1 files changed, 78 insertions, 0 deletions
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
new file mode 100644
index 000000000000..6528a79d998d
--- /dev/null
+++ b/kernel/module_signing.c
@@ -0,0 +1,78 @@
+/* Module signature checker
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <keys/system_keyring.h>
+#include <crypto/public_key.h>
+#include "module-internal.h"
+
+/*
+ * 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 */
+};
+
+/*
+ * Verify the signature on a module.
+ */
+int mod_verify_sig(const void *mod, unsigned long *_modlen)
+{
+	struct module_signature ms;
+	size_t modlen = *_modlen, sig_len;
+
+	pr_devel("==>%s(,%zu)\n", __func__, modlen);
+
+	if (modlen <= sizeof(ms))
+		return -EBADMSG;
+
+	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
+	modlen -= sizeof(ms);
+
+	sig_len = be32_to_cpu(ms.sig_len);
+	if (sig_len >= modlen)
+		return -EBADMSG;
+	modlen -= sig_len;
+	*_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 system_verify_data(mod, modlen, mod + modlen, sig_len,
+				  VERIFYING_MODULE_SIGNATURE);
+}