From fe0bd3cde9665d364e5eedd2c2c2e60d4cdc3786 Mon Sep 17 00:00:00 2001 From: "dtucker@openbsd.org" Date: Tue, 21 Feb 2023 06:48:18 +0000 Subject: [PATCH] upstream: fseek to end of known_hosts before writing to it. POSIX and ANSI C require that applications call fseek or similar between read and writing to a RW file. OpenBSD doesn't enforce this, but some (System V derived) platforms need this to prevent it from writing a spurious extra byte (in this case, a newline). ok djm@ deraadt@ OpenBSD-Commit-ID: 33e680dcd8110582a93a40a8491024e961f45137 --- hostfile.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/hostfile.c b/hostfile.c index f5fa80840..c5669c703 100644 --- a/hostfile.c +++ b/hostfile.c @@ -1,4 +1,4 @@ -/* $OpenBSD: hostfile.c,v 1.94 2023/02/09 09:54:11 dtucker Exp $ */ +/* $OpenBSD: hostfile.c,v 1.95 2023/02/21 06:48:18 dtucker Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -515,7 +515,7 @@ add_host_to_hostfile(const char *filename, const char *host, const struct sshkey *key, int store_hash) { FILE *f; - int success; + int success, addnl = 0; if (key == NULL) return 1; /* XXX ? */ @@ -525,12 +525,13 @@ add_host_to_hostfile(const char *filename, const char *host, return 0; /* Make sure we have a terminating newline. */ if (fseek(f, -1L, SEEK_END) == 0 && fgetc(f) != '\n') - if (fputc('\n', f) != '\n') { - error("Failed to add terminating newline to %s: %s", - filename, strerror(errno)); - fclose(f); - return 0; - } + addnl = 1; + if (fseek(f, 0L, SEEK_END) != 0 || (addnl && fputc('\n', f) != '\n')) { + error("Failed to add terminating newline to %s: %s", + filename, strerror(errno)); + fclose(f); + return 0; + } success = write_host_entry(f, host, NULL, key, store_hash); fclose(f); return success;