// Remove removes all identities with the given public key.
func (r *keyring) Remove(key ssh.PublicKey) error {
	r.mu.Lock()
	defer r.mu.Unlock()
	if r.locked {
		return errLocked
	}

	want := key.Marshal()
	found := false
	for i := 0; i < len(r.keys); {
		if bytes.Equal(r.keys[i].signer.PublicKey().Marshal(), want) {
			found = true
			r.keys[i] = r.keys[len(r.keys)-1]
			r.keys = r.keys[len(r.keys)-1:]
			continue
		} else {
			i++
		}
	}

	if !found {
		return errors.New("agent: key not found")
	}
	return nil
}

func (k *storedHostKey) Check(addr string, remote net.Addr, key ssh.PublicKey) error {
	k.checkCount++
	algo := key.Type()

	if k.keys == nil || bytes.Compare(key.Marshal(), k.keys[algo]) != 0 {
		return fmt.Errorf("host key mismatch. Got %q, want %q", key, k.keys[algo])
	}
	return nil
}

// Sign returns a signature for the data.
func (r *keyring) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	if r.locked {
		return nil, errLocked
	}

	wanted := key.Marshal()
	for _, k := range r.keys {
		if bytes.Equal(k.signer.PublicKey().Marshal(), wanted) {
			return k.signer.Sign(rand.Reader, data)
		}
	}
	return nil, errors.New("not found")
}

func testAgentInterface(t *testing.T, agent Agent, key interface{}, cert *ssh.Certificate) {
	signer, err := ssh.NewSignerFromKey(key)
	if err != nil {
		t.Fatalf("NewSignerFromKey(%T): %v", key, err)
	}
	// The agent should start up empty.
	if keys, err := agent.List(); err != nil {
		t.Fatalf("RequestIdentities: %v", err)
	} else if len(keys) > 0 {
		t.Fatalf("got %d keys, want 0: %v", len(keys), keys)
	}

	// Attempt to insert the key, with certificate if specified.
	var pubKey ssh.PublicKey
	if cert != nil {
		err = agent.Add(key, cert, "comment")
		pubKey = cert
	} else {
		err = agent.Add(key, nil, "comment")
		pubKey = signer.PublicKey()
	}
	if err != nil {
		t.Fatalf("insert(%T): %v", key, err)
	}

	// Did the key get inserted successfully?
	if keys, err := agent.List(); err != nil {
		t.Fatalf("List: %v", err)
	} else if len(keys) != 1 {
		t.Fatalf("got %v, want 1 key", keys)
	} else if keys[0].Comment != "comment" {
		t.Fatalf("key comment: got %v, want %v", keys[0].Comment, "comment")
	} else if !bytes.Equal(keys[0].Blob, pubKey.Marshal()) {
		t.Fatalf("key mismatch")
	}

	// Can the agent make a valid signature?
	data := []byte("hello")
	sig, err := agent.Sign(pubKey, data)
	if err != nil {
		t.Fatalf("Sign(%s): %v", pubKey.Type(), err)
	}

	if err := pubKey.Verify(data, sig); err != nil {
		t.Fatalf("Verify(%s): %v", pubKey.Type(), err)
	}
}

// Check is called during the handshake to check the server's public key for
// unexpected changes. The key argument is in SSH wire format. It can be parsed
// using ssh.ParsePublicKey. The address before DNS resolution is passed in the
// addr argument, so the key can also be checked against the hostname.
// It returns any error encountered while checking the public key. A nil return
// value indicates that the key was either successfully verified (against an
// existing known_hosts entry), or accepted by the user as a new key.
func (kc *HostKeyChecker) Check(addr string, remote net.Addr, key gossh.PublicKey) error {
	remoteAddr, err := kc.addrToHostPort(remote.String())
	if err != nil {
		return err
	}

	algoStr := algoString(key.Type())
	keyFingerprintStr := md5String(md5.Sum(key.Marshal()))

	hostKeys, err := kc.m.GetHostKeys()
	_, ok := err.(*os.PathError)
	if err != nil && !ok {
		log.Errorf("Failed to read known_hosts file %v: %v", kc.m.String(), err)
	}

	mismatched := false
	for pattern, keys := range hostKeys {
		if !matchHost(remoteAddr, pattern) {
			continue
		}
		for _, hostKey := range keys {
			// Any matching key is considered a success, irrespective of previous failures
			if hostKey.Type() == key.Type() && bytes.Compare(hostKey.Marshal(), key.Marshal()) == 0 {
				return nil
			}
			// TODO(jonboulle): could be super friendly like the OpenSSH client
			// and note exactly which key failed (file + line number)
			mismatched = true
		}
	}

	if mismatched {
		fmt.Fprintf(os.Stderr, warningRemoteHostChanged, algoStr, keyFingerprintStr, kc.m.String())
		return ErrUnmatchKey
	}

	// If we get this far, we haven't matched on any of the hostname patterns,
	// so it's considered a new key. Prompt the user to trust it.
	if !kc.trustHost(remoteAddr, algoStr, keyFingerprintStr) {
		fmt.Fprintln(os.Stderr, "Host key verification failed.")
		return ErrUntrustHost
	}

	if err := kc.m.PutHostKey(remoteAddr, key); err != nil {
		fmt.Fprintf(os.Stderr, "Failed to add the host to the list of known hosts (%v).\n", kc.m)
		return nil
	}

	fmt.Fprintf(os.Stderr, "Warning: Permanently added '%v' (%v) to the list of known hosts.\n", remoteAddr, algoStr)
	return nil
}

// Sign has the agent sign the data using a protocol 2 key as defined
// in [PROTOCOL.agent] section 2.6.2.
func (c *client) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
	req := ssh.Marshal(signRequestAgentMsg{
		KeyBlob: key.Marshal(),
		Data:    data,
	})

	msg, err := c.call(req)
	if err != nil {
		return nil, err
	}

	switch msg := msg.(type) {
	case *signResponseAgentMsg:
		var sig ssh.Signature
		if err := ssh.Unmarshal(msg.SigBlob, &sig); err != nil {
			return nil, err
		}

		return &sig, nil
	case *failureAgentMsg:
		return nil, errors.New("agent: failed to sign challenge")
	}
	panic("unreachable")
}

func (c *client) Remove(key ssh.PublicKey) error {
	req := ssh.Marshal(&agentRemoveIdentityMsg{
		KeyBlob: key.Marshal(),
	})
	return c.simpleCall(req)
}

func (k *storedHostKey) Add(key ssh.PublicKey) {
	if k.keys == nil {
		k.keys = map[string][]byte{}
	}
	k.keys[key.Type()] = key.Marshal()
}