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Bug in add_buffer_send while calling Curl_debug with request header data

From: Ates Goral <>
Date: Tue, 13 Nov 2007 11:00:20 -0800

In libcurl 7.17.1, lib/http.c line 987:


      Curl_debug(conn->data, CURLINFO_HEADER_OUT, ptr,

                 (size_t)(amount-included_body_bytes), conn);


Here, it is assumed that the "amount" bytes that were actually sent with
the prior call to Curl_write is exactly "size" bytes (the total bytes
that are available for sending).


#13 0x08074dd3 in Curl_debug (data=0x8f55240, type=CURLINFO_HEADER_OUT,

    ptr=0x8ed5cb8 "POST HTTP/1.0\r\nHost:\r\nProxy-Connection: Keep-Alive\r\nAcc"...,

    size=4294952134, conn=0x0) at sendf.c:663

#14 0x0807d328 in add_buffer_send (in=0x8ed3f10, conn=0x8eaaaf0,

    bytes_written=0x8f5d790, included_body_bytes=27474, socketindex=0)

    at http.c:987


In frame #14, I have:


size = 29022

included_body_bytes = 27474

amount = 12312


And therefore, "amount - included_body_bytes" yields a negative number,
which in turn results in the "4294952134" seen at frame #13. This
eventually results in a crash in our code while we're trying to log the
(allegedly) 4 GB of debug data :-)


I suppose the fix would be something like (sorry, I don't have a patch
at this time as I haven't tested this out):


      size_t size_of_headers = size - included_body_bytes;


      Curl_debug(conn->data, CURLINFO_HEADER_OUT, ptr,

                 amount >= size_of_headers ? size_of_headers : amount,




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Received on 2007-11-13