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[2003:6c:cd4e:dc32:91dc:2265:e2b:ae5b]) by smtp.googlemail.com with ESMTPSA id r126sm20027968wmd.29.2018.03.07.19.53.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Mar 2018 19:53:45 -0800 (PST) From: wm4 To: ffmpeg-devel@ffmpeg.org Date: Thu, 8 Mar 2018 04:53:56 +0100 Message-Id: <20180308035357.18138-2-nfxjfg@googlemail.com> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180308035357.18138-1-nfxjfg@googlemail.com> References: <20180308035357.18138-1-nfxjfg@googlemail.com> Subject: [FFmpeg-devel] [PATCH 2/3] http: avoid out of bound accesses on broken St-Cookie headers X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: wm4 MIME-Version: 1.0 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" It's trivial to craft a HTTP response that will make the code for skipping trailing whitespace access and possibly overwrite bytes outside of the memory allocation. Why this can happen is blindingly obvious: it accesses cstr[strlen(cstr)-1] without checking whether the string is empty. --- libavformat/http.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/libavformat/http.c b/libavformat/http.c index d7a72e7129..59f90ac603 100644 --- a/libavformat/http.c +++ b/libavformat/http.c @@ -750,6 +750,9 @@ static int parse_set_cookie(const char *set_cookie, AVDictionary **dict) { char *param, *next_param, *cstr, *back; + if (!set_cookie[0]) + return 0; + if (!(cstr = av_strdup(set_cookie))) return AVERROR(EINVAL);