From 39df4073e5413fcdbb5a38da0c1ce6f1c0ceb484 Mon Sep 17 00:00:00 2001 From: Daniel Gustafsson Date: Sat, 19 Jan 2019 00:42:47 +0100 Subject: [PATCH] smtp: avoid risk of buffer overflow in strtol If the incoming len 5, but the buffer does not have a termination after 5 bytes, the strtol() call may keep reading through the line buffer until is exceeds its boundary. Fix by ensuring that we are using a bounded read with a temporary buffer on the stack. Bug: https://curl.haxx.se/docs/CVE-2019-3823.html Reported-by: Brian Carpenter (Geeknik Labs) CVE-2019-3823 --- lib/smtp.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/lib/smtp.c +++ b/lib/smtp.c @@ -5,7 +5,7 @@ * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * - * Copyright (C) 1998 - 2018, Daniel Stenberg, , et al. + * Copyright (C) 1998 - 2019, Daniel Stenberg, , et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms @@ -207,8 +207,12 @@ static bool smtp_endofresp(struct connec Section 4. Examples of RFC-4954 but some e-mail servers ignore this and only send the response code instead as per Section 4.2. */ if(line[3] == ' ' || len == 5) { + char tmpline[6]; + result = TRUE; - *resp = curlx_sltosi(strtol(line, NULL, 10)); + memset(tmpline, '\0', sizeof(tmpline)); + memcpy(tmpline, line, (len == 5 ? 5 : 3)); + *resp = curlx_sltosi(strtol(tmpline, NULL, 10)); /* Make sure real server never sends internal value */ if(*resp == 1)