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Message-Id: <20260113-module-hashes-v4-8-0b932db9b56b@weissschuh.net>
Date: Tue, 13 Jan 2026 13:28:52 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Nathan Chancellor <nathan@...nel.org>, Arnd Bergmann <arnd@...db.de>,
Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Daniel Gomez <da.gomez@...sung.com>, Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
Jonathan Corbet <corbet@....net>, Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
Naveen N Rao <naveen@...nel.org>, Mimi Zohar <zohar@...ux.ibm.com>,
Roberto Sassu <roberto.sassu@...wei.com>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
Eric Snowberg <eric.snowberg@...cle.com>,
Nicolas Schier <nicolas.schier@...ux.dev>,
Daniel Gomez <da.gomez@...nel.org>, Aaron Tomlin <atomlin@...mlin.com>,
"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
Nicolas Schier <nsc@...nel.org>,
Nicolas Bouchinet <nicolas.bouchinet@....cyber.gouv.fr>,
Xiu Jianfeng <xiujianfeng@...wei.com>, Nicolas Schier <nsc@...nel.org>,
Christophe Leroy <chleroy@...nel.org>
Cc: Fabian Grünbichler <f.gruenbichler@...xmox.com>,
Arnout Engelen <arnout@...t.net>, Mattia Rizzolo <mattia@...reri.org>,
kpcyrd <kpcyrd@...hlinux.org>, Christian Heusel <christian@...sel.eu>,
Câju Mihai-Drosi <mcaju95@...il.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-modules@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-doc@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-integrity@...r.kernel.org,
Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v4 08/17] module: Deduplicate signature extraction
The logic to extract the signature bits from a module file are
duplicated between the module core and IMA modsig appraisal.
Unify the implementation.
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
include/linux/module_signature.h | 4 +--
kernel/module/signing.c | 52 +++++++------------------------------
kernel/module_signature.c | 41 +++++++++++++++++++++++++++--
security/integrity/ima/ima_modsig.c | 24 ++++-------------
4 files changed, 56 insertions(+), 65 deletions(-)
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 7eb4b00381ac..186a55effa30 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -40,7 +40,7 @@ struct module_signature {
__be32 sig_len; /* Length of signature data */
};
-int mod_check_sig(const struct module_signature *ms, size_t file_len,
- const char *name);
+int mod_split_sig(const void *buf, size_t *buf_len, bool mangled,
+ size_t *sig_len, const u8 **sig, const char *name);
#endif /* _LINUX_MODULE_SIGNATURE_H */
diff --git a/kernel/module/signing.c b/kernel/module/signing.c
index fe3f51ac6199..6d64c0d18d0a 100644
--- a/kernel/module/signing.c
+++ b/kernel/module/signing.c
@@ -37,54 +37,22 @@ void set_module_sig_enforced(void)
sig_enforce = true;
}
-/*
- * Verify the signature on a module.
- */
-static 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);
-
- if (modlen <= sizeof(ms))
- return -EBADMSG;
-
- memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
-
- ret = mod_check_sig(&ms, modlen, "module");
- if (ret)
- return ret;
-
- sig_len = be32_to_cpu(ms.sig_len);
- modlen -= sig_len + sizeof(ms);
- info->len = modlen;
-
- return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
- VERIFY_USE_SECONDARY_KEYRING,
- VERIFYING_MODULE_SIGNATURE,
- NULL, NULL);
-}
-
int module_sig_check(struct load_info *info, int flags)
{
- int err = -ENODATA;
- const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+ int err;
const char *reason;
const void *mod = info->hdr;
+ size_t sig_len;
+ const u8 *sig;
bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
MODULE_INIT_IGNORE_VERMAGIC);
- /*
- * Do not allow mangled modules as a module with version information
- * removed is no longer the module that was signed.
- */
- if (!mangled_module &&
- info->len > markerlen &&
- 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 = mod_split_sig(info->hdr, &info->len, mangled_module, &sig_len, &sig, "module");
+ if (!err) {
+ err = verify_pkcs7_signature(mod, info->len, sig, sig_len,
+ VERIFY_USE_SECONDARY_KEYRING,
+ VERIFYING_MODULE_SIGNATURE,
+ NULL, NULL);
if (!err) {
info->sig_ok = true;
return 0;
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
index 00132d12487c..b2384a73524c 100644
--- a/kernel/module_signature.c
+++ b/kernel/module_signature.c
@@ -8,6 +8,7 @@
#include <linux/errno.h>
#include <linux/printk.h>
+#include <linux/string.h>
#include <linux/module_signature.h>
#include <asm/byteorder.h>
@@ -18,8 +19,8 @@
* @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)
+static 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;
@@ -44,3 +45,39 @@ int mod_check_sig(const struct module_signature *ms, size_t file_len,
return 0;
}
+
+int mod_split_sig(const void *buf, size_t *buf_len, bool mangled,
+ size_t *sig_len, const u8 **sig, const char *name)
+{
+ const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+ struct module_signature ms;
+ size_t modlen = *buf_len;
+ int ret;
+
+ /*
+ * Do not allow mangled modules as a module with version information
+ * removed is no longer the module that was signed.
+ */
+ if (!mangled &&
+ *buf_len > markerlen &&
+ memcmp(buf + modlen - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
+ /* We truncate the module to discard the signature */
+ modlen -= markerlen;
+ }
+
+ if (modlen <= sizeof(ms))
+ return -EBADMSG;
+
+ memcpy(&ms, buf + (modlen - sizeof(ms)), sizeof(ms));
+
+ ret = mod_check_sig(&ms, modlen, name);
+ if (ret)
+ return ret;
+
+ *sig_len = be32_to_cpu(ms.sig_len);
+ modlen -= *sig_len + sizeof(ms);
+ *buf_len = modlen;
+ *sig = buf + modlen;
+
+ return 0;
+}
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index 3265d744d5ce..a57342d39b07 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -40,44 +40,30 @@ struct modsig {
int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
struct modsig **modsig)
{
- const size_t marker_len = strlen(MODULE_SIG_STRING);
- const struct module_signature *sig;
+ size_t buf_len_sz = buf_len;
struct modsig *hdr;
size_t sig_len;
- const void *p;
+ const u8 *sig;
int rc;
- if (buf_len <= marker_len + sizeof(*sig))
- return -ENOENT;
-
- p = buf + buf_len - marker_len;
- if (memcmp(p, MODULE_SIG_STRING, marker_len))
- return -ENOENT;
-
- buf_len -= marker_len;
- sig = (const struct module_signature *)(p - sizeof(*sig));
-
- rc = mod_check_sig(sig, buf_len, func_tokens[func]);
+ rc = mod_split_sig(buf, &buf_len_sz, true, &sig_len, &sig, func_tokens[func]);
if (rc)
return rc;
- sig_len = be32_to_cpu(sig->sig_len);
- buf_len -= sig_len + sizeof(*sig);
-
/* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
hdr = kzalloc(struct_size(hdr, raw_pkcs7, sig_len), GFP_KERNEL);
if (!hdr)
return -ENOMEM;
hdr->raw_pkcs7_len = sig_len;
- hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
+ hdr->pkcs7_msg = pkcs7_parse_message(sig, sig_len);
if (IS_ERR(hdr->pkcs7_msg)) {
rc = PTR_ERR(hdr->pkcs7_msg);
kfree(hdr);
return rc;
}
- memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
+ memcpy(hdr->raw_pkcs7, sig, sig_len);
/* We don't know the hash algorithm yet. */
hdr->hash_algo = HASH_ALGO__LAST;
--
2.52.0
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