1 files changed, 27 insertions, 9 deletions

diff --git a/src/common/crypto_curve25519.c b/src/common/crypto_curve25519.c
index 9e83440e16..290e88d7d8 100644
--- a/src/common/crypto_curve25519.c
+++ b/src/common/crypto_curve25519.c
@@ -63,26 +63,44 @@ curve25519_public_key_is_ok(const curve25519_public_key_t *key)
   return !safe_mem_is_zero(key->public_key, CURVE25519_PUBKEY_LEN);
 }
 
-/** Generate a new keypair and return the secret key.  If <b>extra_strong</b>
- * is true, this key is possibly going to get used more than once, so
- * use a better-than-usual RNG. Return 0 on success, -1 on failure. */
+/**
+ * Generate CURVE25519_SECKEY_LEN random bytes in <b>out</b>. If
+ * <b>extra_strong</b> is true, this key is possibly going to get used more
+ * than once, so use a better-than-usual RNG. Return 0 on success, -1 on
+ * failure.
+ *
+ * This function does not adjust the output of the RNG at all; the will caller
+ * will need to clear or set the appropriate bits to make curve25519 work.
+ */
 int
-curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
-                               int extra_strong)
+curve25519_rand_seckey_bytes(uint8_t *out, int extra_strong)
 {
   uint8_t k_tmp[CURVE25519_SECKEY_LEN];
 
-  if (crypto_rand((char*)key_out->secret_key, CURVE25519_SECKEY_LEN) < 0)
+  if (crypto_rand((char*)out, CURVE25519_SECKEY_LEN) < 0)
     return -1;
   if (extra_strong && !crypto_strongest_rand(k_tmp, CURVE25519_SECKEY_LEN)) {
     /* If they asked for extra-strong entropy and we have some, use it as an
      * HMAC key to improve not-so-good entropy rather than using it directly,
      * just in case the extra-strong entropy is less amazing than we hoped. */
-    crypto_hmac_sha256((char *)key_out->secret_key,
-                    (const char *)k_tmp, sizeof(k_tmp),
-                    (const char *)key_out->secret_key, CURVE25519_SECKEY_LEN);
+    crypto_hmac_sha256((char*) out,
+                       (const char *)k_tmp, sizeof(k_tmp),
+                       (const char *)out, CURVE25519_SECKEY_LEN);
   }
   memwipe(k_tmp, 0, sizeof(k_tmp));
+  return 0;
+}
+
+/** Generate a new keypair and return the secret key.  If <b>extra_strong</b>
+ * is true, this key is possibly going to get used more than once, so
+ * use a better-than-usual RNG. Return 0 on success, -1 on failure. */
+int
+curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
+                               int extra_strong)
+{
+  if (curve25519_rand_seckey_bytes(key_out->secret_key, extra_strong) < 0)
+    return -1;
+
   key_out->secret_key[0] &= 248;
   key_out->secret_key[31] &= 127;
   key_out->secret_key[31] |= 64;