Package ssh

[PROTOCOL.certkeys]: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.certkeys?rev=HEAD
[SSH-PARAMETERS]:    http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xml#ssh-parameters-1

Constants

These constants from [PROTOCOL.certkeys] represent the algorithm names for certificate types supported by this package.

const (
    CertAlgoRSAv01      = "ssh-rsa-cert-v01@openssh.com"
    CertAlgoDSAv01      = "ssh-dss-cert-v01@openssh.com"
    CertAlgoECDSA256v01 = "ecdsa-sha2-nistp256-cert-v01@openssh.com"
    CertAlgoECDSA384v01 = "ecdsa-sha2-nistp384-cert-v01@openssh.com"
    CertAlgoECDSA521v01 = "ecdsa-sha2-nistp521-cert-v01@openssh.com"
    CertAlgoED25519v01  = "ssh-ed25519-cert-v01@openssh.com"
)

Certificate types distinguish between host and user certificates. The values can be set in the CertType field of Certificate.

const (
    UserCert = 1
    HostCert = 2
)

These constants represent the algorithm names for key types supported by this package.

const (
    KeyAlgoRSA      = "ssh-rsa"
    KeyAlgoDSA      = "ssh-dss"
    KeyAlgoECDSA256 = "ecdsa-sha2-nistp256"
    KeyAlgoECDSA384 = "ecdsa-sha2-nistp384"
    KeyAlgoECDSA521 = "ecdsa-sha2-nistp521"
    KeyAlgoED25519  = "ssh-ed25519"
)

POSIX terminal mode flags as listed in RFC 4254 Section 8.

const (
    VINTR         = 1
    VQUIT         = 2
    VERASE        = 3
    VKILL         = 4
    VEOF          = 5
    VEOL          = 6
    VEOL2         = 7
    VSTART        = 8
    VSTOP         = 9
    VSUSP         = 10
    VDSUSP        = 11
    VREPRINT      = 12
    VWERASE       = 13
    VLNEXT        = 14
    VFLUSH        = 15
    VSWTCH        = 16
    VSTATUS       = 17
    VDISCARD      = 18
    IGNPAR        = 30
    PARMRK        = 31
    INPCK         = 32
    ISTRIP        = 33
    INLCR         = 34
    IGNCR         = 35
    ICRNL         = 36
    IUCLC         = 37
    IXON          = 38
    IXANY         = 39
    IXOFF         = 40
    IMAXBEL       = 41
    ISIG          = 50
    ICANON        = 51
    XCASE         = 52
    ECHO          = 53
    ECHOE         = 54
    ECHOK         = 55
    ECHONL        = 56
    NOFLSH        = 57
    TOSTOP        = 58
    IEXTEN        = 59
    ECHOCTL       = 60
    ECHOKE        = 61
    PENDIN        = 62
    OPOST         = 70
    OLCUC         = 71
    ONLCR         = 72
    OCRNL         = 73
    ONOCR         = 74
    ONLRET        = 75
    CS7           = 90
    CS8           = 91
    PARENB        = 92
    PARODD        = 93
    TTY_OP_ISPEED = 128
    TTY_OP_OSPEED = 129
)

CertTimeInfinity can be used for OpenSSHCertV01.ValidBefore to indicate that a certificate does not expire.

const CertTimeInfinity = 1<<64 - 1

func DiscardRequests ¶

func DiscardRequests(in <-chan *Request)

DiscardRequests consumes and rejects all requests from the passed-in channel.

func FingerprintLegacyMD5 ¶

func FingerprintLegacyMD5(pubKey PublicKey) string

FingerprintLegacyMD5 returns the user presentation of the key's fingerprint as described by RFC 4716 section 4.

func FingerprintSHA256 ¶

func FingerprintSHA256(pubKey PublicKey) string

FingerprintSHA256 returns the user presentation of the key's fingerprint as unpadded base64 encoded sha256 hash. This format was introduced from OpenSSH 6.8. https://www.openssh.com/txt/release-6.8 https://tools.ietf.org/html/rfc4648#section-3.2 (unpadded base64 encoding)

func Marshal ¶

func Marshal(msg interface{}) []byte

Marshal serializes the message in msg to SSH wire format. The msg argument should be a struct or pointer to struct. If the first member has the "sshtype" tag set to a number in decimal, that number is prepended to the result. If the last of member has the "ssh" tag set to "rest", its contents are appended to the output.

func MarshalAuthorizedKey ¶

func MarshalAuthorizedKey(key PublicKey) []byte

MarshalAuthorizedKey serializes key for inclusion in an OpenSSH authorized_keys file. The return value ends with newline.

func ParseDSAPrivateKey ¶

func ParseDSAPrivateKey(der []byte) (*dsa.PrivateKey, error)

ParseDSAPrivateKey returns a DSA private key from its ASN.1 DER encoding, as specified by the OpenSSL DSA man page.

func ParseKnownHosts ¶

func ParseKnownHosts(in []byte) (marker string, hosts []string, pubKey PublicKey, comment string, rest []byte, err error)

ParseKnownHosts parses an entry in the format of the known_hosts file.

The known_hosts format is documented in the sshd(8) manual page. This function will parse a single entry from in. On successful return, marker will contain the optional marker value (i.e. "cert-authority" or "revoked") or else be empty, hosts will contain the hosts that this entry matches, pubKey will contain the public key and comment will contain any trailing comment at the end of the line. See the sshd(8) manual page for the various forms that a host string can take.

The unparsed remainder of the input will be returned in rest. This function can be called repeatedly to parse multiple entries.

If no entries were found in the input then err will be io.EOF. Otherwise a non-nil err value indicates a parse error.

func ParseRawPrivateKey ¶

func ParseRawPrivateKey(pemBytes []byte) (interface{}, error)

ParseRawPrivateKey returns a private key from a PEM encoded private key. It supports RSA (PKCS#1), DSA (OpenSSL), and ECDSA private keys.

func ParseRawPrivateKeyWithPassphrase ¶

func ParseRawPrivateKeyWithPassphrase(pemBytes, passPhrase []byte) (interface{}, error)

func Unmarshal ¶

func Unmarshal(data []byte, out interface{}) error

Unmarshal parses data in SSH wire format into a structure. The out argument should be a pointer to struct. If the first member of the struct has the "sshtype" tag set to a '|'-separated set of numbers in decimal, the packet must start with one of those numbers. In case of error, Unmarshal returns a ParseError or UnexpectedMessageError.

type AuthMethod ¶

An AuthMethod represents an instance of an RFC 4252 authentication method.

type AuthMethod interface {
    // contains filtered or unexported methods
}

func KeyboardInteractive ¶

func KeyboardInteractive(challenge KeyboardInteractiveChallenge) AuthMethod

KeyboardInteractive returns a AuthMethod using a prompt/response sequence controlled by the server.

func Password ¶

func Password(secret string) AuthMethod

Password returns an AuthMethod using the given password.

func PasswordCallback ¶

func PasswordCallback(prompt func() (secret string, err error)) AuthMethod

PasswordCallback returns an AuthMethod that uses a callback for fetching a password.

func PublicKeys ¶

func PublicKeys(signers ...Signer) AuthMethod

PublicKeys returns an AuthMethod that uses the given key pairs.

var hostKey ssh.PublicKey
// A public key may be used to authenticate against the remote
// server by using an unencrypted PEM-encoded private key file.
//
// If you have an encrypted private key, the crypto/x509 package
// can be used to decrypt it.
key, err := ioutil.ReadFile("/home/user/.ssh/id_rsa")
if err != nil {
    log.Fatalf("unable to read private key: %v", err)
}

// Create the Signer for this private key.
signer, err := ssh.ParsePrivateKey(key)
if err != nil {
    log.Fatalf("unable to parse private key: %v", err)
}

config := &ssh.ClientConfig{
    User: "user",
    Auth: []ssh.AuthMethod{
        // Use the PublicKeys method for remote authentication.
        ssh.PublicKeys(signer),
    },
    HostKeyCallback: ssh.FixedHostKey(hostKey),
}

// Connect to the remote server and perform the SSH handshake.
client, err := ssh.Dial("tcp", "host.com:22", config)
if err != nil {
    log.Fatalf("unable to connect: %v", err)
}
defer client.Close()

func PublicKeysCallback ¶

func PublicKeysCallback(getSigners func() (signers []Signer, err error)) AuthMethod

PublicKeysCallback returns an AuthMethod that runs the given function to obtain a list of key pairs.

func RetryableAuthMethod ¶

func RetryableAuthMethod(auth AuthMethod, maxTries int) AuthMethod

RetryableAuthMethod is a decorator for other auth methods enabling them to be retried up to maxTries before considering that AuthMethod itself failed. If maxTries is <= 0, will retry indefinitely

This is useful for interactive clients using challenge/response type authentication (e.g. Keyboard-Interactive, Password, etc) where the user could mistype their response resulting in the server issuing a SSH_MSG_USERAUTH_FAILURE (rfc4252 #8 [password] and rfc4256 #3.4 [keyboard-interactive]); Without this decorator, the non-retryable AuthMethod would be removed from future consideration, and never tried again (and so the user would never be able to retry their entry).

user := "testuser"
NumberOfPrompts := 3

// Normally this would be a callback that prompts the user to answer the
// provided questions
Cb := func(user, instruction string, questions []string, echos []bool) (answers []string, err error) {
    return []string{"answer1", "answer2"}, nil
}

config := &ClientConfig{
    HostKeyCallback: InsecureIgnoreHostKey(),
    User:            user,
    Auth: []AuthMethod{
        RetryableAuthMethod(KeyboardInteractiveChallenge(Cb), NumberOfPrompts),
    },
}

if err := tryAuth(t, config); err != nil {
    t.Fatalf("unable to dial remote side: %s", err)
}

type CertChecker ¶

CertChecker does the work of verifying a certificate. Its methods can be plugged into ClientConfig.HostKeyCallback and ServerConfig.PublicKeyCallback. For the CertChecker to work, minimally, the IsAuthority callback should be set.

type CertChecker struct {
    // SupportedCriticalOptions lists the CriticalOptions that the
    // server application layer understands. These are only used
    // for user certificates.
    SupportedCriticalOptions []string

    // IsUserAuthority should return true if the key is recognized as an
    // authority for the given user certificate. This allows for
    // certificates to be signed by other certificates. This must be set
    // if this CertChecker will be checking user certificates.
    IsUserAuthority func(auth PublicKey) bool

    // IsHostAuthority should report whether the key is recognized as
    // an authority for this host. This allows for certificates to be
    // signed by other keys, and for those other keys to only be valid
    // signers for particular hostnames. This must be set if this
    // CertChecker will be checking host certificates.
    IsHostAuthority func(auth PublicKey, address string) bool

    // Clock is used for verifying time stamps. If nil, time.Now
    // is used.
    Clock func() time.Time

    // UserKeyFallback is called when CertChecker.Authenticate encounters a
    // public key that is not a certificate. It must implement validation
    // of user keys or else, if nil, all such keys are rejected.
    UserKeyFallback func(conn ConnMetadata, key PublicKey) (*Permissions, error)

    // HostKeyFallback is called when CertChecker.CheckHostKey encounters a
    // public key that is not a certificate. It must implement host key
    // validation or else, if nil, all such keys are rejected.
    HostKeyFallback HostKeyCallback

    // IsRevoked is called for each certificate so that revocation checking
    // can be implemented. It should return true if the given certificate
    // is revoked and false otherwise. If nil, no certificates are
    // considered to have been revoked.
    IsRevoked func(cert *Certificate) bool
}

func (*CertChecker) Authenticate ¶

func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permissions, error)

Authenticate checks a user certificate. Authenticate can be used as a value for ServerConfig.PublicKeyCallback.

func (*CertChecker) CheckCert ¶

func (c *CertChecker) CheckCert(principal string, cert *Certificate) error

CheckCert checks CriticalOptions, ValidPrincipals, revocation, timestamp and the signature of the certificate.

func (*CertChecker) CheckHostKey ¶

func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key PublicKey) error

CheckHostKey checks a host key certificate. This method can be plugged into ClientConfig.HostKeyCallback.

type Certificate ¶

An Certificate represents an OpenSSH certificate as defined in [PROTOCOL.certkeys]?rev=1.8.

type Certificate struct {
    Nonce           []byte
    Key             PublicKey
    Serial          uint64
    CertType        uint32
    KeyId           string
    ValidPrincipals []string
    ValidAfter      uint64
    ValidBefore     uint64
    Permissions
    Reserved     []byte
    SignatureKey PublicKey
    Signature    *Signature
}

func (*Certificate) Marshal ¶

func (c *Certificate) Marshal() []byte

Marshal serializes c into OpenSSH's wire format. It is part of the PublicKey interface.

func (*Certificate) SignCert ¶

func (c *Certificate) SignCert(rand io.Reader, authority Signer) error

SignCert sets c.SignatureKey to the authority's public key and stores a Signature, by authority, in the certificate.

func (*Certificate) Type ¶

func (c *Certificate) Type() string

Type returns the key name. It is part of the PublicKey interface.

func (*Certificate) Verify ¶

func (c *Certificate) Verify(data []byte, sig *Signature) error

Verify verifies a signature against the certificate's public key. It is part of the PublicKey interface.

type Channel ¶

A Channel is an ordered, reliable, flow-controlled, duplex stream that is multiplexed over an SSH connection.

type Channel interface {
    // Read reads up to len(data) bytes from the channel.
    Read(data []byte) (int, error)

    // Write writes len(data) bytes to the channel.
    Write(data []byte) (int, error)

    // Close signals end of channel use. No data may be sent after this
    // call.
    Close() error

    // CloseWrite signals the end of sending in-band
    // data. Requests may still be sent, and the other side may
    // still send data
    CloseWrite() error

    // SendRequest sends a channel request.  If wantReply is true,
    // it will wait for a reply and return the result as a
    // boolean, otherwise the return value will be false. Channel
    // requests are out-of-band messages so they may be sent even
    // if the data stream is closed or blocked by flow control.
    // If the channel is closed before a reply is returned, io.EOF
    // is returned.
    SendRequest(name string, wantReply bool, payload []byte) (bool, error)

    // Stderr returns an io.ReadWriter that writes to this channel
    // with the extended data type set to stderr. Stderr may
    // safely be read and written from a different goroutine than
    // Read and Write respectively.
    Stderr() io.ReadWriter
}

type Client ¶

Client implements a traditional SSH client that supports shells, subprocesses, TCP port/streamlocal forwarding and tunneled dialing.

type Client struct {
    Conn
    // contains filtered or unexported fields
}

func Dial ¶

func Dial(network, addr string, config *ClientConfig) (*Client, error)

Dial starts a client connection to the given SSH server. It is a convenience function that connects to the given network address, initiates the SSH handshake, and then sets up a Client. For access to incoming channels and requests, use net.Dial with NewClientConn instead.

var hostKey ssh.PublicKey
// An SSH client is represented with a ClientConn.
//
// To authenticate with the remote server you must pass at least one
// implementation of AuthMethod via the Auth field in ClientConfig,
// and provide a HostKeyCallback.
config := &ssh.ClientConfig{
    User: "username",
    Auth: []ssh.AuthMethod{
        ssh.Password("yourpassword"),
    },
    HostKeyCallback: ssh.FixedHostKey(hostKey),
}
client, err := ssh.Dial("tcp", "yourserver.com:22", config)
if err != nil {
    log.Fatal("Failed to dial: ", err)
}

// Each ClientConn can support multiple interactive sessions,
// represented by a Session.
session, err := client.NewSession()
if err != nil {
    log.Fatal("Failed to create session: ", err)
}
defer session.Close()

// Once a Session is created, you can execute a single command on
// the remote side using the Run method.
var b bytes.Buffer
session.Stdout = &b
if err := session.Run("/usr/bin/whoami"); err != nil {
    log.Fatal("Failed to run: " + err.Error())
}
fmt.Println(b.String())

func NewClient ¶

func NewClient(c Conn, chans <-chan NewChannel, reqs <-chan *Request) *Client

NewClient creates a Client on top of the given connection.

func (*Client) Dial ¶

func (c *Client) Dial(n, addr string) (net.Conn, error)

Dial initiates a connection to the addr from the remote host. The resulting connection has a zero LocalAddr() and RemoteAddr().

func (*Client) DialTCP ¶

func (c *Client) DialTCP(n string, laddr, raddr *net.TCPAddr) (net.Conn, error)

DialTCP connects to the remote address raddr on the network net, which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used as the local address for the connection.

func (*Client) HandleChannelOpen ¶

func (c *Client) HandleChannelOpen(channelType string) <-chan NewChannel

HandleChannelOpen returns a channel on which NewChannel requests for the given type are sent. If the type already is being handled, nil is returned. The channel is closed when the connection is closed.

func (*Client) Listen ¶

func (c *Client) Listen(n, addr string) (net.Listener, error)

Listen requests the remote peer open a listening socket on addr. Incoming connections will be available by calling Accept on the returned net.Listener. The listener must be serviced, or the SSH connection may hang. N must be "tcp", "tcp4", "tcp6", or "unix".

var hostKey ssh.PublicKey
config := &ssh.ClientConfig{
    User: "username",
    Auth: []ssh.AuthMethod{
        ssh.Password("password"),
    },
    HostKeyCallback: ssh.FixedHostKey(hostKey),
}
// Dial your ssh server.
conn, err := ssh.Dial("tcp", "localhost:22", config)
if err != nil {
    log.Fatal("unable to connect: ", err)
}
defer conn.Close()

// Request the remote side to open port 8080 on all interfaces.
l, err := conn.Listen("tcp", "0.0.0.0:8080")
if err != nil {
    log.Fatal("unable to register tcp forward: ", err)
}
defer l.Close()

// Serve HTTP with your SSH server acting as a reverse proxy.
http.Serve(l, http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
    fmt.Fprintf(resp, "Hello world!\n")
}))

func (*Client) ListenTCP ¶

func (c *Client) ListenTCP(laddr *net.TCPAddr) (net.Listener, error)

ListenTCP requests the remote peer open a listening socket on laddr. Incoming connections will be available by calling Accept on the returned net.Listener.

func (*Client) ListenUnix ¶

func (c *Client) ListenUnix(socketPath string) (net.Listener, error)

ListenUnix is similar to ListenTCP but uses a Unix domain socket.

func (*Client) NewSession ¶

func (c *Client) NewSession() (*Session, error)

NewSession opens a new Session for this client. (A session is a remote execution of a program.)

type ClientConfig ¶

A ClientConfig structure is used to configure a Client. It must not be modified after having been passed to an SSH function.

type ClientConfig struct {
    // Config contains configuration that is shared between clients and
    // servers.
    Config

    // User contains the username to authenticate as.
    User string

    // Auth contains possible authentication methods to use with the
    // server. Only the first instance of a particular RFC 4252 method will
    // be used during authentication.
    Auth []AuthMethod

    // HostKeyCallback is called during the cryptographic
    // handshake to validate the server's host key. The client
    // configuration must supply this callback for the connection
    // to succeed. The functions InsecureIgnoreHostKey or
    // FixedHostKey can be used for simplistic host key checks.
    HostKeyCallback HostKeyCallback

    // ClientVersion contains the version identification string that will
    // be used for the connection. If empty, a reasonable default is used.
    ClientVersion string

    // HostKeyAlgorithms lists the key types that the client will
    // accept from the server as host key, in order of
    // preference. If empty, a reasonable default is used. Any
    // string returned from PublicKey.Type method may be used, or
    // any of the CertAlgoXxxx and KeyAlgoXxxx constants.
    HostKeyAlgorithms []string

    // Timeout is the maximum amount of time for the TCP connection to establish.
    //
    // A Timeout of zero means no timeout.
    Timeout time.Duration
}

type Config ¶

Config contains configuration data common to both ServerConfig and ClientConfig.

type Config struct {
    // Rand provides the source of entropy for cryptographic
    // primitives. If Rand is nil, the cryptographic random reader
    // in package crypto/rand will be used.
    Rand io.Reader

    // The maximum number of bytes sent or received after which a
    // new key is negotiated. It must be at least 256. If
    // unspecified, a size suitable for the chosen cipher is used.
    RekeyThreshold uint64

    // The allowed key exchanges algorithms. If unspecified then a
    // default set of algorithms is used.
    KeyExchanges []string

    // The allowed cipher algorithms. If unspecified then a sensible
    // default is used.
    Ciphers []string

    // The allowed MAC algorithms. If unspecified then a sensible default
    // is used.
    MACs []string
}

func (*Config) SetDefaults ¶

func (c *Config) SetDefaults()

SetDefaults sets sensible values for unset fields in config. This is exported for testing: Configs passed to SSH functions are copied and have default values set automatically.

type Conn ¶

Conn represents an SSH connection for both server and client roles. Conn is the basis for implementing an application layer, such as ClientConn, which implements the traditional shell access for clients.

type Conn interface {
    ConnMetadata

    // SendRequest sends a global request, and returns the
    // reply. If wantReply is true, it returns the response status
    // and payload. See also RFC4254, section 4.
    SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error)

    // OpenChannel tries to open an channel. If the request is
    // rejected, it returns *OpenChannelError. On success it returns
    // the SSH Channel and a Go channel for incoming, out-of-band
    // requests. The Go channel must be serviced, or the
    // connection will hang.
    OpenChannel(name string, data []byte) (Channel, <-chan *Request, error)

    // Close closes the underlying network connection
    Close() error

    // Wait blocks until the connection has shut down, and returns the
    // error causing the shutdown.
    Wait() error
}

func NewClientConn ¶

func NewClientConn(c net.Conn, addr string, config *ClientConfig) (Conn, <-chan NewChannel, <-chan *Request, error)

NewClientConn establishes an authenticated SSH connection using c as the underlying transport. The Request and NewChannel channels must be serviced or the connection will hang.

type ConnMetadata ¶

ConnMetadata holds metadata for the connection.

type ConnMetadata interface {
    // User returns the user ID for this connection.
    User() string

    // SessionID returns the session hash, also denoted by H.
    SessionID() []byte

    // ClientVersion returns the client's version string as hashed
    // into the session ID.
    ClientVersion() []byte

    // ServerVersion returns the server's version string as hashed
    // into the session ID.
    ServerVersion() []byte

    // RemoteAddr returns the remote address for this connection.
    RemoteAddr() net.Addr

    // LocalAddr returns the local address for this connection.
    LocalAddr() net.Addr
}

type CryptoPublicKey ¶

CryptoPublicKey, if implemented by a PublicKey, returns the underlying crypto.PublicKey form of the key.

type CryptoPublicKey interface {
    CryptoPublicKey() crypto.PublicKey
}

type ExitError ¶

An ExitError reports unsuccessful completion of a remote command.

type ExitError struct {
    Waitmsg
}

func (*ExitError) Error ¶

func (e *ExitError) Error() string

type ExitMissingError ¶

ExitMissingError is returned if a session is torn down cleanly, but the server sends no confirmation of the exit status.

type ExitMissingError struct{}

func (*ExitMissingError) Error ¶

func (e *ExitMissingError) Error() string

type HostKeyCallback ¶

HostKeyCallback is the function type used for verifying server keys. A HostKeyCallback must return nil if the host key is OK, or an error to reject it. It receives the hostname as passed to Dial or NewClientConn. The remote address is the RemoteAddr of the net.Conn underlying the the SSH connection.

type HostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error

func FixedHostKey ¶

func FixedHostKey(key PublicKey) HostKeyCallback

FixedHostKey returns a function for use in ClientConfig.HostKeyCallback to accept only a specific host key.

func InsecureIgnoreHostKey ¶

func InsecureIgnoreHostKey() HostKeyCallback

InsecureIgnoreHostKey returns a function that can be used for ClientConfig.HostKeyCallback to accept any host key. It should not be used for production code.

type KeyboardInteractiveChallenge ¶

KeyboardInteractiveChallenge should print questions, optionally disabling echoing (e.g. for passwords), and return all the answers. Challenge may be called multiple times in a single session. After successful authentication, the server may send a challenge with no questions, for which the user and instruction messages should be printed. RFC 4256 section 3.3 details how the UI should behave for both CLI and GUI environments.

type KeyboardInteractiveChallenge func(user, instruction string, questions []string, echos []bool) (answers []string, err error)

type NewChannel ¶

NewChannel represents an incoming request to a channel. It must either be accepted for use by calling Accept, or rejected by calling Reject.

type NewChannel interface {
    // Accept accepts the channel creation request. It returns the Channel
    // and a Go channel containing SSH requests. The Go channel must be
    // serviced otherwise the Channel will hang.
    Accept() (Channel, <-chan *Request, error)

    // Reject rejects the channel creation request. After calling
    // this, no other methods on the Channel may be called.
    Reject(reason RejectionReason, message string) error

    // ChannelType returns the type of the channel, as supplied by the
    // client.
    ChannelType() string

    // ExtraData returns the arbitrary payload for this channel, as supplied
    // by the client. This data is specific to the channel type.
    ExtraData() []byte
}

type OpenChannelError ¶

OpenChannelError is returned if the other side rejects an OpenChannel request.

type OpenChannelError struct {
    Reason  RejectionReason
    Message string
}

func (*OpenChannelError) Error ¶

func (e *OpenChannelError) Error() string

type Permissions ¶

The Permissions type holds fine-grained permissions that are specific to a user or a specific authentication method for a user. Permissions, except for "source-address", must be enforced in the server application layer, after successful authentication. The Permissions are passed on in ServerConn so a server implementation can honor them.

type Permissions struct {
    // Critical options restrict default permissions. Common
    // restrictions are "source-address" and "force-command". If
    // the server cannot enforce the restriction, or does not
    // recognize it, the user should not authenticate.
    CriticalOptions map[string]string

    // Extensions are extra functionality that the server may
    // offer on authenticated connections. Common extensions are
    // "permit-agent-forwarding", "permit-X11-forwarding". Lack of
    // support for an extension does not preclude authenticating a
    // user.
    Extensions map[string]string
}

type PublicKey ¶

PublicKey is an abstraction of different types of public keys.

type PublicKey interface {
    // Type returns the key's type, e.g. "ssh-rsa".
    Type() string

    // Marshal returns the serialized key data in SSH wire format,
    // with the name prefix.
    Marshal() []byte

    // Verify that sig is a signature on the given data using this
    // key. This function will hash the data appropriately first.
    Verify(data []byte, sig *Signature) error
}

func NewPublicKey ¶

func NewPublicKey(key interface{}) (PublicKey, error)

NewPublicKey takes an *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or ed25519.PublicKey returns a corresponding PublicKey instance. ECDSA keys must use P-256, P-384 or P-521.

func ParseAuthorizedKey ¶

func ParseAuthorizedKey(in []byte) (out PublicKey, comment string, options []string, rest []byte, err error)

ParseAuthorizedKeys parses a public key from an authorized_keys file used in OpenSSH according to the sshd(8) manual page.

func ParsePublicKey ¶

func ParsePublicKey(in []byte) (out PublicKey, err error)

ParsePublicKey parses an SSH public key formatted for use in the SSH wire protocol according to RFC 4253, section 6.6.

type RejectionReason ¶

RejectionReason is an enumeration used when rejecting channel creation requests. See RFC 4254, section 5.1.

type RejectionReason uint32

const (
    Prohibited RejectionReason = iota + 1
    ConnectionFailed
    UnknownChannelType
    ResourceShortage
)

func (RejectionReason) String ¶

func (r RejectionReason) String() string

String converts the rejection reason to human readable form.

type Request ¶

Request is a request sent outside of the normal stream of data. Requests can either be specific to an SSH channel, or they can be global.

type Request struct {
    Type      string
    WantReply bool
    Payload   []byte
    // contains filtered or unexported fields
}

func (*Request) Reply ¶

func (r *Request) Reply(ok bool, payload []byte) error

Reply sends a response to a request. It must be called for all requests where WantReply is true and is a no-op otherwise. The payload argument is ignored for replies to channel-specific requests.

type ServerConfig ¶

ServerConfig holds server specific configuration data.

type ServerConfig struct {
    // Config contains configuration shared between client and server.
    Config

    // NoClientAuth is true if clients are allowed to connect without
    // authenticating.
    NoClientAuth bool

    // MaxAuthTries specifies the maximum number of authentication attempts
    // permitted per connection. If set to a negative number, the number of
    // attempts are unlimited. If set to zero, the number of attempts are limited
    // to 6.
    MaxAuthTries int

    // PasswordCallback, if non-nil, is called when a user
    // attempts to authenticate using a password.
    PasswordCallback func(conn ConnMetadata, password []byte) (*Permissions, error)

    // PublicKeyCallback, if non-nil, is called when a client attempts public
    // key authentication. It must return true if the given public key is
    // valid for the given user. For example, see CertChecker.Authenticate.
    PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error)

    // KeyboardInteractiveCallback, if non-nil, is called when
    // keyboard-interactive authentication is selected (RFC
    // 4256). The client object's Challenge function should be
    // used to query the user. The callback may offer multiple
    // Challenge rounds. To avoid information leaks, the client
    // should be presented a challenge even if the user is
    // unknown.
    KeyboardInteractiveCallback func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error)

    // AuthLogCallback, if non-nil, is called to log all authentication
    // attempts.
    AuthLogCallback func(conn ConnMetadata, method string, err error)

    // ServerVersion is the version identification string to announce in
    // the public handshake.
    // If empty, a reasonable default is used.
    // Note that RFC 4253 section 4.2 requires that this string start with
    // "SSH-2.0-".
    ServerVersion string
    // contains filtered or unexported fields
}

func (*ServerConfig) AddHostKey ¶

func (s *ServerConfig) AddHostKey(key Signer)

AddHostKey adds a private key as a host key. If an existing host key exists with the same algorithm, it is overwritten. Each server config must have at least one host key.

type ServerConn ¶

ServerConn is an authenticated SSH connection, as seen from the server

type ServerConn struct {
    Conn

    // If the succeeding authentication callback returned a
    // non-nil Permissions pointer, it is stored here.
    Permissions *Permissions
}

func NewServerConn ¶

func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewChannel, <-chan *Request, error)

NewServerConn starts a new SSH server with c as the underlying transport. It starts with a handshake and, if the handshake is unsuccessful, it closes the connection and returns an error. The Request and NewChannel channels must be serviced, or the connection will hang.

// Public key authentication is done by comparing
// the public key of a received connection
// with the entries in the authorized_keys file.
authorizedKeysBytes, err := ioutil.ReadFile("authorized_keys")
if err != nil {
    log.Fatalf("Failed to load authorized_keys, err: %v", err)
}

authorizedKeysMap := map[string]bool{}
for len(authorizedKeysBytes) > 0 {
    pubKey, _, _, rest, err := ssh.ParseAuthorizedKey(authorizedKeysBytes)
    if err != nil {
        log.Fatal(err)
    }

    authorizedKeysMap[string(pubKey.Marshal())] = true
    authorizedKeysBytes = rest
}

// An SSH server is represented by a ServerConfig, which holds
// certificate details and handles authentication of ServerConns.
config := &ssh.ServerConfig{
    // Remove to disable password auth.
    PasswordCallback: func(c ssh.ConnMetadata, pass []byte) (*ssh.Permissions, error) {
        // Should use constant-time compare (or better, salt+hash) in
        // a production setting.
        if c.User() == "testuser" && string(pass) == "tiger" {
            return nil, nil
        }
        return nil, fmt.Errorf("password rejected for %q", c.User())
    },

    // Remove to disable public key auth.
    PublicKeyCallback: func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
        if authorizedKeysMap[string(pubKey.Marshal())] {
            return nil, nil
        }
        return nil, fmt.Errorf("unknown public key for %q", c.User())
    },
}

privateBytes, err := ioutil.ReadFile("id_rsa")
if err != nil {
    log.Fatal("Failed to load private key: ", err)
}

private, err := ssh.ParsePrivateKey(privateBytes)
if err != nil {
    log.Fatal("Failed to parse private key: ", err)
}

config.AddHostKey(private)

// Once a ServerConfig has been configured, connections can be
// accepted.
listener, err := net.Listen("tcp", "0.0.0.0:2022")
if err != nil {
    log.Fatal("failed to listen for connection: ", err)
}
nConn, err := listener.Accept()
if err != nil {
    log.Fatal("failed to accept incoming connection: ", err)
}

// Before use, a handshake must be performed on the incoming
// net.Conn.
_, chans, reqs, err := ssh.NewServerConn(nConn, config)
if err != nil {
    log.Fatal("failed to handshake: ", err)
}
// The incoming Request channel must be serviced.
go ssh.DiscardRequests(reqs)

// Service the incoming Channel channel.
for newChannel := range chans {
    // Channels have a type, depending on the application level
    // protocol intended. In the case of a shell, the type is
    // "session" and ServerShell may be used to present a simple
    // terminal interface.
    if newChannel.ChannelType() != "session" {
        newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
        continue
    }
    channel, requests, err := newChannel.Accept()
    if err != nil {
        log.Fatalf("Could not accept channel: %v", err)
    }

    // Sessions have out-of-band requests such as "shell",
    // "pty-req" and "env".  Here we handle only the
    // "shell" request.
    go func(in <-chan *ssh.Request) {
        for req := range in {
            req.Reply(req.Type == "shell", nil)
        }
    }(requests)

    term := terminal.NewTerminal(channel, "> ")

    go func() {
        defer channel.Close()
        for {
            line, err := term.ReadLine()
            if err != nil {
                break
            }
            fmt.Println(line)
        }
    }()
}

type Session ¶

A Session represents a connection to a remote command or shell.

type Session struct {
    // Stdin specifies the remote process's standard input.
    // If Stdin is nil, the remote process reads from an empty
    // bytes.Buffer.
    Stdin io.Reader

    // Stdout and Stderr specify the remote process's standard
    // output and error.
    //
    // If either is nil, Run connects the corresponding file
    // descriptor to an instance of ioutil.Discard. There is a
    // fixed amount of buffering that is shared for the two streams.
    // If either blocks it may eventually cause the remote
    // command to block.
    Stdout io.Writer
    Stderr io.Writer
    // contains filtered or unexported fields
}

func (*Session) Close ¶

func (s *Session) Close() error

func (*Session) CombinedOutput ¶

func (s *Session) CombinedOutput(cmd string) ([]byte, error)

CombinedOutput runs cmd on the remote host and returns its combined standard output and standard error.

func (*Session) Output ¶

func (s *Session) Output(cmd string) ([]byte, error)

Output runs cmd on the remote host and returns its standard output.

func (*Session) RequestPty ¶

func (s *Session) RequestPty(term string, h, w int, termmodes TerminalModes) error

RequestPty requests the association of a pty with the session on the remote host.

var hostKey ssh.PublicKey
// Create client config
config := &ssh.ClientConfig{
    User: "username",
    Auth: []ssh.AuthMethod{
        ssh.Password("password"),
    },
    HostKeyCallback: ssh.FixedHostKey(hostKey),
}
// Connect to ssh server
conn, err := ssh.Dial("tcp", "localhost:22", config)
if err != nil {
    log.Fatal("unable to connect: ", err)
}
defer conn.Close()
// Create a session
session, err := conn.NewSession()
if err != nil {
    log.Fatal("unable to create session: ", err)
}
defer session.Close()
// Set up terminal modes
modes := ssh.TerminalModes{
    ssh.ECHO:          0,     // disable echoing
    ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
    ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
}
// Request pseudo terminal
if err := session.RequestPty("xterm", 40, 80, modes); err != nil {
    log.Fatal("request for pseudo terminal failed: ", err)
}
// Start remote shell
if err := session.Shell(); err != nil {
    log.Fatal("failed to start shell: ", err)
}

func (*Session) RequestSubsystem ¶

func (s *Session) RequestSubsystem(subsystem string) error

RequestSubsystem requests the association of a subsystem with the session on the remote host. A subsystem is a predefined command that runs in the background when the ssh session is initiated

func (*Session) Run ¶

func (s *Session) Run(cmd string) error

Run runs cmd on the remote host. Typically, the remote server passes cmd to the shell for interpretation. A Session only accepts one call to Run, Start, Shell, Output, or CombinedOutput.

The returned error is nil if the command runs, has no problems copying stdin, stdout, and stderr, and exits with a zero exit status.

If the remote server does not send an exit status, an error of type *ExitMissingError is returned. If the command completes unsuccessfully or is interrupted by a signal, the error is of type *ExitError. Other error types may be returned for I/O problems.

func (*Session) SendRequest ¶

func (s *Session) SendRequest(name string, wantReply bool, payload []byte) (bool, error)

SendRequest sends an out-of-band channel request on the SSH channel underlying the session.

func (*Session) Setenv ¶

func (s *Session) Setenv(name, value string) error

Setenv sets an environment variable that will be applied to any command executed by Shell or Run.

func (*Session) Shell ¶

func (s *Session) Shell() error

Shell starts a login shell on the remote host. A Session only accepts one call to Run, Start, Shell, Output, or CombinedOutput.

func (*Session) Signal ¶

func (s *Session) Signal(sig Signal) error

Signal sends the given signal to the remote process. sig is one of the SIG* constants.

func (*Session) Start ¶

func (s *Session) Start(cmd string) error

Start runs cmd on the remote host. Typically, the remote server passes cmd to the shell for interpretation. A Session only accepts one call to Run, Start or Shell.

func (*Session) StderrPipe ¶

func (s *Session) StderrPipe() (io.Reader, error)

StderrPipe returns a pipe that will be connected to the remote command's standard error when the command starts. There is a fixed amount of buffering that is shared between stdout and stderr streams. If the StderrPipe reader is not serviced fast enough it may eventually cause the remote command to block.

func (*Session) StdinPipe ¶

func (s *Session) StdinPipe() (io.WriteCloser, error)

StdinPipe returns a pipe that will be connected to the remote command's standard input when the command starts.

func (*Session) StdoutPipe ¶

func (s *Session) StdoutPipe() (io.Reader, error)

StdoutPipe returns a pipe that will be connected to the remote command's standard output when the command starts. There is a fixed amount of buffering that is shared between stdout and stderr streams. If the StdoutPipe reader is not serviced fast enough it may eventually cause the remote command to block.

func (*Session) Wait ¶

func (s *Session) Wait() error

Wait waits for the remote command to exit.

The returned error is nil if the command runs, has no problems copying stdin, stdout, and stderr, and exits with a zero exit status.

If the remote server does not send an exit status, an error of type *ExitMissingError is returned. If the command completes unsuccessfully or is interrupted by a signal, the error is of type *ExitError. Other error types may be returned for I/O problems.

type Signal ¶

type Signal string

POSIX signals as listed in RFC 4254 Section 6.10.

const (
    SIGABRT Signal = "ABRT"
    SIGALRM Signal = "ALRM"
    SIGFPE  Signal = "FPE"
    SIGHUP  Signal = "HUP"
    SIGILL  Signal = "ILL"
    SIGINT  Signal = "INT"
    SIGKILL Signal = "KILL"
    SIGPIPE Signal = "PIPE"
    SIGQUIT Signal = "QUIT"
    SIGSEGV Signal = "SEGV"
    SIGTERM Signal = "TERM"
    SIGUSR1 Signal = "USR1"
    SIGUSR2 Signal = "USR2"
)

type Signature ¶

Signature represents a cryptographic signature.

type Signature struct {
    Format string
    Blob   []byte
}

type Signer ¶

A Signer can create signatures that verify against a public key.

type Signer interface {
    // PublicKey returns an associated PublicKey instance.
    PublicKey() PublicKey

    // Sign returns raw signature for the given data. This method
    // will apply the hash specified for the keytype to the data.
    Sign(rand io.Reader, data []byte) (*Signature, error)
}

func NewCertSigner ¶

func NewCertSigner(cert *Certificate, signer Signer) (Signer, error)

NewCertSigner returns a Signer that signs with the given Certificate, whose private key is held by signer. It returns an error if the public key in cert doesn't match the key used by signer.

func NewSignerFromKey ¶

func NewSignerFromKey(key interface{}) (Signer, error)

NewSignerFromKey takes an *rsa.PrivateKey, *dsa.PrivateKey, *ecdsa.PrivateKey or any other crypto.Signer and returns a corresponding Signer instance. ECDSA keys must use P-256, P-384 or P-521.

func NewSignerFromSigner ¶

func NewSignerFromSigner(signer crypto.Signer) (Signer, error)

NewSignerFromSigner takes any crypto.Signer implementation and returns a corresponding Signer interface. This can be used, for example, with keys kept in hardware modules.

func ParsePrivateKey ¶

func ParsePrivateKey(pemBytes []byte) (Signer, error)

ParsePrivateKey returns a Signer from a PEM encoded private key. It supports the same keys as ParseRawPrivateKey.

func ParsePrivateKeyWithPassphrase ¶

func ParsePrivateKeyWithPassphrase(pemBytes, passPhrase []byte) (Signer, error)

ParsePrivateKeyWithPassphrase returns a Signer from a PEM encoded private key and passphrase. It supports the same keys as ParseRawPrivateKeyWithPassphrase.

type TerminalModes ¶

type TerminalModes map[uint8]uint32

type Waitmsg ¶

Waitmsg stores the information about an exited remote command as reported by Wait.

type Waitmsg struct {
    // contains filtered or unexported fields
}

func (Waitmsg) ExitStatus ¶

func (w Waitmsg) ExitStatus() int

ExitStatus returns the exit status of the remote command.

func (Waitmsg) Lang ¶

func (w Waitmsg) Lang() string

Lang returns the language tag. See RFC 3066

func (Waitmsg) Msg ¶

func (w Waitmsg) Msg() string

Msg returns the exit message given by the remote command

func (Waitmsg) Signal ¶

func (w Waitmsg) Signal() string

Signal returns the exit signal of the remote command if it was terminated violently.

func (Waitmsg) String ¶

func (w Waitmsg) String() string

Subdirectories