From: Steffan Karger Date: Fri, 29 Dec 2017 09:54:00 +0000 (+0100) Subject: buffer_list_aggregate_separator(): prevent 0-byte malloc X-Git-Tag: v2.4.5~35 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ef4b827d68d8fef75b04f23e6322aa9d2d4ad8a8;p=thirdparty%2Fopenvpn.git buffer_list_aggregate_separator(): prevent 0-byte malloc As pointed out in finding OVPN-05 of the cryptograpy engineering audit (funded by Private Internet Access), buffer_list_aggregate_separator() could perform a 0-byte malloc when called with a list of 0-length buffers and a "" separator. If other could would later try to access that buffer memory, this would result in undefined behaviour. To prevent this, always malloc() 1 byte. To simplify as we go, use alloc_buf() to allocate the buffer. This has the additional benefit that the actual buffer data (not the contents) is zero-terminated, because alloc_buf() calls calloc() and we have 1 extra byte of data. Signed-off-by: Steffan Karger Acked-by: Antonio Quartulli Message-Id: <1514541240-19536-1-git-send-email-steffan.karger@fox-it.com> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16106.html Signed-off-by: Gert Doering (cherry picked from commit 748902f46260fe11cb25726d2bf93bb06ad338f2) --- diff --git a/src/openvpn/buffer.c b/src/openvpn/buffer.c index 7d43d07af..0b75edef9 100644 --- a/src/openvpn/buffer.c +++ b/src/openvpn/buffer.c @@ -1259,8 +1259,7 @@ buffer_list_aggregate_separator(struct buffer_list *bl, const size_t max_len, struct buffer_entry *e = bl->head, *f; ALLOC_OBJ_CLEAR(f, struct buffer_entry); - f->buf.data = malloc(size); - check_malloc_return(f->buf.data); + f->buf = alloc_buf(size + 1); /* prevent 0-byte malloc */ f->buf.capacity = size; for (i = 0; e && i < count; ++i) {