From 607e352b173e8d539111c2ae4400f0f81116b67e Mon Sep 17 00:00:00 2001
From: AJ ONeal <coolaj86@gmail.com>
Date: Thu, 22 Nov 2018 17:21:54 -0700
Subject: [PATCH] v0.8.0: JWK-to-PEM for PKCS#1 and SSH

---
 README.md                                     |  9 ++--
 ...048.jwt.json => privkey-rsa-2048.jwk.json} |  0
 fixtures/pub-rsa-2048.jwk.json                |  5 +++
 lib/encoding.js                               | 20 ++++++++-
 lib/rasha.js                                  |  2 +-
 lib/ssh.js                                    | 44 ++++++++++++++++++-
 package.json                                  |  2 +-
 7 files changed, 74 insertions(+), 8 deletions(-)
 rename fixtures/{privkey-rsa-2048.jwt.json => privkey-rsa-2048.jwk.json} (100%)
 create mode 100644 fixtures/pub-rsa-2048.jwk.json

diff --git a/README.md b/README.md
index 64c17ad..ccb7af7 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,8 @@ It is considered to be complete, but if you find a bug please open an issue. -->
 
 ## PEM-to-JWK
 
-* [x] PKCS#1 (traditional), PKCS#8, SPKI/PKIX
+* [x] PKCS#1 (traditional)
+* [x] PKCS#8, SPKI/PKIX
 * [x] 2048-bit, 4096-bit (and ostensibily all others)
 * [x] SSH (RFC4716), (RFC 4716/SSH2)
 
@@ -45,16 +46,16 @@ Rasha.import({ pem: pem }).then(function (jwk) {
 }
 ```
 
-<!--
 ## JWK-to-PEM
 
-* [x] PKCS#1 (traditional), PKCS#8, SPKI/PKIX
+* [x] PKCS#1 (traditional)
+* [ ] PKCS#8, SPKI/PKIX
 * [x] 2048-bit, 4096-bit (and ostensibily all others)
 * [x] SSH (RFC4716), (RFC 4716/SSH2)
 
 ```js
 var Rasha = require('rasha');
-var jwk = require('rasha/fixtures/privkey-rsa-2038.jwk.json');
+var jwk = require('rasha/fixtures/privkey-rsa-2048.jwk.json');
 
 Rasha.export({ jwk: jwk }).then(function (pem) {
   // PEM in PKCS1 (traditional) format
diff --git a/fixtures/privkey-rsa-2048.jwt.json b/fixtures/privkey-rsa-2048.jwk.json
similarity index 100%
rename from fixtures/privkey-rsa-2048.jwt.json
rename to fixtures/privkey-rsa-2048.jwk.json
diff --git a/fixtures/pub-rsa-2048.jwk.json b/fixtures/pub-rsa-2048.jwk.json
new file mode 100644
index 0000000..333b300
--- /dev/null
+++ b/fixtures/pub-rsa-2048.jwk.json
@@ -0,0 +1,5 @@
+{
+  "kty": "RSA",
+  "n": "m2ttVBxPlWw06ZmGBWVDlfjkPAJ4DgnY0TrDwtCohHzLxGhDNzUJefLukC-xu0LBKylYojT5vTkxaOhxeSYo31syu4WhxbkTBLICOFcCGMob6pSQ38P8LdAIlb0pqDHxEJ9adWomjuFf0SUhN1cP7s9m8Yk9trkpEqjskocn2BOnTB57qAZM6-I70on0_iDZm7-jcqOPgADAmbWHhy67BXkk4yy_YzD4yOGZFXZcNp915_TW5bRd__AKPHUHxJasPiyEFqlNKBR2DSD-LbX5eTmzCh2ikrwTMja7mUdBJf2bK3By5AB0Qi49OykUCfNZeQlEz7UNNj9RGps_50-CNw",
+  "e": "AQAB"
+}
diff --git a/lib/encoding.js b/lib/encoding.js
index 5b66e05..03c44c9 100644
--- a/lib/encoding.js
+++ b/lib/encoding.js
@@ -15,6 +15,10 @@ Enc.bufToHex = function toHex(u8) {
   return hex.join('').toLowerCase();
 };
 
+Enc.hexToBase64 = function (hex) {
+  return Buffer.from(hex, 'hex').toString('base64');
+};
+
 Enc.hexToBuf = function (hex) {
   return Buffer.from(hex, 'hex');
 };
@@ -29,7 +33,7 @@ Enc.numToHex = function numToHex(d) {
 
 Enc.base64ToHex = function base64ToHex(b64) {
   return Enc.bufToHex(Enc.base64ToBuf(b64));
-}
+};
 
 Enc.bufToBase64 = function toHex(u8) {
   // we want to maintain api compatability with browser APIs,
@@ -37,11 +41,25 @@ Enc.bufToBase64 = function toHex(u8) {
   return Buffer.from(u8).toString('base64');
 };
 
+/*
+Enc.bufToUint8 = function bufToUint8(buf) {
+  return new Uint8Array(buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength));
+};
+*/
+
 Enc.bufToUrlBase64 = function toHex(u8) {
   return Enc.bufToBase64(u8)
     .replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
 };
 
+Enc.strToHex = function strToHex(str) {
+  return Buffer.from(str).toString('hex');
+};
+
+Enc.strToBuf = function strToBuf(str) {
+  return Buffer.from(str);
+};
+
 /*
 Enc.strToBin = function strToBin(str) {
   var escstr = encodeURIComponent(str);
diff --git a/lib/rasha.js b/lib/rasha.js
index 111de93..7306709 100644
--- a/lib/rasha.js
+++ b/lib/rasha.js
@@ -100,7 +100,7 @@ RSA.pack = function (opts) {
     } else if (-1 !== [ 'spki', 'pkix' ].indexOf(format)) {
       return PEM.packBlock({ type: "PUBLIC KEY", bytes: x509.packSpki(jwk) });
     } else if (-1 !== [ 'ssh', 'rfc4716' ].indexOf(format)) {
-      return SSH.packSsh(jwk);
+      return SSH.pack({ jwk: jwk, comment: opts.comment });
     } else {
       throw new Error("Sanity Error: reached unreachable code block with format: " + format);
     }
diff --git a/lib/ssh.js b/lib/ssh.js
index 4f04b6a..6304171 100644
--- a/lib/ssh.js
+++ b/lib/ssh.js
@@ -17,6 +17,7 @@ SSH.parse = function (pem, jwk) {
   var offset = (buf.byteOffset || 0);
   // using dataview to be browser-compatible (I do want _some_ code reuse)
   var dv = new DataView(buf.buffer.slice(offset, offset + buf.byteLength));
+  var el;
 
   if (SSH.RSA !== Enc.bufToHex(buf.slice(0, SSH.RSA.length/2))) {
     throw new Error("does not lead with ssh header");
@@ -27,7 +28,12 @@ SSH.parse = function (pem, jwk) {
     if (i > 3) { throw new Error("15+ elements, probably not a public ssh key"); }
     len = dv.getUint32(index, false);
     index += 4;
-    els.push(buf.slice(index, index + len));
+    el = buf.slice(index, index + len);
+    // remove BigUInt '00' prefix
+    if (0x00 === el[0]) {
+      el = el.slice(1);
+    }
+    els.push(el);
     index += len;
   }
 
@@ -36,3 +42,39 @@ SSH.parse = function (pem, jwk) {
 
   return jwk;
 };
+
+SSH.pack = function (opts) {
+  var jwk = opts.jwk;
+  var header = 'ssh-rsa';
+  var comment = opts.comment || 'rsa@localhost';
+  var e = SSH._padHexInt(Enc.base64ToHex(jwk.e));
+  var n = SSH._padHexInt(Enc.base64ToHex(jwk.n));
+  var hex = [
+    SSH._numToUint32Hex(header.length)
+  , Enc.strToHex(header)
+  , SSH._numToUint32Hex(e.length/2)
+  , e
+  , SSH._numToUint32Hex(n.length/2)
+  , n
+  ].join('');
+  return [ header, Enc.hexToBase64(hex), comment ].join(' ');
+};
+
+SSH._numToUint32Hex = function (num) {
+  var hex = num.toString(16);
+  while (hex.length < 8) {
+    hex = '0' + hex;
+  }
+  return hex;
+};
+
+SSH._padHexInt = function (hex) {
+  // BigInt is negative if the high order bit 0x80 is set,
+  // so ASN1, SSH, and many other formats pad with '0x00'
+  // to signifiy a positive number.
+  var i = parseInt(hex.slice(0, 2), 16);
+  if (0x80 & i) {
+    return '00' + hex;
+  }
+  return hex;
+};
diff --git a/package.json b/package.json
index 0b24692..3f8ab9d 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rasha",
-  "version": "0.7.1",
+  "version": "0.8.0",
   "description": "PEM-to-JWK and JWK-to-PEM for RSA keys in a lightweight, zero-dependency library focused on perfect universal compatibility.",
   "homepage": "https://git.coolaj86.com/coolaj86/rasha.js",
   "main": "index.js",