570 lines
13 KiB
Go
570 lines
13 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package agent
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import (
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"crypto/dsa"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rsa"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"log"
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"math/big"
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"golang.org/x/crypto/ed25519"
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"golang.org/x/crypto/ssh"
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)
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// Server wraps an Agent and uses it to implement the agent side of
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// the SSH-agent, wire protocol.
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type server struct {
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agent Agent
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}
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func (s *server) processRequestBytes(reqData []byte) []byte {
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rep, err := s.processRequest(reqData)
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if err != nil {
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if err != errLocked {
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// TODO(hanwen): provide better logging interface?
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log.Printf("agent %d: %v", reqData[0], err)
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}
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return []byte{agentFailure}
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}
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if err == nil && rep == nil {
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return []byte{agentSuccess}
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}
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return ssh.Marshal(rep)
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}
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func marshalKey(k *Key) []byte {
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var record struct {
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Blob []byte
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Comment string
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}
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record.Blob = k.Marshal()
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record.Comment = k.Comment
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return ssh.Marshal(&record)
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}
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// See [PROTOCOL.agent], section 2.5.1.
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const agentV1IdentitiesAnswer = 2
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type agentV1IdentityMsg struct {
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Numkeys uint32 `sshtype:"2"`
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}
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type agentRemoveIdentityMsg struct {
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KeyBlob []byte `sshtype:"18"`
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}
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type agentLockMsg struct {
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Passphrase []byte `sshtype:"22"`
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}
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type agentUnlockMsg struct {
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Passphrase []byte `sshtype:"23"`
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}
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func (s *server) processRequest(data []byte) (interface{}, error) {
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switch data[0] {
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case agentRequestV1Identities:
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return &agentV1IdentityMsg{0}, nil
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case agentRemoveAllV1Identities:
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return nil, nil
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case agentRemoveIdentity:
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var req agentRemoveIdentityMsg
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if err := ssh.Unmarshal(data, &req); err != nil {
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return nil, err
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}
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var wk wireKey
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if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil {
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return nil, err
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}
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return nil, s.agent.Remove(&Key{Format: wk.Format, Blob: req.KeyBlob})
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case agentRemoveAllIdentities:
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return nil, s.agent.RemoveAll()
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case agentLock:
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var req agentLockMsg
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if err := ssh.Unmarshal(data, &req); err != nil {
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return nil, err
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}
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return nil, s.agent.Lock(req.Passphrase)
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case agentUnlock:
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var req agentUnlockMsg
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if err := ssh.Unmarshal(data, &req); err != nil {
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return nil, err
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}
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return nil, s.agent.Unlock(req.Passphrase)
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case agentSignRequest:
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var req signRequestAgentMsg
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if err := ssh.Unmarshal(data, &req); err != nil {
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return nil, err
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}
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var wk wireKey
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if err := ssh.Unmarshal(req.KeyBlob, &wk); err != nil {
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return nil, err
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}
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k := &Key{
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Format: wk.Format,
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Blob: req.KeyBlob,
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}
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var sig *ssh.Signature
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var err error
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if extendedAgent, ok := s.agent.(ExtendedAgent); ok {
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sig, err = extendedAgent.SignWithFlags(k, req.Data, SignatureFlags(req.Flags))
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} else {
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sig, err = s.agent.Sign(k, req.Data)
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}
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if err != nil {
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return nil, err
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}
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return &signResponseAgentMsg{SigBlob: ssh.Marshal(sig)}, nil
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case agentRequestIdentities:
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keys, err := s.agent.List()
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if err != nil {
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return nil, err
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}
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rep := identitiesAnswerAgentMsg{
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NumKeys: uint32(len(keys)),
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}
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for _, k := range keys {
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rep.Keys = append(rep.Keys, marshalKey(k)...)
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}
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return rep, nil
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case agentAddIDConstrained, agentAddIdentity:
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return nil, s.insertIdentity(data)
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case agentExtension:
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// Return a stub object where the whole contents of the response gets marshaled.
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var responseStub struct {
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Rest []byte `ssh:"rest"`
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}
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if extendedAgent, ok := s.agent.(ExtendedAgent); !ok {
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// If this agent doesn't implement extensions, [PROTOCOL.agent] section 4.7
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// requires that we return a standard SSH_AGENT_FAILURE message.
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responseStub.Rest = []byte{agentFailure}
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} else {
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var req extensionAgentMsg
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if err := ssh.Unmarshal(data, &req); err != nil {
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return nil, err
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}
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res, err := extendedAgent.Extension(req.ExtensionType, req.Contents)
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if err != nil {
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// If agent extensions are unsupported, return a standard SSH_AGENT_FAILURE
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// message as required by [PROTOCOL.agent] section 4.7.
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if err == ErrExtensionUnsupported {
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responseStub.Rest = []byte{agentFailure}
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} else {
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// As the result of any other error processing an extension request,
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// [PROTOCOL.agent] section 4.7 requires that we return a
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// SSH_AGENT_EXTENSION_FAILURE code.
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responseStub.Rest = []byte{agentExtensionFailure}
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}
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} else {
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if len(res) == 0 {
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return nil, nil
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}
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responseStub.Rest = res
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}
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}
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return responseStub, nil
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}
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return nil, fmt.Errorf("unknown opcode %d", data[0])
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}
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func parseConstraints(constraints []byte) (lifetimeSecs uint32, confirmBeforeUse bool, extensions []ConstraintExtension, err error) {
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for len(constraints) != 0 {
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switch constraints[0] {
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case agentConstrainLifetime:
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lifetimeSecs = binary.BigEndian.Uint32(constraints[1:5])
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constraints = constraints[5:]
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case agentConstrainConfirm:
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confirmBeforeUse = true
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constraints = constraints[1:]
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case agentConstrainExtension:
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var msg constrainExtensionAgentMsg
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if err = ssh.Unmarshal(constraints, &msg); err != nil {
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return 0, false, nil, err
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}
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extensions = append(extensions, ConstraintExtension{
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ExtensionName: msg.ExtensionName,
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ExtensionDetails: msg.ExtensionDetails,
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})
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constraints = msg.Rest
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default:
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return 0, false, nil, fmt.Errorf("unknown constraint type: %d", constraints[0])
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}
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}
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return
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}
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func setConstraints(key *AddedKey, constraintBytes []byte) error {
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lifetimeSecs, confirmBeforeUse, constraintExtensions, err := parseConstraints(constraintBytes)
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if err != nil {
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return err
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}
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key.LifetimeSecs = lifetimeSecs
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key.ConfirmBeforeUse = confirmBeforeUse
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key.ConstraintExtensions = constraintExtensions
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return nil
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}
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func parseRSAKey(req []byte) (*AddedKey, error) {
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var k rsaKeyMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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if k.E.BitLen() > 30 {
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return nil, errors.New("agent: RSA public exponent too large")
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}
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priv := &rsa.PrivateKey{
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PublicKey: rsa.PublicKey{
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E: int(k.E.Int64()),
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N: k.N,
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},
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D: k.D,
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Primes: []*big.Int{k.P, k.Q},
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}
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priv.Precompute()
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addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseEd25519Key(req []byte) (*AddedKey, error) {
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var k ed25519KeyMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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priv := ed25519.PrivateKey(k.Priv)
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addedKey := &AddedKey{PrivateKey: &priv, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseDSAKey(req []byte) (*AddedKey, error) {
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var k dsaKeyMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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priv := &dsa.PrivateKey{
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PublicKey: dsa.PublicKey{
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Parameters: dsa.Parameters{
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P: k.P,
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Q: k.Q,
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G: k.G,
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},
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Y: k.Y,
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},
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X: k.X,
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}
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addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func unmarshalECDSA(curveName string, keyBytes []byte, privScalar *big.Int) (priv *ecdsa.PrivateKey, err error) {
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priv = &ecdsa.PrivateKey{
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D: privScalar,
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}
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switch curveName {
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case "nistp256":
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priv.Curve = elliptic.P256()
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case "nistp384":
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priv.Curve = elliptic.P384()
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case "nistp521":
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priv.Curve = elliptic.P521()
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default:
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return nil, fmt.Errorf("agent: unknown curve %q", curveName)
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}
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priv.X, priv.Y = elliptic.Unmarshal(priv.Curve, keyBytes)
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if priv.X == nil || priv.Y == nil {
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return nil, errors.New("agent: point not on curve")
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}
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return priv, nil
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}
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func parseEd25519Cert(req []byte) (*AddedKey, error) {
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var k ed25519CertMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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pubKey, err := ssh.ParsePublicKey(k.CertBytes)
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if err != nil {
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return nil, err
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}
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priv := ed25519.PrivateKey(k.Priv)
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cert, ok := pubKey.(*ssh.Certificate)
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if !ok {
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return nil, errors.New("agent: bad ED25519 certificate")
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}
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addedKey := &AddedKey{PrivateKey: &priv, Certificate: cert, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseECDSAKey(req []byte) (*AddedKey, error) {
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var k ecdsaKeyMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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priv, err := unmarshalECDSA(k.Curve, k.KeyBytes, k.D)
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if err != nil {
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return nil, err
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}
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addedKey := &AddedKey{PrivateKey: priv, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseRSACert(req []byte) (*AddedKey, error) {
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var k rsaCertMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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pubKey, err := ssh.ParsePublicKey(k.CertBytes)
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if err != nil {
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return nil, err
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}
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cert, ok := pubKey.(*ssh.Certificate)
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if !ok {
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return nil, errors.New("agent: bad RSA certificate")
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}
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// An RSA publickey as marshaled by rsaPublicKey.Marshal() in keys.go
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var rsaPub struct {
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Name string
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E *big.Int
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N *big.Int
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}
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if err := ssh.Unmarshal(cert.Key.Marshal(), &rsaPub); err != nil {
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return nil, fmt.Errorf("agent: Unmarshal failed to parse public key: %v", err)
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}
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if rsaPub.E.BitLen() > 30 {
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return nil, errors.New("agent: RSA public exponent too large")
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}
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priv := rsa.PrivateKey{
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PublicKey: rsa.PublicKey{
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E: int(rsaPub.E.Int64()),
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N: rsaPub.N,
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},
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D: k.D,
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Primes: []*big.Int{k.Q, k.P},
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}
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priv.Precompute()
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addedKey := &AddedKey{PrivateKey: &priv, Certificate: cert, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseDSACert(req []byte) (*AddedKey, error) {
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var k dsaCertMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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pubKey, err := ssh.ParsePublicKey(k.CertBytes)
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if err != nil {
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return nil, err
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}
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cert, ok := pubKey.(*ssh.Certificate)
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if !ok {
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return nil, errors.New("agent: bad DSA certificate")
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}
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// A DSA publickey as marshaled by dsaPublicKey.Marshal() in keys.go
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var w struct {
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Name string
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P, Q, G, Y *big.Int
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}
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if err := ssh.Unmarshal(cert.Key.Marshal(), &w); err != nil {
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return nil, fmt.Errorf("agent: Unmarshal failed to parse public key: %v", err)
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}
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priv := &dsa.PrivateKey{
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PublicKey: dsa.PublicKey{
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Parameters: dsa.Parameters{
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P: w.P,
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Q: w.Q,
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G: w.G,
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},
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Y: w.Y,
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},
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X: k.X,
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}
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addedKey := &AddedKey{PrivateKey: priv, Certificate: cert, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func parseECDSACert(req []byte) (*AddedKey, error) {
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var k ecdsaCertMsg
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if err := ssh.Unmarshal(req, &k); err != nil {
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return nil, err
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}
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pubKey, err := ssh.ParsePublicKey(k.CertBytes)
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if err != nil {
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return nil, err
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}
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cert, ok := pubKey.(*ssh.Certificate)
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if !ok {
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return nil, errors.New("agent: bad ECDSA certificate")
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}
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// An ECDSA publickey as marshaled by ecdsaPublicKey.Marshal() in keys.go
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var ecdsaPub struct {
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Name string
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ID string
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Key []byte
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}
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if err := ssh.Unmarshal(cert.Key.Marshal(), &ecdsaPub); err != nil {
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return nil, err
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}
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priv, err := unmarshalECDSA(ecdsaPub.ID, ecdsaPub.Key, k.D)
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if err != nil {
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return nil, err
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}
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addedKey := &AddedKey{PrivateKey: priv, Certificate: cert, Comment: k.Comments}
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if err := setConstraints(addedKey, k.Constraints); err != nil {
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return nil, err
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}
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return addedKey, nil
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}
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func (s *server) insertIdentity(req []byte) error {
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var record struct {
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Type string `sshtype:"17|25"`
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Rest []byte `ssh:"rest"`
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}
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if err := ssh.Unmarshal(req, &record); err != nil {
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return err
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}
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var addedKey *AddedKey
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var err error
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switch record.Type {
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case ssh.KeyAlgoRSA:
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addedKey, err = parseRSAKey(req)
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case ssh.KeyAlgoDSA:
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addedKey, err = parseDSAKey(req)
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case ssh.KeyAlgoECDSA256, ssh.KeyAlgoECDSA384, ssh.KeyAlgoECDSA521:
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addedKey, err = parseECDSAKey(req)
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case ssh.KeyAlgoED25519:
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addedKey, err = parseEd25519Key(req)
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case ssh.CertAlgoRSAv01:
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addedKey, err = parseRSACert(req)
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case ssh.CertAlgoDSAv01:
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addedKey, err = parseDSACert(req)
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case ssh.CertAlgoECDSA256v01, ssh.CertAlgoECDSA384v01, ssh.CertAlgoECDSA521v01:
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addedKey, err = parseECDSACert(req)
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case ssh.CertAlgoED25519v01:
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addedKey, err = parseEd25519Cert(req)
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default:
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return fmt.Errorf("agent: not implemented: %q", record.Type)
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}
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if err != nil {
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return err
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}
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return s.agent.Add(*addedKey)
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}
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|
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// ServeAgent serves the agent protocol on the given connection. It
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// returns when an I/O error occurs.
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func ServeAgent(agent Agent, c io.ReadWriter) error {
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s := &server{agent}
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var length [4]byte
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for {
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if _, err := io.ReadFull(c, length[:]); err != nil {
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return err
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}
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l := binary.BigEndian.Uint32(length[:])
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if l == 0 {
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return fmt.Errorf("agent: request size is 0")
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}
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if l > maxAgentResponseBytes {
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// We also cap requests.
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return fmt.Errorf("agent: request too large: %d", l)
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}
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req := make([]byte, l)
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if _, err := io.ReadFull(c, req); err != nil {
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return err
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}
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|
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repData := s.processRequestBytes(req)
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if len(repData) > maxAgentResponseBytes {
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return fmt.Errorf("agent: reply too large: %d bytes", len(repData))
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}
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|
|
binary.BigEndian.PutUint32(length[:], uint32(len(repData)))
|
|
if _, err := c.Write(length[:]); err != nil {
|
|
return err
|
|
}
|
|
if _, err := c.Write(repData); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
}
|