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MODSIGN: Export module signature definitions

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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 mod_check_sig() without having to depend on either
CONFIG_MODULE_SIG or CONFIG_MODULES.

s390 duplicated the definition of struct module_signature so now they can
use the new <linux/module_signature.h> header instead.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Acked-by: Jessica Yu <jeyu@kernel.org>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Thiago Jung Bauermann 2019-07-04 15:57:34 -03:00 committed by Mimi Zohar
parent b36f281f4a
commit c8424e776b
10 changed files with 108 additions and 77 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/s390/Kconfig
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@ -538,7 +538,7 @@ config ARCH_HAS_KEXEC_PURGATORY
config KEXEC_VERIFY_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
depends on KEXEC_FILE && SYSTEM_DATA_VERIFICATION
depends on KEXEC_FILE && MODULE_SIG_FORMAT
help
This option makes kernel signature verification mandatory for
the kexec_file_load() syscall.

24
arch/s390/kernel/machine_kexec_file.c
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@ -10,7 +10,7 @@
#include <linux/elf.h>
#include <linux/errno.h>
#include <linux/kexec.h>
#include <linux/module.h>
#include <linux/module_signature.h>
#include <linux/verification.h>
#include <asm/boot_data.h>
#include <asm/ipl.h>
@ -23,28 +23,6 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
};
#ifdef CONFIG_KEXEC_VERIFY_SIG
/*
* 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 */
};
#define PKEY_ID_PKCS7 2
int s390_verify_sig(const char *kernel, unsigned long kernel_len)
{
const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;

3
include/linux/module.h
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@ -26,9 +26,6 @@
#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)

44
include/linux/module_signature.h Normal file
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@ -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@redhat.com)
*/
#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 mod_check_sig(const struct module_signature *ms, size_t file_len,
const char *name);
#endif /* _LINUX_MODULE_SIGNATURE_H */

6
init/Kconfig
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@ -1930,6 +1930,10 @@ config BASE_SMALL
default 0 if BASE_FULL
default 1 if !BASE_FULL
config MODULE_SIG_FORMAT
def_bool n
select SYSTEM_DATA_VERIFICATION
menuconfig MODULES
bool "Enable loadable module support"
option modules
@ -2007,7 +2011,7 @@ 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

1
kernel/Makefile
View File

@ -58,6 +58,7 @@ endif
obj-$(CONFIG_UID16) += uid16.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_MODULE_SIG) += module_signing.o
obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
obj-$(CONFIG_KALLSYMS) += kallsyms.o
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_CRASH_CORE) += crash_core.o

1
kernel/module.c
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@ -7,6 +7,7 @@
#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>

46
kernel/module_signature.c Normal file
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@ -0,0 +1,46 @@
// SPDX-License-Identifier: GPL-2.0+
/*
* Module signature checker
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/errno.h>
#include <linux/printk.h>
#include <linux/module_signature.h>
#include <asm/byteorder.h>
/**
* mod_check_sig - check that the given signature is sane
*
* @ms: Signature to check.
* @file_len: Size of the file to which @ms is appended.
* @name: What is being checked. Used for error messages.
*/
int mod_check_sig(const struct module_signature *ms, size_t file_len,
const char *name)
{
if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
return -EBADMSG;
if (ms->id_type != PKEY_ID_PKCS7) {
pr_err("%s: Module is not signed with expected PKCS#7 message\n",
name);
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("%s: PKCS#7 signature info has unexpected non-zero params\n",
name);
return -EBADMSG;
}
return 0;
}

56
kernel/module_signing.c
View File

@ -7,37 +7,13 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.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:
*
* - 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 */
};
/*
* Verify the signature on a module.
*/
@ -45,6 +21,7 @@ int mod_verify_sig(const void *mod, struct load_info *info)
{
struct module_signature ms;
size_t sig_len, modlen = info->len;
int ret;
pr_devel("==>%s(,%zu)\n", __func__, modlen);
@ -52,32 +29,15 @@ int mod_verify_sig(const void *mod, struct load_info *info)
return -EBADMSG;
memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
modlen -= sizeof(ms);
ret = mod_check_sig(&ms, modlen, info->name);
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);
info->len = modlen;
if (ms.id_type != PKEY_ID_PKCS7) {
pr_err("%s: Module is not signed with expected PKCS#7 message\n",
info->name);
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("%s: PKCS#7 signature info has unexpected non-zero params\n",
info->name);
return -EBADMSG;
}
return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
VERIFY_USE_SECONDARY_KEYRING,
VERIFYING_MODULE_SIGNATURE,

2
scripts/Makefile
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@ -17,7 +17,7 @@ hostprogs-$(CONFIG_VT) += conmakehash
hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount
hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
hostprogs-$(CONFIG_ASN1) += asn1_compiler
hostprogs-$(CONFIG_MODULE_SIG) += sign-file
hostprogs-$(CONFIG_MODULE_SIG_FORMAT) += sign-file
hostprogs-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += extract-cert
hostprogs-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE) += insert-sys-cert