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-rw-r--r--crypto/p224_spake.cc40
-rw-r--r--crypto/p224_spake.h26
-rw-r--r--crypto/p224_spake_unittest.cc29
3 files changed, 34 insertions, 61 deletions
diff --git a/crypto/p224_spake.cc b/crypto/p224_spake.cc
index 3d83e25..ec0c416 100644
--- a/crypto/p224_spake.cc
+++ b/crypto/p224_spake.cc
@@ -2,7 +2,7 @@
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
-// This code implements SPAKE2, a varient of EKE:
+// This code implements SPAKE2, a variant of EKE:
// http://www.di.ens.fr/~pointche/pub.php?reference=AbPo04
#include <crypto/p224_spake.h>
@@ -96,9 +96,7 @@ const crypto::p224::Point kN = {
namespace crypto {
P224EncryptedKeyExchange::P224EncryptedKeyExchange(
- PeerType peer_type,
- const base::StringPiece& password,
- const base::StringPiece& session)
+ PeerType peer_type, const base::StringPiece& password)
: state_(kStateInitial),
is_server_(peer_type == kPeerTypeServer) {
// x_ is a random scalar.
@@ -108,26 +106,9 @@ P224EncryptedKeyExchange::P224EncryptedKeyExchange(
p224::Point X;
p224::ScalarBaseMult(x_, &X);
- // The "password" in the SPAKE2 protocol is
- // SHA256(P(password) + P(session)) where P is function that prepends a
- // uint32, big-endian length prefix.
- uint8 password_length[4], session_length[4];
- password_length[0] = password.size() >> 24;
- password_length[1] = password.size() >> 16;
- password_length[2] = password.size() >> 8;
- password_length[3] = password.size();
- session_length[0] = session.size() >> 24;
- session_length[1] = session.size() >> 16;
- session_length[2] = session.size() >> 8;
- session_length[3] = session.size();
- SHA256HashString(std::string(reinterpret_cast<const char *>(password_length),
- sizeof(password_length)) +
- password.as_string() +
- std::string(reinterpret_cast<const char *>(session_length),
- sizeof(session_length)) +
- session.as_string(),
- pw_,
- sizeof(pw_));
+ // Calculate |password| hash to get SPAKE password value.
+ SHA256HashString(std::string(password.data(), password.length()),
+ pw_, sizeof(pw_));
// The client masks the Diffie-Hellman value, X, by adding M**pw and the
// server uses N**pw.
@@ -200,7 +181,7 @@ P224EncryptedKeyExchange::Result P224EncryptedKeyExchange::ProcessMessage(
p224::ScalarMult(Y, x_, &k);
// If everything worked out, then K is the same for both parties.
- std::string k_str = k.ToString();
+ key_ = k.ToString();
std::string client_masked_dh, server_masked_dh;
if (is_server_) {
@@ -214,9 +195,9 @@ P224EncryptedKeyExchange::Result P224EncryptedKeyExchange::ProcessMessage(
// Now we calculate the hashes that each side will use to prove to the other
// that they derived the correct value for K.
uint8 client_hash[kSHA256Length], server_hash[kSHA256Length];
- CalculateHash(kPeerTypeClient, client_masked_dh, server_masked_dh, k_str,
+ CalculateHash(kPeerTypeClient, client_masked_dh, server_masked_dh, key_,
client_hash);
- CalculateHash(kPeerTypeServer, client_masked_dh, server_masked_dh, k_str,
+ CalculateHash(kPeerTypeServer, client_masked_dh, server_masked_dh, key_,
server_hash);
const uint8* my_hash = is_server_ ? server_hash : client_hash;
@@ -256,4 +237,9 @@ const std::string& P224EncryptedKeyExchange::error() const {
return error_;
}
+const std::string& P224EncryptedKeyExchange::GetKey() {
+ DCHECK_EQ(state_, kStateDone);
+ return key_;
+}
+
} // namespace crypto
diff --git a/crypto/p224_spake.h b/crypto/p224_spake.h
index 0441efb..01507c9 100644
--- a/crypto/p224_spake.h
+++ b/crypto/p224_spake.h
@@ -12,12 +12,10 @@
namespace crypto {
-// P224EncryptedKeyExchange provides a means to authenticate an
-// encrypted transport using a low-entropy, shared secret.
-//
-// You need a value derived from the master secret of the connection in order
-// to bind the authentication to the encrypted channel. It's the |session|
-// argument to the constructor and can be of any length.
+// P224EncryptedKeyExchange implements SPAKE2, a variant of Encrypted
+// Key Exchange. It allows two parties that have a secret common
+// password to establish a common secure key by exchanging messages
+// over unsecure channel without disclosing the password.
//
// The password can be low entropy as authenticating with an attacker only
// gives the attacker a one-shot password oracle. No other information about
@@ -51,13 +49,11 @@ class CRYPTO_EXPORT P224EncryptedKeyExchange {
};
// peer_type: the type of the local authentication party.
- // password: a, possibly low-entropy, mutually known password.
- // session: a value securely derived from the connection's master secret.
- // Both parties to the authentication must pass the same value. For the
- // case of a TLS connection, see RFC 5705.
+ // password: secret session password. Both parties to the
+ // authentication must pass the same value. For the case of a
+ // TLS connection, see RFC 5705.
P224EncryptedKeyExchange(PeerType peer_type,
- const base::StringPiece& password,
- const base::StringPiece& session);
+ const base::StringPiece& password);
// GetMessage returns a byte string which must be passed to the other party
// in the authentication.
@@ -71,6 +67,10 @@ class CRYPTO_EXPORT P224EncryptedKeyExchange {
// return a human readable error message.
const std::string& error() const;
+ // The key established as result of the key exchange. Must be called
+ // at then end after ProcessMessage() returns kResultSuccess.
+ const std::string& GetKey();
+
private:
// The authentication state machine is very simple and each party proceeds
// through each of these states, in order.
@@ -106,6 +106,8 @@ class CRYPTO_EXPORT P224EncryptedKeyExchange {
// expected_authenticator_ is used to store the hash value expected from the
// other party.
uint8 expected_authenticator_[kSHA256Length];
+
+ std::string key_;
};
} // namespace crypto
diff --git a/crypto/p224_spake_unittest.cc b/crypto/p224_spake_unittest.cc
index e45ec82..bcd448c 100644
--- a/crypto/p224_spake_unittest.cc
+++ b/crypto/p224_spake_unittest.cc
@@ -43,37 +43,24 @@ bool RunExchange(P224EncryptedKeyExchange* client,
}
static const char kPassword[] = "foo";
-static const char kSession[] = "bar";
TEST(MutualAuth, CorrectAuth) {
P224EncryptedKeyExchange client(
- P224EncryptedKeyExchange::kPeerTypeClient,
- kPassword, kSession);
+ P224EncryptedKeyExchange::kPeerTypeClient, kPassword);
P224EncryptedKeyExchange server(
- P224EncryptedKeyExchange::kPeerTypeServer,
- kPassword, kSession);
+ P224EncryptedKeyExchange::kPeerTypeServer, kPassword);
EXPECT_TRUE(RunExchange(&client, &server));
+ EXPECT_EQ(client.GetKey(), server.GetKey());
}
TEST(MutualAuth, IncorrectPassword) {
P224EncryptedKeyExchange client(
P224EncryptedKeyExchange::kPeerTypeClient,
- kPassword, kSession);
- P224EncryptedKeyExchange server(
- P224EncryptedKeyExchange::kPeerTypeServer,
- "wrongpassword", kSession);
-
- EXPECT_FALSE(RunExchange(&client, &server));
-}
-
-TEST(MutualAuth, IncorrectSession) {
- P224EncryptedKeyExchange client(
- P224EncryptedKeyExchange::kPeerTypeClient,
- kPassword, kSession);
+ kPassword);
P224EncryptedKeyExchange server(
P224EncryptedKeyExchange::kPeerTypeServer,
- kPassword, "wrongsession");
+ "wrongpassword");
EXPECT_FALSE(RunExchange(&client, &server));
}
@@ -83,11 +70,9 @@ TEST(MutualAuth, Fuzz) {
for (unsigned i = 0; i < kIterations; i++) {
P224EncryptedKeyExchange client(
- P224EncryptedKeyExchange::kPeerTypeClient,
- kPassword, kSession);
+ P224EncryptedKeyExchange::kPeerTypeClient, kPassword);
P224EncryptedKeyExchange server(
- P224EncryptedKeyExchange::kPeerTypeServer,
- kPassword, kSession);
+ P224EncryptedKeyExchange::kPeerTypeServer, kPassword);
// We'll only be testing small values of i, but we don't want that to bias
// the test coverage. So we disperse the value of i by multiplying by the
generated by cgit v1.1 at 2024-12-23 14:52:21 +0000