Make curve25519_public_to_base64 output padding optional #7869

2 files changed, 25 insertions, 14 deletions

diff --git a/src/lib/crypt_ops/crypto_curve25519.h b/src/lib/crypt_ops/crypto_curve25519.h
index 154a0b94bc..f1e5d1265d 100644
--- a/src/lib/crypt_ops/crypto_curve25519.h
+++ b/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);
diff --git a/src/lib/crypt_ops/crypto_format.c b/src/lib/crypt_ops/crypto_format.c
index 92b8b9372e..4483b7d2f5 100644
--- a/src/lib/crypt_ops/crypto_format.c
+++ b/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),
-                        (const char*)pkey->public_key,
-                        CURVE25519_PUBKEY_LEN, 0);
+  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);