80 lines
2 KiB
JavaScript
80 lines
2 KiB
JavaScript
'use strict';
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var SSH = module.exports;
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var Enc = require('./encoding.js');
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// 7 s s h - r s a
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SSH.RSA = '00000007 73 73 68 2d 72 73 61'.replace(/\s+/g, '').toLowerCase();
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SSH.parse = function (pem, jwk) {
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var parts = pem.split(/\s+/);
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var buf = Enc.base64ToBuf(parts[1]);
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var els = [];
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var index = 0;
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var len;
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var i = 0;
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var offset = (buf.byteOffset || 0);
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// using dataview to be browser-compatible (I do want _some_ code reuse)
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var dv = new DataView(buf.buffer.slice(offset, offset + buf.byteLength));
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var el;
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if (SSH.RSA !== Enc.bufToHex(buf.slice(0, SSH.RSA.length/2))) {
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throw new Error("does not lead with ssh header");
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}
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while (index < buf.byteLength) {
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i += 1;
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if (i > 3) { throw new Error("15+ elements, probably not a public ssh key"); }
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len = dv.getUint32(index, false);
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index += 4;
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el = buf.slice(index, index + len);
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// remove BigUInt '00' prefix
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if (0x00 === el[0]) {
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el = el.slice(1);
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}
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els.push(el);
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index += len;
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}
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jwk.n = Enc.bufToUrlBase64(els[2]);
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jwk.e = Enc.bufToUrlBase64(els[1]);
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return jwk;
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};
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SSH.pack = function (opts) {
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var jwk = opts.jwk;
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var header = 'ssh-rsa';
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var comment = opts.comment || 'rsa@localhost';
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var e = SSH._padHexInt(Enc.base64ToHex(jwk.e));
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var n = SSH._padHexInt(Enc.base64ToHex(jwk.n));
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var hex = [
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SSH._numToUint32Hex(header.length)
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, Enc.strToHex(header)
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, SSH._numToUint32Hex(e.length/2)
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, e
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, SSH._numToUint32Hex(n.length/2)
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, n
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].join('');
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return [ header, Enc.hexToBase64(hex), comment ].join(' ');
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};
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SSH._numToUint32Hex = function (num) {
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var hex = num.toString(16);
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while (hex.length < 8) {
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hex = '0' + hex;
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}
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return hex;
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};
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SSH._padHexInt = function (hex) {
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// BigInt is negative if the high order bit 0x80 is set,
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// so ASN1, SSH, and many other formats pad with '0x00'
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// to signifiy a positive number.
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var i = parseInt(hex.slice(0, 2), 16);
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if (0x80 & i) {
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return '00' + hex;
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}
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return hex;
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};
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