Beispiel #1
0
        /// <summary>
        /// Illustrates various cases of automatic authorization handling.
        /// </summary>
        static void AutomaticAuth(Tpm2 tpm)
        {
            TpmHandle primHandle = CreateRsaPrimaryKey(tpm);

            TpmPublic keyPublic;
            TpmHandle keyHandle = CreateSigningDecryptionKey(tpm, primHandle, out keyPublic);

            byte[] message = Globs.GetRandomBytes(32);

            IAsymSchemeUnion decScheme = new SchemeOaep(TpmAlgId.Sha1);
            ISigSchemeUnion  sigScheme = new SchemeRsassa(TpmAlgId.Sha1);

            //
            // TSS.Net implicitly creates an auth session to authorize keyHandle.
            // It uses the auth value cached in the TpmHandle object.
            //
            byte[] encrypted = tpm.RsaEncrypt(keyHandle, message, decScheme, null);

            Console.WriteLine("Automatic authorization of a decryption key.");

            //
            // An auth session is added automatically when TPM object is not in strict mode.
            //
            byte[] decrypted1 = tpm.RsaDecrypt(keyHandle, encrypted, decScheme, null);

            byte[] nonceTpm;

            Console.WriteLine("Session object construction.");

            //
            // If a session with specific properties is required, an AuthSession object
            // can be built from the session handle returned by the TPM2_StartAuthSession
            // command concatenated, if necessary, with session flags and unencrypted salt
            // value (not used in this example).
            //
            AuthSession auditSess = tpm.StartAuthSession(
                TpmRh.Null,                             // no salt
                TpmRh.Null,                             // no bind object
                Globs.GetRandomBytes(16),               // nonceCaller
                null,                                   // no salt
                TpmSe.Hmac,                             // session type
                new SymDef(),                           // no encryption/decryption
                TpmAlgId.Sha256,                        // authHash
                out nonceTpm)
                                    + (SessionAttr.ContinueSession | SessionAttr.Audit);

            /*
             * Alternatively one of the StartAuthSessionEx helpers can be used). E.g.
             *
             * AuthSession auditSess = tpm.StartAuthSessionEx(TpmSe.Hmac, TpmAlgId.Sha256,
             *                                  SessionAttr.ContinueSession | SessionAttr.Audit);
             */

            //
            // TSS.Net specific call to verify TPM auditing correctness.
            //
            tpm._SetCommandAuditAlgorithm(TpmAlgId.Sha256);

            Console.WriteLine("Automatic authorization using explicitly created session object.");

            //
            // Appropriate auth value is added automatically into the provided session.
            //
            // Note that the call to _Audit() is optional and is only used when one
            // needs the TSS.Net framework to compute the audit digest on its own (e.g.
            // when simulating the TPM functionality without access to an actual TPM).
            //
            byte[] decrypted2 = tpm[auditSess]._Audit()
                                .RsaDecrypt(keyHandle, encrypted, decScheme, null);

            ISignatureUnion signature;
            Attest          attest;

            //
            // A session is added automatically to authorize usage of the permanent
            // handle TpmRh.Endorsement.
            //
            // Note that if auth value of TpmRh.Endorsement is not empty, you need to
            // explicitly assign it to the tpm.EndorsementAuth property of the given
            // Tpm2 object.
            //
            attest = tpm.GetSessionAuditDigest(TpmRh.Endorsement, TpmRh.Null, auditSess,
                                               null, new NullSigScheme(), out signature);

            //
            // But if the corresponding auth value stored in the Tpm2 object is invalid, ...
            //
            AuthValue endorsementAuth = tpm.EndorsementAuth;

            tpm.EndorsementAuth = Globs.ByteArray(16, 0xde);

            //
            // ... the command will fail.
            //
            tpm._ExpectError(TpmRc.BadAuth)
            .GetSessionAuditDigest(TpmRh.Endorsement, TpmRh.Null, auditSess,
                                   null, new NullSigScheme(), out signature);
            //
            // Restore correct auth value.
            //
            tpm.EndorsementAuth = endorsementAuth;

            //
            // Verify that decryption worked correctly.
            //
            Debug.Assert(Globs.ArraysAreEqual(decrypted1, decrypted2));

            //
            // Verify that auditing worked correctly.
            //
            SessionAuditInfo info = (SessionAuditInfo)attest.attested;

            Debug.Assert(Globs.ArraysAreEqual(info.sessionDigest, tpm._GetAuditHash().HashData));

            Console.WriteLine("Auth value tracking by TSS.Net.");

            //
            // Change auth value of the decryption key.
            //
            TpmPrivate newKeyPrivate = tpm.ObjectChangeAuth(keyHandle, primHandle, AuthValue.FromRandom(16));
            TpmHandle  newKeyHandle  = tpm.Load(primHandle, newKeyPrivate, keyPublic);

            //
            // Allow non-exclusive usage of the audit session.
            //
            auditSess.Attrs &= ~SessionAttr.AuditExclusive;

            //
            // Correct auth value (corresponding to newKeyHandle, and different from
            // the one used for keyHandle) will be added to auditSess.
            //
            decrypted1 = tpm[auditSess]._Audit()
                         .RsaDecrypt(newKeyHandle, encrypted, decScheme, null);

            Console.WriteLine("Automatic authorization with multiple sessions.");

            //
            // Now two sessions are auto-generated (for TpmRh.Endorsement and keyHandle).
            //
            attest = tpm.GetSessionAuditDigest(TpmRh.Endorsement, keyHandle, auditSess,
                                               null, sigScheme, out signature);

            //
            // Verify that the previous command worked correctly.
            //
            bool sigOk = keyPublic.VerifySignatureOverData(Marshaller.GetTpmRepresentation(attest),
                                                           signature);

            Debug.Assert(sigOk);

            //
            // In the following example the first session is generated based on session
            // type indicator (Auth.Pw), and the second one is added automatically.
            //
            attest = tpm[Auth.Pw].GetSessionAuditDigest(TpmRh.Endorsement, keyHandle, auditSess,
                                                        null, sigScheme, out signature);

            //
            // Verify that the previous command worked correctly.
            //
            sigOk = keyPublic.VerifySignatureOverData(Marshaller.GetTpmRepresentation(attest),
                                                      signature);
            Debug.Assert(sigOk);

            //
            // Release TPM resources that we do not need anymore.
            //
            tpm.FlushContext(newKeyHandle);
            tpm.FlushContext(auditSess);

            //
            // The following example works correctly only when TPM resource management
            // is not enabled (e.g. with TPM simulator, or when actual TPM is in raw mode).
            //
            if (!tpm._GetUnderlyingDevice().HasRM())
            {
                Console.WriteLine("Using session type indicators.");

                //
                // Deplete TPM's active session storage
                //
                List <AuthSession> landfill = new List <AuthSession>();

                for (;;)
                {
                    tpm._AllowErrors();
                    AuthSession s = tpm.StartAuthSessionEx(TpmSe.Hmac, TpmAlgId.Sha256,
                                                           SessionAttr.ContinueSession);
                    if (!tpm._LastCommandSucceeded())
                    {
                        break;
                    }
                    landfill.Add(s);
                }

                //
                // Check if session type indicators are processed correctly
                //
                tpm[Auth.Hmac]._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);
                //
                // Password authorization protocol session uses a predefined handle value,
                // so it must work even when there are no free session slots in the TPM.
                //
                tpm[Auth.Pw].RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);

                //
                // Check if default session type defined by the TPM device is processed correctly.
                //
                bool needHmac = tpm._GetUnderlyingDevice().NeedsHMAC;

                tpm._GetUnderlyingDevice().NeedsHMAC = true;

                tpm._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);

                tpm[Auth.Default]._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);

                tpm._GetUnderlyingDevice().NeedsHMAC = false;

                tpm.RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);
                tpm[Auth.Default].RsaDecrypt(keyHandle, encrypted, new NullAsymScheme(), null);

                tpm._GetUnderlyingDevice().NeedsHMAC = needHmac;

                landfill.ForEach(s => tpm.FlushContext(s));
            }

            //
            // Release TPM resources.
            //
            tpm.FlushContext(keyHandle);
            tpm.FlushContext(primHandle);

            Console.WriteLine("Done.");
        }
Beispiel #2
0
        void TestAutomaticAuth(Tpm2 tpm, TestContext testCtx)
        {
            TpmHandle hPrim = Substrate.LoadRsaPrimary(tpm);

            // Make an RSA encryption key.
            var    decScheme = new SchemeOaep(Substrate.Random(TpmCfg.HashAlgs));
            var    sigScheme = new SchemeRsassa(Substrate.Random(TpmCfg.HashAlgs));
            ushort keyLength = Substrate.RandomRsaKeySize(decScheme.hashAlg);
            var    inPub     = new TpmPublic(Substrate.Random(TpmCfg.HashAlgs),
                                             ObjectAttr.Decrypt | ObjectAttr.Sign
                                             | ObjectAttr.FixedParent | ObjectAttr.FixedTPM
                                             | ObjectAttr.UserWithAuth | ObjectAttr.SensitiveDataOrigin,
                                             null,
                                             new RsaParms(new SymDefObject(), null, keyLength, 0),
                                             new Tpm2bPublicKeyRsa());

            TpmPublic  keyPublic;
            TpmPrivate keyPrivate = Substrate.Create(tpm, hPrim, inPub, out keyPublic);

            TpmHandle keyHandle = null;

            tpm._Behavior.Strict = true;
            try
            {
                // No auth session is added automatically when TPM object is in strict mode.
                tpm._ExpectError(TpmRc.AuthMissing)
                .Load(hPrim, keyPrivate, keyPublic);

                // Now explicitly request an auth session of appropriate type
                keyHandle = tpm[Auth.Default].Load(hPrim, keyPrivate, keyPublic);
            }
            finally
            {
                tpm._Behavior.Strict = false;
            }

            byte[] message = Substrate.RandBytes(1, TpmHelper.MaxOaepMsgSize(keyLength, decScheme.hashAlg));

            byte[] encrypted = tpm.RsaEncrypt(keyHandle, message, decScheme, null);

            // An auth session is added automatically when TPM object is not in strict mode.
            byte[] decrypted1 = tpm.RsaDecrypt(keyHandle, encrypted, decScheme, null);

            TpmAlgId auditHashAlg = Substrate.Random(TpmCfg.HashAlgs);

            byte[] nonceTpm;

            // AuthSession object can be built from session handle concatenated, if necessary,
            // with session flags and unencrypted salt value (not used in this example).
            AuthSession auditSess = tpm.StartAuthSession(
                TpmRh.Null,                              // no salt
                TpmRh.Null,                              // no bind object
                Substrate.RandomNonce(auditHashAlg),     // nonceCaller
                null,                                    // no salt
                TpmSe.Hmac,                              // session type
                new SymDef(),                            // no encryption/decryption
                auditHashAlg,                            // authHash
                out nonceTpm)
                                    + (SessionAttr.ContinueSession | SessionAttr.Audit);

            /*
             * Alternatively one of the StartAuthSessionEx helpers can be used)
             * AuthSession auditSess = tpm.StartAuthSessionEx(TpmSe.Hmac, auditHashAlg, null,
             *                                                SessionAttr.ContinueSession | SessionAttr.Audit);
             */

            // TSS-specific call to verify TPM auditing correctness.
            tpm._SetCommandAuditAlgorithm(auditHashAlg);

            // Appropriate auth value is added automatically into the provided session
            byte[] decrypted2 = tpm[auditSess]._Audit()
                                .RsaDecrypt(keyHandle, encrypted, decScheme, null);

            ISignatureUnion sig;
            Attest          attest;

            // A session is added automatically to authorize TpmRh.Endorsement usage.
            attest = tpm.GetSessionAuditDigest(TpmRh.Endorsement, TpmRh.Null, auditSess,
                                               null, new NullSigScheme(), out sig);

            // But if the corresponding auth value stored in the Tpm2 object is invalid, ...
            AuthValue endorsementAuth = tpm.EndorsementAuth;

            tpm.EndorsementAuth = Globs.ByteArray(16, 0xde);
            // ... the command will fail
            tpm._ExpectError(TpmRc.BadAuth)
            .GetSessionAuditDigest(TpmRh.Endorsement, TpmRh.Null, auditSess,
                                   null, new NullSigScheme(), out sig);
            // Restore correct auth value.
            tpm.EndorsementAuth = endorsementAuth;

            // Verify that both decryption and auditing worked correctly.
            SessionAuditInfo info = (SessionAuditInfo)attest.attested;

            byte[] auditDigest = tpm._GetAuditHash();
            testCtx.AssertEqual("AuditSessionDigest", info.sessionDigest, auditDigest);
            testCtx.AssertEqual("Decryption", decrypted1, decrypted2);

            // Change auth value of the decryption key.
            TpmPrivate newKeyPrivate = tpm.ObjectChangeAuth(keyHandle, hPrim,
                                                            Substrate.RandomAuth(keyPublic.nameAlg));
            TpmHandle newKeyHandle = tpm.Load(hPrim, newKeyPrivate, keyPublic);

            auditSess.Attrs &= ~SessionAttr.AuditExclusive;
            // Correct auth value (corresponding to newKeyHandle, and different from
            // the one used for keyHandle) will be added to auditSess.
            decrypted1 = tpm[auditSess]._Audit().RsaDecrypt(newKeyHandle, encrypted, decScheme, null);

            // And now two sessions are auto-generated (for TpmRh.Endorsement and keyHandle).
            attest = tpm.GetSessionAuditDigest(TpmRh.Endorsement, keyHandle, auditSess,
                                               null, sigScheme, out sig);
            bool sigOk = keyPublic.VerifySignatureOverData(
                Marshaller.GetTpmRepresentation(attest), sig);

            testCtx.Assert("AuditSessionSignatute.1", sigOk);

            // Here the first session is generated based on session type indicator
            // (Auth.Pw), and the second one is added automatically.
            attest = tpm[Auth.Pw].GetSessionAuditDigest(TpmRh.Endorsement, keyHandle, auditSess,
                                                        null, sigScheme, out sig);

            // Verify that auditing worked correctly.
            sigOk = keyPublic.VerifySignatureOverData(
                Marshaller.GetTpmRepresentation(attest), sig);
            testCtx.Assert("AuditSessionSignatute.2", sigOk);

            tpm.FlushContext(newKeyHandle);
            tpm.FlushContext(auditSess);

            if (!TestCfg.HasTRM)
            {
                // Deplete TPM's active session storage
                List <AuthSession> landfill = new List <AuthSession>();

                for (;;)
                {
                    tpm._AllowErrors();
                    AuthSession s = tpm.StartAuthSessionEx(TpmSe.Hmac, Substrate.Random(TpmCfg.HashAlgs),
                                                           SessionAttr.ContinueSession);
                    if (!tpm._LastCommandSucceeded())
                    {
                        break;
                    }
                    landfill.Add(s);
                }

                // Check if session type indicators are processed correctly
                tpm[Auth.Hmac]._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, null, null);
                tpm[Auth.Pw].RsaDecrypt(keyHandle, encrypted, null, null);

                // Check if default session type defined by the TPM device is processed correctly
                bool needHmac = tpm._GetUnderlyingDevice().NeedsHMAC;

                tpm._GetUnderlyingDevice().NeedsHMAC = true;
                tpm._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, null, null);
                tpm[Auth.Default]._ExpectError(TpmRc.SessionMemory)
                .RsaDecrypt(keyHandle, encrypted, null, null);

                tpm._GetUnderlyingDevice().NeedsHMAC = false;
                tpm.RsaDecrypt(keyHandle, encrypted, null, null);
                tpm[Auth.Default].RsaDecrypt(keyHandle, encrypted, null, null);

                tpm._GetUnderlyingDevice().NeedsHMAC = needHmac;

                landfill.ForEach(s => tpm.FlushContext(s));
            }
            tpm.FlushContext(keyHandle);
        } // TestAutomaticAuth