IMA will use the module_signature format for append signatures, so export the relevant definitions and factor out the code which verifies that the appended signature trailer is valid. Also, add function verify_pkcs7_message_signature which takes a struct pkcs7_message for verification isntead of the raw bytes that verify_pkcs7_signature takes. Finally, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it and be able to use validate_module_signature without having to depend on CONFIG_MODULE_SIG. Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxxxxxxx> --- certs/system_keyring.c | 62 ++++++++++++++++++++++++--------- include/linux/module.h | 3 -- include/linux/module_signature.h | 48 ++++++++++++++++++++++++++ include/linux/verification.h | 10 ++++++ init/Kconfig | 6 +++- kernel/Makefile | 2 +- kernel/module.c | 1 + kernel/module_signing.c | 74 +++++++++++++++++----------------------- 8 files changed, 142 insertions(+), 64 deletions(-) diff --git a/certs/system_keyring.c b/certs/system_keyring.c index 6251d1b27f0c..0597f87a2375 100644 --- a/certs/system_keyring.c +++ b/certs/system_keyring.c @@ -190,33 +190,28 @@ late_initcall(load_system_certificate_list); #ifdef CONFIG_SYSTEM_DATA_VERIFICATION /** - * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data. + * verify_pkcs7_message_signature - Verify PKCS#7-based signature on system data * @data: The data to be verified (NULL if expecting internal data). * @len: Size of @data. - * @raw_pkcs7: The PKCS#7 message that is the signature. - * @pkcs7_len: The size of @raw_pkcs7. + * @pkcs7: The PKCS#7 message that is the signature. * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only, * (void *)1UL for all trusted keys). * @usage: The use to which the key is being put. * @view_content: Callback to gain access to content. * @ctx: Context for callback. */ -int verify_pkcs7_signature(const void *data, size_t len, - const void *raw_pkcs7, size_t pkcs7_len, - struct key *trusted_keys, - enum key_being_used_for usage, - int (*view_content)(void *ctx, - const void *data, size_t len, - size_t asn1hdrlen), - void *ctx) +int verify_pkcs7_message_signature(const void *data, size_t len, + struct pkcs7_message *pkcs7, + struct key *trusted_keys, + enum key_being_used_for usage, + int (*view_content)(void *ctx, + const void *data, + size_t len, + size_t asn1hdrlen), + void *ctx) { - struct pkcs7_message *pkcs7; int ret; - pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len); - if (IS_ERR(pkcs7)) - return PTR_ERR(pkcs7); - /* The data should be detached - so we need to supply it. */ if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) { pr_err("PKCS#7 signature with non-detached data\n"); @@ -258,6 +253,41 @@ int verify_pkcs7_signature(const void *data, size_t len, } error: + pr_devel("<==%s() = %d\n", __func__, ret); + return ret; +} + +/** + * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data. + * @data: The data to be verified (NULL if expecting internal data). + * @len: Size of @data. + * @raw_pkcs7: The PKCS#7 message that is the signature. + * @pkcs7_len: The size of @raw_pkcs7. + * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only, + * (void *)1UL for all trusted keys). + * @usage: The use to which the key is being put. + * @view_content: Callback to gain access to content. + * @ctx: Context for callback. + */ +int verify_pkcs7_signature(const void *data, size_t len, + const void *raw_pkcs7, size_t pkcs7_len, + struct key *trusted_keys, + enum key_being_used_for usage, + int (*view_content)(void *ctx, + const void *data, size_t len, + size_t asn1hdrlen), + void *ctx) +{ + struct pkcs7_message *pkcs7; + int ret; + + pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len); + if (IS_ERR(pkcs7)) + return PTR_ERR(pkcs7); + + ret = verify_pkcs7_message_signature(data, len, pkcs7, trusted_keys, + usage, view_content, ctx); + pkcs7_free_message(pkcs7); pr_devel("<==%s() = %d\n", __func__, ret); return ret; diff --git a/include/linux/module.h b/include/linux/module.h index 21f56393602f..76a233f120ba 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -23,9 +23,6 @@ #include <linux/percpu.h> #include <asm/module.h> -/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */ -#define MODULE_SIG_STRING "~Module signature appended~\n" - /* Not Yet Implemented */ #define MODULE_SUPPORTED_DEVICE(name) diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h new file mode 100644 index 000000000000..4e49fa059931 --- /dev/null +++ b/include/linux/module_signature.h @@ -0,0 +1,48 @@ +/* Module signature handling. + * + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@xxxxxxxxxx) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#ifndef _LINUX_MODULE_SIGNATURE_H +#define _LINUX_MODULE_SIGNATURE_H + +/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */ +#define MODULE_SIG_STRING "~Module signature appended~\n" + +enum pkey_id_type { + PKEY_ID_PGP, /* OpenPGP generated key ID */ + PKEY_ID_X509, /* X.509 arbitrary subjectKeyIdentifier */ + PKEY_ID_PKCS7, /* Signature in PKCS#7 message */ +}; + +/* + * Module signature information block. + * + * The constituents of the signature section are, in order: + * + * - Signer's name + * - Key identifier + * - Signature data + * - Information block + */ +struct module_signature { + u8 algo; /* Public-key crypto algorithm [0] */ + u8 hash; /* Digest algorithm [0] */ + u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */ + u8 signer_len; /* Length of signer's name [0] */ + u8 key_id_len; /* Length of key identifier [0] */ + u8 __pad[3]; + __be32 sig_len; /* Length of signature data */ +}; + +int validate_module_signature(const struct module_signature *ms, + size_t file_len); +int mod_verify_sig(const void *mod, unsigned long *_modlen); + +#endif /* _LINUX_MODULE_SIGNATURE_H */ diff --git a/include/linux/verification.h b/include/linux/verification.h index a10549a6c7cd..c7cb8db06ced 100644 --- a/include/linux/verification.h +++ b/include/linux/verification.h @@ -29,6 +29,7 @@ extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR]; #ifdef CONFIG_SYSTEM_DATA_VERIFICATION struct key; +struct pkcs7_message; extern int verify_pkcs7_signature(const void *data, size_t len, const void *raw_pkcs7, size_t pkcs7_len, @@ -38,6 +39,15 @@ extern int verify_pkcs7_signature(const void *data, size_t len, const void *data, size_t len, size_t asn1hdrlen), void *ctx); +extern int verify_pkcs7_message_signature(const void *data, size_t len, + struct pkcs7_message *pkcs7, + struct key *trusted_keys, + enum key_being_used_for usage, + int (*view_content)(void *ctx, + const void *data, + size_t len, + size_t asn1hdrlen), + void *ctx); #ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION extern int verify_pefile_signature(const void *pebuf, unsigned pelen, diff --git a/init/Kconfig b/init/Kconfig index 1d3475fc9496..5f20513098ff 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2063,7 +2063,7 @@ config MODULE_SRCVERSION_ALL config MODULE_SIG bool "Module signature verification" depends on MODULES - select SYSTEM_DATA_VERIFICATION + select MODULE_SIG_FORMAT help Check modules for valid signatures upon load: the signature is simply appended to the module. For more information see @@ -2078,6 +2078,10 @@ config MODULE_SIG debuginfo strip done by some packagers (such as rpmbuild) and inclusion into an initramfs that wants the module size reduced. +config MODULE_SIG_FORMAT + def_bool n + select SYSTEM_DATA_VERIFICATION + config MODULE_SIG_FORCE bool "Require modules to be validly signed" depends on MODULE_SIG diff --git a/kernel/Makefile b/kernel/Makefile index 72aa080f91f0..dcb548b68084 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -56,7 +56,7 @@ obj-y += up.o endif obj-$(CONFIG_UID16) += uid16.o obj-$(CONFIG_MODULES) += module.o -obj-$(CONFIG_MODULE_SIG) += module_signing.o +obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signing.o obj-$(CONFIG_KALLSYMS) += kallsyms.o obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o obj-$(CONFIG_CRASH_CORE) += crash_core.o diff --git a/kernel/module.c b/kernel/module.c index 4a3665f8f837..0f973856d6d2 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -19,6 +19,7 @@ #include <linux/export.h> #include <linux/extable.h> #include <linux/moduleloader.h> +#include <linux/module_signature.h> #include <linux/trace_events.h> #include <linux/init.h> #include <linux/kallsyms.h> diff --git a/kernel/module_signing.c b/kernel/module_signing.c index 937c844bee4a..421e3e668714 100644 --- a/kernel/module_signing.c +++ b/kernel/module_signing.c @@ -11,36 +11,38 @@ #include <linux/kernel.h> #include <linux/errno.h> +#include <linux/module_signature.h> #include <linux/string.h> #include <linux/verification.h> #include <crypto/public_key.h> #include "module-internal.h" -enum pkey_id_type { - PKEY_ID_PGP, /* OpenPGP generated key ID */ - PKEY_ID_X509, /* X.509 arbitrary subjectKeyIdentifier */ - PKEY_ID_PKCS7, /* Signature in PKCS#7 message */ -}; - -/* - * Module signature information block. - * - * The constituents of the signature section are, in order: +/** + * validate_module_signature - validate that the given signature is sane * - * - Signer's name - * - Key identifier - * - Signature data - * - Information block + * @ms: Signature to validate. + * @file_len: Size of the file to which @ms is appended. */ -struct module_signature { - u8 algo; /* Public-key crypto algorithm [0] */ - u8 hash; /* Digest algorithm [0] */ - u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */ - u8 signer_len; /* Length of signer's name [0] */ - u8 key_id_len; /* Length of key identifier [0] */ - u8 __pad[3]; - __be32 sig_len; /* Length of signature data */ -}; +int validate_module_signature(const struct module_signature *ms, size_t file_len) +{ + if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms)) + return -EBADMSG; + else if (ms->id_type != PKEY_ID_PKCS7) { + pr_err("Module is not signed with expected PKCS#7 message\n"); + return -ENOPKG; + } else if (ms->algo != 0 || + ms->hash != 0 || + ms->signer_len != 0 || + ms->key_id_len != 0 || + ms->__pad[0] != 0 || + ms->__pad[1] != 0 || + ms->__pad[2] != 0) { + pr_err("PKCS#7 signature info has unexpected non-zero params\n"); + return -EBADMSG; + } + + return 0; +} /* * Verify the signature on a module. @@ -49,6 +51,7 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen) { struct module_signature ms; size_t modlen = *_modlen, sig_len; + int ret; pr_devel("==>%s(,%zu)\n", __func__, modlen); @@ -56,30 +59,15 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen) return -EBADMSG; memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms)); - modlen -= sizeof(ms); + + ret = validate_module_signature(&ms, modlen); + if (ret) + return ret; sig_len = be32_to_cpu(ms.sig_len); - if (sig_len >= modlen) - return -EBADMSG; - modlen -= sig_len; + modlen -= sig_len + sizeof(ms); *_modlen = modlen; - if (ms.id_type != PKEY_ID_PKCS7) { - pr_err("Module is not signed with expected PKCS#7 message\n"); - return -ENOPKG; - } - - if (ms.algo != 0 || - ms.hash != 0 || - ms.signer_len != 0 || - ms.key_id_len != 0 || - ms.__pad[0] != 0 || - ms.__pad[1] != 0 || - ms.__pad[2] != 0) { - pr_err("PKCS#7 signature info has unexpected non-zero params\n"); - return -EBADMSG; - } - return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len, NULL, VERIFYING_MODULE_SIGNATURE, NULL, NULL); -- 2.7.4