1 files changed, 140 insertions, 0 deletions
diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
new file mode 100644
index 000000000..6dc075144
--- /dev/null
+++ b/security/integrity/digsig_asymmetric.c
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2013 Intel Corporation
+ *
+ * Author:
+ * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/err.h>
+#include <linux/ratelimit.h>
+#include <linux/key-type.h>
+#include <crypto/public_key.h>
+#include <crypto/hash_info.h>
+#include <keys/asymmetric-type.h>
+#include <keys/system_keyring.h>
+
+#include "integrity.h"
+
+/*
+ * Request an asymmetric key.
+ */
+static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
+{
+	struct key *key;
+	char name[12];
+
+	sprintf(name, "id:%08x", keyid);
+
+	pr_debug("key search: \"%s\"\n", name);
+
+	key = get_ima_blacklist_keyring();
+	if (key) {
+		key_ref_t kref;
+
+		kref = keyring_search(make_key_ref(key, 1),
+				     &key_type_asymmetric, name);
+		if (!IS_ERR(kref)) {
+			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
+			return ERR_PTR(-EKEYREJECTED);
+		}
+	}
+
+	if (keyring) {
+		/* search in specific keyring */
+		key_ref_t kref;
+
+		kref = keyring_search(make_key_ref(keyring, 1),
+				      &key_type_asymmetric, name);
+		if (IS_ERR(kref))
+			key = ERR_CAST(kref);
+		else
+			key = key_ref_to_ptr(kref);
+	} else {
+		key = request_key(&key_type_asymmetric, name, NULL);
+	}
+
+	if (IS_ERR(key)) {
+		pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
+				   name, PTR_ERR(key));
+		switch (PTR_ERR(key)) {
+			/* Hide some search errors */
+		case -EACCES:
+		case -ENOTDIR:
+		case -EAGAIN:
+			return ERR_PTR(-ENOKEY);
+		default:
+			return key;
+		}
+	}
+
+	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
+
+	return key;
+}
+
+int asymmetric_verify(struct key *keyring, const char *sig,
+		      int siglen, const char *data, int datalen)
+{
+	struct public_key_signature pks;
+	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
+	struct key *key;
+	int ret = -ENOMEM;
+
+	if (siglen <= sizeof(*hdr))
+		return -EBADMSG;
+
+	siglen -= sizeof(*hdr);
+
+	if (siglen != be16_to_cpu(hdr->sig_size))
+		return -EBADMSG;
+
+	if (hdr->hash_algo >= HASH_ALGO__LAST)
+		return -ENOPKG;
+
+	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	memset(&pks, 0, sizeof(pks));
+
+	pks.pkey_algo = "rsa";
+	pks.hash_algo = hash_algo_name[hdr->hash_algo];
+	pks.digest = (u8 *)data;
+	pks.digest_size = datalen;
+	pks.s = hdr->sig;
+	pks.s_size = siglen;
+	ret = verify_signature(key, &pks);
+	key_put(key);
+	pr_debug("%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+/**
+ * integrity_kernel_module_request - prevent crypto-pkcs1pad(rsa,*) requests
+ * @kmod_name: kernel module name
+ *
+ * We have situation, when public_key_verify_signature() in case of RSA
+ * algorithm use alg_name to store internal information in order to
+ * construct an algorithm on the fly, but crypto_larval_lookup() will try
+ * to use alg_name in order to load kernel module with same name.
+ * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
+ * we are safe to fail such module request from crypto_larval_lookup().
+ *
+ * In this way we prevent modprobe execution during digsig verification
+ * and avoid possible deadlock if modprobe and/or it's dependencies
+ * also signed with digsig.
+ */
+int integrity_kernel_module_request(char *kmod_name)
+{
+	if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
+		return -EINVAL;
+
+	return 0;
+}