[PATCH] Fix http-backend reading till EOF, ignoring CONTENT_LENGTH, violating rfc3875 -- WAS: Problem with git-http-backend.exe as iis cgi
- From
- Florian Manschwetus <manschwetus@cs-software-gmbh.de>
- Date
- Mar 29, 2016, 10:38 UTC
- Message-ID
- <F0F5A56A22F20D4CB4A03BB8D6658797E261A3D6@SERVER2011.CS-SOFTWARE.local>
-----Ursprüngliche Nachricht----- Von: Chris Packham [mailto:judge.packham@gmail.com] Gesendet: Dienstag, 29. März 2016 11:28 An: Florian Manschwetus Cc: Konstantin Khomoutov; git@vger.kernel.org Betreff: Re: Problem with git-http-backend.exe as iis cgi
Hi Florian
On Tue, Mar 29, 2016 at 7:01 PM, Florian Manschwetus <manschwetus@cs-software-gmbh.de> wrote:
Show 61 quoted lines
> Hi,
> I put together a first patch for the issue.
>
> Mit freundlichen Grüßen / With kind regards Florian Manschwetus
>
> E-Mail: manschwetus@cs-software-gmbh.de
> Tel.: +49-(0)611-8908534
>
> CS Software Concepts and Solutions GmbH Geschäftsführer / Managing
> director: Dr. Werner Alexi Amtsgericht Wiesbaden HRB 10004 (Commercial
> registry) Schiersteiner Straße 31
> D-65187 Wiesbaden
> Germany
> Tel.: 0611/8908555
>
>
> -----Ursprüngliche Nachricht-----
> Von: Konstantin Khomoutov [mailto:kostix+git@007spb.ru]
> Gesendet: Donnerstag, 10. März 2016 13:55
> An: Florian Manschwetus
> Cc: git@vger.kernel.org
> Betreff: Re: Problem with git-http-backend.exe as iis cgi
>
> On Thu, 10 Mar 2016 07:28:50 +0000
> Florian Manschwetus <manschwetus@cs-software-gmbh.de> wrote:
>
>> I tried to setup git-http-backend with iis, as iis provides proper
>> impersonation for cgi under windows, which leads to have the
>> filesystem access performed with the logon user, therefore the
>> webserver doesn't need generic access to the files. I stumbled across
>> a problem, ending up with post requests hanging forever. After some
>> investigation I managed to get it work by wrapping the http-backend
>> into a bash script, giving a lot of control about the environmental
>> things, I was unable to solve within IIS configuration. The
>> workaround, I use currently, is to use "/bin/head -c
>> ${CONTENT_LENGTH}
>> | ./git-http-backend.exe", which directly shows the issue. Git
>> http-backend should check if CONTENT_LENGTH is set to something
>> reasonable (e.g. >0) and should in this case read only CONTENT_LENGTH
>> bytes from stdin, instead of reading till EOF what I suspect it is
>> doing currently.
>
> The rfc [1] states in its section 4.2:
>
> | A request-body is supplied with the request if the CONTENT_LENGTH is
> | not NULL. The server MUST make at least that many bytes available
> | for the script to read. The server MAY signal an end-of-file
> | condition after CONTENT_LENGTH bytes have been read or it MAY supply
> | extension data. Therefore, the script MUST NOT attempt to read more
> | than CONTENT_LENGTH bytes, even if more data is available. However,
> | it is not obliged to read any of the data.
>
> So yes, if Git currently reads until EOF, it's an error.
> The correct way would be:
>
> 1) Check to see if the CONTENT_LENGTH variable is available in the
> environment. If no, read nothing.
>
> 2) Otherwise read as many bytes it specifies, and no more.
>
> 1. https://www.ietf.org/rfc/rfc3875Your patch description seems well thought out but if you want someone to notice it you should have a read of https://git.kernel.org/cgit/git/git.git/tree/Documentation/SubmittingPatches
Moin, I have cloned git and created a more clean patch...
Signed-off-by: Florian Manschwetus <manschwetus@cs-software-gmbh.de> --- http-backend.c | 48 +++++++++++++++++++++++++++++++----------------- 1 file changed, 31 insertions(+), 17 deletions(-)
diff --git a/http-backend.c b/http-backend.c index 8870a26..94976df 100644 --- a/http-backend.c +++ b/http-backend.c @@ -277,16 +277,32 @@ static struct rpc_service *select_service(const char *name) */ static ssize_t read_request(int fd, unsigned char **out) { - size_t len = 0, alloc = 8192; - unsigned char *buf = xmalloc(alloc); + unsigned char *buf = null; + size_t len = 0; + /* get request size */ + size_t req_len = git_env_ulong("CONTENT_LENGTH", + 0); + + /* check request size */ + if (max_request_buffer < req_len) { + die("request was larger than our maximum size (%lu);" + " try setting GIT_HTTP_MAX_REQUEST_BUFFER", + max_request_buffer); + } + + if (req_len <= 0) { + *out = null; + return 0; + } + + /* allocate buffer */ + buf = xmalloc(req_len) - if (max_request_buffer < alloc) - max_request_buffer = alloc; while (1) { ssize_t cnt; - cnt = read_in_full(fd, buf + len, alloc - len); + cnt = read_in_full(fd, buf + len, req_len - len); if (cnt < 0) { free(buf); return -1; @@ -294,21 +310,18 @@ static ssize_t read_request(int fd, unsigned char **out) /* partial read from read_in_full means we hit EOF */ len += cnt; - if (len < alloc) { + if (len < req_len) { + /* TODO request incomplete?? */ + /* maybe just remove this block and condition along with the loop, */ + /* if read_in_full is prooven reliable */ *out = buf; return len; + } else { + /* request complete */ + *out = buf; + return len; + } - - /* otherwise, grow and try again (if we can) */ - if (alloc == max_request_buffer) - die("request was larger than our maximum size (%lu);" - " try setting GIT_HTTP_MAX_REQUEST_BUFFER", - max_request_buffer); - - alloc = alloc_nr(alloc); - if (alloc > max_request_buffer) - alloc = max_request_buffer; - REALLOC_ARRAY(buf, alloc); } } @@ -701,3 +714,4 @@ int main(int argc, char **argv) cmd->imp(cmd_arg); return 0; } +
-- 2.7.2.windows.1 Mit freundlichen Grüßen / With kind regards Florian Manschwetus CS Software Concepts and Solutions GmbH Geschäftsführer / Managing director: Dr. Werner Alexi Amtsgericht Wiesbaden HRB 10004 (Commercial registry) Schiersteiner Straße 31 D-65187 Wiesbaden Germany