Use the correct SIGNED_KEY_TYPE value for signing->link certs

Our code was using [01] as for the key type of signed->link certs,
which was incorrect.  The value should be [03], to indicate that the
value as the SHA256 of an x.509 cert.

Fortunately, nothing cares about this value, so there shouldn't be
compatibility issues.

Fixes bug 40124; bugfix on 0.2.7.2-alpha.

changes/ticket40124

+  o Minor bugfixes (spec conformance):
+    - Use the correct key type when generating signing->link
+      certificates.  Fixes bug 40124; bugfix on 0.2.7.2-alpha.

src/feature/nodelist/torcert.c

@@ -37,11 +37,11 @@
 
 #include "core/or/or_handshake_certs_st.h"
 
-/** Helper for tor_cert_create_*(): signs any 32 bytes, not just an ed25519
- * key.
+/** As tor_cert_create(), but accept an arbitrary signed_key_type as the
+ * subject key -- not just an ed25519 key.
  */
-static tor_cert_t *
-tor_cert_sign_impl(const ed25519_keypair_t *signing_key,
+tor_cert_t *
+tor_cert_create_raw(const ed25519_keypair_t *signing_key,
                       uint8_t cert_type,
                       uint8_t signed_key_type,
                       const uint8_t signed_key_info[32],
@@ -134,7 +134,7 @@ tor_cert_create_ed25519(const ed25519_keypair_t *signing_key,
                 time_t now, time_t lifetime,
                 uint32_t flags)
 {
-  return tor_cert_sign_impl(signing_key, cert_type,
+  return tor_cert_create_raw(signing_key, cert_type,
                             SIGNED_KEY_TYPE_ED25519, signed_key->pubkey,
                             now, lifetime, flags);
 }

src/feature/nodelist/torcert.h

@@ -11,7 +11,9 @@
 
 #include "lib/crypt_ops/crypto_ed25519.h"
 
-#define SIGNED_KEY_TYPE_ED25519     0x01
+#define SIGNED_KEY_TYPE_ED25519        0x01
+#define SIGNED_KEY_TYPE_SHA256_OF_RSA  0x02
+#define SIGNED_KEY_TYPE_SHA256_OF_X509 0x03
 
 #define CERT_TYPE_ID_SIGNING        0x04
 #define CERT_TYPE_SIGNING_LINK      0x05
@@ -61,6 +63,12 @@ tor_cert_t *tor_cert_create_ed25519(const ed25519_keypair_t *signing_key,
                             const ed25519_public_key_t *signed_key,
                             time_t now, time_t lifetime,
                             uint32_t flags);
+tor_cert_t * tor_cert_create_raw(const ed25519_keypair_t *signing_key,
+                      uint8_t cert_type,
+                      uint8_t signed_key_type,
+                      const uint8_t signed_key_info[32],
+                      time_t now, time_t lifetime,
+                      uint32_t flags);
 
 tor_cert_t *tor_cert_parse(const uint8_t *cert, size_t certlen);
 

src/feature/relay/routerkeys.c

@@ -387,12 +387,10 @@ generate_ed_link_cert(const or_options_t *options, time_t now,
     return 0;
   }
 
-  ed25519_public_key_t dummy_key;
-  memcpy(dummy_key.pubkey, digests->d[DIGEST_SHA256], DIGEST256_LEN);
-
-  link_cert = tor_cert_create_ed25519(get_master_signing_keypair(),
+  link_cert = tor_cert_create_raw(get_master_signing_keypair(),
                               CERT_TYPE_SIGNING_LINK,
-                              &dummy_key,
+                              SIGNED_KEY_TYPE_SHA256_OF_X509,
+                              (const uint8_t*)digests->d[DIGEST_SHA256],
                               now,
                               options->TestingLinkCertLifetime, 0);