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179 lines
8.1 KiB
179 lines
8.1 KiB
--- channels/chan_sip.c (revision 183280)
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+++ channels/chan_sip.c (working copy)
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@@ -1266,7 +1266,7 @@
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static int transmit_response_with_unsupported(struct sip_pvt *p, const char *msg, const struct sip_request *req, const char *unsupported);
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static int transmit_response_with_auth(struct sip_pvt *p, const char *msg, const struct sip_request *req, const char *rand, enum xmittype reliable, const char *header, int stale);
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static int transmit_response_with_allow(struct sip_pvt *p, const char *msg, const struct sip_request *req, enum xmittype reliable);
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-static void transmit_fake_auth_response(struct sip_pvt *p, struct sip_request *req, enum xmittype reliable);
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+static void transmit_fake_auth_response(struct sip_pvt *p, int sipmethod, struct sip_request *req, enum xmittype reliable);
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static int transmit_request(struct sip_pvt *p, int sipmethod, int inc, enum xmittype reliable, int newbranch);
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static int transmit_request_with_auth(struct sip_pvt *p, int sipmethod, int seqno, enum xmittype reliable, int newbranch);
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static int transmit_invite(struct sip_pvt *p, int sipmethod, int sdp, int init);
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@@ -8873,10 +8873,96 @@
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/*! \brief Send a fake 401 Unauthorized response when the administrator
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wants to hide the names of local users/peers from fishers
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*/
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-static void transmit_fake_auth_response(struct sip_pvt *p, struct sip_request *req, enum xmittype reliable)
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+static void transmit_fake_auth_response(struct sip_pvt *p, int sipmethod, struct sip_request *req, enum xmittype reliable)
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{
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- ast_string_field_build(p, randdata, "%08lx", ast_random()); /* Create nonce for challenge */
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- transmit_response_with_auth(p, "401 Unauthorized", req, p->randdata, reliable, "WWW-Authenticate", 0);
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+ /* We have to emulate EXACTLY what we'd get with a good peer
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+ * and a bad password, or else we leak information. */
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+ const char *response = "407 Proxy Authentication Required";
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+ const char *reqheader = "Proxy-Authorization";
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+ const char *respheader = "Proxy-Authenticate";
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+ const char *authtoken;
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+ struct ast_dynamic_str *buf;
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+ char *c;
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+
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+ /* table of recognised keywords, and their value in the digest */
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+ enum keys { K_NONCE, K_LAST };
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+ struct x {
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+ const char *key;
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+ const char *s;
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+ } *i, keys[] = {
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+ [K_NONCE] = { "nonce=", "" },
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+ [K_LAST] = { NULL, NULL}
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+ };
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+
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+ if (sipmethod == SIP_REGISTER || sipmethod == SIP_SUBSCRIBE) {
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+ response = "401 Unauthorized";
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+ reqheader = "Authorization";
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+ respheader = "WWW-Authenticate";
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+ }
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+ authtoken = get_header(req, reqheader);
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+ if (ast_test_flag(req, SIP_PKT_IGNORE) && !ast_strlen_zero(p->randdata) && ast_strlen_zero(authtoken)) {
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+ /* This is a retransmitted invite/register/etc, don't reconstruct authentication
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+ * information */
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+ transmit_response_with_auth(p, response, req, p->randdata, 0, respheader, 0);
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+ /* Schedule auto destroy in 32 seconds (according to RFC 3261) */
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+ sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
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+ return;
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+ } else if (ast_strlen_zero(p->randdata) || ast_strlen_zero(authtoken)) {
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+ /* We have no auth, so issue challenge and request authentication */
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+ ast_string_field_build(p, randdata, "%08lx", ast_random()); /* Create nonce for challenge */
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+ transmit_response_with_auth(p, response, req, p->randdata, 0, respheader, 0);
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+ /* Schedule auto destroy in 32 seconds */
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+ sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
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+ return;
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+ }
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+
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+ if (!(buf = ast_dynamic_str_thread_get(&check_auth_buf, CHECK_AUTH_BUF_INITLEN))) {
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+ transmit_response(p, "403 Forbidden (Bad auth)", &p->initreq);
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+ return;
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+ }
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+
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+ /* Make a copy of the response and parse it */
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+ if (ast_dynamic_str_thread_set(&buf, 0, &check_auth_buf, "%s", authtoken) == AST_DYNSTR_BUILD_FAILED) {
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+ transmit_response(p, "403 Forbidden (Bad auth)", &p->initreq);
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+ return;
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+ }
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+
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+ c = buf->str;
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+
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+ while (c && *(c = ast_skip_blanks(c))) { /* lookup for keys */
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+ for (i = keys; i->key != NULL; i++) {
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+ const char *separator = ","; /* default */
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+
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+ if (strncasecmp(c, i->key, strlen(i->key)) != 0) {
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+ continue;
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+ }
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+ /* Found. Skip keyword, take text in quotes or up to the separator. */
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+ c += strlen(i->key);
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+ if (*c == '"') { /* in quotes. Skip first and look for last */
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+ c++;
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+ separator = "\"";
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+ }
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+ i->s = c;
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+ strsep(&c, separator);
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+ break;
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+ }
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+ if (i->key == NULL) { /* not found, jump after space or comma */
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+ strsep(&c, " ,");
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+ }
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+ }
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+
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+ /* Verify nonce from request matches our nonce. If not, send 401 with new nonce */
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+ if (strcasecmp(p->randdata, keys[K_NONCE].s)) {
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+ if (!ast_test_flag(req, SIP_PKT_IGNORE)) {
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+ ast_string_field_build(p, randdata, "%08lx", ast_random());
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+ }
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+ transmit_response_with_auth(p, response, req, p->randdata, reliable, respheader, FALSE);
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+
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+ /* Schedule auto destroy in 32 seconds */
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+ sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
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+ } else {
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+ transmit_response(p, "403 Forbidden (Bad auth)", &p->initreq);
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+ }
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}
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/*! \brief Verify registration of user
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@@ -9010,6 +9096,14 @@
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}
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}
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}
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+ if (!peer && global_alwaysauthreject) {
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+ /* If we found a peer, we transmit a 100 Trying. Therefore, if we're
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+ * trying to avoid leaking information, we MUST also transmit the same
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+ * response when we DON'T find a peer. */
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+ transmit_response(p, "100 Trying", req);
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+ /* Insert a fake delay between the 100 and the subsequent failure. */
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+ sched_yield();
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+ }
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if (!res) {
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ast_device_state_changed("SIP/%s", peer->name);
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}
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@@ -9020,7 +9114,7 @@
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transmit_response(p, "403 Forbidden (Bad auth)", &p->initreq);
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break;
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case AUTH_USERNAME_MISMATCH:
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- /* Username and digest username does not match.
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+ /* Username and digest username does not match.
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Asterisk uses the From: username for authentication. We need the
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users to use the same authentication user name until we support
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proper authentication by digest auth name */
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@@ -9030,7 +9124,7 @@
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case AUTH_PEER_NOT_DYNAMIC:
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case AUTH_ACL_FAILED:
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if (global_alwaysauthreject) {
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- transmit_fake_auth_response(p, &p->initreq, XMIT_UNRELIABLE);
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+ transmit_fake_auth_response(p, SIP_REGISTER, &p->initreq, XMIT_UNRELIABLE);
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} else {
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/* URI not found */
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if (res == AUTH_PEER_NOT_DYNAMIC)
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@@ -14557,7 +14651,7 @@
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if (res < 0) { /* Something failed in authentication */
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if (res == AUTH_FAKE_AUTH) {
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ast_log(LOG_NOTICE, "Sending fake auth rejection for user %s\n", get_header(req, "From"));
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- transmit_fake_auth_response(p, req, XMIT_RELIABLE);
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+ transmit_fake_auth_response(p, SIP_INVITE, req, XMIT_RELIABLE);
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} else {
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ast_log(LOG_NOTICE, "Failed to authenticate user %s\n", get_header(req, "From"));
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transmit_response_reliable(p, "403 Forbidden", req);
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@@ -15594,7 +15688,7 @@
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if (res < 0) {
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if (res == AUTH_FAKE_AUTH) {
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ast_log(LOG_NOTICE, "Sending fake auth rejection for user %s\n", get_header(req, "From"));
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- transmit_fake_auth_response(p, req, XMIT_UNRELIABLE);
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+ transmit_fake_auth_response(p, SIP_SUBSCRIBE, req, XMIT_UNRELIABLE);
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} else {
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ast_log(LOG_NOTICE, "Failed to authenticate user %s for SUBSCRIBE\n", get_header(req, "From"));
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transmit_response_reliable(p, "403 Forbidden", req);
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--- configs/sip.conf.sample (revision 183280)
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+++ configs/sip.conf.sample (working copy)
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@@ -141,9 +141,11 @@
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;callevents=no ; generate manager events when sip ua
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; performs events (e.g. hold)
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;alwaysauthreject = yes ; When an incoming INVITE or REGISTER is to be rejected,
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- ; for any reason, always reject with '401 Unauthorized'
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+ ; for any reason, always reject with an identical response
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+ ; equivalent to valid username and invalid password/hash
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; instead of letting the requester know whether there was
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- ; a matching user or peer for their request
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+ ; a matching user or peer for their request. This reduces
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+ ; the ability of an attacker to scan for valid SIP usernames.
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;g726nonstandard = yes ; If the peer negotiates G726-32 audio, use AAL2 packing
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; order instead of RFC3551 packing order (this is required
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