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Use pg_parse_lsn() for IDENTIFY_SYSTEM responses in libpqwalreceiver

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libpqwalreceiver parses the WAL flush location returned by
IDENTIFY_SYSTEM using sscanf("%X/%X") into uint32 values. This
accepts overlong components and trailing characters, potentially
producing a different LSN from the one supplied by the upstream server.

Use pg_parse_lsn() instead, requiring one to eight hexadecimal digits
per component and no trailing characters, as for pg_lsn input. Reject
malformed locations with the existing protocol violation error.

Suggested-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Author: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Jan Nidzwetzki <jan@planetscale.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/tencent_C6ED19DF1759CDD37E786F7EE0B5207D0009@qq.com
This commit is contained in:
Fujii Masao
2026-10-22 16:45:45 +09:00
parent 4a842a1d65
commit ba6d9ee259
1 changed files with 2 additions and 5 deletions
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7
src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
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@@ -23,6 +23,7 @@
#include <sys/time.h>
#include "common/connect.h"
#include "common/pg_parse_lsn.h"
#include "funcapi.h"
#include "libpq-fe.h"
#include "libpq/libpq-be-fe-helpers.h"
@@ -458,15 +459,11 @@ libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli,
/* Column 2 is the server's current WAL flush position */
if (server_lsn)
{
uint32 hi,
lo;
if (sscanf(PQgetvalue(res, 0, 2), "%X/%X", &hi, &lo) != 2)
if (!pg_parse_lsn(PQgetvalue(res, 0, 2), server_lsn))
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("could not parse WAL location \"%s\"",
PQgetvalue(res, 0, 2))));
*server_lsn = ((uint64) hi) << 32 | lo;
}
PQclear(res);