "trust_vfs"},
{Opt_err, NULL}
};
@@ -1062,6 +1063,9 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
case Opt_permit_directio:
entry->flags |= IMA_PERMIT_DIRECTIO;
break;
+ case Opt_trust_vfs:
+ entry->flags |= IMA_TRUST_VFS;
+ break;
case Opt_pcr:
if (entry->action != MEASURE) {
result = -EINVAL;
@@ -1358,6 +1362,8 @@ int ima_policy_show(struct seq_file *m, void *v)
seq_puts(m, "appraise_type=imasig ");
if (entry->flags & IMA_PERMIT_DIRECTIO)
seq_puts(m, "permit_directio ");
+ if (entry->flags & IMA_TRUST_VFS)
+ seq_puts(m, "trust_vfs ");
rcu_read_unlock();
seq_puts(m, "\n");
return 0;
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 513b457ae900..26f71c5805f0 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -291,7 +291,7 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
inode = file_inode(event_data->file);
hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
ima_hash_algo : HASH_ALGO_SHA1;
- result = ima_calc_file_hash(event_data->file, &hash.hdr);
+ result = ima_calc_file_hash(event_data->file, &hash.hdr, false);
if (result) {
integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
event_data->filename, "collect_data",
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7de59f44cba3..a03f859c1602 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -36,6 +36,7 @@
#define IMA_NEW_FILE 0x04000000
#define EVM_IMMUTABLE_DIGSIG 0x08000000
#define IMA_FAIL_UNVERIFIABLE_SIGS 0x10000000
+#define IMA_TRUST_VFS 0x20000000
#define IMA_DO_MASK (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
IMA_HASH | IMA_APPRAISE_SUBMASK)
--
2.21.0.1020.gf2820cf01a-goog
