From 50f0add12a4856f6e7d5e6d1b18530fea05d50e6 Mon Sep 17 00:00:00 2001 From: Andrew Tridgell Date: Tue, 30 Dec 2025 18:49:34 +1100 Subject: [PATCH 24/60] reject negative token values in compressed stream receivers Validate that token numbers read from compressed streams are non-negative. A negative token value would cause the return value of recv_*_token() to become positive, which callers interpret as literal data length, but no data pointer is set on this code path. While this only causes the receiver to crash (which is process-isolated and only affects the attacker's own connection), it's still undefined behavior. Reported-by: Will Sergeant --- token.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) Index: rsync-3.1.3/token.c =================================================================== --- rsync-3.1.3.orig/token.c +++ rsync-3.1.3/token.c @@ -530,8 +530,13 @@ static int32 recv_deflated_token(int f, if (flag & TOKEN_REL) { rx_token += flag & 0x3f; flag >>= 6; - } else + } else { rx_token = read_int(f); + if (rx_token < 0) { + rprintf(FERROR, "invalid token number in compressed stream\n"); + exit_cleanup(RERR_PROTOCOL); + } + } if (flag & 1) { rx_run = read_byte(f); rx_run += read_byte(f) << 8;