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sshlogin.go
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sshlogin.go
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/*
Copyright 2015 Gravitational, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package web
import (
"crypto/x509"
"encoding/json"
"fmt"
"io"
"net"
"net/http"
"net/http/httptest"
"net/url"
"os/exec"
"runtime"
"strings"
"time"
log "github.com/Sirupsen/logrus"
"github.com/gravitational/roundtrip"
"github.com/gravitational/trace"
"github.com/mailgun/lemma/secret"
"github.com/tstranex/u2f"
)
const (
// HTTPS is https prefix
HTTPS = "https"
// WSS is secure web sockets prefix
WSS = "wss"
)
type sealData struct {
Value []byte `json:"value"`
Nonce []byte `json:"nonce"`
}
// SSHAgentOIDCLogin is used by SSH Agent (tsh) to login using OpenID connect
func SSHAgentOIDCLogin(proxyAddr, connectorID string, pubKey []byte, ttl time.Duration, insecure bool, pool *x509.CertPool) (*SSHLoginResponse, error) {
clt, proxyURL, err := initClient(proxyAddr, insecure, pool)
if err != nil {
return nil, trace.Wrap(err)
}
// create one time encoding secret that we will use to verify
// callback from proxy that is received over untrusted channel (HTTP)
keyBytes, err := secret.NewKey()
if err != nil {
return nil, trace.Wrap(err)
}
decryptor, err := secret.New(&secret.Config{KeyBytes: keyBytes})
if err != nil {
return nil, trace.Wrap(err)
}
waitC := make(chan *SSHLoginResponse, 1)
errorC := make(chan error, 1)
proxyURL.Path = "/web/msg/error/login_failed"
redirectErrorURL := proxyURL.String()
proxyURL.Path = "/web/msg/info/login_success"
redirectSuccessURL := proxyURL.String()
makeHandler := func(fn func(http.ResponseWriter, *http.Request) (*SSHLoginResponse, error)) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
response, err := fn(w, r)
if err != nil {
if trace.IsNotFound(err) {
http.NotFound(w, r)
return
}
errorC <- err
http.Redirect(w, r, redirectErrorURL, http.StatusFound)
return
}
waitC <- response
http.Redirect(w, r, redirectSuccessURL, http.StatusFound)
})
}
server := httptest.NewServer(makeHandler(func(w http.ResponseWriter, r *http.Request) (*SSHLoginResponse, error) {
if r.URL.Path != "/callback" {
return nil, trace.NotFound("path not found")
}
encrypted := r.URL.Query().Get("response")
if encrypted == "" {
return nil, trace.BadParameter("missing required query parameters in %v", r.URL.String())
}
var encryptedData *secret.SealedBytes
err := json.Unmarshal([]byte(encrypted), &encryptedData)
if err != nil {
return nil, trace.BadParameter("failed to decode response in %v", r.URL.String())
}
out, err := decryptor.Open(encryptedData)
if err != nil {
return nil, trace.BadParameter("failed to decode response: in %v, err: %v", r.URL.String(), err)
}
var re *SSHLoginResponse
err = json.Unmarshal([]byte(out), &re)
if err != nil {
return nil, trace.BadParameter("failed to decode response: in %v, err: %v", r.URL.String(), err)
}
return re, nil
}))
defer server.Close()
u, err := url.Parse(server.URL + "/callback")
if err != nil {
return nil, trace.Wrap(err)
}
query := u.Query()
query.Set("secret", secret.KeyToEncodedString(keyBytes))
u.RawQuery = query.Encode()
out, err := clt.PostJSON(clt.Endpoint("webapi", "oidc", "login", "console"), oidcLoginConsoleReq{
RedirectURL: u.String(),
PublicKey: pubKey,
CertTTL: ttl,
ConnectorID: connectorID,
})
if err != nil {
return nil, trace.Wrap(err)
}
var re *oidcLoginConsoleResponse
err = json.Unmarshal(out.Bytes(), &re)
if err != nil {
return nil, trace.Wrap(err)
}
fmt.Printf("If browser window does not open automatically, open it by clicking on the link:\n %v\n", re.RedirectURL)
var command = "sensible-browser"
if runtime.GOOS == "darwin" {
command = "open"
}
path, err := exec.LookPath(command)
if err == nil {
exec.Command(path, re.RedirectURL).Start()
}
log.Infof("waiting for response on %v", server.URL)
select {
case err := <-errorC:
log.Debugf("got error: %v", err)
return nil, trace.Wrap(err)
case response := <-waitC:
log.Debugf("got response")
return response, nil
case <-time.After(60 * time.Second):
log.Debugf("got timeout waiting for callback")
return nil, trace.Wrap(trace.Errorf("timeout waiting for callback"))
}
}
// Ping is used to validate HTTPS endpoing of Teleport proxy. This leads to better
// user experience: they get connection errors before being asked for passwords
func Ping(proxyAddr string, insecure bool, pool *x509.CertPool) error {
clt, _, err := initClient(proxyAddr, insecure, pool)
if err != nil {
return trace.Wrap(err)
}
_, err = clt.Get(clt.Endpoint("webapi"), url.Values{})
if err != nil {
return trace.Wrap(err)
}
return nil
}
// SSHAgentLogin issues call to web proxy and receives temp certificate
// if credentials are valid
//
// proxyAddr must be specified as host:port
func SSHAgentLogin(proxyAddr, user, password, otpToken string, pubKey []byte, ttl time.Duration, insecure bool, pool *x509.CertPool) (*SSHLoginResponse, error) {
clt, _, err := initClient(proxyAddr, insecure, pool)
if err != nil {
return nil, trace.Wrap(err)
}
re, err := clt.PostJSON(clt.Endpoint("webapi", "ssh", "certs"), createSSHCertReq{
User: user,
Password: password,
OTPToken: otpToken,
PubKey: pubKey,
TTL: ttl,
})
if err != nil {
return nil, trace.Wrap(err)
}
var out *SSHLoginResponse
err = json.Unmarshal(re.Bytes(), &out)
if err != nil {
return nil, trace.Wrap(err)
}
return out, nil
}
// SSHAgentU2FLogin requests a U2F sign request (authentication challenge) via the proxy.
// If the credentials are valid, the proxy wiil return a challenge.
// We then call the official u2f-host binary to perform the signing and pass the signature to the proxy.
// If the authentication succeeds, we will get a temporary certificate back
func SSHAgentU2FLogin(proxyAddr, user, password string, pubKey []byte, ttl time.Duration, insecure bool, pool *x509.CertPool) (*SSHLoginResponse, error) {
clt, _, err := initClient(proxyAddr, insecure, pool)
if err != nil {
return nil, trace.Wrap(err)
}
u2fSignRequest, err := clt.PostJSON(clt.Endpoint("webapi", "u2f", "signrequest"), u2fSignRequestReq{
User: user,
Pass: password,
})
if err != nil {
return nil, trace.Wrap(err)
}
// Pass the JSON-encoded data undecoded to the u2f-host binary
facet := "https://" + strings.ToLower(proxyAddr)
cmd := exec.Command("u2f-host", "-aauthenticate", "-o", facet)
stdin, err := cmd.StdinPipe()
if err != nil {
return nil, trace.Wrap(err)
}
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, trace.Wrap(err)
}
stderr, err := cmd.StderrPipe()
if err != nil {
return nil, trace.Wrap(err)
}
cmd.Start()
stdin.Write(u2fSignRequest.Bytes())
stdin.Close()
fmt.Println("Please press the button on your U2F key")
// The origin URL is passed back base64-encoded and the keyHandle is passed back as is.
// A very long proxy hostname or keyHandle can overflow a fixed-size buffer.
signResponseLen := 500 + len(u2fSignRequest.Bytes()) + len(proxyAddr)*4/3
signResponseBuf := make([]byte, signResponseLen)
signResponseLen, err = io.ReadFull(stdout, signResponseBuf)
// unexpected EOF means we have read the data completely.
if err == nil {
return nil, trace.LimitExceeded("u2f sign response exceeded buffer size")
}
// Read error message (if any). 100 bytes is more than enough for any error message u2f-host outputs
errMsgBuf := make([]byte, 100)
errMsgLen, err := io.ReadFull(stderr, errMsgBuf)
if err == nil {
return nil, trace.LimitExceeded("u2f error message exceeded buffer size")
}
err = cmd.Wait()
if err != nil {
return nil, trace.AccessDenied("u2f-host returned error: " + string(errMsgBuf[:errMsgLen]))
} else if signResponseLen == 0 {
return nil, trace.NotFound("u2f-host returned no error and no sign response")
}
var u2fSignResponse *u2f.SignResponse
err = json.Unmarshal(signResponseBuf[:signResponseLen], &u2fSignResponse)
if err != nil {
return nil, trace.Wrap(err)
}
re, err := clt.PostJSON(clt.Endpoint("webapi", "u2f", "certs"), createSSHCertWithU2FReq{
User: user,
U2FSignResponse: *u2fSignResponse,
PubKey: pubKey,
TTL: ttl,
})
if err != nil {
return nil, trace.Wrap(err)
}
var out *SSHLoginResponse
err = json.Unmarshal(re.Bytes(), &out)
if err != nil {
return nil, trace.Wrap(err)
}
return out, nil
}
// initClient creates and initializes HTTPS client for talking to teleport proxy HTTPS
// endpoint.
func initClient(proxyAddr string, insecure bool, pool *x509.CertPool) (*webClient, *url.URL, error) {
log.Debugf("HTTPS client init(insecure=%v)", insecure)
// validate proxyAddr:
host, port, err := net.SplitHostPort(proxyAddr)
if err != nil || host == "" || port == "" {
if err != nil {
log.Error(err)
}
return nil, nil, trace.BadParameter("'%v' is not a valid proxy address", proxyAddr)
}
proxyAddr = "https://" + net.JoinHostPort(host, port)
u, err := url.Parse(proxyAddr)
if err != nil {
return nil, nil, trace.BadParameter("'%v' is not a valid proxy address", proxyAddr)
}
var opts []roundtrip.ClientParam
if insecure {
// skip https cert verification, oh no!
fmt.Printf("WARNING: You are using insecure connection to SSH proxy %v\n", proxyAddr)
opts = append(opts, roundtrip.HTTPClient(newInsecureClient()))
} else if pool != nil {
// use custom set of trusted CAs
opts = append(opts, roundtrip.HTTPClient(newClientWithPool(pool)))
}
clt, err := newWebClient(proxyAddr, opts...)
if err != nil {
return nil, nil, trace.Wrap(err)
}
return clt, u, nil
}