webcrypto-shim.js

/**
 * @file Web Cryptography API shim
 * @author Artem S Vybornov <vybornov@gmail.com>
 * @license MIT
 */
(function (global, factory) {
    if (typeof define === 'function' && define.amd) {
        // AMD. Register as an anonymous module.
        define([], function () {
            return factory(global);
        });
    } else if (typeof module === 'object' && module.exports) {
        // CommonJS-like environments that support module.exports
        module.exports = factory(global);
    } else {
        factory(global);
    }
}(typeof self !== 'undefined' ? self : this, function (global) {
    'use strict';

    if ( typeof Promise !== 'function' )
        throw "Promise support required";

    var _crypto = global.crypto || global.msCrypto;
    if ( !_crypto ) return;

    var _subtle = _crypto.subtle || _crypto.webkitSubtle;
    if ( !_subtle ) return;

    var _Crypto     = global.Crypto || _crypto.constructor || Object,
        _SubtleCrypto = global.SubtleCrypto || _subtle.constructor || Object,
        _CryptoKey  = global.CryptoKey || global.Key || Object;

    var isEdge = global.navigator.userAgent.indexOf('Edge/') > -1;
    var isIE    = !!global.msCrypto && !isEdge;
    var isWebkit = !_crypto.subtle && !!_crypto.webkitSubtle;
    if ( !isIE && !isWebkit ) return;

    function s2a ( s ) {
        return btoa(s).replace(/\=+$/, '').replace(/\+/g, '-').replace(/\//g, '_');
    }

    function a2s ( s ) {
        s += '===', s = s.slice( 0, -s.length % 4 );
        return atob( s.replace(/-/g, '+').replace(/_/g, '/') );
    }

    function s2b ( s ) {
        var b = new Uint8Array(s.length);
        for ( var i = 0; i < s.length; i++ ) b[i] = s.charCodeAt(i);
        return b;
    }

    function b2s ( b ) {
        if ( b instanceof ArrayBuffer ) b = new Uint8Array(b);
        return String.fromCharCode.apply( String, b );
    }

    function alg ( a ) {
        var r = { 'name': (a.name || a || '').toUpperCase().replace('V','v') };
        switch ( r.name ) {
            case 'SHA-1':
            case 'SHA-256':
            case 'SHA-384':
            case 'SHA-512':
                break;
            case 'AES-CBC':
            case 'AES-GCM':
            case 'AES-KW':
                if ( a.length ) r['length'] = a.length;
                break;
            case 'HMAC':
                if ( a.hash ) r['hash'] = alg(a.hash);
                if ( a.length ) r['length'] = a.length;
                break;
            case 'RSAES-PKCS1-v1_5':
                if ( a.publicExponent ) r['publicExponent'] = new Uint8Array(a.publicExponent);
                if ( a.modulusLength ) r['modulusLength'] = a.modulusLength;
                break;
            case 'RSASSA-PKCS1-v1_5':
            case 'RSA-OAEP':
                if ( a.hash ) r['hash'] = alg(a.hash);
                if ( a.publicExponent ) r['publicExponent'] = new Uint8Array(a.publicExponent);
                if ( a.modulusLength ) r['modulusLength'] = a.modulusLength;
                break;
            default:
                throw new SyntaxError("Bad algorithm name");
        }
        return r;
    };

    function jwkAlg ( a ) {
        return {
            'HMAC': {
                'SHA-1': 'HS1',
                'SHA-256': 'HS256',
                'SHA-384': 'HS384',
                'SHA-512': 'HS512',
            },
            'RSASSA-PKCS1-v1_5': {
                'SHA-1': 'RS1',
                'SHA-256': 'RS256',
                'SHA-384': 'RS384',
                'SHA-512': 'RS512',
            },
            'RSAES-PKCS1-v1_5': {
                '': 'RSA1_5',
            },
            'RSA-OAEP': {
                'SHA-1': 'RSA-OAEP',
                'SHA-256': 'RSA-OAEP-256',
            },
            'AES-KW': {
                '128': 'A128KW',
                '192': 'A192KW',
                '256': 'A256KW',
            },
            'AES-GCM': {
                '128': 'A128GCM',
                '192': 'A192GCM',
                '256': 'A256GCM',
            },
            'AES-CBC': {
                '128': 'A128CBC',
                '192': 'A192CBC',
                '256': 'A256CBC',
            },
        }[a.name][ ( a.hash || {} ).name || a.length || '' ];
    }

    function b2jwk ( k ) {
        if ( k instanceof ArrayBuffer || k instanceof Uint8Array ) k = JSON.parse( decodeURIComponent( escape( b2s(k) ) ) );
        var jwk = { 'kty': k.kty, 'alg': k.alg, 'ext': k.ext || k.extractable };
        switch ( jwk.kty ) {
            case 'oct':
                jwk.k = k.k;
            case 'RSA':
                [ 'n', 'e', 'd', 'p', 'q', 'dp', 'dq', 'qi', 'oth' ].forEach( function ( x ) { if ( x in k ) jwk[x] = k[x] } );
                break;
            default:
                throw new TypeError("Unsupported key type");
        }
        return jwk;
    }

    function jwk2b ( k ) {
        var jwk = b2jwk(k);
        if ( isIE ) jwk['extractable'] = jwk.ext, delete jwk.ext;
        return s2b( unescape( encodeURIComponent( JSON.stringify(jwk) ) ) ).buffer;
    }

    function pkcs2jwk ( k ) {
        var info = b2der(k), prv = false;
        if ( info.length > 2 ) prv = true, info.shift(); // remove version from PKCS#8 PrivateKeyInfo structure
        var jwk = { 'ext': true };
        switch ( info[0][0] ) {
            case '1.2.840.113549.1.1.1':
                var rsaComp = [ 'n', 'e', 'd', 'p', 'q', 'dp', 'dq', 'qi' ],
                    rsaKey  = b2der( info[1] );
                if ( prv ) rsaKey.shift(); // remove version from PKCS#1 RSAPrivateKey structure
                for ( var i = 0; i < rsaKey.length; i++ ) {
                    if ( !rsaKey[i][0] ) rsaKey[i] = rsaKey[i].subarray(1);
                    jwk[ rsaComp[i] ] = s2a( b2s( rsaKey[i] ) );
                }
                jwk['kty'] = 'RSA';
                break;
            default:
                throw new TypeError("Unsupported key type");
        }
        return jwk;
    }

    function jwk2pkcs ( k ) {
        var key, info = [ [ '', null ] ], prv = false;
        switch ( k.kty ) {
            case 'RSA':
                var rsaComp = [ 'n', 'e', 'd', 'p', 'q', 'dp', 'dq', 'qi' ],
                    rsaKey = [];
                for ( var i = 0; i < rsaComp.length; i++ ) {
                    if ( !( rsaComp[i] in k ) ) break;
                    var b = rsaKey[i] = s2b( a2s( k[ rsaComp[i] ] ) );
                    if ( b[0] & 0x80 ) rsaKey[i] = new Uint8Array(b.length + 1), rsaKey[i].set( b, 1 );
                }
                if ( rsaKey.length > 2 ) prv = true, rsaKey.unshift( new Uint8Array([0]) ); // add version to PKCS#1 RSAPrivateKey structure
                info[0][0] = '1.2.840.113549.1.1.1';
                key = rsaKey;
                break;
            default:
                throw new TypeError("Unsupported key type");
        }
        info.push( new Uint8Array( der2b(key) ).buffer );
        if ( !prv ) info[1] = { 'tag': 0x03, 'value': info[1] };
        else info.unshift( new Uint8Array([0]) ); // add version to PKCS#8 PrivateKeyInfo structure
        return new Uint8Array( der2b(info) ).buffer;
    }

    var oid2str = { 'KoZIhvcNAQEB': '1.2.840.113549.1.1.1' },
        str2oid = { '1.2.840.113549.1.1.1': 'KoZIhvcNAQEB' };

    function b2der ( buf, ctx ) {
        if ( buf instanceof ArrayBuffer ) buf = new Uint8Array(buf);
        if ( !ctx ) ctx = { pos: 0, end: buf.length };

        if ( ctx.end - ctx.pos < 2 || ctx.end > buf.length ) throw new RangeError("Malformed DER");

        var tag = buf[ctx.pos++],
            len = buf[ctx.pos++];

        if ( len >= 0x80 ) {
            len &= 0x7f;
            if ( ctx.end - ctx.pos < len ) throw new RangeError("Malformed DER");
            for ( var xlen = 0; len--; ) xlen <<= 8, xlen |= buf[ctx.pos++];
            len = xlen;
        }

        if ( ctx.end - ctx.pos < len ) throw new RangeError("Malformed DER");

        var rv;

        switch ( tag ) {
            case 0x02: // Universal Primitive INTEGER
                rv = buf.subarray( ctx.pos, ctx.pos += len );
                break;
            case 0x03: // Universal Primitive BIT STRING
                if ( buf[ctx.pos++] ) throw new Error( "Unsupported bit string" );
                len--;
            case 0x04: // Universal Primitive OCTET STRING
                rv = new Uint8Array( buf.subarray( ctx.pos, ctx.pos += len ) ).buffer;
                break;
            case 0x05: // Universal Primitive NULL
                rv = null;
                break;
            case 0x06: // Universal Primitive OBJECT IDENTIFIER
                var oid = btoa( b2s( buf.subarray( ctx.pos, ctx.pos += len ) ) );
                if ( !( oid in oid2str ) ) throw new Error( "Unsupported OBJECT ID " + oid );
                rv = oid2str[oid];
                break;
            case 0x30: // Universal Constructed SEQUENCE
                rv = [];
                for ( var end = ctx.pos + len; ctx.pos < end; ) rv.push( b2der( buf, ctx ) );
                break;
            default:
                throw new Error( "Unsupported DER tag 0x" + tag.toString(16) );
        }

        return rv;
    }

    function der2b ( val, buf ) {
        if ( !buf ) buf = [];

        var tag = 0, len = 0,
            pos = buf.length + 2;

        buf.push( 0, 0 ); // placeholder

        if ( val instanceof Uint8Array ) {  // Universal Primitive INTEGER
            tag = 0x02, len = val.length;
            for ( var i = 0; i < len; i++ ) buf.push( val[i] );
        }
        else if ( val instanceof ArrayBuffer ) { // Universal Primitive OCTET STRING
            tag = 0x04, len = val.byteLength, val = new Uint8Array(val);
            for ( var i = 0; i < len; i++ ) buf.push( val[i] );
        }
        else if ( val === null ) { // Universal Primitive NULL
            tag = 0x05, len = 0;
        }
        else if ( typeof val === 'string' && val in str2oid ) { // Universal Primitive OBJECT IDENTIFIER
            var oid = s2b( atob( str2oid[val] ) );
            tag = 0x06, len = oid.length;
            for ( var i = 0; i < len; i++ ) buf.push( oid[i] );
        }
        else if ( val instanceof Array ) { // Universal Constructed SEQUENCE
            for ( var i = 0; i < val.length; i++ ) der2b( val[i], buf );
            tag = 0x30, len = buf.length - pos;
        }
        else if ( typeof val === 'object' && val.tag === 0x03 && val.value instanceof ArrayBuffer ) { // Tag hint
            val = new Uint8Array(val.value), tag = 0x03, len = val.byteLength;
            buf.push(0); for ( var i = 0; i < len; i++ ) buf.push( val[i] );
            len++;
        }
        else {
            throw new Error( "Unsupported DER value " + val );
        }

        if ( len >= 0x80 ) {
            var xlen = len, len = 4;
            buf.splice( pos, 0, (xlen >> 24) & 0xff, (xlen >> 16) & 0xff, (xlen >> 8) & 0xff, xlen & 0xff );
            while ( len > 1 && !(xlen >> 24) ) xlen <<= 8, len--;
            if ( len < 4 ) buf.splice( pos, 4 - len );
            len |= 0x80;
        }

        buf.splice( pos - 2, 2, tag, len );

        return buf;
    }

    function CryptoKey ( key, alg, ext, use ) {
        Object.defineProperties( this, {
            _key: {
                value: key
            },
            type: {
                value: key.type,
                enumerable: true,
            },
            extractable: {
                value: (ext === undefined) ? key.extractable : ext,
                enumerable: true,
            },
            algorithm: {
                value: (alg === undefined) ? key.algorithm : alg,
                enumerable: true,
            },
            usages: {
                value: (use === undefined) ? key.usages : use,
                enumerable: true,
            },
        });
    }

    function isPubKeyUse ( u ) {
        return u === 'verify' || u === 'encrypt' || u === 'wrapKey';
    }

    function isPrvKeyUse ( u ) {
        return u === 'sign' || u === 'decrypt' || u === 'unwrapKey';
    }

    [ 'generateKey', 'importKey', 'unwrapKey' ]
        .forEach( function ( m ) {
            var _fn = _subtle[m];

            _subtle[m] = function ( a, b, c ) {
                var args = [].slice.call(arguments),
                    ka, kx, ku;

                switch ( m ) {
                    case 'generateKey':
                        ka = alg(a), kx = b, ku = c;
                        break;
                    case 'importKey':
                        ka = alg(c), kx = args[3], ku = args[4];
                        if ( a === 'jwk' ) {
                            b = b2jwk(b);
                            if ( !b.alg ) b.alg = jwkAlg(ka);
                            if ( !b.key_ops ) b.key_ops = ( b.kty !== 'oct' ) ? ( 'd' in b ) ? ku.filter(isPrvKeyUse) : ku.filter(isPubKeyUse) : ku.slice();
                            args[1] = jwk2b(b);
                        }
                        break;
                    case 'unwrapKey':
                        ka = args[4], kx = args[5], ku = args[6];
                        args[2] = c._key;
                        break;
                }

                if ( m === 'generateKey' && ka.name === 'HMAC' && ka.hash ) {
                    ka.length = ka.length || { 'SHA-1': 512, 'SHA-256': 512, 'SHA-384': 1024, 'SHA-512': 1024 }[ka.hash.name];
                    return _subtle.importKey( 'raw', _crypto.getRandomValues( new Uint8Array( (ka.length+7)>>3 ) ), ka, kx, ku );
                }

                if ( isWebkit && m === 'generateKey' && ka.name === 'RSASSA-PKCS1-v1_5' && ( !ka.modulusLength || ka.modulusLength >= 2048 ) ) {
                    a = alg(a), a.name = 'RSAES-PKCS1-v1_5', delete a.hash;
                    return _subtle.generateKey( a, true, [ 'encrypt', 'decrypt' ] )
                        .then( function ( k ) {
                            return Promise.all([
                                _subtle.exportKey( 'jwk', k.publicKey ),
                                _subtle.exportKey( 'jwk', k.privateKey ),
                            ]);
                        })
                        .then( function ( keys ) {
                            keys[0].alg = keys[1].alg = jwkAlg(ka);
                            keys[0].key_ops = ku.filter(isPubKeyUse), keys[1].key_ops = ku.filter(isPrvKeyUse);
                            return Promise.all([
                                _subtle.importKey( 'jwk', keys[0], ka, true, keys[0].key_ops ),
                                _subtle.importKey( 'jwk', keys[1], ka, kx, keys[1].key_ops ),
                            ]);
                        })
                        .then( function ( keys ) {
                            return {
                                publicKey: keys[0],
                                privateKey: keys[1],
                            };
                        });
                }

                if ( ( isWebkit || ( isIE && ( ka.hash || {} ).name === 'SHA-1' ) )
                        && m === 'importKey' && a === 'jwk' && ka.name === 'HMAC' && b.kty === 'oct' ) {
                    return _subtle.importKey( 'raw', s2b( a2s(b.k) ), c, args[3], args[4] );
                }

                if ( isWebkit && m === 'importKey' && ( a === 'spki' || a === 'pkcs8' ) ) {
                    return _subtle.importKey( 'jwk', pkcs2jwk(b), c, args[3], args[4] );
                }

                if ( isIE && m === 'unwrapKey' ) {
                    return _subtle.decrypt( args[3], c, b )
                        .then( function ( k ) {
                            return _subtle.importKey( a, k, args[4], args[5], args[6] );
                        });
                }

                var op;
                try {
                    op = _fn.apply( _subtle, args );
                }
                catch ( e ) {
                    return Promise.reject(e);
                }

                if ( isIE ) {
                    op = new Promise( function ( res, rej ) {
                        op.onabort =
                        op.onerror =    function ( e ) { rej(e)               };
                        op.oncomplete = function ( r ) { res(r.target.result) };
                    });
                }

                op = op.then( function ( k ) {
                    if ( ka.name === 'HMAC' ) {
                        if ( !ka.length ) ka.length = 8 * k.algorithm.length;
                    }
                    if ( ka.name.search('RSA') == 0 ) {
                        if ( !ka.modulusLength ) ka.modulusLength = (k.publicKey || k).algorithm.modulusLength;
                        if ( !ka.publicExponent ) ka.publicExponent = (k.publicKey || k).algorithm.publicExponent;
                    }
                    if ( k.publicKey && k.privateKey ) {
                        k = {
                            publicKey: new CryptoKey( k.publicKey, ka, kx, ku.filter(isPubKeyUse) ),
                            privateKey: new CryptoKey( k.privateKey, ka, kx, ku.filter(isPrvKeyUse) ),
                        };
                    }
                    else {
                        k = new CryptoKey( k, ka, kx, ku );
                    }
                    return k;
                });

                return op;
            }
        });

    [ 'exportKey', 'wrapKey' ]
        .forEach( function ( m ) {
            var _fn = _subtle[m];

            _subtle[m] = function ( a, b, c ) {
                var args = [].slice.call(arguments);

                switch ( m ) {
                    case 'exportKey':
                        args[1] = b._key;
                        break;
                    case 'wrapKey':
                        args[1] = b._key, args[2] = c._key;
                        break;
                }

                if ( ( isWebkit || ( isIE && ( b.algorithm.hash || {} ).name === 'SHA-1' ) )
                        && m === 'exportKey' && a === 'jwk' && b.algorithm.name === 'HMAC' ) {
                    args[0] = 'raw';
                }

                if ( isWebkit && m === 'exportKey' && ( a === 'spki' || a === 'pkcs8' ) ) {
                    args[0] = 'jwk';
                }

                if ( isIE && m === 'wrapKey' ) {
                    return _subtle.exportKey( a, b )
                        .then( function ( k ) {
                            if ( a === 'jwk' ) k = s2b( unescape( encodeURIComponent( JSON.stringify( b2jwk(k) ) ) ) );
                            return  _subtle.encrypt( args[3], c, k );
                        });
                }

                var op;
                try {
                    op = _fn.apply( _subtle, args );
                }
                catch ( e ) {
                    return Promise.reject(e);
                }

                if ( isIE ) {
                    op = new Promise( function ( res, rej ) {
                        op.onabort =
                        op.onerror =    function ( e ) { rej(e)               };
                        op.oncomplete = function ( r ) { res(r.target.result) };
                    });
                }

                if ( m === 'exportKey' && a === 'jwk' ) {
                    op = op.then( function ( k ) {
                        if ( ( isWebkit || ( isIE && ( b.algorithm.hash || {} ).name === 'SHA-1' ) )
                                && b.algorithm.name === 'HMAC') {
                            return { 'kty': 'oct', 'alg': jwkAlg(b.algorithm), 'key_ops': b.usages.slice(), 'ext': true, 'k': s2a( b2s(k) ) };
                        }
                        k = b2jwk(k);
                        if ( !k.alg ) k['alg'] = jwkAlg(b.algorithm);
                        if ( !k.key_ops ) k['key_ops'] = ( b.type === 'public' ) ? b.usages.filter(isPubKeyUse) : ( b.type === 'private' ) ? b.usages.filter(isPrvKeyUse) : b.usages.slice();
                        return k;
                    });
                }

                if ( isWebkit && m === 'exportKey' && ( a === 'spki' || a === 'pkcs8' ) ) {
                    op = op.then( function ( k ) {
                        k = jwk2pkcs( b2jwk(k) );
                        return k;
                    });
                }

                return op;
            }
        });

    [ 'encrypt', 'decrypt', 'sign', 'verify' ]
        .forEach( function ( m ) {
            var _fn = _subtle[m];

            _subtle[m] = function ( a, b, c, d ) {
                if ( isIE && ( !c.byteLength || ( d && !d.byteLength ) ) )
                    throw new Error("Empty input is not allowed");

                var args = [].slice.call(arguments),
                    ka = alg(a);

                if ( isIE && ( m === 'sign' || m === 'verify') && ( a === 'RSASSA-PKCS1-v1_5' || a === 'HMAC' ) ) {
                    args[0] = { name: a };
                }

                if ( isIE && b.algorithm.hash ) {
                    args[0].hash = args[0].hash || b.algorithm.hash;
                }

                if ( isIE && m === 'decrypt' && ka.name === 'AES-GCM' ) {
                    var tl = a.tagLength >> 3;
                    args[2] = (c.buffer || c).slice( 0, c.byteLength - tl ),
                    a.tag = (c.buffer || c).slice( c.byteLength - tl );
                }

                if ( isIE && ka.name === 'AES-GCM' && args[0].tagLength === undefined ) {
                    args[0].tagLength = 128;
                }

                args[1] = b._key;

                var op;
                try {
                    op = _fn.apply( _subtle, args );
                }
                catch ( e ) {
                    return Promise.reject(e);
                }

                if ( isIE ) {
                    op = new Promise( function ( res, rej ) {
                        op.onabort =
                        op.onerror = function ( e ) {
                            rej(e);
                        };

                        op.oncomplete = function ( r ) {
                            var r = r.target.result;

                            if ( m === 'encrypt' && r instanceof AesGcmEncryptResult ) {
                                var c = r.ciphertext, t = r.tag;
                                r = new Uint8Array( c.byteLength + t.byteLength );
                                r.set( new Uint8Array(c), 0 );
                                r.set( new Uint8Array(t), c.byteLength );
                                r = r.buffer;
                            }

                            res(r);
                        };
                    });
                }

                return op;
            }
        });

    if ( isIE ) {
        var _digest = _subtle.digest;

        _subtle['digest'] = function ( a, b ) {
            if ( !b.byteLength )
                throw new Error("Empty input is not allowed");

            var op;
            try {
                op = _digest.call( _subtle, a, b );
            }
            catch ( e ) {
                return Promise.reject(e);
            }

            op = new Promise( function ( res, rej ) {
                op.onabort =
                op.onerror =    function ( e ) { rej(e)               };
                op.oncomplete = function ( r ) { res(r.target.result) };
            });

            return op;
        };

        global.crypto = Object.create( _crypto, {
            getRandomValues: { value: function ( a ) { return _crypto.getRandomValues(a) } },
            subtle:          { value: _subtle },
        });

        global.CryptoKey = CryptoKey;
    }

    if ( isWebkit ) {
        _crypto.subtle = _subtle;

        global.Crypto = _Crypto;
        global.SubtleCrypto = _SubtleCrypto;
        global.CryptoKey = CryptoKey;
    }
}));