1 files changed, 46 insertions, 0 deletions
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
new file mode 100644
index 000000000..00132d124
--- /dev/null
+++ b/kernel/module_signature.c
@@ -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: 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;
+}