PKCS 1: Add function for checking v1.5 RSA signature

This could be used as a step towards replacing more specific functions
used in X.509 and TLS processing.

Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/src/tls/pkcs1.c b/src/tls/pkcs1.c
index ea3e6171a1d12185b34a7b32a86918f0646b68d5..381b7a03879f1f4362a0d7dcccf200d8203df946 100644 (file)
--- a/src/tls/pkcs1.c
+++ b/src/tls/pkcs1.c
@@ -1,6 +1,6 @@
 /*
  * PKCS #1 (RSA Encryption)
- * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2006-2014, Jouni Malinen <j@w1.fi>
  *
  * This software may be distributed under the terms of the BSD license.
  * See README for more details.
@@ -9,7 +9,9 @@
 #include "includes.h"
 
 #include "common.h"
+#include "crypto/crypto.h"
 #include "rsa.h"
+#include "asn1.h"
 #include "pkcs1.h"
 
 
@@ -189,3 +191,130 @@ int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
 
        return 0;
 }
+
+
+int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
+                     const u8 *s, size_t s_len,
+                     const struct asn1_oid *hash_alg,
+                     const u8 *hash, size_t hash_len)
+{
+       int res;
+       u8 *decrypted;
+       size_t decrypted_len;
+       const u8 *pos, *end, *next, *da_end;
+       struct asn1_hdr hdr;
+       struct asn1_oid oid;
+
+       decrypted = os_malloc(s_len);
+       if (decrypted == NULL)
+               return -1;
+       decrypted_len = s_len;
+       res = crypto_public_key_decrypt_pkcs1(pk, s, s_len, decrypted,
+                                             &decrypted_len);
+       if (res < 0) {
+               wpa_printf(MSG_INFO, "PKCS #1: RSA decrypt failed");
+               os_free(decrypted);
+               return -1;
+       }
+       wpa_hexdump(MSG_DEBUG, "Decrypted(S)", decrypted, decrypted_len);
+
+       /*
+        * PKCS #1 v1.5, 10.1.2:
+        *
+        * DigestInfo ::= SEQUENCE {
+        *     digestAlgorithm DigestAlgorithmIdentifier,
+        *     digest Digest
+        * }
+        *
+        * DigestAlgorithmIdentifier ::= AlgorithmIdentifier
+        *
+        * Digest ::= OCTET STRING
+        *
+        */
+       if (asn1_get_next(decrypted, decrypted_len, &hdr) < 0 ||
+           hdr.class != ASN1_CLASS_UNIVERSAL ||
+           hdr.tag != ASN1_TAG_SEQUENCE) {
+               wpa_printf(MSG_DEBUG,
+                          "PKCS #1: Expected SEQUENCE (DigestInfo) - found class %d tag 0x%x",
+                          hdr.class, hdr.tag);
+               os_free(decrypted);
+               return -1;
+       }
+
+       pos = hdr.payload;
+       end = pos + hdr.length;
+
+       /*
+        * X.509:
+        * AlgorithmIdentifier ::= SEQUENCE {
+        *     algorithm            OBJECT IDENTIFIER,
+        *     parameters           ANY DEFINED BY algorithm OPTIONAL
+        * }
+        */
+
+       if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
+           hdr.class != ASN1_CLASS_UNIVERSAL ||
+           hdr.tag != ASN1_TAG_SEQUENCE) {
+               wpa_printf(MSG_DEBUG,
+                          "PKCS #1: Expected SEQUENCE (AlgorithmIdentifier) - found class %d tag 0x%x",
+                          hdr.class, hdr.tag);
+               os_free(decrypted);
+               return -1;
+       }
+       da_end = hdr.payload + hdr.length;
+
+       if (asn1_get_oid(hdr.payload, hdr.length, &oid, &next)) {
+               wpa_printf(MSG_DEBUG,
+                          "PKCS #1: Failed to parse digestAlgorithm");
+               os_free(decrypted);
+               return -1;
+       }
+
+       if (!asn1_oid_equal(&oid, hash_alg)) {
+               char txt[100], txt2[100];
+               asn1_oid_to_str(&oid, txt, sizeof(txt));
+               asn1_oid_to_str(hash_alg, txt2, sizeof(txt2));
+               wpa_printf(MSG_DEBUG,
+                          "PKCS #1: Hash alg OID mismatch: was %s, expected %s",
+                          txt, txt2);
+               os_free(decrypted);
+               return -1;
+       }
+
+       /* Digest ::= OCTET STRING */
+       pos = da_end;
+       end = decrypted + decrypted_len;
+
+       if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
+           hdr.class != ASN1_CLASS_UNIVERSAL ||
+           hdr.tag != ASN1_TAG_OCTETSTRING) {
+               wpa_printf(MSG_DEBUG,
+                          "PKCS #1: Expected OCTETSTRING (Digest) - found class %d tag 0x%x",
+                          hdr.class, hdr.tag);
+               os_free(decrypted);
+               return -1;
+       }
+       wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Decrypted Digest",
+                   hdr.payload, hdr.length);
+
+       if (hdr.length != hash_len ||
+           os_memcmp(hdr.payload, hash, hdr.length) != 0) {
+               wpa_printf(MSG_INFO, "PKCS #1: Digest value does not match calculated hash");
+               os_free(decrypted);
+               return -1;
+       }
+
+       os_free(decrypted);
+
+       if (hdr.payload + hdr.length != end) {
+               wpa_printf(MSG_INFO,
+                          "PKCS #1: Extra data after signature - reject");
+
+               wpa_hexdump(MSG_DEBUG, "PKCS #1: Extra data",
+                           hdr.payload + hdr.length,
+                           end - hdr.payload - hdr.length);
+               return -1;
+       }
+
+       return 0;
+}

diff --git a/src/tls/pkcs1.h b/src/tls/pkcs1.h
index ed64defaafe089b57edd46d1b7f0ae0d4d5d4e73..f37ebf3875eaada66b0571cd5a8e1c9a14467e6d 100644 (file)
--- a/src/tls/pkcs1.h
+++ b/src/tls/pkcs1.h
@@ -9,6 +9,9 @@
 #ifndef PKCS1_H
 #define PKCS1_H
 
+struct crypto_public_key;
+struct asn1_oid;
+
 int pkcs1_encrypt(int block_type, struct crypto_rsa_key *key,
                  int use_private, const u8 *in, size_t inlen,
                  u8 *out, size_t *outlen);
@@ -18,5 +21,9 @@ int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key *key,
 int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
                             const u8 *crypt, size_t crypt_len,
                             u8 *plain, size_t *plain_len);
+int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
+                     const u8 *s, size_t s_len,
+                     const struct asn1_oid *hash_alg,
+                     const u8 *hash, size_t hash_len);
 
 #endif /* PKCS1_H */