tor

commit 26e0909e516a91281c2ad1fcac23405f3cc1ee11
parent d5eea977be405b984e651564736179df4b27b31c
Author: Nick Mathewson <nickm@torproject.org>
Date:   Fri, 27 Oct 2017 14:28:02 -0400

In the hsdescv3 fuzzer, replace the decryption function.

The new decryption function performs no decryption, skips the salt,
and doesn't check the mac.  This allows us to fuzz the
hs_descriptor.c code using unencrypted descriptor test, and exercise
more of the code.

Related to 21509.

Diffstat:
A
changes/hsdescv3_fuzz_more
 | 
3
+++
M
src/or/hs_descriptor.c
 | 
12
++++++------
M
src/or/hs_descriptor.h
 | 
7
+++++++
M
src/test/fuzz/fuzz_hsdescv3.c
 | 
19
+++++++++++++++++++

4 files changed, 35 insertions(+), 6 deletions(-)
diff --git a/changes/hsdescv3_fuzz_more b/changes/hsdescv3_fuzz_more
@@ -0,0 +1,3 @@
+  o Minor features (testing):
+    - Our fuzzing tests now test the encrypted portions of the
+      v3 hidden service descriptors.  Implements more of 21509.
diff --git a/src/or/hs_descriptor.c b/src/or/hs_descriptor.c
@@ -1303,12 +1303,12 @@ encrypted_data_length_is_valid(size_t len)
  *  generate the right decryption keys; set <b>decrypted_out</b> to the
  *  plaintext. If <b>is_superencrypted_layer</b> is set, this is the outter
  *  encrypted layer of the descriptor. */
-static size_t
-decrypt_desc_layer(const hs_descriptor_t *desc,
-                   const uint8_t *encrypted_blob,
-                   size_t encrypted_blob_size,
-                   int is_superencrypted_layer,
-                   char **decrypted_out)
+MOCK_IMPL(STATIC size_t,
+decrypt_desc_layer,(const hs_descriptor_t *desc,
+                    const uint8_t *encrypted_blob,
+                    size_t encrypted_blob_size,
+                    int is_superencrypted_layer,
+                    char **decrypted_out))
 {
   uint8_t *decrypted = NULL;
   uint8_t secret_key[HS_DESC_ENCRYPTED_KEY_LEN], secret_iv[CIPHER_IV_LEN];
diff --git a/src/or/hs_descriptor.h b/src/or/hs_descriptor.h
@@ -261,6 +261,13 @@ STATIC size_t decode_superencrypted(const char *message, size_t message_len,
                                    uint8_t **encrypted_out);
 STATIC void desc_plaintext_data_free_contents(hs_desc_plaintext_data_t *desc);
 
+MOCK_DECL(STATIC size_t, decrypt_desc_layer,(const hs_descriptor_t *desc,
+                                             const uint8_t *encrypted_blob,
+                                             size_t encrypted_blob_size,
+                                             int is_superencrypted_layer,
+                                             char **decrypted_out));
+
+
 #endif /* defined(HS_DESCRIPTOR_PRIVATE) */
 
 #endif /* !defined(TOR_HS_DESCRIPTOR_H) */
diff --git a/src/test/fuzz/fuzz_hsdescv3.c b/src/test/fuzz/fuzz_hsdescv3.c
@@ -35,12 +35,31 @@ mock_rsa_ed25519_crosscert_check(const uint8_t *crosscert,
   return 0;
 }
 
+static size_t
+mock_decrypt_desc_layer(const hs_descriptor_t *desc,
+                        const uint8_t *encrypted_blob,
+                        size_t encrypted_blob_size,
+                        int is_superencrypted_layer,
+                        char **decrypted_out)
+{
+  (void)is_superencrypted_layer;
+  (void)desc;
+  const size_t overhead = HS_DESC_ENCRYPTED_SALT_LEN + DIGEST256_LEN;
+  if (encrypted_blob_size < overhead)
+    return 0;
+  *decrypted_out = tor_memdup_nulterm(
+                   encrypted_blob + HS_DESC_ENCRYPTED_SALT_LEN,
+                   encrypted_blob_size - overhead);
+  return strlen(*decrypted_out);
+}
+
 int
 fuzz_init(void)
 {
   disable_signature_checking();
   MOCK(dump_desc, mock_dump_desc__nodump);
   MOCK(rsa_ed25519_crosscert_check, mock_rsa_ed25519_crosscert_check);
+  MOCK(decrypt_desc_layer, mock_decrypt_desc_layer);
   ed25519_init();
   return 0;
 }