435c0d9fc8
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
814 lines
22 KiB
Go
814 lines
22 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 implements the ssh-agent protocol, and provides both
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// a client and a server. The client can talk to a standard ssh-agent
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// that uses UNIX sockets, and one could implement an alternative
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// ssh-agent process using the sample server.
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//
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// References:
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// [PROTOCOL.agent]: https://tools.ietf.org/html/draft-miller-ssh-agent-00
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package agent // import "golang.org/x/crypto/ssh/agent"
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import (
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"bytes"
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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/base64"
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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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"math/big"
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"sync"
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"crypto"
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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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// SignatureFlags represent additional flags that can be passed to the signature
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// requests an defined in [PROTOCOL.agent] section 4.5.1.
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type SignatureFlags uint32
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// SignatureFlag values as defined in [PROTOCOL.agent] section 5.3.
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const (
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SignatureFlagReserved SignatureFlags = 1 << iota
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SignatureFlagRsaSha256
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SignatureFlagRsaSha512
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)
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// Agent represents the capabilities of an ssh-agent.
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type Agent interface {
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// List returns the identities known to the agent.
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List() ([]*Key, error)
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// Sign has the agent sign the data using a protocol 2 key as defined
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// in [PROTOCOL.agent] section 2.6.2.
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Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error)
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// Add adds a private key to the agent.
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Add(key AddedKey) error
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// Remove removes all identities with the given public key.
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Remove(key ssh.PublicKey) error
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// RemoveAll removes all identities.
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RemoveAll() error
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// Lock locks the agent. Sign and Remove will fail, and List will empty an empty list.
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Lock(passphrase []byte) error
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// Unlock undoes the effect of Lock
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Unlock(passphrase []byte) error
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// Signers returns signers for all the known keys.
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Signers() ([]ssh.Signer, error)
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}
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type ExtendedAgent interface {
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Agent
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// SignWithFlags signs like Sign, but allows for additional flags to be sent/received
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SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFlags) (*ssh.Signature, error)
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// Extension processes a custom extension request. Standard-compliant agents are not
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// required to support any extensions, but this method allows agents to implement
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// vendor-specific methods or add experimental features. See [PROTOCOL.agent] section 4.7.
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// If agent extensions are unsupported entirely this method MUST return an
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// ErrExtensionUnsupported error. Similarly, if just the specific extensionType in
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// the request is unsupported by the agent then ErrExtensionUnsupported MUST be
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// returned.
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//
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// In the case of success, since [PROTOCOL.agent] section 4.7 specifies that the contents
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// of the response are unspecified (including the type of the message), the complete
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// response will be returned as a []byte slice, including the "type" byte of the message.
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Extension(extensionType string, contents []byte) ([]byte, error)
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}
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// ConstraintExtension describes an optional constraint defined by users.
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type ConstraintExtension struct {
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// ExtensionName consist of a UTF-8 string suffixed by the
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// implementation domain following the naming scheme defined
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// in Section 4.2 of [RFC4251], e.g. "foo@example.com".
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ExtensionName string
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// ExtensionDetails contains the actual content of the extended
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// constraint.
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ExtensionDetails []byte
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}
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// AddedKey describes an SSH key to be added to an Agent.
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type AddedKey struct {
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// PrivateKey must be a *rsa.PrivateKey, *dsa.PrivateKey,
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// ed25519.PrivateKey or *ecdsa.PrivateKey, which will be inserted into the
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// agent.
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PrivateKey interface{}
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// Certificate, if not nil, is communicated to the agent and will be
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// stored with the key.
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Certificate *ssh.Certificate
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// Comment is an optional, free-form string.
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Comment string
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// LifetimeSecs, if not zero, is the number of seconds that the
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// agent will store the key for.
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LifetimeSecs uint32
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// ConfirmBeforeUse, if true, requests that the agent confirm with the
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// user before each use of this key.
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ConfirmBeforeUse bool
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// ConstraintExtensions are the experimental or private-use constraints
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// defined by users.
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ConstraintExtensions []ConstraintExtension
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}
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// See [PROTOCOL.agent], section 3.
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const (
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agentRequestV1Identities = 1
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agentRemoveAllV1Identities = 9
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// 3.2 Requests from client to agent for protocol 2 key operations
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agentAddIdentity = 17
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agentRemoveIdentity = 18
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agentRemoveAllIdentities = 19
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agentAddIDConstrained = 25
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// 3.3 Key-type independent requests from client to agent
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agentAddSmartcardKey = 20
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agentRemoveSmartcardKey = 21
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agentLock = 22
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agentUnlock = 23
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agentAddSmartcardKeyConstrained = 26
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// 3.7 Key constraint identifiers
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agentConstrainLifetime = 1
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agentConstrainConfirm = 2
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agentConstrainExtension = 3
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)
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// maxAgentResponseBytes is the maximum agent reply size that is accepted. This
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// is a sanity check, not a limit in the spec.
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const maxAgentResponseBytes = 16 << 20
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// Agent messages:
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// These structures mirror the wire format of the corresponding ssh agent
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// messages found in [PROTOCOL.agent].
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// 3.4 Generic replies from agent to client
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const agentFailure = 5
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type failureAgentMsg struct{}
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const agentSuccess = 6
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type successAgentMsg struct{}
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// See [PROTOCOL.agent], section 2.5.2.
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const agentRequestIdentities = 11
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type requestIdentitiesAgentMsg struct{}
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// See [PROTOCOL.agent], section 2.5.2.
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const agentIdentitiesAnswer = 12
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type identitiesAnswerAgentMsg struct {
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NumKeys uint32 `sshtype:"12"`
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Keys []byte `ssh:"rest"`
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}
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// See [PROTOCOL.agent], section 2.6.2.
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const agentSignRequest = 13
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type signRequestAgentMsg struct {
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KeyBlob []byte `sshtype:"13"`
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Data []byte
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Flags uint32
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}
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// See [PROTOCOL.agent], section 2.6.2.
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// 3.6 Replies from agent to client for protocol 2 key operations
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const agentSignResponse = 14
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type signResponseAgentMsg struct {
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SigBlob []byte `sshtype:"14"`
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}
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type publicKey struct {
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Format string
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Rest []byte `ssh:"rest"`
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}
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// 3.7 Key constraint identifiers
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type constrainLifetimeAgentMsg struct {
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LifetimeSecs uint32 `sshtype:"1"`
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}
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type constrainExtensionAgentMsg struct {
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ExtensionName string `sshtype:"3"`
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ExtensionDetails []byte
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// Rest is a field used for parsing, not part of message
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Rest []byte `ssh:"rest"`
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}
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// See [PROTOCOL.agent], section 4.7
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const agentExtension = 27
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const agentExtensionFailure = 28
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// ErrExtensionUnsupported indicates that an extension defined in
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// [PROTOCOL.agent] section 4.7 is unsupported by the agent. Specifically this
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// error indicates that the agent returned a standard SSH_AGENT_FAILURE message
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// as the result of a SSH_AGENTC_EXTENSION request. Note that the protocol
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// specification (and therefore this error) does not distinguish between a
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// specific extension being unsupported and extensions being unsupported entirely.
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var ErrExtensionUnsupported = errors.New("agent: extension unsupported")
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type extensionAgentMsg struct {
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ExtensionType string `sshtype:"27"`
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Contents []byte
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}
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// Key represents a protocol 2 public key as defined in
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// [PROTOCOL.agent], section 2.5.2.
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type Key struct {
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Format string
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Blob []byte
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Comment string
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}
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func clientErr(err error) error {
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return fmt.Errorf("agent: client error: %v", err)
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}
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// String returns the storage form of an agent key with the format, base64
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// encoded serialized key, and the comment if it is not empty.
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func (k *Key) String() string {
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s := string(k.Format) + " " + base64.StdEncoding.EncodeToString(k.Blob)
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if k.Comment != "" {
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s += " " + k.Comment
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}
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return s
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}
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// Type returns the public key type.
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func (k *Key) Type() string {
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return k.Format
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}
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// Marshal returns key blob to satisfy the ssh.PublicKey interface.
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func (k *Key) Marshal() []byte {
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return k.Blob
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}
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// Verify satisfies the ssh.PublicKey interface.
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func (k *Key) Verify(data []byte, sig *ssh.Signature) error {
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pubKey, err := ssh.ParsePublicKey(k.Blob)
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if err != nil {
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return fmt.Errorf("agent: bad public key: %v", err)
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}
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return pubKey.Verify(data, sig)
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}
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type wireKey struct {
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Format string
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Rest []byte `ssh:"rest"`
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}
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func parseKey(in []byte) (out *Key, rest []byte, err error) {
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var record struct {
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Blob []byte
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Comment string
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Rest []byte `ssh:"rest"`
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}
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if err := ssh.Unmarshal(in, &record); err != nil {
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return nil, nil, err
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}
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var wk wireKey
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if err := ssh.Unmarshal(record.Blob, &wk); err != nil {
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return nil, nil, err
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}
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return &Key{
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Format: wk.Format,
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Blob: record.Blob,
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Comment: record.Comment,
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}, record.Rest, nil
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}
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// client is a client for an ssh-agent process.
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type client struct {
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// conn is typically a *net.UnixConn
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conn io.ReadWriter
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// mu is used to prevent concurrent access to the agent
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mu sync.Mutex
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}
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// NewClient returns an Agent that talks to an ssh-agent process over
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// the given connection.
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func NewClient(rw io.ReadWriter) ExtendedAgent {
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return &client{conn: rw}
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}
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// call sends an RPC to the agent. On success, the reply is
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// unmarshaled into reply and replyType is set to the first byte of
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// the reply, which contains the type of the message.
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func (c *client) call(req []byte) (reply interface{}, err error) {
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buf, err := c.callRaw(req)
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if err != nil {
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return nil, err
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}
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reply, err = unmarshal(buf)
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if err != nil {
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return nil, clientErr(err)
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}
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return reply, nil
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}
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// callRaw sends an RPC to the agent. On success, the raw
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// bytes of the response are returned; no unmarshalling is
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// performed on the response.
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func (c *client) callRaw(req []byte) (reply []byte, err error) {
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c.mu.Lock()
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defer c.mu.Unlock()
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msg := make([]byte, 4+len(req))
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binary.BigEndian.PutUint32(msg, uint32(len(req)))
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copy(msg[4:], req)
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if _, err = c.conn.Write(msg); err != nil {
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return nil, clientErr(err)
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}
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var respSizeBuf [4]byte
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if _, err = io.ReadFull(c.conn, respSizeBuf[:]); err != nil {
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return nil, clientErr(err)
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}
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respSize := binary.BigEndian.Uint32(respSizeBuf[:])
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if respSize > maxAgentResponseBytes {
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return nil, clientErr(errors.New("response too large"))
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}
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buf := make([]byte, respSize)
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if _, err = io.ReadFull(c.conn, buf); err != nil {
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return nil, clientErr(err)
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}
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return buf, nil
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}
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func (c *client) simpleCall(req []byte) error {
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resp, err := c.call(req)
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if err != nil {
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return err
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}
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if _, ok := resp.(*successAgentMsg); ok {
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return nil
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}
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return errors.New("agent: failure")
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}
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func (c *client) RemoveAll() error {
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return c.simpleCall([]byte{agentRemoveAllIdentities})
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}
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func (c *client) Remove(key ssh.PublicKey) error {
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req := ssh.Marshal(&agentRemoveIdentityMsg{
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KeyBlob: key.Marshal(),
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})
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return c.simpleCall(req)
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}
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func (c *client) Lock(passphrase []byte) error {
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req := ssh.Marshal(&agentLockMsg{
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Passphrase: passphrase,
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})
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return c.simpleCall(req)
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}
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func (c *client) Unlock(passphrase []byte) error {
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req := ssh.Marshal(&agentUnlockMsg{
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Passphrase: passphrase,
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})
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return c.simpleCall(req)
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}
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// List returns the identities known to the agent.
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func (c *client) List() ([]*Key, error) {
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// see [PROTOCOL.agent] section 2.5.2.
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req := []byte{agentRequestIdentities}
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msg, err := c.call(req)
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if err != nil {
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return nil, err
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}
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switch msg := msg.(type) {
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case *identitiesAnswerAgentMsg:
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if msg.NumKeys > maxAgentResponseBytes/8 {
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return nil, errors.New("agent: too many keys in agent reply")
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}
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keys := make([]*Key, msg.NumKeys)
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data := msg.Keys
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for i := uint32(0); i < msg.NumKeys; i++ {
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var key *Key
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var err error
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if key, data, err = parseKey(data); err != nil {
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return nil, err
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}
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keys[i] = key
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}
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return keys, nil
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case *failureAgentMsg:
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return nil, errors.New("agent: failed to list keys")
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}
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panic("unreachable")
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}
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// Sign has the agent sign the data using a protocol 2 key as defined
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// in [PROTOCOL.agent] section 2.6.2.
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func (c *client) Sign(key ssh.PublicKey, data []byte) (*ssh.Signature, error) {
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return c.SignWithFlags(key, data, 0)
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}
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func (c *client) SignWithFlags(key ssh.PublicKey, data []byte, flags SignatureFlags) (*ssh.Signature, error) {
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req := ssh.Marshal(signRequestAgentMsg{
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KeyBlob: key.Marshal(),
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Data: data,
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Flags: uint32(flags),
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})
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msg, err := c.call(req)
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if err != nil {
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return nil, err
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}
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switch msg := msg.(type) {
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case *signResponseAgentMsg:
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var sig ssh.Signature
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if err := ssh.Unmarshal(msg.SigBlob, &sig); err != nil {
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return nil, err
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}
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return &sig, nil
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case *failureAgentMsg:
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return nil, errors.New("agent: failed to sign challenge")
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}
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panic("unreachable")
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}
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// unmarshal parses an agent message in packet, returning the parsed
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// form and the message type of packet.
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func unmarshal(packet []byte) (interface{}, error) {
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if len(packet) < 1 {
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return nil, errors.New("agent: empty packet")
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}
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var msg interface{}
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switch packet[0] {
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case agentFailure:
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return new(failureAgentMsg), nil
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case agentSuccess:
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return new(successAgentMsg), nil
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case agentIdentitiesAnswer:
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msg = new(identitiesAnswerAgentMsg)
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case agentSignResponse:
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msg = new(signResponseAgentMsg)
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case agentV1IdentitiesAnswer:
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msg = new(agentV1IdentityMsg)
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default:
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return nil, fmt.Errorf("agent: unknown type tag %d", packet[0])
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}
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if err := ssh.Unmarshal(packet, msg); err != nil {
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return nil, err
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}
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return msg, nil
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}
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type rsaKeyMsg struct {
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Type string `sshtype:"17|25"`
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N *big.Int
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E *big.Int
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D *big.Int
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Iqmp *big.Int // IQMP = Inverse Q Mod P
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P *big.Int
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Q *big.Int
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Comments string
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Constraints []byte `ssh:"rest"`
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}
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type dsaKeyMsg struct {
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Type string `sshtype:"17|25"`
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P *big.Int
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Q *big.Int
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G *big.Int
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Y *big.Int
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X *big.Int
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Comments string
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Constraints []byte `ssh:"rest"`
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}
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type ecdsaKeyMsg struct {
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Type string `sshtype:"17|25"`
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Curve string
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KeyBytes []byte
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D *big.Int
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Comments string
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Constraints []byte `ssh:"rest"`
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}
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type ed25519KeyMsg struct {
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Type string `sshtype:"17|25"`
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Pub []byte
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Priv []byte
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Comments string
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Constraints []byte `ssh:"rest"`
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}
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// Insert adds a private key to the agent.
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func (c *client) insertKey(s interface{}, comment string, constraints []byte) error {
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var req []byte
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switch k := s.(type) {
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case *rsa.PrivateKey:
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if len(k.Primes) != 2 {
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return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes))
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}
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k.Precompute()
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req = ssh.Marshal(rsaKeyMsg{
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Type: ssh.KeyAlgoRSA,
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N: k.N,
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E: big.NewInt(int64(k.E)),
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D: k.D,
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Iqmp: k.Precomputed.Qinv,
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P: k.Primes[0],
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Q: k.Primes[1],
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Comments: comment,
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Constraints: constraints,
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})
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case *dsa.PrivateKey:
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req = ssh.Marshal(dsaKeyMsg{
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Type: ssh.KeyAlgoDSA,
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P: k.P,
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Q: k.Q,
|
|
G: k.G,
|
|
Y: k.Y,
|
|
X: k.X,
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
case *ecdsa.PrivateKey:
|
|
nistID := fmt.Sprintf("nistp%d", k.Params().BitSize)
|
|
req = ssh.Marshal(ecdsaKeyMsg{
|
|
Type: "ecdsa-sha2-" + nistID,
|
|
Curve: nistID,
|
|
KeyBytes: elliptic.Marshal(k.Curve, k.X, k.Y),
|
|
D: k.D,
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
case ed25519.PrivateKey:
|
|
req = ssh.Marshal(ed25519KeyMsg{
|
|
Type: ssh.KeyAlgoED25519,
|
|
Pub: []byte(k)[32:],
|
|
Priv: []byte(k),
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
// This function originally supported only *ed25519.PrivateKey, however the
|
|
// general idiom is to pass ed25519.PrivateKey by value, not by pointer.
|
|
// We still support the pointer variant for backwards compatibility.
|
|
case *ed25519.PrivateKey:
|
|
req = ssh.Marshal(ed25519KeyMsg{
|
|
Type: ssh.KeyAlgoED25519,
|
|
Pub: []byte(*k)[32:],
|
|
Priv: []byte(*k),
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
default:
|
|
return fmt.Errorf("agent: unsupported key type %T", s)
|
|
}
|
|
|
|
// if constraints are present then the message type needs to be changed.
|
|
if len(constraints) != 0 {
|
|
req[0] = agentAddIDConstrained
|
|
}
|
|
|
|
resp, err := c.call(req)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if _, ok := resp.(*successAgentMsg); ok {
|
|
return nil
|
|
}
|
|
return errors.New("agent: failure")
|
|
}
|
|
|
|
type rsaCertMsg struct {
|
|
Type string `sshtype:"17|25"`
|
|
CertBytes []byte
|
|
D *big.Int
|
|
Iqmp *big.Int // IQMP = Inverse Q Mod P
|
|
P *big.Int
|
|
Q *big.Int
|
|
Comments string
|
|
Constraints []byte `ssh:"rest"`
|
|
}
|
|
|
|
type dsaCertMsg struct {
|
|
Type string `sshtype:"17|25"`
|
|
CertBytes []byte
|
|
X *big.Int
|
|
Comments string
|
|
Constraints []byte `ssh:"rest"`
|
|
}
|
|
|
|
type ecdsaCertMsg struct {
|
|
Type string `sshtype:"17|25"`
|
|
CertBytes []byte
|
|
D *big.Int
|
|
Comments string
|
|
Constraints []byte `ssh:"rest"`
|
|
}
|
|
|
|
type ed25519CertMsg struct {
|
|
Type string `sshtype:"17|25"`
|
|
CertBytes []byte
|
|
Pub []byte
|
|
Priv []byte
|
|
Comments string
|
|
Constraints []byte `ssh:"rest"`
|
|
}
|
|
|
|
// Add adds a private key to the agent. If a certificate is given,
|
|
// that certificate is added instead as public key.
|
|
func (c *client) Add(key AddedKey) error {
|
|
var constraints []byte
|
|
|
|
if secs := key.LifetimeSecs; secs != 0 {
|
|
constraints = append(constraints, ssh.Marshal(constrainLifetimeAgentMsg{secs})...)
|
|
}
|
|
|
|
if key.ConfirmBeforeUse {
|
|
constraints = append(constraints, agentConstrainConfirm)
|
|
}
|
|
|
|
cert := key.Certificate
|
|
if cert == nil {
|
|
return c.insertKey(key.PrivateKey, key.Comment, constraints)
|
|
}
|
|
return c.insertCert(key.PrivateKey, cert, key.Comment, constraints)
|
|
}
|
|
|
|
func (c *client) insertCert(s interface{}, cert *ssh.Certificate, comment string, constraints []byte) error {
|
|
var req []byte
|
|
switch k := s.(type) {
|
|
case *rsa.PrivateKey:
|
|
if len(k.Primes) != 2 {
|
|
return fmt.Errorf("agent: unsupported RSA key with %d primes", len(k.Primes))
|
|
}
|
|
k.Precompute()
|
|
req = ssh.Marshal(rsaCertMsg{
|
|
Type: cert.Type(),
|
|
CertBytes: cert.Marshal(),
|
|
D: k.D,
|
|
Iqmp: k.Precomputed.Qinv,
|
|
P: k.Primes[0],
|
|
Q: k.Primes[1],
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
case *dsa.PrivateKey:
|
|
req = ssh.Marshal(dsaCertMsg{
|
|
Type: cert.Type(),
|
|
CertBytes: cert.Marshal(),
|
|
X: k.X,
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
case *ecdsa.PrivateKey:
|
|
req = ssh.Marshal(ecdsaCertMsg{
|
|
Type: cert.Type(),
|
|
CertBytes: cert.Marshal(),
|
|
D: k.D,
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
case ed25519.PrivateKey:
|
|
req = ssh.Marshal(ed25519CertMsg{
|
|
Type: cert.Type(),
|
|
CertBytes: cert.Marshal(),
|
|
Pub: []byte(k)[32:],
|
|
Priv: []byte(k),
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
// This function originally supported only *ed25519.PrivateKey, however the
|
|
// general idiom is to pass ed25519.PrivateKey by value, not by pointer.
|
|
// We still support the pointer variant for backwards compatibility.
|
|
case *ed25519.PrivateKey:
|
|
req = ssh.Marshal(ed25519CertMsg{
|
|
Type: cert.Type(),
|
|
CertBytes: cert.Marshal(),
|
|
Pub: []byte(*k)[32:],
|
|
Priv: []byte(*k),
|
|
Comments: comment,
|
|
Constraints: constraints,
|
|
})
|
|
default:
|
|
return fmt.Errorf("agent: unsupported key type %T", s)
|
|
}
|
|
|
|
// if constraints are present then the message type needs to be changed.
|
|
if len(constraints) != 0 {
|
|
req[0] = agentAddIDConstrained
|
|
}
|
|
|
|
signer, err := ssh.NewSignerFromKey(s)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if bytes.Compare(cert.Key.Marshal(), signer.PublicKey().Marshal()) != 0 {
|
|
return errors.New("agent: signer and cert have different public key")
|
|
}
|
|
|
|
resp, err := c.call(req)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if _, ok := resp.(*successAgentMsg); ok {
|
|
return nil
|
|
}
|
|
return errors.New("agent: failure")
|
|
}
|
|
|
|
// Signers provides a callback for client authentication.
|
|
func (c *client) Signers() ([]ssh.Signer, error) {
|
|
keys, err := c.List()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var result []ssh.Signer
|
|
for _, k := range keys {
|
|
result = append(result, &agentKeyringSigner{c, k})
|
|
}
|
|
return result, nil
|
|
}
|
|
|
|
type agentKeyringSigner struct {
|
|
agent *client
|
|
pub ssh.PublicKey
|
|
}
|
|
|
|
func (s *agentKeyringSigner) PublicKey() ssh.PublicKey {
|
|
return s.pub
|
|
}
|
|
|
|
func (s *agentKeyringSigner) Sign(rand io.Reader, data []byte) (*ssh.Signature, error) {
|
|
// The agent has its own entropy source, so the rand argument is ignored.
|
|
return s.agent.Sign(s.pub, data)
|
|
}
|
|
|
|
func (s *agentKeyringSigner) SignWithOpts(rand io.Reader, data []byte, opts crypto.SignerOpts) (*ssh.Signature, error) {
|
|
var flags SignatureFlags
|
|
if opts != nil {
|
|
switch opts.HashFunc() {
|
|
case crypto.SHA256:
|
|
flags = SignatureFlagRsaSha256
|
|
case crypto.SHA512:
|
|
flags = SignatureFlagRsaSha512
|
|
}
|
|
}
|
|
return s.agent.SignWithFlags(s.pub, data, flags)
|
|
}
|
|
|
|
// Calls an extension method. It is up to the agent implementation as to whether or not
|
|
// any particular extension is supported and may always return an error. Because the
|
|
// type of the response is up to the implementation, this returns the bytes of the
|
|
// response and does not attempt any type of unmarshalling.
|
|
func (c *client) Extension(extensionType string, contents []byte) ([]byte, error) {
|
|
req := ssh.Marshal(extensionAgentMsg{
|
|
ExtensionType: extensionType,
|
|
Contents: contents,
|
|
})
|
|
buf, err := c.callRaw(req)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
if len(buf) == 0 {
|
|
return nil, errors.New("agent: failure; empty response")
|
|
}
|
|
// [PROTOCOL.agent] section 4.7 indicates that an SSH_AGENT_FAILURE message
|
|
// represents an agent that does not support the extension
|
|
if buf[0] == agentFailure {
|
|
return nil, ErrExtensionUnsupported
|
|
}
|
|
if buf[0] == agentExtensionFailure {
|
|
return nil, errors.New("agent: generic extension failure")
|
|
}
|
|
|
|
return buf, nil
|
|
}
|