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

• 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
  • dnssec: .key file format output by dnssec-keygen etc
  • putty: the PuTTY .ppk file format (supports truncated variant without all the lines from Private-Lines: onwards)
• options -- Optional Object, extra options, with keys:
  • filename -- Optional String, name for the key being parsed (eg. the filename that was opened). Used to generate Error messages
  • passphrase -- Optional String, encryption passphrase used to decrypt an encrypted PEM file

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'[, hashType = 'ssh']])

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
• hashType -- String name of fingerprint hash type to use, valid options are ssh (the type of fingerprint used by OpenSSH, e.g. in ssh-keygen), spki (used by HPKP, some OpenSSL applications)

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'[, options]])

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
  • dnssec: .private format output by dnssec-keygen etc.
• options -- Optional Object, extra options, with keys:
  • filename -- Optional String, name for the key being parsed (eg. the filename that was opened). Used to generate Error messages
  • passphrase -- Optional String, encryption passphrase used to decrypt an encrypted PEM file

generatePrivateKey(type[, options])

Generates a new private key of a certain key type, from random data.

Parameters

• type -- String, type of key to generate. Currently supported are 'ecdsa' and 'ed25519'
• options -- optional Object, with keys:
  • curve -- optional String, for 'ecdsa' keys, specifies the curve to use. If ECDSA is specified and this option is not given, defaults to using 'nistp256'.

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[, options])

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
• options -- Optional Object, with properties:
  • algorithms -- Array of strings, names of hash algorithms to limit support to. If fingerprint uses a hash algorithm not on this list, throws InvalidAlgorithmError.
  • hashType -- String, the type of hash the fingerprint uses, either ssh or spki (normally auto-detected based on the format, but can be overridden)
  • type -- String, the entity this fingerprint identifies, either key or certificate

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(keyOrCertificate)

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

Note that a Key-type Fingerprint will always return false if asked to match a Certificate and vice versa.

Parameters

• keyOrCertificate -- a Key object or Certificate object, the entity 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').

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 only very minimal support for key usage 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

• data -- a Buffer or String
• format -- a String, format to use, one of 'openssh', 'pem' (X.509 in a PEM wrapper), or 'x509' (raw DER encoded)

createSelfSignedCertificate(subject, privateKey[, options])

Parameters

• subject -- an Identity, the subject of the certificate
• privateKey -- a PrivateKey, the key of the subject: will be used both to be placed in the certificate and also to sign it (since this is a self-signed certificate)
• options -- optional Object, with keys:
  • lifetime -- optional Number, lifetime of the certificate from now in seconds
  • validFrom, validUntil -- optional Dates, beginning and end of certificate validity period. If given lifetime will be ignored
  • serial -- optional Buffer, the serial number of the certificate
  • purposes -- optional Array of String, X.509 key usage restrictions

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

Parameters

• subject -- an Identity, the subject of the certificate
• key -- a Key, the public key of the subject
• issuer -- an Identity, the issuer of the certificate who will sign it
• issuerKey -- a PrivateKey, the issuer's private key for signing
• options -- optional Object, with keys:
  • lifetime -- optional Number, lifetime of the certificate from now in seconds
  • validFrom, validUntil -- optional Dates, beginning and end of certificate validity period. If given lifetime will be ignored
  • serial -- optional Buffer, the serial number of the certificate
  • purposes -- optional Array of String, X.509 key usage restrictions

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#purposes

Array of Strings indicating the X.509 key usage purposes that this certificate is valid for. The possible strings at the moment are:

• 'signature' -- key can be used for digital signatures
• 'identity' -- key can be used to attest about the identity of the signer (X.509 calls this nonRepudiation)
• 'codeSigning' -- key can be used to sign executable code
• 'keyEncryption' -- key can be used to encrypt other keys
• 'encryption' -- key can be used to encrypt data (only applies for RSA)
• 'keyAgreement' -- key can be used for key exchange protocols such as Diffie-Hellman
• 'ca' -- key can be used to sign other certificates (is a Certificate Authority)
• 'crl' -- key can be used to sign Certificate Revocation Lists (CRLs)

Certificate#getExtension(nameOrOid)

Retrieves information about a certificate extension, if present, or returns undefined if not. The string argument nameOrOid should be either the OID (for X509 extensions) or the name (for OpenSSH extensions) of the extension to retrieve.

The object returned will have the following properties:

• format -- String, set to either 'x509' or 'openssh'
• name or oid -- String, only one set based on value of format
• data -- Buffer, the raw data inside the extension

Certificate#getExtensions()

Returns an Array of all present certificate extensions, in the same manner and format as getExtension().

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

• when -- optional Date, if specified, tests whether the Certificate was or will be expired at the specified time instead of now

Returns a Boolean.

Certificate#isSignedByKey(key)

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

Parameters

• key -- a Key instance

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

• certificate -- another Certificate instance

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

• hashAlgo -- an optional String, any hash function name

Certificate#toBuffer([format])

Serializes the Certificate to a Buffer and returns it.

Parameters

• format -- an optional String, output format, one of 'openssh', 'pem' or 'x509'. Defaults to 'x509'.

Returns a Buffer.

Certificate#toString([format])

• format -- an optional String, output format, one of 'openssh', 'pem' or 'x509'. Defaults to 'pem'.

Returns a String.

Certificate identities

identityForHost(hostname)

Constructs a host-type Identity for a given hostname.

Parameters

• hostname -- the fully qualified DNS name of the host

Returns an Identity instance.

identityForUser(uid)

Constructs a user-type Identity for a given UID.

Parameters

• uid -- a String, user identifier (login name)

Returns an Identity instance.

identityForEmail(email)

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

Parameters

• email -- a String, email address

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

• dn -- a String

Returns an Identity instance.

identityFromArray(arr)

Constructs an Identity from an array of DN components (see Identity#toArray() for the format).

Parameters

• arr -- an Array of Objects, DN components with name and value

Returns an Identity instance.

Supported attributes in DNs:

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. It's probably better to use the #get() method instead of this property.

Identity#get(name[, asArray])

Returns the value of a named attribute in the Identity DN. If there is no attribute of the given name, returns undefined. If multiple components of the DN contain an attribute of this name, an exception is thrown unless the asArray argument is given as true -- then they will be returned as an Array in the same order they appear in the DN.

Parameters

• name -- a String
• asArray -- an optional Boolean

Identity#toArray()

Returns the Identity as an Array of DN component objects. This looks like:

[ {
  "name": "cn",
  "value": "Joe Bloggs"
},
{
  "name": "o",
  "value": "Organisation Ltd"
} ]

Each object has a name and a value property. The returned objects may be safely modified.

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 -- filename that was given to parseKey
• format -- the format that was trying to parse the key (see parseKey)
• innerErr -- the inner Error thrown by the format parser

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

• keyName -- filename that was given to parseKey
• format -- the format that was trying to parse the key (currently can only be "pem")

CertificateParseError

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

Properties

• certName -- filename that was given to parseCertificate
• format -- the format that was trying to parse the key (see parseCertificate)
• 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