[PATCH v2 5/6] MODSIGN: Export module signature definitions.
Thiago Jung Bauermann
bauerman at linux.vnet.ibm.com
Thu Jun 8 11:49:14 AEST 2017
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 at linux.vnet.ibm.com>
---
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 at redhat.com)
+ *
+ * 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
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