dom/webauthn/WebAuthnCBORUtil.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "cbor-cpp/src/cbor.h"
   8 #include "mozilla/dom/WebAuthnCBORUtil.h"
   9 #include "mozilla/dom/WebAuthnUtil.h"
  10
  11 namespace mozilla::dom {
  12
  13 nsresult CBOREncodePublicKeyObj(const CryptoBuffer& aPubKeyBuf,
  14                                 /* out */ CryptoBuffer& aPubKeyObj) {
  15   mozilla::dom::CryptoBuffer xBuf, yBuf;
  16   nsresult rv = U2FDecomposeECKey(aPubKeyBuf, xBuf, yBuf);
  17   if (NS_FAILED(rv)) {
  18     return rv;
  19   }
  20
  21   // COSE_Key object. See https://tools.ietf.org/html/rfc8152#section-7
  22   cbor::output_dynamic cborPubKeyOut;
  23   cbor::encoder encoder(cborPubKeyOut);
  24   encoder.write_map(5);
  25   {
  26     encoder.write_int(1);   // kty
  27     encoder.write_int(2);   // EC2
  28     encoder.write_int(3);   // alg
  29     encoder.write_int(-7);  // ES256
  30
  31     // See https://tools.ietf.org/html/rfc8152#section-13.1
  32     encoder.write_int(-1);  // crv
  33     encoder.write_int(1);   // P-256
  34     encoder.write_int(-2);  // x
  35     encoder.write_bytes(xBuf.Elements(), xBuf.Length());
  36     encoder.write_int(-3);  // y
  37     encoder.write_bytes(yBuf.Elements(), yBuf.Length());
  38   }
  39
  40   if (!aPubKeyObj.Assign(cborPubKeyOut.data(), cborPubKeyOut.size())) {
  41     return NS_ERROR_OUT_OF_MEMORY;
  42   }
  43   return NS_OK;
  44 }
  45
  46 nsresult CBOREncodeFidoU2FAttestationObj(
  47     const CryptoBuffer& aAuthDataBuf, const CryptoBuffer& aAttestationCertBuf,
  48     const CryptoBuffer& aSignatureBuf,
  49     /* out */ CryptoBuffer& aAttestationObj) {
  50   /*
  51   Attestation Object, encoded in CBOR (description is CDDL)
  52
  53   attObj = {
  54               authData: bytes,
  55               $$attStmtType
  56            }
  57   $$attStmtType //= (
  58                         fmt: "fido-u2f",
  59                         attStmt: u2fStmtFormat
  60                     )
  61   u2fStmtFormat = {
  62                       x5c: [ attestnCert: bytes, * (caCert: bytes) ],
  63                       sig: bytes
  64                   }
  65   */
  66   cbor::output_dynamic cborAttOut;
  67   cbor::encoder encoder(cborAttOut);
  68   encoder.write_map(3);
  69   {
  70     encoder.write_string("fmt");
  71     encoder.write_string("fido-u2f");
  72
  73     encoder.write_string("attStmt");
  74     encoder.write_map(2);
  75     {
  76       encoder.write_string("sig");
  77       encoder.write_bytes(aSignatureBuf.Elements(), aSignatureBuf.Length());
  78
  79       encoder.write_string("x5c");
  80       // U2F wire protocol can only deliver 1 certificate, so it's never a chain
  81       encoder.write_array(1);
  82       encoder.write_bytes(aAttestationCertBuf.Elements(),
  83                           aAttestationCertBuf.Length());
  84     }
  85
  86     encoder.write_string("authData");
  87     encoder.write_bytes(aAuthDataBuf.Elements(), aAuthDataBuf.Length());
  88   }
  89
  90   if (!aAttestationObj.Assign(cborAttOut.data(), cborAttOut.size())) {
  91     return NS_ERROR_OUT_OF_MEMORY;
  92   }
  93   return NS_OK;
  94 }
  95
  96 nsresult CBOREncodeNoneAttestationObj(const CryptoBuffer& aAuthDataBuf,
  97                                       /* out */ CryptoBuffer& aAttestationObj) {
  98   /*
  99   Attestation Object, encoded in CBOR (description is CDDL)
 100
 101   $$attStmtType //= (
 102                           fmt: "none",
 103                           attStmt: emptyMap
 104                       )
 105
 106   emptyMap = {}
 107   */
 108   cbor::output_dynamic cborAttOut;
 109   cbor::encoder encoder(cborAttOut);
 110   encoder.write_map(3);
 111   {
 112     encoder.write_string("fmt");
 113     encoder.write_string("none");
 114
 115     encoder.write_string("attStmt");
 116     encoder.write_map(0);
 117
 118     encoder.write_string("authData");
 119     encoder.write_bytes(aAuthDataBuf.Elements(), aAuthDataBuf.Length());
 120   }
 121
 122   if (!aAttestationObj.Assign(cborAttOut.data(), cborAttOut.size())) {
 123     return NS_ERROR_OUT_OF_MEMORY;
 124   }
 125   return NS_OK;
 126 }
 127
 128 }  // namespace mozilla::dom