[PATCH v5 3/6] kexec_file: Don't opencode appended signature verification.

Michal Suchanek
2022-01-11T11:38:04Z

Module verification already implements appeded signature verification.

Reuse it for kexec_file.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
v3: - Philipp Rudo <prudo@redhat.com>: Update the dependency on
MODULE_SIG_FORMAT to MODULE_SIG
- Include linux/verification.h - previously added in earlier patch
v4: - kernel test robot <lkp@intel.com>: Use unsigned long rather than size_t for data length
- Update the code in kernel/module_signing.c to use pointer rather
than memcpy as the kexec and IMA code does
---
arch/powerpc/Kconfig | 2 +-
arch/powerpc/kexec/elf_64.c | 19 +++------------
arch/s390/Kconfig | 2 +-
arch/s390/kernel/machine_kexec_file.c | 18 ++------------
include/linux/verification.h | 3 +++
kernel/module-internal.h | 2 --
kernel/module.c | 4 +++-
kernel/module_signing.c | 34 ++++++++++++++++-----------
8 files changed, 33 insertions(+), 51 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1cde9b6c5987..4092187474ff 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -562,7 +562,7 @@ config ARCH_HAS_KEXEC_PURGATORY

config KEXEC_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
- depends on KEXEC_FILE && MODULE_SIG_FORMAT
+ depends on KEXEC_FILE && MODULE_SIG
help
This option makes kernel signature verification mandatory for
the kexec_file_load() syscall.
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 98d1cb5135b4..64cd314cce0d 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -23,6 +23,7 @@
#include <linux/of_fdt.h>
#include <linux/slab.h>
#include <linux/types.h>
+#include <linux/verification.h>
#include <linux/module_signature.h>

static void *elf64_load(struct kimage *image, char *kernel_buf,
@@ -156,9 +157,6 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
int elf64_verify_sig(const char *kernel, unsigned long kernel_len)
{
const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
- struct module_signature *ms;
- unsigned long sig_len;
- int ret;

if (marker_len > kernel_len)
return -EKEYREJECTED;
@@ -168,19 +166,8 @@ int elf64_verify_sig(const char *kernel, unsigned long kernel_len)
return -EKEYREJECTED;
kernel_len -= marker_len;

- ms = (void *)kernel + kernel_len - sizeof(*ms);
- ret = mod_check_sig(ms, kernel_len, "kexec");
- if (ret)
- return ret;
-
- sig_len = be32_to_cpu(ms->sig_len);
- kernel_len -= sizeof(*ms) + sig_len;
-
- return verify_pkcs7_signature(kernel, kernel_len,
- kernel + kernel_len, sig_len,
- VERIFY_USE_PLATFORM_KEYRING,
- VERIFYING_MODULE_SIGNATURE,
- NULL, NULL);
+ return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
+ "kexec_file");
}
#endif /* CONFIG_KEXEC_SIG */

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 2a5bb4f29cfe..cece7152ea35 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -544,7 +544,7 @@ config ARCH_HAS_KEXEC_PURGATORY

config KEXEC_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
- depends on KEXEC_FILE && MODULE_SIG_FORMAT
+ depends on KEXEC_FILE && MODULE_SIG
help
This option makes kernel signature verification mandatory for
the kexec_file_load() syscall.
diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index c944d71316c7..345f2eab6e04 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -29,9 +29,6 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
int s390_verify_sig(const char *kernel, unsigned long kernel_len)
{
const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
- struct module_signature *ms;
- unsigned long sig_len;
- int ret;

/* Skip signature verification when not secure IPLed. */
if (!ipl_secure_flag)
@@ -45,19 +42,8 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
return -EKEYREJECTED;
kernel_len -= marker_len;

- ms = (void *)kernel + kernel_len - sizeof(*ms);
- ret = mod_check_sig(ms, kernel_len, "kexec");
- if (ret)
- return ret;
-
- sig_len = be32_to_cpu(ms->sig_len);
- kernel_len -= sizeof(*ms) + sig_len;
-
- return verify_pkcs7_signature(kernel, kernel_len,
- kernel + kernel_len, sig_len,
- VERIFY_USE_PLATFORM_KEYRING,
- VERIFYING_MODULE_SIGNATURE,
- NULL, NULL);
+ return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
+ "kexec_file");
}
#endif /* CONFIG_KEXEC_SIG */

diff --git a/include/linux/verification.h b/include/linux/verification.h
index a655923335ae..32db9287a7b0 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -60,5 +60,8 @@ extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
enum key_being_used_for usage);
#endif

+int verify_appended_signature(const void *data, unsigned long *len,
+ struct key *trusted_keys, const char *what);
+
#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
#endif /* _LINUX_VERIFY_PEFILE_H */
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
index 33783abc377b..80461e14bf29 100644
--- a/kernel/module-internal.h
+++ b/kernel/module-internal.h
@@ -27,5 +27,3 @@ struct load_info {
unsigned int sym, str, mod, vers, info, pcpu;
} index;
};
-
-extern int mod_verify_sig(const void *mod, struct load_info *info);
diff --git a/kernel/module.c b/kernel/module.c
index 84a9141a5e15..8481933dfa92 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -57,6 +57,7 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
+#include <linux/verification.h>
#include <uapi/linux/module.h>
#include "module-internal.h"

@@ -2894,7 +2895,8 @@ static int module_sig_check(struct load_info *info, int flags)
memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
/* We truncate the module to discard the signature */
info->len -= markerlen;
- err = mod_verify_sig(mod, info);
+ err = verify_appended_signature(mod, &info->len,
+ VERIFY_USE_SECONDARY_KEYRING, "module");
if (!err) {
info->sig_ok = true;
return 0;
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 8723ae70ea1f..30149969f21f 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -14,32 +14,38 @@
#include <crypto/public_key.h>
#include "module-internal.h"

-/*
- * Verify the signature on a module.
+/**
+ * verify_appended_signature - Verify the signature on a module with the
+ * signature marker stripped.
+ * @data: The data to be verified
+ * @len: Size of @data.
+ * @trusted_keys: Keyring to use for verification
+ * @what: Informational string for log messages
*/
-int mod_verify_sig(const void *mod, struct load_info *info)
+int verify_appended_signature(const void *data, unsigned long *len,
+ struct key *trusted_keys, const char *what)
{
- struct module_signature ms;
- size_t sig_len, modlen = info->len;
+ struct module_signature *ms;
+ unsigned long sig_len, modlen = *len;
int ret;

- pr_devel("==>%s(,%zu)\n", __func__, modlen);
+ pr_devel("==>%s(,%lu)\n", __func__, modlen);

- if (modlen <= sizeof(ms))
+ if (modlen <= sizeof(*ms))
return -EBADMSG;

- memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
+ ms = data + modlen - sizeof(*ms);

- ret = mod_check_sig(&ms, modlen, "module");
+ ret = mod_check_sig(ms, modlen, what);
if (ret)
return ret;

- sig_len = be32_to_cpu(ms.sig_len);
- modlen -= sig_len + sizeof(ms);
- info->len = modlen;
+ sig_len = be32_to_cpu(ms->sig_len);
+ modlen -= sig_len + sizeof(*ms);
+ *len = modlen;

- return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
- VERIFY_USE_SECONDARY_KEYRING,
+ return verify_pkcs7_signature(data, modlen, data + modlen, sig_len,
+ trusted_keys,
VERIFYING_MODULE_SIGNATURE,
NULL, NULL);
}
--
2.31.1