[PATCH v5 4/6] module: strip the signature marker in the verification function.

Michal Suchanek
2022-01-11T11:38:06Z

It is stripped by each caller separately.

Note: this changes the error for kexec_file from EKEYREJECTED to ENODATA
when the signature marker is missing.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
v3: - Philipp Rudo <prudo@redhat.com>: Update the commit with note about
change of raturn value
- the module_signature.h is now no longer needed for kexec_file
---
arch/powerpc/kexec/elf_64.c | 11 -----------
arch/s390/kernel/machine_kexec_file.c | 11 -----------
kernel/module.c | 7 +------
kernel/module_signing.c | 12 ++++++++++--
4 files changed, 11 insertions(+), 30 deletions(-)

diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 64cd314cce0d..6dec8151ef73 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -24,7 +24,6 @@
#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,
unsigned long kernel_len, char *initrd,
@@ -156,16 +155,6 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
#ifdef CONFIG_KEXEC_SIG
int elf64_verify_sig(const char *kernel, unsigned long kernel_len)
{
- const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
-
- if (marker_len > kernel_len)
- return -EKEYREJECTED;
-
- if (memcmp(kernel + kernel_len - marker_len, MODULE_SIG_STRING,
- marker_len))
- return -EKEYREJECTED;
- kernel_len -= marker_len;
-
return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
"kexec_file");
}
diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index 345f2eab6e04..c3deccf1da83 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -12,7 +12,6 @@
#include <linux/elf.h>
#include <linux/errno.h>
#include <linux/kexec.h>
-#include <linux/module_signature.h>
#include <linux/verification.h>
#include <linux/vmalloc.h>
#include <asm/boot_data.h>
@@ -28,20 +27,10 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
#ifdef CONFIG_KEXEC_SIG
int s390_verify_sig(const char *kernel, unsigned long kernel_len)
{
- const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
-
/* Skip signature verification when not secure IPLed. */
if (!ipl_secure_flag)
return 0;

- if (marker_len > kernel_len)
- return -EKEYREJECTED;
-
- if (memcmp(kernel + kernel_len - marker_len, MODULE_SIG_STRING,
- marker_len))
- return -EKEYREJECTED;
- kernel_len -= marker_len;
-
return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
"kexec_file");
}
diff --git a/kernel/module.c b/kernel/module.c
index 8481933dfa92..d91ca0f93a40 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2882,7 +2882,6 @@ static inline void kmemleak_load_module(const struct module *mod,
static int module_sig_check(struct load_info *info, int flags)
{
int err = -ENODATA;
- const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
const char *reason;
const void *mod = info->hdr;

@@ -2890,11 +2889,7 @@ static int module_sig_check(struct load_info *info, int flags)
* Require flags == 0, as a module with version information
* removed is no longer the module that was signed
*/
- if (flags == 0 &&
- info->len > markerlen &&
- memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
- /* We truncate the module to discard the signature */
- info->len -= markerlen;
+ if (flags == 0) {
err = verify_appended_signature(mod, &info->len,
VERIFY_USE_SECONDARY_KEYRING, "module");
if (!err) {
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 30149969f21f..39a6dd7c6dd2 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -15,8 +15,7 @@
#include "module-internal.h"

/**
- * verify_appended_signature - Verify the signature on a module with the
- * signature marker stripped.
+ * verify_appended_signature - Verify the signature on a module
* @data: The data to be verified
* @len: Size of @data.
* @trusted_keys: Keyring to use for verification
@@ -25,12 +24,21 @@
int verify_appended_signature(const void *data, unsigned long *len,
struct key *trusted_keys, const char *what)
{
+ const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
struct module_signature *ms;
unsigned long sig_len, modlen = *len;
int ret;

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

+ if (markerlen > modlen)
+ return -ENODATA;
+
+ if (memcmp(data + modlen - markerlen, MODULE_SIG_STRING,
+ markerlen))
+ return -ENODATA;
+ modlen -= markerlen;
+
if (modlen <= sizeof(*ms))
return -EBADMSG;

--
2.31.1