[php-src] PHP-8.4: [mysqlnd] Fix result set field metadata length buffer over-read

Author: Ilia Alshanetsky (iliaal)
Date: 2026-08-30T11:16:49-04:00

Commit: https://github.com/php/php-src/commit/9c74d7d1bcd254b4ad64a9b21fe41f546e764cd4
Raw diff: https://github.com/php/php-src/commit/9c74d7d1bcd254b4ad64a9b21fe41f546e764cd4.diff

[mysqlnd] Fix result set field metadata length buffer over-read

The rset_field metadata reader trusted each length-encoded string size:
a hostile server could send a length marker at the end of a field packet
whose value exceeds the remaining payload, advancing p past header.size
and past the command buffer before the next dereference, and recording
attacker-controlled lengths on pointers outside the packet that later
feed memcpy() into the field memory pool. Bound each metadata string by
bailing once p leaves the payload and rejecting lengths larger than the
remaining bytes, matching php_mysqlnd_auth_response_read() from
GHSA-h35g-vwh6-m678; an audit found no other users of the READ_RSET_FIELD
macro and the trailing default-value check never dereferences its length.

Closes GH-23496

Changed paths:
  A  ext/mysqli/tests/mysqlnd_rset_field_len_over_read.phpt
  A  ext/mysqli/tests/mysqlnd_rset_field_len_past_packet.phpt
  M  ext/mysqli/tests/fake_server.inc
  M  ext/mysqlnd/mysqlnd_wireprotocol.c


Diff:

diff --git a/ext/mysqli/tests/fake_server.inc b/ext/mysqli/tests/fake_server.inc
index 4056b9fb78cf..3af5c7459159 100644
--- a/ext/mysqli/tests/fake_server.inc
+++ b/ext/mysqli/tests/fake_server.inc
@@ -829,6 +829,50 @@ function my_mysqli_test_stmt_response_row_read_two_fields(my_mysqli_fake_server_
     }
 }
 
+function my_mysqli_test_rset_field_metadata_len_over_read(my_mysqli_fake_server_conn $conn): void
+{
+    $rh = $conn->packet_generator->server_tabular_query_response();
+
+    $qr2 = new my_mysqli_fake_packet();
+    $qr2->packet_length = "0c0000";
+    $qr2->packet_number = "02";
+    $qr2->catalog_length_plus_name = "0161";
+    $qr2->db_length_plus_name = "0162";
+    $qr2->table_length_plus_name = "0163";
+    $qr2->original_t = "0164";
+    $qr2->name_length_plus_name = "0165";
+    $qr2->original_n = "fcff";
+
+    $conn->send_server_greetings();
+    $conn->read_packets(1);
+    $conn->send_server_ok();
+    $conn->read_packets(1);
+    $conn->send($conn->packets_to_bytes([$rh[0], $qr2]), "Malicious Tabular Response [metadata string length past the packet size]");
+    $conn->read();
+}
+
+function my_mysqli_test_rset_field_metadata_len_past_packet(my_mysqli_fake_server_conn $conn): void
+{
+    $rh = $conn->packet_generator->server_tabular_query_response();
+
+    $qr2 = new my_mysqli_fake_packet();
+    $qr2->packet_length = "0c0000";
+    $qr2->packet_number = "02";
+    $qr2->catalog_length_plus_name = "0161";
+    $qr2->db_length_plus_name = "0162";
+    $qr2->table_length_plus_name = "0163";
+    $qr2->original_t = "0164";
+    $qr2->name_length_plus_name = "0165";
+    $qr2->original_n = "0561";
+
+    $conn->send_server_greetings();
+    $conn->read_packets(1);
+    $conn->send_server_ok();
+    $conn->read_packets(1);
+    $conn->send($conn->packets_to_bytes([$rh[0], $qr2]), "Malicious Tabular Response [metadata string length past the packet size]");
+    $conn->read();
+}
+
 function my_mysqli_test_query_response_row_length_overflow(my_mysqli_fake_server_conn $conn): void
 {
     $rh = $conn->packet_generator->server_query_execute_data_response('strval');
diff --git a/ext/mysqli/tests/mysqlnd_rset_field_len_over_read.phpt b/ext/mysqli/tests/mysqlnd_rset_field_len_over_read.phpt
new file mode 100644
index 000000000000..274468ded63d
--- /dev/null
+++ b/ext/mysqli/tests/mysqlnd_rset_field_len_over_read.phpt
@@ -0,0 +1,42 @@
+--TEST--
+mysqlnd result set field metadata string length buffer over-read (len clamped to packet size)
+--EXTENSIONS--
+mysqli
+--FILE--
+<?php
+require_once 'fake_server.inc';
+
+$servername = "127.0.0.1";
+$username = "root";
+$password = "";
+
+$process = run_fake_server_in_background('rset_field_metadata_len_over_read');
+$process->wait();
+
+try {
+    $conn = new mysqli( $servername, $username, $password, "", $process->getPort());
+    var_dump($conn->query("SELECT * from users"));
+} catch (Exception $e) {
+    echo $e::class, ": ", $e->getMessage(), PHP_EOL;
+}
+
+$conn->close();
+
+$process->terminate();
+
+print "done!";
+?>
+--EXPECTF--
+[*] Server started on 127.0.0.1:%d
+[*] Connection established
+[*] Sending - Server Greeting: 580000000a352e352e352d31302e352e31382d4d6172696144420003000000473e3f6047257c6700fef7080200ff81150000000000000f0000006c6b55463f49335f686c6431006d7973716c5f6e61746976655f70617373776f7264
+[*] Received: %s
+[*] Sending - Server OK: 0700000200000002000000
+[*] Received: %s
+[*] Sending - Malicious Tabular Response [metadata string length past the packet size]: 01000001010c00000201610162016301640165fcff
+
+Warning: mysqli::query(): Premature end of data (mysqlnd_wireprotocol.c:%d) in %s on line %d
+
+Warning: mysqli::query(): Result set field packet %d bytes shorter than expected in %s on line %d
+bool(false)
+done!
diff --git a/ext/mysqli/tests/mysqlnd_rset_field_len_past_packet.phpt b/ext/mysqli/tests/mysqlnd_rset_field_len_past_packet.phpt
new file mode 100644
index 000000000000..020d28d95b25
--- /dev/null
+++ b/ext/mysqli/tests/mysqlnd_rset_field_len_past_packet.phpt
@@ -0,0 +1,40 @@
+--TEST--
+mysqlnd result set field metadata string length exceeds remaining packet bytes
+--EXTENSIONS--
+mysqli
+--FILE--
+<?php
+require_once 'fake_server.inc';
+
+$servername = "127.0.0.1";
+$username = "root";
+$password = "";
+
+$process = run_fake_server_in_background('rset_field_metadata_len_past_packet');
+$process->wait();
+
+try {
+    $conn = new mysqli( $servername, $username, $password, "", $process->getPort());
+    var_dump($conn->query("SELECT * from users"));
+} catch (Exception $e) {
+    echo $e::class, ": ", $e->getMessage(), PHP_EOL;
+}
+
+$conn->close();
+
+$process->terminate();
+
+print "done!";
+?>
+--EXPECTF--
+[*] Server started on 127.0.0.1:%d
+[*] Connection established
+[*] Sending - Server Greeting: %s
+[*] Received: %s
+[*] Sending - Server OK: %s
+[*] Received: %s
+[*] Sending - Malicious Tabular Response [metadata string length past the packet size]: %s
+
+Warning: mysqli::query(): Result set field metadata string length is past the packet size in %s on line %d
+bool(false)
+done!
diff --git a/ext/mysqlnd/mysqlnd_wireprotocol.c b/ext/mysqlnd/mysqlnd_wireprotocol.c
index 80b4b37591ab..f0f95a970899 100644
--- a/ext/mysqlnd/mysqlnd_wireprotocol.c
+++ b/ext/mysqlnd/mysqlnd_wireprotocol.c
@@ -1176,10 +1176,17 @@ void php_mysqlnd_rset_header_free_mem(void * _packet)
 /* }}} */
 
 #define READ_RSET_FIELD(field_name) do { \
+		BAIL_IF_NO_MORE_DATA; \
 		len = php_mysqlnd_net_field_length(&p); \
 		if (UNEXPECTED(len == MYSQLND_NULL_LENGTH)) { \
 			goto faulty_or_fake; \
 		} else if (len != 0) { \
+			BAIL_IF_NO_MORE_DATA; \
+			if (UNEXPECTED((p - begin) > packet->header.size || packet->header.size - (p - begin) < len)) { \
+				DBG_ERR_FMT("Result set field metadata string length is past the packet size"); \
+				php_error_docref(NULL, E_WARNING, "Result set field metadata string length is past the packet size"); \
+				DBG_RETURN(FAIL); \
+			} \
 			meta->field_name = (const char *)p; \
 			meta->field_name ## _length = len; \
 			p += len; \
@@ -1248,7 +1255,7 @@ php_mysqlnd_rset_field_read(MYSQLND_CONN_DATA * conn, void * _packet)
 	READ_RSET_FIELD(name);
 	READ_RSET_FIELD(org_name);
 
-	/* 1 byte length */
+	BAIL_IF_NO_MORE_DATA;
 	if (UNEXPECTED(12 != *p)) {
 		DBG_ERR_FMT("Protocol error. Server sent false length. Expected 12 got %d", (int) *p);
 		php_error_docref(NULL, E_WARNING, "Protocol error. Server sent false length. Expected 12");