Merge branch 'remove-padding-fix-7869-v2'

changes/ticket7869

@@ -0,0 +1,3 @@
+  o Minor feature (directory authorities):
+    - Create new consensus method that removes the unecessary = padding 
+      from ntor-onion-key. Closes ticket 7869. Patch by Daniel Pinto.

src/feature/dirauth/dirvote.c

@@ -3848,11 +3848,10 @@ dirvote_create_microdescriptor(const routerinfo_t *ri, int consensus_method)
   smartlist_add_asprintf(chunks, "onion-key\n%s", key);
 
   if (ri->onion_curve25519_pkey) {
-    char kbuf[128];
-    base64_encode(kbuf, sizeof(kbuf),
-                  (const char*)ri->onion_curve25519_pkey->public_key,
-                  CURVE25519_PUBKEY_LEN, BASE64_ENCODE_MULTILINE);
-    smartlist_add_asprintf(chunks, "ntor-onion-key %s", kbuf);
+    char kbuf[CURVE25519_BASE64_PADDED_LEN + 1];
+    bool add_padding = (consensus_method < MIN_METHOD_FOR_UNPADDED_NTOR_KEY);
+    curve25519_public_to_base64(kbuf, ri->onion_curve25519_pkey, add_padding);
+    smartlist_add_asprintf(chunks, "ntor-onion-key %s\n", kbuf);
   }
 
   if (family) {
@@ -3963,6 +3962,8 @@ static const struct consensus_method_range_t {
   {MIN_SUPPORTED_CONSENSUS_METHOD,
    MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS - 1},
   {MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS,
+   MIN_METHOD_FOR_UNPADDED_NTOR_KEY - 1},
+  {MIN_METHOD_FOR_UNPADDED_NTOR_KEY,
    MAX_SUPPORTED_CONSENSUS_METHOD},
   {-1, -1}
 };

src/feature/dirauth/dirvote.h

@@ -53,7 +53,7 @@
 #define MIN_SUPPORTED_CONSENSUS_METHOD 28
 
 /** The highest consensus method that we currently support. */
-#define MAX_SUPPORTED_CONSENSUS_METHOD 29
+#define MAX_SUPPORTED_CONSENSUS_METHOD 30
 
 /**
  * Lowest consensus method where microdescriptor lines are put in canonical
@@ -61,6 +61,10 @@
  **/
 #define MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS 29
 
+/** Lowest consensus method where an unpadded base64 onion-key-ntor is allowed
+ * See #7869 */
+#define MIN_METHOD_FOR_UNPADDED_NTOR_KEY 30
+
 /** Default bandwidth to clip unmeasured bandwidths to using method >=
  * MIN_METHOD_TO_CLIP_UNMEASURED_BW.  (This is not a consensus method; do not
  * get confused with the above macros.) */

src/feature/hs/hs_descriptor.c

@@ -55,6 +55,7 @@
 /* For unit tests.*/
 #define HS_DESCRIPTOR_PRIVATE
 
+#include <stdbool.h>
 #include "core/or/or.h"
 #include "app/config/config.h"
 #include "trunnel/ed25519_cert.h" /* Trunnel interface. */
@@ -404,7 +405,7 @@ encode_enc_key(const hs_desc_intro_point_t *ip)
   tor_assert(ip);
 
   /* Base64 encode the encryption key for the "enc-key" field. */
-  curve25519_public_to_base64(key_b64, &ip->enc_key);
+  curve25519_public_to_base64(key_b64, &ip->enc_key, true);
   if (tor_cert_encode_ed22519(ip->enc_key_cert, &encoded_cert) < 0) {
     goto done;
   }
@@ -430,7 +431,7 @@ encode_onion_key(const hs_desc_intro_point_t *ip)
   tor_assert(ip);
 
   /* Base64 encode the encryption key for the "onion-key" field. */
-  curve25519_public_to_base64(key_b64, &ip->onion_key);
+  curve25519_public_to_base64(key_b64, &ip->onion_key, true);
   tor_asprintf(&encoded, "%s ntor %s", str_ip_onion_key, key_b64);
 
   return encoded;
@@ -813,7 +814,7 @@ get_outer_encrypted_layer_plaintext(const hs_descriptor_t *desc,
     tor_assert(!fast_mem_is_zero((char *) ephemeral_pubkey->public_key,
                                 CURVE25519_PUBKEY_LEN));
 
-    curve25519_public_to_base64(ephemeral_key_base64, ephemeral_pubkey);
+    curve25519_public_to_base64(ephemeral_key_base64, ephemeral_pubkey, true);
     smartlist_add_asprintf(lines, "%s %s\n",
                            str_desc_auth_key, ephemeral_key_base64);
 

src/feature/relay/router.c

@@ -2936,11 +2936,9 @@ router_dump_router_to_string(routerinfo_t *router,
   }
 
   if (router->onion_curve25519_pkey) {
-    char kbuf[128];
-    base64_encode(kbuf, sizeof(kbuf),
-                  (const char *)router->onion_curve25519_pkey->public_key,
-                  CURVE25519_PUBKEY_LEN, BASE64_ENCODE_MULTILINE);
-    smartlist_add_asprintf(chunks, "ntor-onion-key %s", kbuf);
+    char kbuf[CURVE25519_BASE64_PADDED_LEN + 1];
+    curve25519_public_to_base64(kbuf, router->onion_curve25519_pkey, false);
+    smartlist_add_asprintf(chunks, "ntor-onion-key %s\n", kbuf);
   } else {
     /* Authorities will start rejecting relays without ntor keys in 0.2.9 */
     log_err(LD_BUG, "A relay must have an ntor onion key");

src/lib/crypt_ops/crypto_curve25519.h

@@ -9,6 +9,7 @@
 #ifndef TOR_CRYPTO_CURVE25519_H
 #define TOR_CRYPTO_CURVE25519_H
 
+#include <stdbool.h>
 #include "lib/testsupport/testsupport.h"
 #include "lib/cc/torint.h"
 #include "lib/crypt_ops/crypto_digest.h"
@@ -77,7 +78,8 @@ STATIC int curve25519_basepoint_impl(uint8_t *output, const uint8_t *secret);
 int curve25519_public_from_base64(curve25519_public_key_t *pkey,
                                   const char *input);
 void curve25519_public_to_base64(char *output,
-                                 const curve25519_public_key_t *pkey);
+                                 const curve25519_public_key_t *pkey,
+                                 bool pad);
 
 void curve25519_set_impl_params(int use_ed);
 void curve25519_init(void);

src/lib/crypt_ops/crypto_format.c

@@ -131,9 +131,10 @@ crypto_read_tagged_contents_from_file(const char *fname,
   return r;
 }
 
-/** Encode <b>pkey</b> as a base64-encoded string, including trailing "="
- * characters, in the buffer <b>output</b>, which must have at least
- * CURVE25519_BASE64_PADDED_LEN+1 bytes available.
+/** Encode <b>pkey</b> as a base64-encoded string in the buffer <b>output</b>.
+ * If <b>pad</b> is false do not include trailing "=" characters, otherwise
+ * include them. <b>output</b> must have at least
+ * CURVE25519_BASE64_PADDED_LEN+1 bytes available, even if <b>pad</b> is false.
  * Can not fail.
  *
  * Careful! CURVE25519_BASE64_PADDED_LEN is one byte longer than
@@ -141,17 +142,25 @@ crypto_read_tagged_contents_from_file(const char *fname,
  */
 void
 curve25519_public_to_base64(char *output,
-                            const curve25519_public_key_t *pkey)
+                            const curve25519_public_key_t *pkey, bool pad)
 {
-  char buf[128];
-  int n = base64_encode(buf, sizeof(buf),
+  int n, expected_len;
+  if (pad) {
+    n = base64_encode(output, CURVE25519_BASE64_PADDED_LEN+1,
                       (const char*)pkey->public_key,
                       CURVE25519_PUBKEY_LEN, 0);
+    expected_len = CURVE25519_BASE64_PADDED_LEN;
+  } else {
+    n = base64_encode_nopad(output, CURVE25519_BASE64_PADDED_LEN+1,
+                            (const uint8_t*)pkey->public_key,
+                            CURVE25519_PUBKEY_LEN);
+    expected_len = CURVE25519_BASE64_LEN;
+  }
+
   /* These asserts should always succeed, unless there is a bug in
    * base64_encode(). */
-  tor_assert(n == CURVE25519_BASE64_PADDED_LEN);
-  tor_assert(buf[CURVE25519_BASE64_PADDED_LEN] == '\0');
-  memcpy(output, buf, CURVE25519_BASE64_PADDED_LEN+1);
+  tor_assert(n == expected_len);
+  tor_assert(output[expected_len] == '\0');
 }
 
 /** Try to decode a base64-encoded curve25519 public key from <b>input</b>
@@ -162,11 +171,11 @@ curve25519_public_from_base64(curve25519_public_key_t *pkey,
                               const char *input)
 {
   size_t len = strlen(input);
-  if (len == CURVE25519_BASE64_PADDED_LEN - 1) {
+  if (len == CURVE25519_BASE64_LEN) {
     /* not padded */
     return digest256_from_base64((char*)pkey->public_key, input);
   } else if (len == CURVE25519_BASE64_PADDED_LEN) {
-    char buf[128];
+    char buf[CURVE25519_BASE64_PADDED_LEN+1];
     if (base64_decode(buf, sizeof(buf), input, len) != CURVE25519_PUBKEY_LEN)
       return -1;
     memcpy(pkey->public_key, buf, CURVE25519_PUBKEY_LEN);

src/lib/defs/x25519_sizes.h

@@ -36,6 +36,9 @@
 /** Length of a Curve25519 key when encoded in base 64, with padding. */
 #define CURVE25519_BASE64_PADDED_LEN 44
 
+/** Length of a Curve25519 key when encoded in base 64, without padding. */
+#define CURVE25519_BASE64_LEN 43
+
 /** Length of a Ed25519 key when encoded in base 64, without padding. */
 #define ED25519_BASE64_LEN 43
 /** Length of a Ed25519 signature when encoded in base 64, without padding. */

src/test/test_crypto.c

@@ -2107,21 +2107,21 @@ test_crypto_curve25519_encode(void *arg)
 {
   curve25519_secret_key_t seckey;
   curve25519_public_key_t key1, key2, key3;
-  char buf[64];
+  char buf[64], buf_nopad[64];
 
   (void)arg;
 
   curve25519_secret_key_generate(&seckey, 0);
   curve25519_public_key_generate(&key1, &seckey);
-  curve25519_public_to_base64(buf, &key1);
+  curve25519_public_to_base64(buf, &key1, true);
   tt_int_op(CURVE25519_BASE64_PADDED_LEN, OP_EQ, strlen(buf));
 
   tt_int_op(0, OP_EQ, curve25519_public_from_base64(&key2, buf));
   tt_mem_op(key1.public_key,OP_EQ, key2.public_key, CURVE25519_PUBKEY_LEN);
 
-  buf[CURVE25519_BASE64_PADDED_LEN - 1] = '\0';
-  tt_int_op(CURVE25519_BASE64_PADDED_LEN-1, OP_EQ, strlen(buf));
-  tt_int_op(0, OP_EQ, curve25519_public_from_base64(&key3, buf));
+  curve25519_public_to_base64(buf_nopad, &key1, false);
+  tt_int_op(CURVE25519_BASE64_LEN, OP_EQ, strlen(buf_nopad));
+  tt_int_op(0, OP_EQ, curve25519_public_from_base64(&key3, buf_nopad));
   tt_mem_op(key1.public_key,OP_EQ, key3.public_key, CURVE25519_PUBKEY_LEN);
 
   /* Now try bogus parses. */

src/test/test_dir.c

@@ -397,18 +397,14 @@ get_new_ntor_onion_key_line(const curve25519_public_key_t *ntor_onion_pubkey)
 {
   char *line = NULL;
   char cert_buf[256];
-  int rv = 0;
 
   tor_assert(ntor_onion_pubkey);
 
-  rv = base64_encode(cert_buf, sizeof(cert_buf),
-                     (const char*)ntor_onion_pubkey->public_key, 32,
-                     BASE64_ENCODE_MULTILINE);
-  tor_assert(rv > 0);
+  curve25519_public_to_base64(cert_buf, ntor_onion_pubkey, false);
   tor_assert(strlen(cert_buf) > 0);
 
   tor_asprintf(&line,
-               "ntor-onion-key %s",
+               "ntor-onion-key %s\n",
                cert_buf);
   tor_assert(line);