2018-02-12 23:22:41 +00:00
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//
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// Copyright (c) 2018, Joyent, Inc. All rights reserved.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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//
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package authentication
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import (
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"crypto/md5"
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"crypto/sha256"
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"encoding/base64"
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"fmt"
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"net"
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"os"
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"strings"
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pkgerrors "github.com/pkg/errors"
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"golang.org/x/crypto/ssh"
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"golang.org/x/crypto/ssh/agent"
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)
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var (
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ErrUnsetEnvVar = pkgerrors.New("environment variable SSH_AUTH_SOCK not set")
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)
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type SSHAgentSigner struct {
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formattedKeyFingerprint string
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keyFingerprint string
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algorithm string
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accountName string
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userName string
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keyIdentifier string
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agent agent.Agent
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key ssh.PublicKey
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}
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type SSHAgentSignerInput struct {
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KeyID string
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AccountName string
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Username string
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}
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func NewSSHAgentSigner(input SSHAgentSignerInput) (*SSHAgentSigner, error) {
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sshAgentAddress, agentOk := os.LookupEnv("SSH_AUTH_SOCK")
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if !agentOk {
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return nil, ErrUnsetEnvVar
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}
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conn, err := net.Dial("unix", sshAgentAddress)
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if err != nil {
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return nil, pkgerrors.Wrap(err, "unable to dial SSH agent")
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}
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ag := agent.NewClient(conn)
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signer := &SSHAgentSigner{
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keyFingerprint: input.KeyID,
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accountName: input.AccountName,
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agent: ag,
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}
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2018-07-06 16:09:34 +00:00
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if input.Username != "" {
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signer.userName = input.Username
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}
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2018-02-12 23:22:41 +00:00
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matchingKey, err := signer.MatchKey()
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if err != nil {
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return nil, err
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}
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signer.key = matchingKey
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signer.formattedKeyFingerprint = formatPublicKeyFingerprint(signer.key, true)
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_, algorithm, err := signer.SignRaw("HelloWorld")
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if err != nil {
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return nil, fmt.Errorf("Cannot sign using ssh agent: %s", err)
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}
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signer.algorithm = algorithm
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return signer, nil
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}
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func (s *SSHAgentSigner) MatchKey() (ssh.PublicKey, error) {
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keys, err := s.agent.List()
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if err != nil {
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return nil, pkgerrors.Wrap(err, "unable to list keys in SSH Agent")
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}
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keyFingerprintStripped := strings.TrimPrefix(s.keyFingerprint, "MD5:")
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keyFingerprintStripped = strings.TrimPrefix(keyFingerprintStripped, "SHA256:")
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keyFingerprintStripped = strings.Replace(keyFingerprintStripped, ":", "", -1)
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var matchingKey ssh.PublicKey
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for _, key := range keys {
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keyMD5 := md5.New()
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keyMD5.Write(key.Marshal())
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finalizedMD5 := fmt.Sprintf("%x", keyMD5.Sum(nil))
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keySHA256 := sha256.New()
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keySHA256.Write(key.Marshal())
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finalizedSHA256 := base64.RawStdEncoding.EncodeToString(keySHA256.Sum(nil))
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if keyFingerprintStripped == finalizedMD5 || keyFingerprintStripped == finalizedSHA256 {
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matchingKey = key
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}
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}
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if matchingKey == nil {
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return nil, fmt.Errorf("No key in the SSH Agent matches fingerprint: %s", s.keyFingerprint)
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}
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return matchingKey, nil
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}
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2018-07-06 16:09:34 +00:00
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func (s *SSHAgentSigner) Sign(dateHeader string, isManta bool) (string, error) {
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2018-02-12 23:22:41 +00:00
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const headerName = "date"
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signature, err := s.agent.Sign(s.key, []byte(fmt.Sprintf("%s: %s", headerName, dateHeader)))
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if err != nil {
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return "", pkgerrors.Wrap(err, "unable to sign date header")
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}
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keyFormat, err := keyFormatToKeyType(signature.Format)
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if err != nil {
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return "", pkgerrors.Wrap(err, "unable to format signature")
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}
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2018-07-06 16:09:34 +00:00
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key := &KeyID{
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UserName: s.userName,
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AccountName: s.accountName,
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Fingerprint: s.formattedKeyFingerprint,
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IsManta: isManta,
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}
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2018-02-12 23:22:41 +00:00
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var authSignature httpAuthSignature
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switch keyFormat {
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case "rsa":
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authSignature, err = newRSASignature(signature.Blob)
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if err != nil {
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return "", pkgerrors.Wrap(err, "unable to read RSA signature")
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}
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case "ecdsa":
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authSignature, err = newECDSASignature(signature.Blob)
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if err != nil {
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return "", pkgerrors.Wrap(err, "unable to read ECDSA signature")
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}
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default:
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return "", fmt.Errorf("Unsupported algorithm from SSH agent: %s", signature.Format)
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}
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2018-07-06 16:09:34 +00:00
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return fmt.Sprintf(authorizationHeaderFormat, key.generate(),
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2018-02-12 23:22:41 +00:00
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authSignature.SignatureType(), headerName, authSignature.String()), nil
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}
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func (s *SSHAgentSigner) SignRaw(toSign string) (string, string, error) {
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signature, err := s.agent.Sign(s.key, []byte(toSign))
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if err != nil {
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return "", "", pkgerrors.Wrap(err, "unable to sign string")
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}
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keyFormat, err := keyFormatToKeyType(signature.Format)
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if err != nil {
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return "", "", pkgerrors.Wrap(err, "unable to format key")
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}
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var authSignature httpAuthSignature
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switch keyFormat {
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case "rsa":
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authSignature, err = newRSASignature(signature.Blob)
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if err != nil {
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return "", "", pkgerrors.Wrap(err, "unable to read RSA signature")
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}
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case "ecdsa":
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authSignature, err = newECDSASignature(signature.Blob)
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if err != nil {
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return "", "", pkgerrors.Wrap(err, "unable to read ECDSA signature")
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}
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default:
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return "", "", fmt.Errorf("Unsupported algorithm from SSH agent: %s", signature.Format)
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}
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return authSignature.String(), authSignature.SignatureType(), nil
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}
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func (s *SSHAgentSigner) KeyFingerprint() string {
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return s.formattedKeyFingerprint
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}
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func (s *SSHAgentSigner) DefaultAlgorithm() string {
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return s.algorithm
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}
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