Auth work to support new auth protocol

BUG=345759

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269445

Review URL: https://codereview.chromium.org/254083007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270007 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/api/cast_channel/cast_auth_util_nss.cc

@@ -15,40 +15,173 @@
 #include "chrome/browser/extensions/api/cast_channel/cast_message_util.h"
 #include "crypto/nss_util.h"
 #include "crypto/scoped_nss_types.h"
+#include "net/base/hash_value.h"
+#include "net/cert/x509_certificate.h"
 
 namespace {
 
-// Public key of the certificate with which the peer cert should be signed.
-static const unsigned char kCAPublicKeyDER[] = {
-    0x30, 0x82, 0x01, 0x0a, 0x02, 0x82, 0x01, 0x01, 0x00, 0xbc, 0x22, 0x80,
-    0xbd, 0x80, 0xf6, 0x3a, 0x21, 0x00, 0x3b, 0xae, 0x76, 0x5e, 0x35, 0x7f,
-    0x3d, 0xc3, 0x64, 0x5c, 0x55, 0x94, 0x86, 0x34, 0x2f, 0x05, 0x87, 0x28,
-    0xcd, 0xf7, 0x69, 0x8c, 0x17, 0xb3, 0x50, 0xa7, 0xb8, 0x82, 0xfa, 0xdf,
-    0xc7, 0x43, 0x2d, 0xd6, 0x7e, 0xab, 0xa0, 0x6f, 0xb7, 0x13, 0x72, 0x80,
-    0xa4, 0x47, 0x15, 0xc1, 0x20, 0x99, 0x50, 0xcd, 0xec, 0x14, 0x62, 0x09,
-    0x5b, 0xa4, 0x98, 0xcd, 0xd2, 0x41, 0xb6, 0x36, 0x4e, 0xff, 0xe8, 0x2e,
-    0x32, 0x30, 0x4a, 0x81, 0xa8, 0x42, 0xa3, 0x6c, 0x9b, 0x33, 0x6e, 0xca,
-    0xb2, 0xf5, 0x53, 0x66, 0xe0, 0x27, 0x53, 0x86, 0x1a, 0x85, 0x1e, 0xa7,
-    0x39, 0x3f, 0x4a, 0x77, 0x8e, 0xfb, 0x54, 0x66, 0x66, 0xfb, 0x58, 0x54,
-    0xc0, 0x5e, 0x39, 0xc7, 0xf5, 0x50, 0x06, 0x0b, 0xe0, 0x8a, 0xd4, 0xce,
-    0xe1, 0x6a, 0x55, 0x1f, 0x8b, 0x17, 0x00, 0xe6, 0x69, 0xa3, 0x27, 0xe6,
-    0x08, 0x25, 0x69, 0x3c, 0x12, 0x9d, 0x8d, 0x05, 0x2c, 0xd6, 0x2e, 0xa2,
-    0x31, 0xde, 0xb4, 0x52, 0x50, 0xd6, 0x20, 0x49, 0xde, 0x71, 0xa0, 0xf9,
-    0xad, 0x20, 0x40, 0x12, 0xf1, 0xdd, 0x25, 0xeb, 0xd5, 0xe6, 0xb8, 0x36,
-    0xf4, 0xd6, 0x8f, 0x7f, 0xca, 0x43, 0xdc, 0xd7, 0x10, 0x5b, 0xe6, 0x3f,
-    0x51, 0x8a, 0x85, 0xb3, 0xf3, 0xff, 0xf6, 0x03, 0x2d, 0xcb, 0x23, 0x4f,
-    0x9c, 0xad, 0x18, 0xe7, 0x93, 0x05, 0x8c, 0xac, 0x52, 0x9a, 0xf7, 0x4c,
-    0xe9, 0x99, 0x7a, 0xbe, 0x6e, 0x7e, 0x4d, 0x0a, 0xe3, 0xc6, 0x1c, 0xa9,
-    0x93, 0xfa, 0x3a, 0xa5, 0x91, 0x5d, 0x1c, 0xbd, 0x66, 0xeb, 0xcc, 0x60,
-    0xdc, 0x86, 0x74, 0xca, 0xcf, 0xf8, 0x92, 0x1c, 0x98, 0x7d, 0x57, 0xfa,
-    0x61, 0x47, 0x9e, 0xab, 0x80, 0xb7, 0xe4, 0x48, 0x80, 0x2a, 0x92, 0xc5,
-    0x1b, 0x02, 0x03, 0x01, 0x00, 0x01 };
+// Fingerprints and public keys of the allowed / trusted ICAs.
+static const net::SHA1HashValue kFingerprintICA1 = { {
+    0x57,0x16,0xE2,0xAD,0x73,0x2E,0xBE,0xDA,0xEB,0x18,
+    0xE8,0x47,0x15,0xA8,0xDE,0x90,0x3B,0x5E,0x2A,0xF4
+} };
+static const unsigned char kPublicKeyICA1[] = {
+    0x30,0x82,0x01,0x0A,0x02,0x82,0x01,0x01,0x00,0xBC,0x22,0x80,
+    0xBD,0x80,0xF6,0x3A,0x21,0x00,0x3B,0xAE,0x76,0x5E,0x35,0x7F,
+    0x3D,0xC3,0x64,0x5C,0x55,0x94,0x86,0x34,0x2F,0x05,0x87,0x28,
+    0xCD,0xF7,0x69,0x8C,0x17,0xB3,0x50,0xA7,0xB8,0x82,0xFA,0xDF,
+    0xC7,0x43,0x2D,0xD6,0x7E,0xAB,0xA0,0x6F,0xB7,0x13,0x72,0x80,
+    0xA4,0x47,0x15,0xC1,0x20,0x99,0x50,0xCD,0xEC,0x14,0x62,0x09,
+    0x5B,0xA4,0x98,0xCD,0xD2,0x41,0xB6,0x36,0x4E,0xFF,0xE8,0x2E,
+    0x32,0x30,0x4A,0x81,0xA8,0x42,0xA3,0x6C,0x9B,0x33,0x6E,0xCA,
+    0xB2,0xF5,0x53,0x66,0xE0,0x27,0x53,0x86,0x1A,0x85,0x1E,0xA7,
+    0x39,0x3F,0x4A,0x77,0x8E,0xFB,0x54,0x66,0x66,0xFB,0x58,0x54,
+    0xC0,0x5E,0x39,0xC7,0xF5,0x50,0x06,0x0B,0xE0,0x8A,0xD4,0xCE,
+    0xE1,0x6A,0x55,0x1F,0x8B,0x17,0x00,0xE6,0x69,0xA3,0x27,0xE6,
+    0x08,0x25,0x69,0x3C,0x12,0x9D,0x8D,0x05,0x2C,0xD6,0x2E,0xA2,
+    0x31,0xDE,0xB4,0x52,0x50,0xD6,0x20,0x49,0xDE,0x71,0xA0,0xF9,
+    0xAD,0x20,0x40,0x12,0xF1,0xDD,0x25,0xEB,0xD5,0xE6,0xB8,0x36,
+    0xF4,0xD6,0x8F,0x7F,0xCA,0x43,0xDC,0xD7,0x10,0x5B,0xE6,0x3F,
+    0x51,0x8A,0x85,0xB3,0xF3,0xFF,0xF6,0x03,0x2D,0xCB,0x23,0x4F,
+    0x9C,0xAD,0x18,0xE7,0x93,0x05,0x8C,0xAC,0x52,0x9A,0xF7,0x4C,
+    0xE9,0x99,0x7A,0xBE,0x6E,0x7E,0x4D,0x0A,0xE3,0xC6,0x1C,0xA9,
+    0x93,0xFA,0x3A,0xA5,0x91,0x5D,0x1C,0xBD,0x66,0xEB,0xCC,0x60,
+    0xDC,0x86,0x74,0xCA,0xCF,0xF8,0x92,0x1C,0x98,0x7D,0x57,0xFA,
+    0x61,0x47,0x9E,0xAB,0x80,0xB7,0xE4,0x48,0x80,0x2A,0x92,0xC5,
+    0x1B,0x02,0x03,0x01,0x00,0x01
+};
+
+static const net::SHA1HashValue kFingerprintICA2 = { {
+    0x1B,0xA2,0x9E,0xC9,0x8E,0x4E,0xB3,0x80,0xEE,0x55,
+    0xB2,0x97,0xFD,0x2E,0x2B,0x2C,0xB6,0x8E,0x0B,0x2F
+} };
+static const unsigned char kPublicKeyICA2[] = {
+    0x30,0x82,0x01,0x0A,0x02,0x82,0x01,0x01,0x00,0xBC,0x22,0x80,
+    0xBD,0x80,0xF6,0x3A,0x21,0x00,0x3B,0xAE,0x76,0x5E,0x35,0x7F,
+    0x3D,0xC3,0x64,0x5C,0x55,0x94,0x86,0x34,0x2F,0x05,0x87,0x28,
+    0xCD,0xF7,0x69,0x8C,0x17,0xB3,0x50,0xA7,0xB8,0x82,0xFA,0xDF,
+    0xC7,0x43,0x2D,0xD6,0x7E,0xAB,0xA0,0x6F,0xB7,0x13,0x72,0x80,
+    0xA4,0x47,0x15,0xC1,0x20,0x99,0x50,0xCD,0xEC,0x14,0x62,0x09,
+    0x5B,0xA4,0x98,0xCD,0xD2,0x41,0xB6,0x36,0x4E,0xFF,0xE8,0x2E,
+    0x32,0x30,0x4A,0x81,0xA8,0x42,0xA3,0x6C,0x9B,0x33,0x6E,0xCA,
+    0xB2,0xF5,0x53,0x66,0xE0,0x27,0x53,0x86,0x1A,0x85,0x1E,0xA7,
+    0x39,0x3F,0x4A,0x77,0x8E,0xFB,0x54,0x66,0x66,0xFB,0x58,0x54,
+    0xC0,0x5E,0x39,0xC7,0xF5,0x50,0x06,0x0B,0xE0,0x8A,0xD4,0xCE,
+    0xE1,0x6A,0x55,0x1F,0x8B,0x17,0x00,0xE6,0x69,0xA3,0x27,0xE6,
+    0x08,0x25,0x69,0x3C,0x12,0x9D,0x8D,0x05,0x2C,0xD6,0x2E,0xA2,
+    0x31,0xDE,0xB4,0x52,0x50,0xD6,0x20,0x49,0xDE,0x71,0xA0,0xF9,
+    0xAD,0x20,0x40,0x12,0xF1,0xDD,0x25,0xEB,0xD5,0xE6,0xB8,0x36,
+    0xF4,0xD6,0x8F,0x7F,0xCA,0x43,0xDC,0xD7,0x10,0x5B,0xE6,0x3F,
+    0x51,0x8A,0x85,0xB3,0xF3,0xFF,0xF6,0x03,0x2D,0xCB,0x23,0x4F,
+    0x9C,0xAD,0x18,0xE7,0x93,0x05,0x8C,0xAC,0x52,0x9A,0xF7,0x4C,
+    0xE9,0x99,0x7A,0xBE,0x6E,0x7E,0x4D,0x0A,0xE3,0xC6,0x1C,0xA9,
+    0x93,0xFA,0x3A,0xA5,0x91,0x5D,0x1C,0xBD,0x66,0xEB,0xCC,0x60,
+    0xDC,0x86,0x74,0xCA,0xCF,0xF8,0x92,0x1C,0x98,0x7D,0x57,0xFA,
+    0x61,0x47,0x9E,0xAB,0x80,0xB7,0xE4,0x48,0x80,0x2A,0x92,0xC5,
+    0x1B,0x02,0x03,0x01,0x00,0x01
+};
+
+static const net::SHA1HashValue kFingerprintICA3 = { {
+    0x97,0x05,0xCE,0xF6,0x3F,0xA9,0x5E,0x0F,0xE7,0x61,
+    0xFB,0x08,0x44,0x31,0xBE,0xDE,0x01,0xB8,0xFB,0xEB
+} };
+static const unsigned char kPublicKeyICA3[] = {
+    0x30,0x82,0x01,0x0A,0x02,0x82,0x01,0x01,0x00,0xB7,0xE8,0xC3,
+    0xE4,0x2C,0xDE,0x74,0x53,0xF2,0x49,0x95,0x6D,0xD1,0xDA,0x69,
+    0x57,0x0D,0x86,0xE5,0xED,0xB4,0xB9,0xE6,0x73,0x9F,0x6C,0xAD,
+    0x3B,0x64,0x85,0x03,0x0D,0x08,0x44,0xAF,0x18,0x69,0x82,0xAD,
+    0xA9,0x74,0x64,0x37,0x47,0xE1,0xE7,0x26,0x19,0x33,0x3C,0xE2,
+    0xD0,0xB5,0x84,0x3C,0xD7,0xAC,0x63,0xAE,0xC4,0x32,0x23,0xF6,
+    0xDC,0x14,0x10,0x4B,0x95,0x7F,0xE8,0x98,0xD7,0x7A,0x9E,0x43,
+    0x3D,0x68,0x8B,0x2A,0x70,0xF7,0x1E,0x43,0x70,0xBA,0xA5,0xA5,
+    0x93,0xAD,0x8A,0xD4,0x9F,0xAC,0x83,0x16,0xF3,0x48,0x5F,0xC5,
+    0xE0,0xA5,0x44,0xB8,0x4F,0xD9,0xD8,0x75,0x90,0x25,0x8B,0xE3,
+    0x1C,0x6C,0xDA,0x88,0xFF,0x09,0x2B,0xCA,0x1E,0x48,0xDD,0x76,
+    0x0F,0x68,0x56,0x7B,0x15,0x9D,0xCA,0x6B,0x1C,0xF7,0x48,0xC2,
+    0x89,0xC6,0x93,0x0A,0x31,0xF2,0x78,0x27,0x45,0x3D,0xF1,0x0D,
+    0x5B,0x6E,0x55,0x32,0xEF,0x49,0xA0,0xD6,0xAF,0xA6,0x30,0x91,
+    0xF2,0x21,0x2F,0xDB,0xA4,0x29,0xB9,0x9B,0x22,0xBC,0xCD,0x0B,
+    0xA6,0x8B,0xA6,0x22,0x79,0xFD,0xCF,0x95,0x93,0x96,0xB3,0x23,
+    0xC9,0xC6,0x30,0x8E,0xC0,0xE9,0x1F,0xEC,0xFB,0xF5,0x88,0xDD,
+    0x97,0x72,0x16,0x29,0x08,0xFA,0x42,0xE7,0x4F,0xCA,0xAE,0xD7,
+    0x0F,0x23,0x48,0x9B,0x82,0xA7,0x37,0x4A,0xDD,0x60,0x04,0x75,
+    0xDC,0xDE,0x09,0x98,0xD2,0x16,0x23,0x04,0x70,0x4D,0x99,0x9F,
+    0x4A,0x82,0x28,0xE6,0xBE,0x8F,0x9D,0xBF,0xA1,0x4B,0xA2,0xBA,
+    0xF5,0xB2,0x51,0x1E,0x4E,0xE7,0x80,0x9E,0x7A,0x38,0xA1,0xC7,
+    0x09,0x02,0x03,0x01,0x00,0x01
+};
+
+static const net::SHA1HashValue kFingerprintICA4 = { {
+    0x01,0xF5,0x28,0x56,0x33,0x80,0x9B,0x31,0xE7,0xD9,
+    0xF7,0x4E,0xAA,0xDD,0x97,0x37,0xA0,0x28,0xE7,0x24
+} };
+static const unsigned char kPublicKeyICA4[] = {
+    0x30,0x82,0x01,0x0A,0x02,0x82,0x01,0x01,0x00,0xB0,0x0E,0x5E,
+    0x07,0x3A,0xDF,0xA4,0x5F,0x68,0xF7,0x21,0xC7,0x64,0xDB,0xB6,
+    0x76,0xEF,0xEE,0x8B,0x93,0xF8,0xF6,0x1B,0x88,0xE1,0x93,0xB7,
+    0x17,0xF0,0x15,0x1E,0x7E,0x52,0x55,0x77,0x3C,0x02,0x8D,0x7B,
+    0x4A,0x6C,0xD3,0xBD,0xD6,0xC1,0x9C,0x72,0xC8,0xB3,0x15,0xCF,
+    0x11,0xC1,0xF5,0x46,0xC4,0xD5,0x20,0x47,0xFB,0x30,0xF4,0xE4,
+    0x61,0x0C,0x68,0xF0,0x5E,0xAB,0x37,0x8E,0x9B,0xE1,0xBC,0x81,
+    0xC3,0x70,0x8A,0x78,0xD6,0x83,0x34,0x32,0x9C,0x19,0x62,0xEB,
+    0xE4,0x9C,0xED,0xE3,0x64,0x6C,0x41,0x1D,0x9C,0xD2,0x8B,0x48,
+    0x4C,0x23,0x90,0x95,0xB3,0xE7,0x52,0xEA,0x05,0x57,0xCC,0x60,
+    0xB3,0xBA,0x14,0xE4,0xBA,0x00,0x39,0xE4,0x46,0x55,0x74,0xCE,
+    0x5A,0x8E,0x7A,0x67,0x23,0xDA,0x68,0x0A,0xFA,0xC4,0x84,0x1E,
+    0xB4,0xC5,0xA1,0xA2,0x6A,0x73,0x1F,0x6E,0xC8,0x2E,0x2F,0x9A,
+    0x9E,0xA8,0xB1,0x0E,0xFD,0x87,0xA6,0x8F,0x4D,0x3D,0x4B,0x05,
+    0xD5,0x35,0x5A,0x74,0x4D,0xBC,0x8E,0x82,0x44,0x96,0xF4,0xB5,
+    0x95,0x60,0x4E,0xA5,0xDF,0x27,0x3D,0x41,0x5C,0x07,0xA3,0xB4,
+    0x35,0x5A,0xB3,0x9E,0xF2,0x05,0x24,0xCA,0xCD,0x31,0x5A,0x0D,
+    0x26,0x4C,0xD4,0xD3,0xFD,0x50,0xE1,0x34,0xE9,0x4C,0x81,0x58,
+    0x30,0xB2,0xC7,0x7A,0xDD,0x81,0x89,0xA6,0xD4,0x3A,0x38,0x84,
+    0x03,0xB7,0x34,0x9E,0x77,0x3F,0xFF,0x78,0x07,0x5B,0x99,0xC1,
+    0xB2,0x1F,0x35,0x56,0x6E,0x3A,0x3C,0x0C,0x25,0xE1,0x57,0xF6,
+    0x8A,0x7E,0x49,0xC0,0xCC,0x83,0x11,0x35,0xE7,0x91,0x6D,0x2E,
+    0x65,0x02,0x03,0x01,0x00,0x01
+};
+
+// Info for trusted ICA certs.
+struct ICACertInfo {
+  net::SHA1HashValue fingerprint;
+  SECItem public_key;
+};
+
+// List of allowed / trusted ICAs.
+static const ICACertInfo kAllowedICAs[] = {
+  { kFingerprintICA1,
+    { siDERCertBuffer,
+      const_cast<unsigned char*>(kPublicKeyICA1),
+      sizeof(kPublicKeyICA1) } },
+  { kFingerprintICA2,
+    { siDERCertBuffer,
+      const_cast<unsigned char*>(kPublicKeyICA2),
+      sizeof(kPublicKeyICA2) } },
+  { kFingerprintICA3,
+    { siDERCertBuffer,
+      const_cast<unsigned char*>(kPublicKeyICA3),
+      sizeof(kPublicKeyICA3) } },
+  { kFingerprintICA4,
+    { siDERCertBuffer,
+      const_cast<unsigned char*>(kPublicKeyICA4),
+      sizeof(kPublicKeyICA4) } },
+};
 
 typedef scoped_ptr<
     CERTCertificate,
     crypto::NSSDestroyer<CERTCertificate, CERT_DestroyCertificate> >
         ScopedCERTCertificate;
 
+// Returns the index of the ICA whose fingerprint matches |fingerprint|.
+// Returns -1, if no such ICA is found.
+static int GetICAWithFingerprint(const net::SHA1HashValue& fingerprint) {
+  for (size_t i = 0; i < arraysize(kAllowedICAs); ++i) {
+    if (fingerprint.Equals(kAllowedICAs[i].fingerprint))
+      return static_cast<int>(i);
+  }
+  return -1;
+}
+
 // Parses out DeviceAuthMessage from CastMessage
 static bool ParseAuthMessage(
     const extensions::api::cast_channel::CastMessage& challenge_reply,
@@ -81,9 +214,34 @@ static bool ParseAuthMessage(
 // Authenticates the given credentials:
 // 1. |signature| verification of |data| using |certificate|.
 // 2. |certificate| is signed by a trusted CA.
-bool VerifyCredentials(const std::string& certificate,
-                       const std::string& signature,
+bool VerifyCredentials(
+    const extensions::api::cast_channel::AuthResponse& response,
     const std::string& data) {
+  const std::string& certificate = response.client_auth_certificate();
+  const std::string& signature = response.signature();
+
+  const SECItem* trusted_ca_key_der;
+
+  // If the list of intermediates is empty then use kPublicKeyICA1 as
+  // the trusted CA (legacy case).
+  // Otherwise, use the first intermediate in the list as long as it
+  // is in the allowed list of intermediates.
+  int num_intermediates = response.intermediate_certificate_size();
+  VLOG(1) << "Response has " << num_intermediates << " intermediates";
+  if (num_intermediates <= 0) {
+    trusted_ca_key_der = &kAllowedICAs[0].public_key;
+  } else {
+    const std::string& ica = response.intermediate_certificate(0);
+    scoped_refptr<net::X509Certificate> ica_cert
+        = net::X509Certificate::CreateFromBytes(ica.data(), ica.length());
+    int index = GetICAWithFingerprint(ica_cert->fingerprint());
+    if (index == -1) {
+      VLOG(1) << "Disallowed intermdiate cert";
+      return false;
+    }
+    trusted_ca_key_der = &kAllowedICAs[index].public_key;
+  }
+
   crypto::EnsureNSSInit();
   SECItem der_cert;
   der_cert.type = siDERCertBuffer;
@@ -101,18 +259,19 @@ bool VerifyCredentials(const std::string& certificate,
   }
 
   // Check that the certificate is signed by trusted CA.
-  SECItem trusted_ca_key_der_item;
-  trusted_ca_key_der_item.type = siDERCertBuffer;
-  trusted_ca_key_der_item.data = const_cast<unsigned char*>(kCAPublicKeyDER);
-  trusted_ca_key_der_item.len = sizeof(kCAPublicKeyDER);
+  // NOTE: We const_cast trusted_ca_key_der since on some platforms
+  // SECKEY_ImportDERPublicKey API takes in SECItem* and not const
+  // SECItem*.
   crypto::ScopedSECKEYPublicKey ca_public_key(
-      SECKEY_ImportDERPublicKey(&trusted_ca_key_der_item, CKK_RSA));
+      SECKEY_ImportDERPublicKey(
+          const_cast<SECItem*>(trusted_ca_key_der), CKK_RSA));
   SECStatus verified = CERT_VerifySignedDataWithPublicKey(
       &cert->signatureWrap, ca_public_key.get(), NULL);
   if (verified != SECSuccess) {
     VLOG(1)<< "Cert not signed by trusted CA";
     return false;
   }
+  VLOG(1) << "Cert signed by trusted CA";
 
   // Verify that the |signature| matches |data|.
   crypto::ScopedSECKEYPublicKey public_key(CERT_ExtractPublicKey(cert.get()));
@@ -137,6 +296,7 @@ bool VerifyCredentials(const std::string& certificate,
     VLOG(1) << "Signed blobs did not match.";
     return false;
   }
+  VLOG(1) << "Signature verification succeeded";
   return true;
 }
 
@@ -157,9 +317,7 @@ bool AuthenticateChallengeReply(const CastMessage& challenge_reply,
     return false;
 
   const AuthResponse& response = auth_message.response();
-  return VerifyCredentials(response.client_auth_certificate(),
-                           response.signature(),
-                           peer_cert);
+  return VerifyCredentials(response, peer_cert);
 }
 
 }  // namespace cast_channel

chrome/browser/extensions/api/cast_channel/cast_channel.proto

@@ -53,19 +53,31 @@ message CastMessage {
   optional bytes payload_binary = 7;
 }
 
+enum SignatureAlgorithm {
+  UNSPECIFIED = 0;
+  RSASSA_PKCS1v15 = 1;
+  RSASSA_PSS = 2;
+}
+
 // Messages for authentication protocol between a sender and a receiver.
 message AuthChallenge {
+  optional SignatureAlgorithm signature_algorithm = 1
+      [default = RSASSA_PKCS1v15];
 }
 
 message AuthResponse {
   required bytes signature = 1;
   required bytes client_auth_certificate = 2;
+  repeated bytes intermediate_certificate = 3;
+  optional SignatureAlgorithm signature_algorithm = 4
+      [default = RSASSA_PKCS1v15];
 }
 
 message AuthError {
   enum ErrorType {
     INTERNAL_ERROR = 0;
     NO_TLS = 1;  // The underlying connection is not TLS
+    SIGNATURE_ALGORITHM_UNAVAILABLE = 2;
   }
   required ErrorType error_type = 1;
 }