Work with PkDecryption keys by their private keys

Change interface to allow the app to get the private part of the
key and instantiate a decryption object from just the private part
of the key.

Changes the function generating a key from random bytes to be
initialising a key with a private key (because it's exactly the
same thing). Exports & imports private key parts as ArrayBuffer at
JS level rather than base64 assuming we are moving that way in
general.

2 files changed, 44 insertions, 2 deletions

diff --git a/javascript/olm_pk.js b/javascript/olm_pk.js
index 25e0fee..2212470 100644
--- a/javascript/olm_pk.js
+++ b/javascript/olm_pk.js
@@ -118,16 +118,32 @@ PkDecryption.prototype['free'] = function() {
     free(this.ptr);
 }
 
+PkDecryption.prototype['init_with_private_key'] = restore_stack(function (private_key) {
+    var private_key_buffer = stack(private_key.length);
+    Module['HEAPU8'].set(private_key, private_key_buffer);
+
+    var pubkey_length = pk_decryption_method(
+        Module['_olm_pk_key_length']
+    )();
+    var pubkey_buffer = stack(pubkey_length + NULL_BYTE_PADDING_LENGTH);
+    pk_decryption_method(Module['_olm_pk_key_from_private'])(
+        this.ptr,
+        pubkey_buffer, pubkey_length,
+        private_key_buffer, private_key.length
+    );
+    return Pointer_stringify(pubkey_buffer);
+});
+
 PkDecryption.prototype['generate_key'] = restore_stack(function () {
     var random_length = pk_decryption_method(
-        Module['_olm_pk_generate_key_random_length']
+        Module['_olm_pk_private_key_length']
     )();
     var random_buffer = random_stack(random_length);
     var pubkey_length = pk_encryption_method(
         Module['_olm_pk_key_length']
     )();
     var pubkey_buffer = stack(pubkey_length + NULL_BYTE_PADDING_LENGTH);
-    pk_decryption_method(Module['_olm_pk_generate_key'])(
+    pk_decryption_method(Module['_olm_pk_key_from_private'])(
         this.ptr,
         pubkey_buffer, pubkey_length,
         random_buffer, random_length
@@ -135,6 +151,18 @@ PkDecryption.prototype['generate_key'] = restore_stack(function () {
     return Pointer_stringify(pubkey_buffer);
 });
 
+PkDecryption.prototype['get_private_key'] = restore_stack(function () {
+    var privkey_length = pk_encryption_method(
+        Module['_olm_pk_private_key_length']
+    )();
+    var privkey_buffer  = stack(privkey_length);
+    pk_decryption_method(Module['_olm_pk_get_private_key'])(
+        this.ptr,
+        privkey_buffer, privkey_length
+    );
+    return new Uint8Array(Module['HEAPU8'].buffer, privkey_buffer, privkey_length);
+});
+
 PkDecryption.prototype['pickle'] = restore_stack(function (key) {
     var key_array = array_from_string(key);
     var pickle_length = pk_decryption_method(
diff --git a/javascript/test/pk.spec.js b/javascript/test/pk.spec.js
index 007882f..d155cf5 100644
--- a/javascript/test/pk.spec.js
+++ b/javascript/test/pk.spec.js
@@ -49,6 +49,20 @@ describe("pk", function() {
         }
     });
 
+    it('should import & export keys from private parts', function () {
+        var alice_private = new Uint8Array([
+            0x77, 0x07, 0x6D, 0x0A, 0x73, 0x18, 0xA5, 0x7D,
+            0x3C, 0x16, 0xC1, 0x72, 0x51, 0xB2, 0x66, 0x45,
+            0xDF, 0x4C, 0x2F, 0x87, 0xEB, 0xC0, 0x99, 0x2A,
+            0xB1, 0x77, 0xFB, 0xA5, 0x1D, 0xB9, 0x2C, 0x2A
+        ]);
+        var alice_public = decryption.init_with_private_key(alice_private);
+        expect(alice_public).toEqual("hSDwCYkwp1R0i33ctD73Wg2/Og0mOBr066SpjqqbTmo");
+
+        var alice_private_out = decryption.get_private_key();
+        expect(alice_private_out).toEqual(alice_private);
+    });
+
     it('should encrypt and decrypt', function () {
         var TEST_TEXT='têst1';
         var pubkey = decryption.generate_key();