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On Tue, Aug 30, 2016 at 06:48:19PM +0200, Marco Angaroni wrote:
> Current parsing methods for SIP headers do not properly manage
> continuation lines: in case of Call-ID header the first character of
> Call-ID header value is truncated. As a result IPVS SIP persistence
> engine hashes over a call-id that is not exactly the one present in
> the originale message.
>
> Example: "Call-ID: \r\n abcdeABCDE1234"
> results in extracted call-id equal to "bcdeABCDE1234".
>
> In above example Call-ID is represented as a string in C language.
> Obviously in real message the first bytes after colon (":") are
> "20 0d 0a 20".
>
> Proposed fix is in nf_conntrack_sip module.
> Since sip_follow_continuation() function walks past the leading
> spaces or tabs of the continuation line, sip_skip_whitespace()
> should simply return the ouput of sip_follow_continuation().
> Otherwise another iteration of the for loop is done and dptr
> is incremented by one pointing to the second character of the
> first word in the header.
>
> Below is an extract of relevant SIP ABNF syntax.
>
> Call-ID = ( "Call-ID" / "i" ) HCOLON callid
> callid = word [ "@" word ]
>
> HCOLON = *( SP / HTAB ) ":" SWS
> SWS = [LWS] ; sep whitespace
> LWS = [*WSP CRLF] 1*WSP ; linear whitespace
> WSP = SP / HTAB
> word = 1*(alphanum / "-" / "." / "!" / "%" / "*" /
> "_" / "+" / "`" / "'" / "~" /
> "(" / ")" / "<" / ">" /
> ":" / "\" / DQUOTE /
> "/" / "[" / "]" / "?" /
> "{" / "}" )
>
> Signed-off-by: Marco Angaroni <marcoangaroni@xxxxxxxxx>
> ---
> net/netfilter/nf_conntrack_sip.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_sip.c
> b/net/netfilter/nf_conntrack_sip.c
> index 8971109..c23249e 100644
> --- a/net/netfilter/nf_conntrack_sip.c
> +++ b/net/netfilter/nf_conntrack_sip.c
> @@ -335,8 +335,7 @@ static const char *sip_skip_whitespace(const char *dptr,
> const char *limit)
> if (*dptr != '\r' && *dptr != '\n')
> break;
> dptr = sip_follow_continuation(dptr, limit);
> - if (dptr == NULL)
> - return NULL;
> + return dptr;
I'd suggest you use the break statement here instead, ie.
- if (dptr == NULL)
- return NULL;
+ break;
> }
> return dptr;
> }
> --
> 1.8.3.1
>
> --
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