This library has been extracted from node-http-signature (work by Mark Cavage and Dave Eddy) and node-ssh-fingerprint (work by Dave Eddy), with additions (including ECDSA support) by Alex Wilson.

Install

npm install sshpk

Examples

var sshpk = require('sshpk');

var fs = require('fs');

/* Read in an OpenSSH-format public key */
var keyPub = fs.readFileSync('id_rsa.pub');
var key = sshpk.parseKey(keyPub, 'ssh');

/* Get metadata about the key */
console.log('type => %s', key.type);
console.log('size => %d bits', key.size);
console.log('comment => %s', key.comment);

/* Compute key fingerprints, in new OpenSSH (>6.7) format, and old MD5 */
console.log('fingerprint => %s', key.fingerprint().toString());
console.log('old-style fingerprint => %s', key.fingerprint('md5').toString());

Example output:

type => rsa
size => 2048 bits
comment => foo@foo.com
fingerprint => SHA256:PYC9kPVC6J873CSIbfp0LwYeczP/W4ffObNCuDJ1u5w
old-style fingerprint => a0:c8:ad:6c:32:9a:32:fa:59:cc:a9:8c:0a:0d:6e:bd

More examples: converting between formats:

/* Read in a PEM public key */
var keyPem = fs.readFileSync('id_rsa.pem');
var key = sshpk.parseKey(keyPem, 'pem');

/* Convert to PEM PKCS#8 public key format */
var pemBuf = key.toBuffer('pkcs8');

/* Convert to SSH public key format (and return as a string) */
var sshKey = key.toString('ssh');

Signing and verifying:

/* Read in an OpenSSH/PEM *private* key */
var keyPriv = fs.readFileSync('id_ecdsa');
var key = sshpk.parsePrivateKey(keyPriv, 'pem');

var data = 'some data';

/* Sign some data with the key */
var s = key.createSign('sha1');
s.update(data);
var signature = s.sign();

/* Now load the public key (could also use just key.toPublic()) */
var keyPub = fs.readFileSync('id_ecdsa.pub');
key = sshpk.parseKey(keyPub, 'ssh');

/* Make a crypto.Verifier with this key */
var v = key.createVerify('sha1');
v.update(data);
var valid = v.verify(signature);
/* => true! */

Matching fingerprints with keys:

var fp = sshpk.parseFingerprint('SHA256:PYC9kPVC6J873CSIbfp0LwYeczP/W4ffObNCuDJ1u5w');

var keys = [sshpk.parseKey(...), sshpk.parseKey(...), ...];

keys.forEach(function (key) {
	if (fp.matches(key))
		console.log('found it!');
});

Usage

Public keys

`parseKey(data[, format = 'auto'[, name]])`

Parses a key from a given data format and returns a new Key object.

Parameters

data -- Either a Buffer or String, containing the key
format -- String name of format to use, valid options are:
- auto: choose automatically from all below
- pem: supports both PKCS#1 and PKCS#8
- ssh: standard OpenSSH format,
- pkcs1, pkcs8: variants of pem
- rfc4253: raw OpenSSH wire format
- openssh: new post-OpenSSH 6.5 internal format, produced by ssh-keygen -o
name -- Optional name for the key being parsed (eg. the filename that was opened). Used to generate Error messages

`Key.isKey(obj)`

Returns true if the given object is a valid Key object created by a version of sshpk compatible with this one.

Parameters

obj -- Object to identify

`Key#type`

String, the type of key. Valid options are rsa, dsa, ecdsa.

`Key#size`

Integer, "size" of the key in bits. For RSA/DSA this is the size of the modulus; for ECDSA this is the bit size of the curve in use.

`Key#comment`

Optional string, a key comment used by some formats (eg the ssh format).

`Key#curve`

Only present if this.type === 'ecdsa', string containing the name of the named curve used with this key. Possible values include nistp256, nistp384 and nistp521.

`Key#toBuffer([format = 'ssh'])`

Convert the key into a given data format and return the serialized key as a Buffer.

Parameters

format -- String name of format to use, for valid options see parseKey()

`Key#toString([format = 'ssh])`

Same as this.toBuffer(format).toString().

`Key#fingerprint([algorithm = 'sha256'])`

Creates a new Fingerprint object representing this Key's fingerprint.

Parameters

algorithm -- String name of hash algorithm to use, valid options are md5, sha1, sha256, sha384, sha512

`Key#createVerify([hashAlgorithm])`

Creates a crypto.Verifier specialized to use this Key (and the correct public key algorithm to match it). The returned Verifier has the same API as a regular one, except that the verify() function takes only the target signature as an argument.

Parameters

hashAlgorithm -- optional String name of hash algorithm to use, any supported by OpenSSL are valid, usually including sha1, sha256.

v.verify(signature[, format]) Parameters

signature -- either a Signature object, or a Buffer or String
format -- optional String, name of format to interpret given String with. Not valid if signature is a Signature or Buffer.

`Key#createDiffieHellman()`

`Key#createDH()`

Creates a Diffie-Hellman key exchange object initialized with this key and all necessary parameters. This has the same API as a crypto.DiffieHellman instance, except that functions take Key and PrivateKey objects as arguments, and return them where indicated for.

This is only valid for keys belonging to a cryptosystem that supports DHE or a close analogue (i.e. dsa, ecdsa and curve25519 keys). An attempt to call this function on other keys will yield an Error.

Private keys

`parsePrivateKey(data[, format = 'auto'[, name]])`

Parses a private key from a given data format and returns a new PrivateKey object.

Parameters

data -- Either a Buffer or String, containing the key
format -- String name of format to use, valid options are:
- auto: choose automatically from all below
- pem: supports both PKCS#1 and PKCS#8
- ssh, openssh: new post-OpenSSH 6.5 internal format, produced by ssh-keygen -o
- pkcs1, pkcs8: variants of pem
- rfc4253: raw OpenSSH wire format
name -- Optional name for the key being parsed (eg. the filename that was opened). Used to generate Error messages

`PrivateKey.isPrivateKey(obj)`

Returns true if the given object is a valid PrivateKey object created by a version of sshpk compatible with this one.

Parameters

obj -- Object to identify

`PrivateKey#type`

String, the type of key. Valid options are rsa, dsa, ecdsa.

`PrivateKey#size`

Integer, "size" of the key in bits. For RSA/DSA this is the size of the modulus; for ECDSA this is the bit size of the curve in use.

`PrivateKey#curve`

Only present if this.type === 'ecdsa', string containing the name of the named curve used with this key. Possible values include nistp256, nistp384 and nistp521.

`PrivateKey#toBuffer([format = 'pkcs1'])`

Convert the key into a given data format and return the serialized key as a Buffer.

Parameters

format -- String name of format to use, valid options are listed under parsePrivateKey. Note that ED25519 keys default to openssh format instead (as they have no pkcs1 representation).

`PrivateKey#toString([format = 'pkcs1'])`

Same as this.toBuffer(format).toString().

`PrivateKey#toPublic()`

Extract just the public part of this private key, and return it as a Key object.

`PrivateKey#fingerprint([algorithm = 'sha256'])`

Same as this.toPublic().fingerprint().

`PrivateKey#createVerify([hashAlgorithm])`

Same as this.toPublic().createVerify().

`PrivateKey#createSign([hashAlgorithm])`

Creates a crypto.Sign specialized to use this PrivateKey (and the correct key algorithm to match it). The returned Signer has the same API as a regular one, except that the sign() function takes no arguments, and returns a Signature object.

Parameters

hashAlgorithm -- optional String name of hash algorithm to use, any supported by OpenSSL are valid, usually including sha1, sha256.

v.sign() Parameters

none

`PrivateKey#derive(newType)`

Derives a related key of type newType from this key. Currently this is only supported to change between ed25519 and curve25519 keys which are stored with the same private key (but usually distinct public keys in order to avoid degenerate keys that lead to a weak Diffie-Hellman exchange).

Parameters

newType -- String, type of key to derive, either ed25519 or curve25519

Fingerprints

`parseFingerprint(fingerprint[, algorithms])`

Pre-parses a fingerprint, creating a Fingerprint object that can be used to quickly locate a key by using the Fingerprint#matches function.

Parameters

fingerprint -- String, the fingerprint value, in any supported format
algorithms -- Optional list of strings, names of hash algorithms to limit support to. If fingerprint uses a hash algorithm not on this list, throws InvalidAlgorithmError.

`Fingerprint.isFingerprint(obj)`

Returns true if the given object is a valid Fingerprint object created by a version of sshpk compatible with this one.

Parameters

obj -- Object to identify

`Fingerprint#toString([format])`

Returns a fingerprint as a string, in the given format.

Parameters

format -- Optional String, format to use, valid options are hex and base64. If this Fingerprint uses the md5 algorithm, the default format is hex. Otherwise, the default is base64.

`Fingerprint#matches(key)`

Verifies whether or not this Fingerprint matches a given Key. This function uses double-hashing to avoid leaking timing information. Returns a boolean.

Parameters

key -- a Key object, the key to match this fingerprint against

Signatures

`parseSignature(signature, algorithm, format)`

Parses a signature in a given format, creating a Signature object. Useful for converting between the SSH and ASN.1 (PKCS/OpenSSL) signature formats, and also returned as output from PrivateKey#createSign().sign().

A Signature object can also be passed to a verifier produced by Key#createVerify() and it will automatically be converted internally into the correct format for verification.

Parameters

signature -- a Buffer (binary) or String (base64), data of the actual signature in the given format
algorithm -- a String, name of the algorithm to be used, possible values are rsa, dsa, ecdsa
format -- a String, either asn1 or ssh

`Signature.isSignature(obj)`

Returns true if the given object is a valid Signature object created by a version of sshpk compatible with this one.

Parameters

obj -- Object to identify

`Signature#toBuffer([format = 'asn1'])`

Converts a Signature to the given format and returns it as a Buffer.

Parameters

format -- a String, either asn1 or ssh

`Signature#toString([format = 'asn1'])`

Same as this.toBuffer(format).toString('base64').

Errors

`InvalidAlgorithmError`

The specified algorithm is not valid, either because it is not supported, or because it was not included on a list of allowed algorithms.

Thrown by Fingerprint.parse, Key#fingerprint.

Properties

algorithm -- the algorithm that could not be validated

`FingerprintFormatError`

The fingerprint string given could not be parsed as a supported fingerprint format, or the specified fingerprint format is invalid.

Thrown by Fingerprint.parse, Fingerprint#toString.

Properties

fingerprint -- if caused by a fingerprint, the string value given
format -- if caused by an invalid format specification, the string value given

`KeyParseError`

The key data given could not be parsed as a valid key.

Properties

keyName -- name that was given to Key#parse
format -- the format that was trying to parse the key
innerErr -- the inner Error thrown by the format parser

Friends of sshpk

sshpk-agent is a library for speaking the ssh-agent protocol from node.js, which uses sshpk