New AuthDirPinKeys option to enable/disable keypinning enforcement

Implements ticket #17135.  We're going to need this one to avoid
chaos as everybody figures out how ed25519 keys work.

4 files changed, 51 insertions, 26 deletions

diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index 53b450cef5..8d9f166556 100644
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -248,6 +248,7 @@ dirserv_router_get_status(const routerinfo_t *router, const char **msg,
                           int severity)
 {
   char d[DIGEST_LEN];
+  const int key_pinning = get_options()->AuthDirPinKeys;
 
   if (crypto_pk_get_digest(router->identity_pkey, d)) {
     log_warn(LD_BUG,"Error computing fingerprint");
@@ -261,14 +262,16 @@ dirserv_router_get_status(const routerinfo_t *router, const char **msg,
     if (KEYPIN_MISMATCH ==
         keypin_check((const uint8_t*)router->cache_info.identity_digest,
                      router->signing_key_cert->signing_key.pubkey)) {
-      if (msg) {
-        *msg = "Ed25519 identity key or RSA identity key has changed.";
-      }
       log_fn(severity, LD_DIR,
              "Descriptor from router %s has an Ed25519 key, "
                "but the <rsa,ed25519> keys don't match what they were before.",
                router_describe(router));
-      return FP_REJECT;
+      if (key_pinning) {
+        if (msg) {
+          *msg = "Ed25519 identity key or RSA identity key has changed.";
+        }
+        return FP_REJECT;
+      }
     }
   } else {
     /* No ed25519 key */
@@ -277,13 +280,15 @@ dirserv_router_get_status(const routerinfo_t *router, const char **msg,
       log_fn(severity, LD_DIR,
                "Descriptor from router %s has no Ed25519 key, "
                "when we previously knew an Ed25519 for it. Ignoring for now, "
-               "since Tor 0.2.6 is under development.",
+               "since Ed25519 keys are fairly new.",
                router_describe(router));
 #ifdef DISABLE_DISABLING_ED25519
-      if (msg) {
-        *msg = "Ed25519 identity key has disappeared.";
+      if (key_pinning) {
+        if (msg) {
+          *msg = "Ed25519 identity key has disappeared.";
+        }
+        return FP_REJECT;
       }
-      return FP_REJECT;
 #endif
     }
   }
@@ -582,6 +587,7 @@ dirserv_add_descriptor(routerinfo_t *ri, const char **msg, const char *source)
   char *desc, *nickname;
   const size_t desclen = ri->cache_info.signed_descriptor_len +
       ri->cache_info.annotations_len;
+  const int key_pinning = get_options()->AuthDirPinKeys;
   *msg = NULL;
 
   /* If it's too big, refuse it now. Otherwise we'll cache it all over the
@@ -626,7 +632,8 @@ dirserv_add_descriptor(routerinfo_t *ri, const char **msg, const char *source)
   if (ri->signing_key_cert) {
     keypin_status = keypin_check_and_add(
       (const uint8_t*)ri->cache_info.identity_digest,
-      ri->signing_key_cert->signing_key.pubkey);
+      ri->signing_key_cert->signing_key.pubkey,
+      ! key_pinning);
   } else {
     keypin_status = keypin_check_lone_rsa(
       (const uint8_t*)ri->cache_info.identity_digest);
@@ -635,7 +642,7 @@ dirserv_add_descriptor(routerinfo_t *ri, const char **msg, const char *source)
       keypin_status = KEYPIN_NOT_FOUND;
 #endif
   }
-  if (keypin_status == KEYPIN_MISMATCH) {
+  if (keypin_status == KEYPIN_MISMATCH && key_pinning) {
     log_info(LD_DIRSERV, "Dropping descriptor from %s (source: %s) because "
              "its key did not match an older RSA/Ed25519 keypair",
              router_describe(ri), source);
diff --git a/src/or/keypin.c b/src/or/keypin.c
index 0c99429962..047d2b069b 100644
--- a/src/or/keypin.c
+++ b/src/or/keypin.c
@@ -48,7 +48,9 @@ static int keypin_journal_append_entry(const uint8_t *rsa_id_digest,
                                        const uint8_t *ed25519_id_key);
 static int keypin_check_and_add_impl(const uint8_t *rsa_id_digest,
                                      const uint8_t *ed25519_id_key,
-                                     int do_not_add);
+                                     const int do_not_add,
+                                     const int replace);
+static int keypin_add_or_replace_entry_in_map(keypin_ent_t *ent);
 
 static HT_HEAD(rsamap, keypin_ent_st) the_rsa_map = HT_INITIALIZER();
 static HT_HEAD(edmap, keypin_ent_st) the_ed_map = HT_INITIALIZER();
@@ -100,12 +102,17 @@ HT_GENERATE2(edmap, keypin_ent_st, edmap_node, keypin_ent_hash_ed,
  * return KEYPIN_FOUND. If we find an entry that matches one key but
  * not the other, return KEYPIN_MISMATCH.  If we have no entry for either
  * key, add such an entry to the table and return KEYPIN_ADDED.
+ *
+ * If <b>replace_existing_entry</b> is true, then any time we would have said
+ * KEYPIN_FOUND, we instead add this entry anyway and return KEYPIN_ADDED.
  */
 int
 keypin_check_and_add(const uint8_t *rsa_id_digest,
-                     const uint8_t *ed25519_id_key)
+                     const uint8_t *ed25519_id_key,
+                     const int replace_existing_entry)
 {
-  return keypin_check_and_add_impl(rsa_id_digest, ed25519_id_key, 0);
+  return keypin_check_and_add_impl(rsa_id_digest, ed25519_id_key, 0,
+                                   replace_existing_entry);
 }
 
 /**
@@ -116,7 +123,7 @@ int
 keypin_check(const uint8_t *rsa_id_digest,
              const uint8_t *ed25519_id_key)
 {
-  return keypin_check_and_add_impl(rsa_id_digest, ed25519_id_key, 1);
+  return keypin_check_and_add_impl(rsa_id_digest, ed25519_id_key, 1, 0);
 }
 
 /**
@@ -125,7 +132,8 @@ keypin_check(const uint8_t *rsa_id_digest,
 static int
 keypin_check_and_add_impl(const uint8_t *rsa_id_digest,
                           const uint8_t *ed25519_id_key,
-                          int do_not_add)
+                          const int do_not_add,
+                          const int replace)
 {
   keypin_ent_t search, *ent;
   memset(&search, 0, sizeof(search));
@@ -139,18 +147,21 @@ keypin_check_and_add_impl(const uint8_t *rsa_id_digest,
     if (tor_memeq(ent->ed25519_key, ed25519_id_key,sizeof(ent->ed25519_key))) {
       return KEYPIN_FOUND; /* Match on both keys. Great. */
     } else {
-      return KEYPIN_MISMATCH; /* Found RSA with different Ed key */
+      if (!replace)
+        return KEYPIN_MISMATCH; /* Found RSA with different Ed key */
     }
   }
 
   /* See if we know a different RSA key for this ed key */
-  ent = HT_FIND(edmap, &the_ed_map, &search);
-  if (ent) {
-    /* If we got here, then the ed key matches and the RSA doesn't */
-    tor_assert(fast_memeq(ent->ed25519_key, ed25519_id_key,
-                          sizeof(ent->ed25519_key)));
-    tor_assert(fast_memneq(ent->rsa_id, rsa_id_digest, sizeof(ent->rsa_id)));
-    return KEYPIN_MISMATCH;
+  if (! replace) {
+    ent = HT_FIND(edmap, &the_ed_map, &search);
+    if (ent) {
+      /* If we got here, then the ed key matches and the RSA doesn't */
+      tor_assert(fast_memeq(ent->ed25519_key, ed25519_id_key,
+                            sizeof(ent->ed25519_key)));
+      tor_assert(fast_memneq(ent->rsa_id, rsa_id_digest, sizeof(ent->rsa_id)));
+      return KEYPIN_MISMATCH;
+    }
   }
 
   /* Okay, this one is new to us. */
@@ -158,7 +169,12 @@ keypin_check_and_add_impl(const uint8_t *rsa_id_digest,
     return KEYPIN_NOT_FOUND;
 
   ent = tor_memdup(&search, sizeof(search));
-  keypin_add_entry_to_map(ent);
+  int r = keypin_add_or_replace_entry_in_map(ent);
+  if (! replace) {
+    tor_assert(r == 1);
+  } else {
+    tor_assert(r != 0);
+  }
   keypin_journal_append_entry(rsa_id_digest, ed25519_id_key);
   return KEYPIN_ADDED;
 }
diff --git a/src/or/keypin.h b/src/or/keypin.h
index 2a5b3f1786..798ac1fedb 100644
--- a/src/or/keypin.h
+++ b/src/or/keypin.h
@@ -7,7 +7,8 @@
 #include "testsupport.h"
 
 int keypin_check_and_add(const uint8_t *rsa_id_digest,
-                         const uint8_t *ed25519_id_key);
+                         const uint8_t *ed25519_id_key,
+                         const int replace_existing_entry);
 int keypin_check(const uint8_t *rsa_id_digest,
                  const uint8_t *ed25519_id_key);
 
diff --git a/src/test/test_keypin.c b/src/test/test_keypin.c
index 033578cae8..bd0f6fdd52 100644
--- a/src/test/test_keypin.c
+++ b/src/test/test_keypin.c
@@ -131,7 +131,8 @@ test_keypin_parse_file(void *arg)
   smartlist_free(mock_addent_got);
 }
 
-#define ADD(a,b) keypin_check_and_add((const uint8_t*)(a),(const uint8_t*)(b))
+#define ADD(a,b) keypin_check_and_add((const uint8_t*)(a),\
+                                      (const uint8_t*)(b),0)
 #define LONE_RSA(a) keypin_check_lone_rsa((const uint8_t*)(a))
 
 static void