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Re: [Sip] Using TLS in the first hop - Bug in RFC 5630

Iñaki Baz Castillo <ibc@aliax.net> Thu, 15 September 2011 14:23 UTC

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Date: Thu, 15 Sep 2011 16:25:24 +0200
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From: Iñaki Baz Castillo <ibc@aliax.net>
To: "Olle E. Johansson" <oej@edvina.net>
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Cc: sip@ietf.org
Subject: Re: [Sip] Using TLS in the first hop - Bug in RFC 5630
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2011/9/15 Olle E. Johansson <oej@edvina.net>:
> This means thet the request URI of the ACK will be using SIPS, and then section 8.1.1.8 comes into play
> and requires the other side to also use a SIPS uri in their contact.
>
> In this case, both UAs need a TLS certificate.

No, that's incorrect. I show two call flows in which TLS is just used
by one of the enpoints.



CASE 1)
- Alice uses TLS.
- Bob uses UDP.
- Proxy/registrar does loose-routing.
- Alice calls Bob, Bob answers and later Bob hangs up.


F1 INVITE Alice -> SIP Proxy (transport TLS)

INVITE sip:bob@atlanta.com SIP/2.0
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bK56sdasks
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 70
Contact: <sips:alice@93.12.40.105:20565;transport=tcp>
Content-Type: application/sdp


F2 100 Trying SIP Proxy -> Alice (transport TLS)

SIP/2.0 100 Trying
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bK56sdasks
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE


F3 INVITE SIP Proxy -> Carol (transport UDP)

INVITE sip:bob@77.123.45.23:5060 SIP/2.0
Via: SIP/2.0/UDP 100.100.100.100;branch=z9hG4bKhjhjqw32c
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bK56sdasks
Record-Route: <sip:100.100.100.100;transport=udp>,
  <sips:100.100.100.100;transport=tcp>
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sips:alice@93.12.40.105:20565;transport=tcp>
Content-Type: application/sdp


F4 200 OK Carol -> SIP Proxy (transport UDP)

SIP/2.0 200 OK
Via: SIP/2.0/UDP 100.100.100.100;branch=z9hG4bKhjhjqw32c
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bK56sdasks
Record-Route: <sip:100.100.100.100;transport=udp>,
  <sips:100.100.100.100;transport=tcp>
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sip:bob@77.123.45.23:5060;transport=udp>
Content-Type: application/sdp


F5 200 OK SIP Proxy -> Alice (transport TLS)

SIP/2.0 200 OK
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bK56sdasks
Record-Route: <sip:100.100.100.100;transport=udp>,
  <sips:100.100.100.100;transport=tcp>
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sip:bob@77.123.45.23:5060;transport=udp>
Content-Type: application/sdp


F6 ACK Alice -> SIP Proxy (transport TLS)

ACK sip:bob@77.123.45.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bKhgqqp090
Route: <sips:100.100.100.100;transport=tcp>,
  <sip:100.100.100.100;transport=udp>
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 ACK
Max-Forwards: 70


F7 ACK SIP Proxy -> Carol (transport UDP)

ACK sip:bob@77.123.45.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/UDP 100.100.100.100;branch=z9hG4bKhwpoc80zzx
Via: SIP/2.0/TLS 93.12.40.105:20565;branch=z9hG4bKhgqqp090
From: sip:alice@atlanta.com;tag=asdyka899
To: sip:bob@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 ACK
Max-Forwards: 69


F8 BYE Carol -> SIP Proxy (transport UDP)

BYE sips:alice@93.12.40.105:20565;transport=tcp SIP/2.0
Via: SIP/2.0/UDP 77.123.45.23;branch=z9hG4bKbiuiansd001
Route: <sip:100.100.100.100;transport=udp>,
  <sips:100.100.100.100;transport=tcp>
From: sip:bob@atlanta.com;tag=bmqkjhsd
To: sip:alice@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE
Max-Forwards: 70


F9 BYE SIP Proxy -> Alice (transport TLS)

BYE sips:alice@93.12.40.105:20565;transport=tcp SIP/2.0
Via: SIP/2.0/TLS 100.100.100.100;branch=z9hG4bKmma01m3r5
Via: SIP/2.0/UDP 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:bob@atlanta.com;tag=bmqkjhsd
To: sip:alice@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE
Max-Forwards: 69


F10 200 OK Alice -> SIP Proxy (transport TLS)

SIP/2.0 200 OK
Via: SIP/2.0/TLS 100.100.100.100;branch=z9hG4bKmma01m3r5
Via: SIP/2.0/UDP 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:bob@atlanta.com;tag=bmqkjhsd
To: sip:alice@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE


F11 200 OK SIP Proxy -> Carol (transport UDP)

SIP/2.0 200 OK
Via: SIP/2.0/UDP 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:bob@atlanta.com;tag=bmqkjhsd
To: sip:alice@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE







CASE 2)
- Alice uses TLS.
- Bob uses UDP.
- Proxy/registrar does loose-routing.
- Bob calls Alice, Alice answers and later Alice hangs up.


F1 INVITE Bob -> SIP Proxy (transport UDP)

INVITE sip:alice@atlanta.com SIP/2.0
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bK56sdasks
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 70
Contact: <sip:bob@77.123.45.23:5060;transport=udp>
Content-Type: application/sdp


F2 100 Trying SIP Proxy -> Bob (transport TLS)

SIP/2.0 100 Trying
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bK56sdasks
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE


F3 INVITE SIP Proxy -> Alice (transport TLS)

INVITE sips:alice@93.12.40.105:20565 SIP/2.0
Via: SIP/2.0/TLS 100.100.100.100;branch=z9hG4bKhjhjqw32c
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bK56sdasks
Record-Route: <sips:100.100.100.100;transport=tcp>,
  <sip:100.100.100.100;transport=udp>
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sip:bob@77.123.45.23:5060;transport=udp>
Content-Type: application/sdp


F4 200 OK Alice -> SIP Proxy (transport TLS)

SIP/2.0 200 OK
Via: SIP/2.0/TLS 100.100.100.100;branch=z9hG4bKhjhjqw32c
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bK56sdasks
Record-Route: <sips:100.100.100.100;transport=tcp>,
  <sip:100.100.100.100;transport=udp>
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sips:alice@93.12.40.105:20565;transport=tcp>
Content-Type: application/sdp


F5 200 OK SIP Proxy -> Bob (transport UDP)

SIP/2.0 200 OK
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bK56sdasks
Record-Route: <sips:100.100.100.100;transport=tcp>,
  <sip:100.100.100.100;transport=udp>
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 INVITE
Max-Forwards: 69
Contact: <sips:alice@93.12.40.105:20565;transport=tcp>
Content-Type: application/sdp


F6 ACK Bob -> SIP Proxy (transport UDP)

ACK sips:alice@93.12.40.105:20565;transport=tcp SIP/2.0
Via: SIP/2.0/TLS 77.123.45.23:5060;branch=z9hG4bKhgqqp090
Route: <sip:100.100.100.100;transport=udp>,
  <sips:100.100.100.100;transport=tcp>
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 ACK
Max-Forwards: 70


F7 ACK SIP Proxy -> Alice (transport TLS)

ACK sips:alice@93.12.40.105:20565;transport=tcp SIP/2.0
Via: SIP/2.0/TLS 100.100.100.100;branch=z9hG4bKhwpoc80zzx
Via: SIP/2.0/UDP 77.123.45.23:5060;branch=z9hG4bKhgqqp090
From: sip:bob@atlanta.com;tag=asdyka899
To: sip:alice@atlanta.com;tag=bmqkjhsd
Call-ID: asidkj3ss
CSeq: 1 ACK
Max-Forwards: 69


F8 BYE Alice -> SIP Proxy (transport TLS)

BYE sip:bob@77.123.45.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/TLS 77.123.45.23;branch=z9hG4bKbiuiansd001
Route: <sips:100.100.100.100;transport=tcp>,
  <sip:100.100.100.100;transport=udp>
From: sip:alice@atlanta.com;tag=bmqkjhsd
To: sip:bob@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE
Max-Forwards: 70


F9 BYE SIP Proxy -> Bob (transport UDP)

BYE sip:bob@77.123.45.23:5060;transport=udp SIP/2.0
Via: SIP/2.0/UDP 100.100.100.100;branch=z9hG4bKmma01m3r5
Via: SIP/2.0/TLS 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:alice@atlanta.com;tag=bmqkjhsd
To: sip:bob@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE
Max-Forwards: 69


F10 200 OK Bob -> SIP Proxy (transport UDP)

SIP/2.0 200 OK
Via: SIP/2.0/UDP 100.100.100.100;branch=z9hG4bKmma01m3r5
Via: SIP/2.0/TLS 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:alice@atlanta.com;tag=bmqkjhsd
To: sip:bob@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE


F11 200 OK SIP Proxy -> Alice (transport TLS)

SIP/2.0 200 OK
Via: SIP/2.0/TLS 77.123.45.23;branch=z9hG4bKbiuiansd001
From: sip:alice@atlanta.com;tag=bmqkjhsd
To: sip:bob@atlanta.com;tag=asdyka899
Call-ID: asidkj3ss
CSeq: 1201 BYE




These flows are inspired in real scenarios, so both are real and working flows.


-- 
Iñaki Baz Castillo
<ibc@aliax.net>

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