rpc: Fix serialization of NULL mechanism pointer

A NULL mechanism pointer is valid for C_*Init functions to cancel the operation. Since 852ccd8 we encoded it with a CK_MECHANISM_TYPE 0 as an indicator, though it clashes with CKM_RSA_PKCS_KEY_PAIR_GEN (0). This patch changes the encoding to use a special value (0xffffffff) to indicate that and also properly advance the offset when reading. Signed-off-by: Daiki Ueno <[email protected]>
p11-glue · Nov 14, 2023 · 36da777 · 36da777
1 parent 66d6b42
commit 36da777
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/p11-kit/rpc-client.c b/p11-kit/rpc-client.c
@@ -430,9 +430,12 @@ proto_write_mechanism (p11_rpc_message *msg,
 	/* Make sure this is in the right order */
 	assert (!msg->signature || p11_rpc_message_verify_part (msg, "M"));
 
-	/* This case is valid for C_*Init () functions to cancel operation */
+	/*
+	 * The NULL mech is used for C_*Init () functions to cancel operation.
+	 * We use 0xffffffff as a marker to indicate that.
+	 */
 	if (mech == NULL) {
-		p11_rpc_buffer_add_uint32 (msg->output, 0);
+		p11_rpc_buffer_add_uint32 (msg->output, 0xffffffff);
 		return p11_buffer_failed (msg->output) ? CKR_HOST_MEMORY : CKR_OK;
 	}
 

diff --git a/p11-kit/rpc-server.c b/p11-kit/rpc-server.c
@@ -480,8 +480,13 @@ proto_read_mechanism (p11_rpc_message *msg,
 		return PARSE_ERROR;
 	}
 
-	if (temp.mechanism == 0) {
+	/*
+	 * The NULL mech is used for C_*Init () functions to cancel operation.
+	 * We use 0xffffffff as a marker to indicate that.
+	 */
+	if (temp.mechanism == 0xffffffff) {
 		*mech = NULL;
+		msg->parsed = offset;
 		return CKR_OK;
 	}