sip user Authentication and 401

There are two forms of authentication in SIP – authentication of a user agent (UA) by a proxy, redirect, or registration server and authentication of one UA by another. With Transport Layer Security (TLS), mutual authentication of proxies or a proxy and UA is accomplished using certificates. Authentication is used to allow only authorized access to a service or feature and prevent malicious or unauthorized use by other applications.

• SIP and WebRTC
• Voip Design
• VoIP Software

Digest Authentication

Digest authentication is a simple challenge/response method based on HTTP. For RFC 2069, it employs a MD5 hash algorithm to encode the username, realm, password, digest URI, and server generated nonce as follows:

• H1 = MD5(username : realm : password)
• H2 = MD5(method : digestURI)
• Response = MD5(H1 : nonce : H2)

RFC 2617 added a client generated nonce and quality of protection (QoP) to improve security as follows:

• Response = MD5(H1 : nonce : nonceCount : nonceClient : QoP : H2)

SIP Proxy and User Authentication

As depicted in the figure, the message flow for both proxy and user agent authentication is illustrated. The initial INVITE is challenged with a 407 Proxy authorization required. The UA responds with an ACK and then reissues the INVITE containing the authentication credentials. The next proxy server or end UA responds with a 401 Unauthorized message back to the source UA to again reissue the INVITE with the proper authentication credentials and complete the authentication process.

Via: SIP/2.0/UDP 192.168.23.113:;branch=z9hG4bK.rxkOqoU6K;rport
From: "sabresd" <sip:@192.168.23.100>;tag=i-ljgBYGN
To: sip:@192.168.23.100
CSeq: INVITE
Call-ID: c2kQFPZtPJ
Max-Forwards:
Supported: replaces, outbound
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO, UPDATE
Content-Type: application/sdp
Content-Length:
Contact: <sip:@192.168.23.113;transport=udp>;+sip.instance="<urn:uuid:b13bc5f4-aefc-412f-b586-7a409b46e058>"
User-Agent: LinphoneAndroid/ (belle-sip/1.5.)
Authorization: Digest realm="asterisk", nonce="1007a06b", algorithm=MD5, username="", uri="sip:2007@192.168.23.100", response="45316d80ffca2b4094333af2631d0c9f"v=
o= IN IP4 192.168.23.113
s=Talk
c=IN IP4 192.168.23.113
b=AS:
t=
a=rtcp-xr:rcvr-rtt=all: stat-summary=loss,dup,jitt,TTL voip-metrics
m=audio RTP/AVP
a=rtpmap: opus//
a=fmtp: useinbandfec=
a=rtpmap: SILK/
a=rtpmap: speex/
a=fmtp: vbr=on
a=rtpmap: speex/
a=fmtp: vbr=on
a=rtpmap: telephone-event/
a=rtpmap: telephone-event/
a=rtpmap: telephone-event/
m=video RTP/AVP
a=rtpmap: H264/
a=fmtp: profile-level-id=42801F
a=rtcp-fb: nack pli
a=rtcp-fb: ccm fir