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sshpk

Parse, convert, fingerprint and use SSH keys (both public and private) in pure node -- no ssh-keygen or other external dependencies.

Supports RSA, DSA, ECDSA (nistp-*) and ED25519 key types, in PEM (PKCS#1, PKCS#8) and OpenSSH formats.

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'[, options]])

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

Parameters

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

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

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

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

v.verify(signature[, format]) Parameters

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'[, options]])

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

Parameters

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

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

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

v.sign() Parameters

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

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.isFingerprint(obj)

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

Parameters

Fingerprint#toString([format])

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

Parameters

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

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.isSignature(obj)

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

Parameters

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

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

Parameters

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

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

Certificates

sshpk includes basic support for parsing certificates in X.509 (PEM) format and the OpenSSH certificate format. This feature is intended to be used mainly to access basic metadata about certificates, extract public keys from them, and also to generate simple self-signed certificates from an existing key.

Notably, there is no implementation of CA chain-of-trust verification, and no support for key usage restrictions (or other kinds of restrictions). Please do the security world a favour, and DO NOT use this code for certificate verification in the traditional X.509 CA chain style.

parseCertificate(data, format)

Parameters

createSelfSignedCertificate(subject, privateKey[, options])

Parameters

createCertificate(subject, key, issuer, issuerKey[, options])

Parameters

Certificate#subjects

Array of Identity instances describing the subject of this certificate.

Certificate#issuer

The Identity of the Certificate's issuer (signer).

Certificate#subjectKey

The public key of the subject of the certificate, as a Key instance.

Certificate#issuerKey

The public key of the signing issuer of this certificate, as a Key instance. May be undefined if the issuer's key is unknown (e.g. on an X509 certificate).

Certificate#serial

The serial number of the certificate. As this is normally a 64-bit or wider integer, it is returned as a Buffer.

Certificate#isExpired([when])

Tests whether the Certificate is currently expired (i.e. the validFrom and validUntil dates specify a range of time that does not include the current time).

Parameters

Returns a Boolean.

Certificate#isSignedByKey(key)

Tests whether the Certificate was validly signed by the given (public) Key.

Parameters

Returns a Boolean.

Certificate#isSignedBy(certificate)

Tests whether this Certificate was validly signed by the subject of the given certificate. Also tests that the issuer Identity of this Certificate and the subject Identity of the other Certificate are equivalent.

Parameters

Returns a Boolean.

Certificate#fingerprint([hashAlgo])

Returns the X509-style fingerprint of the entire certificate (as a Fingerprint instance). This matches what a web-browser or similar would display as the certificate fingerprint and should not be confused with the fingerprint of the subject's public key.

Parameters

Certificate#toBuffer([format])

Serializes the Certificate to a Buffer and returns it.

Parameters

Returns a Buffer.

Certificate#toString([format])

Returns a String.

Certificate identities

identityForHost(hostname)

Constructs a host-type Identity for a given hostname.

Parameters

Returns an Identity instance.

identityForUser(uid)

Constructs a user-type Identity for a given UID.

Parameters

Returns an Identity instance.

identityForEmail(email)

Constructs an email-type Identity for a given email address.

Parameters

Returns an Identity instance.

identityFromDN(dn)

Parses an LDAP-style DN string (e.g. 'CN=foo, C=US') and turns it into an Identity instance.

Parameters

Returns an Identity instance.

Identity#toString()

Returns the identity as an LDAP-style DN string. e.g. 'CN=foo, O=bar corp, C=us'

Identity#type

The type of identity. One of 'host', 'user', 'email' or 'unknown'

Identity#hostname

Identity#uid

Identity#email

Set when type is 'host', 'user', or 'email', respectively. Strings.

Identity#cn

The value of the first CN= in the DN, if any.

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

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

KeyParseError

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

Properties

KeyEncryptedError

The key is encrypted with a symmetric key (ie, it is password protected). The parsing operation would succeed if it was given the passphrase option.

Properties

CertificateParseError

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

Properties

Friends of sshpk