third_party/tlslite/patches/fallback_scsv.patch

   1 diff --git a/third_party/tlslite/tlslite/constants.py b/third_party/tlslite/tlslite/constants.py
   2 index 8720de6..69e6067 100644
   3 --- a/third_party/tlslite/tlslite/constants.py
   4 +++ b/third_party/tlslite/tlslite/constants.py
   5 @@ -107,6 +107,7 @@ class AlertDescription:
   6      protocol_version = 70
   7      insufficient_security = 71
   8      internal_error = 80
   9 +    inappropriate_fallback = 86
  10      user_canceled = 90
  11      no_renegotiation = 100
  12      unknown_psk_identity = 115
  13 @@ -118,6 +119,9 @@ class CipherSuite:
  14      # We actually don't do any renegotiation, but this
  15      # prevents renegotiation attacks
  16      TLS_EMPTY_RENEGOTIATION_INFO_SCSV = 0x00FF
  17 +
  18 +    # draft-ietf-tls-downgrade-scsv-03
  19 +    TLS_FALLBACK_SCSV = 0x5600
  20
  21      TLS_SRP_SHA_WITH_3DES_EDE_CBC_SHA  = 0xC01A
  22      TLS_SRP_SHA_WITH_AES_128_CBC_SHA = 0xC01D
  23 diff --git a/third_party/tlslite/tlslite/errors.py b/third_party/tlslite/tlslite/errors.py
  24 index 22c298c..001ef33 100644
  25 --- a/third_party/tlslite/tlslite/errors.py
  26 +++ b/third_party/tlslite/tlslite/errors.py
  27 @@ -63,6 +63,7 @@ class TLSAlert(TLSError):
  28          AlertDescription.protocol_version: "protocol_version",\
  29          AlertDescription.insufficient_security: "insufficient_security",\
  30          AlertDescription.internal_error: "internal_error",\
  31 +        AlertDescription.inappropriate_fallback: "inappropriate_fallback",\
  32          AlertDescription.user_canceled: "user_canceled",\
  33          AlertDescription.no_renegotiation: "no_renegotiation",\
  34          AlertDescription.unknown_psk_identity: "unknown_psk_identity"}
  35 diff --git a/third_party/tlslite/tlslite/tlsconnection.py b/third_party/tlslite/tlslite/tlsconnection.py
  36 index 4dedc5f..0563fb5f 100644
  37 --- a/third_party/tlslite/tlslite/tlsconnection.py
  38 +++ b/third_party/tlslite/tlslite/tlsconnection.py
  39 @@ -969,7 +969,8 @@ class TLSConnection(TLSRecordLayer):
  40                          reqCAs = None,
  41                          tacks=None, activationFlags=0,
  42                          nextProtos=None, anon=False,
  43 -                        tlsIntolerant=None, signedCertTimestamps=None):
  44 +                        tlsIntolerant=None, signedCertTimestamps=None,
  45 +                        fallbackSCSV=False):
  46          """Perform a handshake in the role of server.
  47
  48          This function performs an SSL or TLS handshake.  Depending on
  49 @@ -1048,6 +1049,11 @@ class TLSConnection(TLSRecordLayer):
  50          binary 8-bit string) that will be sent as a TLS extension whenever
  51          the client announces support for the extension.
  52
  53 +        @type fallbackSCSV: bool
  54 +        @param fallbackSCSV: if true, the server will implement
  55 +        TLS_FALLBACK_SCSV and thus reject connections using less than the
  56 +        server's maximum TLS version that include this cipher suite.
  57 +
  58          @raise socket.error: If a socket error occurs.
  59          @raise tlslite.errors.TLSAbruptCloseError: If the socket is closed
  60          without a preceding alert.
  61 @@ -1060,7 +1066,8 @@ class TLSConnection(TLSRecordLayer):
  62                  checker, reqCAs,
  63                  tacks=tacks, activationFlags=activationFlags,
  64                  nextProtos=nextProtos, anon=anon, tlsIntolerant=tlsIntolerant,
  65 -                signedCertTimestamps=signedCertTimestamps):
  66 +                signedCertTimestamps=signedCertTimestamps,
  67 +                fallbackSCSV=fallbackSCSV):
  68              pass
  69
  70
  71 @@ -1071,7 +1078,8 @@ class TLSConnection(TLSRecordLayer):
  72                               tacks=None, activationFlags=0,
  73                               nextProtos=None, anon=False,
  74                               tlsIntolerant=None,
  75 -                             signedCertTimestamps=None
  76 +                             signedCertTimestamps=None,
  77 +                             fallbackSCSV=False
  78                               ):
  79          """Start a server handshake operation on the TLS connection.
  80
  81 @@ -1092,7 +1100,8 @@ class TLSConnection(TLSRecordLayer):
  82              tacks=tacks, activationFlags=activationFlags,
  83              nextProtos=nextProtos, anon=anon,
  84              tlsIntolerant=tlsIntolerant,
  85 -            signedCertTimestamps=signedCertTimestamps)
  86 +            signedCertTimestamps=signedCertTimestamps,
  87 +            fallbackSCSV=fallbackSCSV)
  88          for result in self._handshakeWrapperAsync(handshaker, checker):
  89              yield result
  90
  91 @@ -1102,7 +1111,7 @@ class TLSConnection(TLSRecordLayer):
  92                               settings, reqCAs,
  93                               tacks, activationFlags,
  94                               nextProtos, anon,
  95 -                             tlsIntolerant, signedCertTimestamps):
  96 +                             tlsIntolerant, signedCertTimestamps, fallbackSCSV):
  97
  98          self._handshakeStart(client=False)
  99
 100 @@ -1137,7 +1146,7 @@ class TLSConnection(TLSRecordLayer):
 101          # Handle ClientHello and resumption
 102          for result in self._serverGetClientHello(settings, certChain,\
 103                                              verifierDB, sessionCache,
 104 -                                            anon, tlsIntolerant):
 105 +                                            anon, tlsIntolerant, fallbackSCSV):
 106              if result in (0,1): yield result
 107              elif result == None:
 108                  self._handshakeDone(resumed=True)
 109 @@ -1237,7 +1246,7 @@ class TLSConnection(TLSRecordLayer):
 110
 111
 112      def _serverGetClientHello(self, settings, certChain, verifierDB,
 113 -                                sessionCache, anon, tlsIntolerant):
 114 +                                sessionCache, anon, tlsIntolerant, fallbackSCSV):
 115          #Initialize acceptable cipher suites
 116          cipherSuites = []
 117          if verifierDB:
 118 @@ -1283,6 +1292,14 @@ class TLSConnection(TLSRecordLayer):
 119          elif clientHello.client_version > settings.maxVersion:
 120              self.version = settings.maxVersion
 121
 122 +        #Detect if the client performed an inappropriate fallback.
 123 +        elif fallbackSCSV and clientHello.client_version < settings.maxVersion:
 124 +            self.version = clientHello.client_version
 125 +            if CipherSuite.TLS_FALLBACK_SCSV in clientHello.cipher_suites:
 126 +                for result in self._sendError(\
 127 +                        AlertDescription.inappropriate_fallback):
 128 +                    yield result
 129 +
 130          else:
 131              #Set the version to the client's version
 132              self.version = clientHello.client_version