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Guard against short server scramble in sha256_password auth #22356

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Guard against short server scramble in sha256_password auth #22356

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14 changes: 14 additions & 0 deletions ext/mysqli/tests/fake_server.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -818,6 +818,20 @@ function my_mysqli_test_query_response_row_read_two_fields(my_mysqli_fake_server
}
}

function my_mysqli_test_sha256_password_short_scramble(my_mysqli_fake_server_conn $conn): void
{
$conn->send_server_greetings();
$conn->read();
// AuthSwitchRequest (0xfe) to sha256_password carrying a scramble shorter
// than SCRAMBLE_LENGTH (20). mnd_emalloc sizes the heap copy to this
// length, so the sha256 plugin's 20-byte XOR over-reads it without the
// length guard.
$payload = "\xfe" . "sha256_password\x00" . str_repeat("\x41", 8);
$header = substr(pack('V', strlen($payload)), 0, 3) . "\x02";
$conn->send($header . $payload, "Auth Switch Request [short sha256 scramble]");
$conn->read();
}

function run_fake_server(string $test_function, int|string $port = 0): int
{
$host = '127.0.0.1';
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26 changes: 26 additions & 0 deletions ext/mysqli/tests/mysqli_sha256_password_short_scramble.phpt
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@@ -0,0 +1,26 @@
--TEST--
mysqlnd sha256_password: reject server scramble shorter than 20 bytes
--EXTENSIONS--
mysqli
mysqlnd
openssl
--FILE--
<?php
require_once 'fake_server.inc';

mysqli_report(MYSQLI_REPORT_OFF);

$process = run_fake_server_in_background('sha256_password_short_scramble');
$process->wait();

$link = @new mysqli("127.0.0.1", "root", "", "", $process->getPort());
printf("[%d] %s\n", mysqli_connect_errno(), mysqli_connect_error());

$process->terminate();
print "done!\n";
?>
--EXPECTF--
[*] Server started on 127.0.0.1:%d
%A
[2027] The server sent wrong length for scramble
done!
5 changes: 5 additions & 0 deletions ext/mysqlnd/mysqlnd_auth.c
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Original file line number Diff line number Diff line change
Expand Up @@ -908,6 +908,11 @@ mysqlnd_sha256_auth_get_auth_data(struct st_mysqlnd_authentication_plugin * self
DBG_ENTER("mysqlnd_sha256_auth_get_auth_data");
DBG_INF_FMT("salt(%zu)=[%.*s]", auth_plugin_data_len, (int) auth_plugin_data_len, auth_plugin_data);

if (auth_plugin_data_len < SCRAMBLE_LENGTH) {
SET_CLIENT_ERROR(conn->error_info, CR_MALFORMED_PACKET, UNKNOWN_SQLSTATE, "The server sent wrong length for scramble");
DBG_ERR_FMT("The server sent wrong length for scramble %zu. Expected %u", auth_plugin_data_len, SCRAMBLE_LENGTH);
DBG_RETURN(NULL);
}

if (conn->vio->data->ssl) {
DBG_INF("simple clear text under SSL");
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