The only secure compare function currently needed is one to compare 2 public keys.

3 files changed, 9 insertions, 19 deletions

diff --git a/toxcore/crypto_core.c b/toxcore/crypto_core.c
index a364084a..418edcad 100644
--- a/toxcore/crypto_core.c
+++ b/toxcore/crypto_core.c
@@ -29,26 +29,16 @@
 
 #include "crypto_core.h"
 
+#if crypto_box_PUBLICKEYBYTES != 32
+#error crypto_box_PUBLICKEYBYTES is required to be 32 bytes for public_key_cmp to work,
+#endif
 
-/* Use this instead of memcmp; not vulnerable to timing attacks.
+/* compare 2 public keys of length crypto_box_PUBLICKEYBYTES, not vulnerable to timing attacks.
    returns 0 if both mem locations of length are equal,
    return -1 if they are not. */
-int crypto_cmp(const uint8_t *mem1, const uint8_t *mem2, size_t length)
+int public_key_cmp(const uint8_t *pk1, const uint8_t *pk2)
 {
-    if (length == 16) {
-        return crypto_verify_16(mem1, mem2);
-    } else if (length == 32) {
-        return crypto_verify_32(mem1, mem2);
-    }
-
-    unsigned int check = 0;
-    size_t i;
-
-    for (i = 0; i < length; ++i) {
-        check |= mem1[i] ^ mem2[i];
-    }
-
-    return (1 & ((check - 1) >> 8)) - 1;
+    return crypto_verify_32(pk1, pk2);
 }
 
 /*  return a random number.
diff --git a/toxcore/crypto_core.h b/toxcore/crypto_core.h
index decc7fb9..d7306a8a 100644
--- a/toxcore/crypto_core.h
+++ b/toxcore/crypto_core.h
@@ -40,10 +40,10 @@
 
 #define crypto_box_KEYBYTES (crypto_box_BEFORENMBYTES)
 
-/* Use this instead of memcmp; not vulnerable to timing attacks.
+/* compare 2 public keys of length crypto_box_PUBLICKEYBYTES, not vulnerable to timing attacks.
    returns 0 if both mem locations of length are equal,
    return -1 if they are not. */
-int crypto_cmp(const uint8_t *mem1, const uint8_t *mem2, size_t length);
+int public_key_cmp(const uint8_t *pk1, const uint8_t *pk2);
 
 /*  return a random number.
  *
diff --git a/toxcore/net_crypto.c b/toxcore/net_crypto.c
index bd9969f5..38fd85b7 100644
--- a/toxcore/net_crypto.c
+++ b/toxcore/net_crypto.c
@@ -341,7 +341,7 @@ static int handle_crypto_handshake(const Net_Crypto *c, uint8_t *nonce, uint8_t
         return -1;
 
     if (expected_real_pk)
-        if (crypto_cmp(cookie_plain, expected_real_pk, crypto_box_PUBLICKEYBYTES) != 0)
+        if (public_key_cmp(cookie_plain, expected_real_pk) != 0)
             return -1;
 
     uint8_t cookie_hash[crypto_hash_sha512_BYTES];