Refactor the API for setting up a block cipher.

It allows us more flexibility on the backend if the user needs to
specify the key and IV at setup time.

1 files changed, 37 insertions, 121 deletions

diff --git a/src/common/crypto.c b/src/common/crypto.c
index 02f3d2fbba..2bd2e1e4d2 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -119,6 +119,7 @@ struct crypto_pk_t
 struct crypto_cipher_t
 {
   char key[CIPHER_KEY_LEN]; /**< The raw key. */
+  char iv[CIPHER_IV_LEN]; /**< The initial IV. */
   aes_cnt_cipher_t *cipher; /**< The key in format usable for counter-mode AES
                              * encryption */
 };
@@ -383,48 +384,37 @@ crypto_pk_free(crypto_pk_t *env)
   tor_free(env);
 }
 
-/** Create a new symmetric cipher for a given key and encryption flag
- * (1=encrypt, 0=decrypt).  Return the crypto object on success; NULL
- * on failure.
+/** Allocate and return a new symmetric cipher using the provided key and iv.
+ * The key is CIPHER_KEY_LEN bytes; the IV is CIPHER_IV_LEN bytes.  If you
+ * provide NULL in place of either one, it is generated at random.
  */
 crypto_cipher_t *
-crypto_create_init_cipher(const char *key, int encrypt_mode)
+crypto_cipher_new_with_iv(const char *key, const char *iv)
 {
-  int r;
-  crypto_cipher_t *crypto = NULL;
-
-  if (! (crypto = crypto_cipher_new())) {
-    log_warn(LD_CRYPTO, "Unable to allocate crypto object");
-    return NULL;
-  }
+  crypto_cipher_t *env;
 
-  crypto_cipher_set_key(crypto, key);
+  env = tor_malloc_zero(sizeof(crypto_cipher_t));
 
-  if (encrypt_mode)
-    r = crypto_cipher_encrypt_init_cipher(crypto);
+  if (key == NULL)
+    crypto_rand(env->key, CIPHER_KEY_LEN);
+  else
+    memcpy(env->key, key, CIPHER_KEY_LEN);
+  if (iv == NULL)
+    crypto_rand(env->iv, CIPHER_IV_LEN);
   else
-    r = crypto_cipher_decrypt_init_cipher(crypto);
+    memcpy(env->iv, iv, CIPHER_IV_LEN);
 
-  if (r)
-    goto error;
-  return crypto;
+  env->cipher = aes_new_cipher(env->key, env->iv);
 
- error:
-  if (crypto)
-    crypto_cipher_free(crypto);
-  return NULL;
+  return env;
 }
 
-/** Allocate and return a new symmetric cipher.
- */
 crypto_cipher_t *
-crypto_cipher_new(void)
+crypto_cipher_new(const char *key)
 {
-  crypto_cipher_t *env;
-
-  env = tor_malloc_zero(sizeof(crypto_cipher_t));
-  env->cipher = aes_new_cipher();
-  return env;
+  char zeroiv[CIPHER_IV_LEN];
+  memset(zeroiv, 0, sizeof(zeroiv));
+  return crypto_cipher_new_with_iv(key, zeroiv);
 }
 
 /** Free a symmetric cipher.
@@ -1043,12 +1033,8 @@ crypto_pk_public_hybrid_encrypt(crypto_pk_t *env,
   tor_assert(tolen >= fromlen + overhead + CIPHER_KEY_LEN);
   tor_assert(tolen >= pkeylen);
 
-  cipher = crypto_cipher_new();
-  if (!cipher) return -1;
-  if (crypto_cipher_generate_key(cipher)<0)
-    goto err;
-  if (crypto_cipher_encrypt_init_cipher(cipher)<0)
-    goto err;
+  cipher = crypto_cipher_new(NULL); /* generate a new key. */
+
   buf = tor_malloc(pkeylen+1);
   memcpy(buf, cipher->key, CIPHER_KEY_LEN);
   memcpy(buf+CIPHER_KEY_LEN, from, pkeylen-overhead-CIPHER_KEY_LEN);
@@ -1113,7 +1099,7 @@ crypto_pk_private_hybrid_decrypt(crypto_pk_t *env,
            "No room for a symmetric key");
     goto err;
   }
-  cipher = crypto_create_init_cipher(buf, 0);
+  cipher = crypto_cipher_new(buf);
   if (!cipher) {
     goto err;
   }
@@ -1301,49 +1287,6 @@ crypto_pk_check_fingerprint_syntax(const char *s)
 
 /* symmetric crypto */
 
-/** Generate a new random key for the symmetric cipher in <b>env</b>.
- * Return 0 on success, -1 on failure.  Does not initialize the cipher.
- */
-int
-crypto_cipher_generate_key(crypto_cipher_t *env)
-{
-  tor_assert(env);
-
-  return crypto_rand(env->key, CIPHER_KEY_LEN);
-}
-
-/** Set the symmetric key for the cipher in <b>env</b> to the first
- * CIPHER_KEY_LEN bytes of <b>key</b>. Does not initialize the cipher.
- */
-void
-crypto_cipher_set_key(crypto_cipher_t *env, const char *key)
-{
-  tor_assert(env);
-  tor_assert(key);
-
-  memcpy(env->key, key, CIPHER_KEY_LEN);
-}
-
-/** Generate an initialization vector for our AES-CTR cipher; store it
- * in the first CIPHER_IV_LEN bytes of <b>iv_out</b>. */
-void
-crypto_cipher_generate_iv(char *iv_out)
-{
-  crypto_rand(iv_out, CIPHER_IV_LEN);
-}
-
-/** Adjust the counter of <b>env</b> to point to the first byte of the block
- * corresponding to the encryption of the CIPHER_IV_LEN bytes at
- * <b>iv</b>.  */
-int
-crypto_cipher_set_iv(crypto_cipher_t *env, const char *iv)
-{
-  tor_assert(env);
-  tor_assert(iv);
-  aes_set_iv(env->cipher, iv);
-  return 0;
-}
-
 /** Return a pointer to the key set for the cipher in <b>env</b>.
  */
 const char *
@@ -1352,30 +1295,6 @@ crypto_cipher_get_key(crypto_cipher_t *env)
   return env->key;
 }
 
-/** Initialize the cipher in <b>env</b> for encryption.  Return 0 on
- * success, -1 on failure.
- */
-int
-crypto_cipher_encrypt_init_cipher(crypto_cipher_t *env)
-{
-  tor_assert(env);
-
-  aes_set_key(env->cipher, env->key, CIPHER_KEY_LEN*8);
-  return 0;
-}
-
-/** Initialize the cipher in <b>env</b> for decryption. Return 0 on
- * success, -1 on failure.
- */
-int
-crypto_cipher_decrypt_init_cipher(crypto_cipher_t *env)
-{
-  tor_assert(env);
-
-  aes_set_key(env->cipher, env->key, CIPHER_KEY_LEN*8);
-  return 0;
-}
-
 /** Encrypt <b>fromlen</b> bytes from <b>from</b> using the cipher
  * <b>env</b>; on success, store the result to <b>to</b> and return 0.
  * On failure, return -1.
@@ -1424,20 +1343,17 @@ crypto_cipher_crypt_inplace(crypto_cipher_t *env, char *buf, size_t len)
 }
 
 /** Encrypt <b>fromlen</b> bytes (at least 1) from <b>from</b> with the key in
- * <b>cipher</b> to the buffer in <b>to</b> of length
+ * <b>key</b> to the buffer in <b>to</b> of length
  * <b>tolen</b>. <b>tolen</b> must be at least <b>fromlen</b> plus
  * CIPHER_IV_LEN bytes for the initialization vector. On success, return the
  * number of bytes written, on failure, return -1.
- *
- * This function adjusts the current position of the counter in <b>cipher</b>
- * to immediately after the encrypted data.
  */
 int
-crypto_cipher_encrypt_with_iv(crypto_cipher_t *cipher,
+crypto_cipher_encrypt_with_iv(const char *key,
                               char *to, size_t tolen,
                               const char *from, size_t fromlen)
 {
-  tor_assert(cipher);
+  crypto_cipher_t *cipher;
   tor_assert(from);
   tor_assert(to);
   tor_assert(fromlen < INT_MAX);
@@ -1447,28 +1363,27 @@ crypto_cipher_encrypt_with_iv(crypto_cipher_t *cipher,
   if (tolen < fromlen + CIPHER_IV_LEN)
     return -1;
 
-  crypto_cipher_generate_iv(to);
-  if (crypto_cipher_set_iv(cipher, to)<0)
-    return -1;
+  cipher = crypto_cipher_new_with_iv(key, NULL);
+
+  memcpy(to, cipher->iv, CIPHER_IV_LEN);
   crypto_cipher_encrypt(cipher, to+CIPHER_IV_LEN, from, fromlen);
+  crypto_cipher_free(cipher);
   return (int)(fromlen + CIPHER_IV_LEN);
 }
 
 /** Decrypt <b>fromlen</b> bytes (at least 1+CIPHER_IV_LEN) from <b>from</b>
- * with the key in <b>cipher</b> to the buffer in <b>to</b> of length
+ * with the key in <b>key</b> to the buffer in <b>to</b> of length
  * <b>tolen</b>. <b>tolen</b> must be at least <b>fromlen</b> minus
  * CIPHER_IV_LEN bytes for the initialization vector. On success, return the
  * number of bytes written, on failure, return -1.
- *
- * This function adjusts the current position of the counter in <b>cipher</b>
- * to immediately after the decrypted data.
  */
 int
-crypto_cipher_decrypt_with_iv(crypto_cipher_t *cipher,
+crypto_cipher_decrypt_with_iv(const char *key,
                               char *to, size_t tolen,
                               const char *from, size_t fromlen)
 {
-  tor_assert(cipher);
+  crypto_cipher_t *cipher;
+  tor_assert(key);
   tor_assert(from);
   tor_assert(to);
   tor_assert(fromlen < INT_MAX);
@@ -1478,9 +1393,10 @@ crypto_cipher_decrypt_with_iv(crypto_cipher_t *cipher,
   if (tolen < fromlen - CIPHER_IV_LEN)
     return -1;
 
-  if (crypto_cipher_set_iv(cipher, from)<0)
-    return -1;
+  cipher = crypto_cipher_new_with_iv(key, from);
+
   crypto_cipher_encrypt(cipher, to, from+CIPHER_IV_LEN, fromlen-CIPHER_IV_LEN);
+  crypto_cipher_free(cipher);
   return (int)(fromlen - CIPHER_IV_LEN);
 }