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, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it and be able to use validate_module_sig() without having to depend on CONFIG_MODULE_SIG. Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx> Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> Cc: Jessica Yu <jeyu@xxxxxxxxxx> --- include/linux/module.h | 3 -- include/linux/module_signature.h | 44 +++++++++++++++++++++++ init/Kconfig | 6 +++- kernel/Makefile | 2 +- kernel/module.c | 1 + kernel/module_signing.c | 77 ++++++++++++++++++---------------------- 6 files changed, 85 insertions(+), 48 deletions(-) diff --git a/include/linux/module.h b/include/linux/module.h index d44df9b2c131..275cbc2579eb 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -24,9 +24,6 @@ #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..890135437b6b --- /dev/null +++ b/include/linux/module_signature.h @@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Module signature handling. + * + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@xxxxxxxxxx) + */ + +#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_sig(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/init/Kconfig b/init/Kconfig index f013afc74b11..b2e8a635fa7b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1759,7 +1759,7 @@ 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 @@ -1774,6 +1774,10 @@ 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 f85ae5dfa474..a4c7a7a0cce7 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -58,7 +58,7 @@ 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 ce8066b88178..7c6928f2c540 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..a7c2c461c598 100644 --- a/kernel/module_signing.c +++ b/kernel/module_signing.c @@ -11,36 +11,41 @@ #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. +/** + * validate_module_sig - validate that the given signature is sane * - * The constituents of the signature section are, in order: - * - * - 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_sig(const struct module_signature *ms, size_t file_len) +{ + if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms)) + return -EBADMSG; + + 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 0; +} /* * Verify the signature on a module. @@ -49,6 +54,7 @@ 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 +62,15 @@ 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_sig(&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);