chan_sip: Do not allow non-SP/HTAB between header key and colon.

RFC says SIP headers look like:

    HCOLON  =  *( SP / HTAB ) ":" SWS
    SWS     =  [LWS]                    ; sep whitespace
    LWS     =  [*WSP CRLF] 1*WSP        ; linear whitespace
    WSP     =  SP / HTAB                ; from rfc2234

chan_sip implemented this:

    HCOLON  =  *( LOWCTL / SP ) ":" SWS
    LOWCTL  = %x00-1F                   ; CTL without DEL

This discrepancy meant that SIP proxies in front of Asterisk with
chan_sip could pass on unknown headers with \x00-\x1F in them, which
would be treated by Asterisk as a different (known) header.  For
example, the "To\x01:" header would gladly be forwarded by some proxies
as irrelevant, but chan_sip would treat it as the relevant "To:" header.

Those relying on a SIP proxy to scrub certain headers could mistakenly
get unexpected and unvalidated data fed to Asterisk.

This change fixes so chan_sip only considers SP/HTAB as valid tokens
before the colon, making it agree on the headers with other speakers of
SIP.

ASTERISK-26433 #close
AST-2016-009

Change-Id: I78086fbc524ac733b8f7f78cb423c91075fd489b
(cherry picked from commit 26dd464dbd0ad7439bc29ce59ec55903d518ec6e)

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index c99ea5db7050346859803e2cee9ae24d0aa642b0..800a43a76985faefee1731e9160765cf0f31efa2 100644 (file)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -8143,8 +8143,6 @@ static const char *__get_header(const struct sip_request *req, const char *name,
         * one afterwards.  If you shouldn't do it, what absolute idiot decided it was
         * a good idea to say you can do it, and if you can do it, why in the hell would.
         * you say you shouldn't.
-        * Anyways, pedanticsipchecking controls whether we allow spaces before ':',
-        * and we always allow spaces after that for compatibility.
         */
        const char *sname = find_alias(name, NULL);
        int x, len = strlen(name), slen = (sname ? 1 : 0);
@@ -8157,10 +8155,10 @@ static const char *__get_header(const struct sip_request *req, const char *name,
                if (match || smatch) {
                        /* skip name */
                        const char *r = header + (match ? len : slen );
-                       if (sip_cfg.pedanticsipchecking) {
-                               r = ast_skip_blanks(r);
+                       /* HCOLON has optional SP/HTAB; skip past those */
+                       while (*r == ' ' || *r == '\t') {
+                               ++r;
                        }
-
                        if (*r == ':') {
                                *start = x+1;
                                return ast_skip_blanks(r+1);