From: Vsevolod Stakhov <vsevolod@rspamd.com>
Date: Sun, 5 Oct 2025 14:03:48 +0000 (+0100)
Subject: [Fix] Fix reply decryption when using only separate read/write keys
X-Git-Tag: 3.13.2~1^2~4
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9744f46f4e5219f47b43a228ba9c53d00b688399;p=thirdparty%2Frspamd.git

[Fix] Fix reply decryption when using only separate read/write keys

In fuzzy_process_reply(), the tag was accessed from encrypted data before
decryption, leading to incorrect key selection. When only separate
read_encryption_key and write_encryption_key were configured (without common
encryption_key), the fallback to NULL keys caused crashes.

Now the function tries decryption with all available key pairs (read, write,
and common) until MAC verification succeeds, properly handling all key
configuration scenarios.
---

diff --git a/src/plugins/fuzzy_check.c b/src/plugins/fuzzy_check.c
index edbd292958..ec4cef64a5 100644
--- a/src/plugins/fuzzy_check.c
+++ b/src/plugins/fuzzy_check.c
@@ -2465,44 +2465,55 @@ fuzzy_process_reply(unsigned char **pos, int *r, GPtrArray *req,
 		*pos += required_size;
 		*r -= required_size;
 
-		/* Find matching command to determine operation type */
-		struct rspamd_cryptobox_keypair *local_key = NULL;
-		struct rspamd_cryptobox_pubkey *peer_key = NULL;
-
-		for (i = 0; i < req->len; i++) {
-			io = g_ptr_array_index(req, i);
-			if (io->tag == encrep.rep.v1.tag) {
-				/* Determine which keys to use based on command type */
-				if (io->cmd.cmd == FUZZY_DEL || io->cmd.cmd == FUZZY_WRITE) {
-					/* Write operation */
-					local_key = rule->write_local_key ? rule->write_local_key : rule->local_key;
-					peer_key = rule->write_peer_key ? rule->write_peer_key : rule->peer_key;
-				}
-				else {
-					/* Read operation (CHECK, STAT, PING, etc.) */
-					local_key = rule->read_local_key ? rule->read_local_key : rule->local_key;
-					peer_key = rule->read_peer_key ? rule->read_peer_key : rule->peer_key;
-				}
-				break;
+		/* Try to decrypt with available keys, starting with read keys (more common) */
+		struct rspamd_cryptobox_keypair *local_keys[3];
+		struct rspamd_cryptobox_pubkey *peer_keys[3];
+		int nkeys = 0;
+		gboolean decrypted = FALSE;
+
+		/* Try read keys first (most common for CHECK operations) */
+		if (rule->read_peer_key && rule->read_local_key) {
+			local_keys[nkeys] = rule->read_local_key;
+			peer_keys[nkeys] = rule->read_peer_key;
+			nkeys++;
+		}
+		/* Then try write keys */
+		if (rule->write_peer_key && rule->write_local_key &&
+			(rule->write_peer_key != rule->read_peer_key)) {
+			local_keys[nkeys] = rule->write_local_key;
+			peer_keys[nkeys] = rule->write_peer_key;
+			nkeys++;
+		}
+		/* Finally try common keys if they differ from specific ones */
+		if (rule->peer_key && rule->local_key &&
+			(rule->peer_key != rule->read_peer_key) &&
+			(rule->peer_key != rule->write_peer_key)) {
+			local_keys[nkeys] = rule->local_key;
+			peer_keys[nkeys] = rule->peer_key;
+			nkeys++;
+		}
+
+		/* Try decryption with each key pair */
+		for (i = 0; i < nkeys && !decrypted; i++) {
+			struct rspamd_fuzzy_encrypted_reply encrep_copy;
+			memcpy(&encrep_copy, &encrep, sizeof(encrep_copy));
+
+			rspamd_keypair_cache_process(rule->ctx->keypairs_cache,
+										 local_keys[i], peer_keys[i]);
+
+			if (rspamd_cryptobox_decrypt_nm_inplace((unsigned char *) &encrep_copy.rep,
+													sizeof(encrep_copy.rep),
+													encrep_copy.hdr.nonce,
+													rspamd_pubkey_get_nm(peer_keys[i], local_keys[i]),
+													encrep_copy.hdr.mac)) {
+				/* Successfully decrypted */
+				memcpy(&encrep, &encrep_copy, sizeof(encrep));
+				decrypted = TRUE;
 			}
 		}
 
-		if (!local_key || !peer_key) {
-			/* Fallback to common keys if command not found or keys not set */
-			local_key = rule->local_key;
-			peer_key = rule->peer_key;
-		}
-
-		/* Try to decrypt reply */
-		rspamd_keypair_cache_process(rule->ctx->keypairs_cache,
-									 local_key, peer_key);
-
-		if (!rspamd_cryptobox_decrypt_nm_inplace((unsigned char *) &encrep.rep,
-												 sizeof(encrep.rep),
-												 encrep.hdr.nonce,
-												 rspamd_pubkey_get_nm(peer_key, local_key),
-												 encrep.hdr.mac)) {
-			msg_info("cannot decrypt reply");
+		if (!decrypted) {
+			msg_info("cannot decrypt reply with any available keys");
 			return NULL;
 		}