[tor-bugs] #9167 [Flashproxy]: Find a more stable key pinning scheme for www.google.com

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#9167: Find a more stable key pinning scheme for www.google.com
------------------------+---------------------------------------------------
 Reporter:  dcf         |          Owner:  dcf
     Type:  defect      |         Status:  new
 Priority:  normal      |      Milestone:     
Component:  Flashproxy  |        Version:     
 Keywords:              |         Parent:     
   Points:              |   Actualpoints:     
------------------------+---------------------------------------------------
 I've had to update the public key pin for www.google.com in
 [https://gitweb.torproject.org/flashproxy.git/blob/HEAD:/flashproxy-reg-
 appspot flashproxy-reg-appspot] often:
 [https://gitweb.torproject.org/flashproxy.git/commitdiff/b159ab5b1a00bd774aa9b4a01215be62f0f1d05a
 March 31],
 [https://gitweb.torproject.org/flashproxy.git/commitdiff/b48bfc63db523303f7dde5c0c5bc96c68c71f042
 June 13], and again today on June 28.

 [https://src.chromium.org/viewvc/chrome/trunk/src/net/http/transport_security_state_static.h?revision=209003&view=markup
 transport_security_state_static.h] in the Chromium source code is where
 the pins are stored, I believe. That file
 [https://src.chromium.org/viewvc/chrome/trunk/src/net/http/transport_security_state_static.h?view=log
 hasn't had any google.com changes] since March 28. That makes me think
 we're doing something wrong and hashing more than we're supposed to.

 [https://github.com/agl/transport-security-state-
 generate/blob/master/transport_security_state_static_generate.go
 transport_security_state_static_generate.go] is the program used to
 generate the Chromium file. It does:
 {{{
         h := sha1.New()
         h.Write(cert.RawSubjectPublicKeyInfo)
 }}}
 Whereas flashproxy-reg-appspot does:
 {{{
         pubkey_der = cert.get_pubkey().as_der()
         pubkey_digest = sha1(pubkey_der).digest()
 }}}

 The Chromium source code says:
 {{{
 // This file is automatically generated by
 transport_security_state_static_generate.go

 // These are SubjectPublicKeyInfo hashes for public key pinning. The
 // hashes are SHA1 digests.

 ...

 static const char kSPKIHash_Google1024[] =
         "\x40\xc5\x40\x1d\x6f\x8c\xba\xf0\x8b\x00"
         "\xed\xef\xb1\xee\x87\xd0\x05\xb3\xb9\xcd";

 static const char kSPKIHash_Google2048[] =
         "\x01\xb9\x21\xc5\x8d\x0b\xdf\x8d\xe0\x29"
         "\xff\x9c\x92\x2e\xcd\x55\x6a\x7e\xa3\x39";

 static const char kSPKIHash_GoogleBackup1024[] =
         "\x7d\x5b\xa3\xca\x8e\x37\x65\x1d\x7c\x71"
         "\xc3\xe3\xb7\x74\xcd\xe9\x7b\x1b\x59\x43";

 static const char kSPKIHash_GoogleBackup2048[] =
         "\xbe\xae\xce\xca\x34\xa7\xa8\xe7\x28\xf6"
         "\x7c\x8c\x08\x31\x9d\xcb\xbe\xde\x8a\x33";

 static const char kSPKIHash_GoogleG2[] =
         "\x43\xda\xd6\x30\xee\x53\xf8\xa9\x80\xca"
         "\x6e\xfd\x85\xf4\x6a\xa3\x79\x90\xe0\xea";

 ...

 static const char* const kGoogleAcceptableCerts[] = {
         kSPKIHash_VeriSignClass3,
         kSPKIHash_VeriSignClass3_G3,
         kSPKIHash_Google1024,
         kSPKIHash_Google2048,
         kSPKIHash_GoogleBackup1024,
         kSPKIHash_GoogleBackup2048,
         kSPKIHash_GoogleG2,
         kSPKIHash_EquifaxSecureCA,
         kSPKIHash_GeoTrustGlobal,
         NULL,
 };
 }}}

 None of these digests match what we have in flashproxy-reg-appspot:
 {{{
 # SHA-1 digest of expected public keys. Any of these is valid. See
 # http://www.imperialviolet.org/2011/05/04/pinning.html for the reason
 behind
 # hashing the public key, not the entire certificate.
 PUBKEY_SHA1 = tuple(x.decode("hex") for x in (
     "c70ccd442ff4528c603aefef85206fd693990e09",
     "1697e17a8a3317f031721b7b6293cd50643bbbd3",
     "291e750bafedac444486327e50f26f64d840991a",
     "1e3f66cfa0eb03136297fdb238ad6619c30ff375",
 ))
 }}}

 Our other programs using pins (flashproxy-reg-email and facilitator-email-
 poller) have been more stable historically but could benefit from whatever
 works for flashproxy-reg-appspot.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/9167>
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