prop224: Change encryption keys descriptor encoding

A descriptor only contains the curve25519 public key in the enc-key field so
the private key should not be in that data structure. The service data
structures will have access to the full keypair (#20657).

Furthermore, ticket #21871 has highlighted an issue in the proposal 224 about
the encryption key and legacy key being mutually exclusive. This is very wrong
and this commit fixes the code to follow the change to the proposal of that
ticket.

Signed-off-by: David Goulet <dgoulet@torproject.org>

2 files changed, 34 insertions, 21 deletions

diff --git a/src/test/hs_test_helpers.c b/src/test/hs_test_helpers.c
index a17bf0f0a2..3f0d6a9413 100644
--- a/src/test/hs_test_helpers.c
+++ b/src/test/hs_test_helpers.c
@@ -51,15 +51,36 @@ hs_helper_build_intro_point(const ed25519_keypair_t *signing_kp, time_t now,
   tt_assert(ip->auth_key_cert);
 
   if (legacy) {
-    ip->enc_key.legacy = crypto_pk_new();
-    ip->enc_key_type = HS_DESC_KEY_TYPE_LEGACY;
-    tt_assert(ip->enc_key.legacy);
-    ret = crypto_pk_generate_key(ip->enc_key.legacy);
+    ip->legacy.key = crypto_pk_new();
+    tt_assert(ip->legacy.key);
+    ret = crypto_pk_generate_key(ip->legacy.key);
     tt_int_op(ret, ==, 0);
-  } else {
-    ret = curve25519_keypair_generate(&ip->enc_key.curve25519, 0);
+    ssize_t cert_len = tor_make_rsa_ed25519_crosscert(
+                                    &signing_kp->pubkey, ip->legacy.key,
+                                    now + HS_DESC_CERT_LIFETIME,
+                                    &ip->legacy.cert.encoded);
+    tt_assert(ip->legacy.cert.encoded);
+    tt_u64_op(cert_len, OP_GT, 0);
+    ip->legacy.cert.len = cert_len;
+  }
+
+  /* Encryption key. */
+  {
+    int signbit;
+    curve25519_keypair_t curve25519_kp;
+    ed25519_keypair_t ed25519_kp;
+    tor_cert_t *cross_cert;
+
+    ret = curve25519_keypair_generate(&curve25519_kp, 0);
     tt_int_op(ret, ==, 0);
-    ip->enc_key_type = HS_DESC_KEY_TYPE_CURVE25519;
+    ed25519_keypair_from_curve25519_keypair(&ed25519_kp, &signbit,
+                                            &curve25519_kp);
+    cross_cert = tor_cert_create(signing_kp, CERT_TYPE_CROSS_HS_IP_KEYS,
+                                 &ed25519_kp.pubkey, time(NULL),
+                                 HS_DESC_CERT_LIFETIME,
+                                 CERT_FLAG_INCLUDE_SIGNING_KEY);
+    tt_assert(cross_cert);
+    ip->enc_key_cert = cross_cert;
   }
 
   intro_point = ip;
@@ -192,19 +213,11 @@ hs_helper_desc_equal(const hs_descriptor_t *desc1,
                             *ip2 = smartlist_get(desc2->encrypted_data
                                                  .intro_points, i);
       tt_assert(tor_cert_eq(ip1->auth_key_cert, ip2->auth_key_cert));
-      tt_int_op(ip1->enc_key_type, OP_EQ, ip2->enc_key_type);
-      tt_assert(ip1->enc_key_type == HS_DESC_KEY_TYPE_LEGACY ||
-                ip1->enc_key_type == HS_DESC_KEY_TYPE_CURVE25519);
-      switch (ip1->enc_key_type) {
-        case HS_DESC_KEY_TYPE_LEGACY:
-          tt_int_op(crypto_pk_cmp_keys(ip1->enc_key.legacy,
-                                       ip2->enc_key.legacy), OP_EQ, 0);
-          break;
-        case HS_DESC_KEY_TYPE_CURVE25519:
-          tt_mem_op(ip1->enc_key.curve25519.pubkey.public_key, OP_EQ,
-                    ip2->enc_key.curve25519.pubkey.public_key,
-                    CURVE25519_PUBKEY_LEN);
-          break;
+      if (ip1->legacy.key) {
+        tt_int_op(crypto_pk_cmp_keys(ip1->legacy.key, ip2->legacy.key),
+                  OP_EQ, 0);
+      } else {
+        tt_mem_op(&ip1->enc_key, OP_EQ, &ip2->enc_key, CURVE25519_PUBKEY_LEN);
       }
 
       tt_int_op(smartlist_len(ip1->link_specifiers), ==,
diff --git a/src/test/test_hs_descriptor.c b/src/test/test_hs_descriptor.c
index b4c58937c4..b1abe381d4 100644
--- a/src/test/test_hs_descriptor.c
+++ b/src/test/test_hs_descriptor.c
@@ -410,7 +410,7 @@ test_decode_invalid_intro_point(void *arg)
   const char *enc_key =
     "enc-key ntor bpZKLsuhxP6woDQ3yVyjm5gUKSk7RjfAijT2qrzbQk0=";
   const char *enc_key_cert =
-    "enc-key-certification\n"
+    "enc-key-cert\n"
     "-----BEGIN ED25519 CERT-----\n"
     "AQsACOhZAUpNvCZ1aJaaR49lS6MCdsVkhVGVrRqoj0Y2T4SzroAtAQAgBABFOcGg\n"
     "lbTt1DF5nKTE/gU3Fr8ZtlCIOhu1A+F5LM7fqCUupfesg0KTHwyIZOYQbJuM5/he\n"