20 files changed, 281 insertions, 120 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index fa1eccb..6b450b4 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,3 +1,15 @@
+Changes in latest release
+
+BREAKING CHANGE: Olm now uses WebAssembly which means it needs
+to load the wasm file asynchronously, and therefore needs to be
+started up asynchronously. The imported module now has an init()
+method which returns a promise. The library cannot be used until
+this promise resolves. It will reject if the library fails to start.
+
+olm_pk_generate_key() and olm_pk_generate_key_random_length() have
+been removed: to generate a random key, use olm_pk_key_from_private()
+with random bytes as the private key.
+
 Changes in `2.3.0 <http://matrix.org/git/olm/commit/?h=2.3.0>`_
 
 This release includes the following changes since 2.2.2:
diff --git a/Makefile b/Makefile
index 154954c..d99c8fc 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,8 @@ DEBUG_TARGET := $(BUILD_DIR)/libolm_debug.so.$(VERSION)
 JS_TARGET := javascript/olm.js
 
 JS_EXPORTED_FUNCTIONS := javascript/exported_functions.json
+JS_EXTRA_EXPORTED_RUNTIME_METHODS := ALLOC_STACK
+JS_EXTERNS := javascript/externs.js
 
 PUBLIC_HEADERS := include/olm/olm.h include/olm/outbound_group_session.h include/olm/inbound_group_session.h include/olm/pk.h
 
@@ -39,11 +41,22 @@ FUZZER_BINARIES := $(addprefix $(BUILD_DIR)/,$(basename $(FUZZER_SOURCES)))
 FUZZER_DEBUG_BINARIES := $(patsubst $(BUILD_DIR)/fuzzers/fuzz_%,$(BUILD_DIR)/fuzzers/debug_%,$(FUZZER_BINARIES))
 TEST_BINARIES := $(patsubst tests/%,$(BUILD_DIR)/tests/%,$(basename $(TEST_SOURCES)))
 JS_OBJECTS := $(addprefix $(BUILD_DIR)/javascript/,$(OBJECTS))
+
+# pre & post are the js-pre/js-post options to emcc.
+# They are injected inside the modularised code and
+# processed by the optimiser.
 JS_PRE := $(wildcard javascript/*pre.js)
 JS_POST := javascript/olm_outbound_group_session.js \
     javascript/olm_inbound_group_session.js \
     javascript/olm_pk.js \
     javascript/olm_post.js
+
+# The prefix & suffix are just added onto the start & end
+# of what comes out emcc, so are outside of the modularised
+# code and not seen by the opimiser.
+JS_PREFIX := javascript/olm_prefix.js
+JS_SUFFIX := javascript/olm_suffix.js
+
 DOCS := tracing/README.html \
     docs/megolm.html \
     docs/olm.html \
@@ -60,11 +73,20 @@ CFLAGS += -Wall -Werror -std=c99 -fPIC
 CXXFLAGS += -Wall -Werror -std=c++11 -fPIC
 LDFLAGS += -Wall -Werror
 
-EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0
+EMCCFLAGS = --closure 1 --memory-init-file 0 -s NO_FILESYSTEM=1 -s INVOKE_RUN=0 -s MODULARIZE=1
 # NO_BROWSER is kept for compatibility with emscripten 1.35.24, but is no
 # longer needed.
 EMCCFLAGS += -s NO_BROWSER=1
 
+# Olm generally doesn't need a lot of memory to encrypt / decrypt its usual
+# payloads (ie. Matrix messages), but we do need about 128K of heap to encrypt
+# a 64K event (enough to store the ciphertext and the plaintext, bearing in
+# mind that the plaintext can only be 48K because base64). We also have about
+# 36K of statics. So let's have 256K of memory.
+# (This can't be changed by the app with wasm since it's baked into the wasm).
+EMCCFLAGS += -s TOTAL_STACK=65536 -s TOTAL_MEMORY=262144
+
+
 EMCC.c = $(EMCC) $(CFLAGS) $(CPPFLAGS) -c
 EMCC.cc = $(EMCC) $(CXXFLAGS) $(CPPFLAGS) -c
 EMCC_LINK = $(EMCC) $(LDFLAGS) $(EMCCFLAGS)
@@ -145,12 +167,19 @@ $(STATIC_RELEASE_TARGET): $(RELEASE_OBJECTS)
 js: $(JS_TARGET)
 .PHONY: js
 
-$(JS_TARGET): $(JS_OBJECTS) $(JS_PRE) $(JS_POST) $(JS_EXPORTED_FUNCTIONS)
-	$(EMCC_LINK) \
+# Note that the output file we give to emcc determines the name of the
+# wasm file baked into the js, hence messing around outputting to olm.js
+# and then renaming it.
+$(JS_TARGET): $(JS_OBJECTS) $(JS_PRE) $(JS_POST) $(JS_EXPORTED_FUNCTIONS) $(JS_PREFIX) $(JS_SUFFIX)
+	EMCC_CLOSURE_ARGS="--externs $(JS_EXTERNS)" $(EMCC_LINK) \
                $(foreach f,$(JS_PRE),--pre-js $(f)) \
                $(foreach f,$(JS_POST),--post-js $(f)) \
                -s "EXPORTED_FUNCTIONS=@$(JS_EXPORTED_FUNCTIONS)" \
+               -s "EXTRA_EXPORTED_RUNTIME_METHODS=$(JS_EXTRA_EXPORTED_RUNTIME_METHODS)" \
                $(JS_OBJECTS) -o $@
+	       mv $@ javascript/olmtmp.js
+	       cat $(JS_PREFIX) javascript/olmtmp.js $(JS_SUFFIX) > $@
+	       rm javascript/olmtmp.js
 
 build_tests: $(TEST_BINARIES)
 
diff --git a/include/olm/error.h b/include/olm/error.h
index 9d44a94..ee2187c 100644
--- a/include/olm/error.h
+++ b/include/olm/error.h
@@ -51,6 +51,13 @@ enum OlmErrorCode {
      */
     OLM_BAD_SIGNATURE = 14,
 
+    OLM_INPUT_BUFFER_TOO_SMALL = 15,
+
+    // Not an error code, just here to pad out the enum past 16 because
+    // otherwise the compiler warns about a redunant check. If you're
+    // adding an error code, replace this one!
+    OLM_ERROR_NOT_INVENTED_YET = 16,
+
     /* remember to update the list of string constants in error.c when updating
      * this list. */
 };
diff --git a/include/olm/pk.h b/include/olm/pk.h
index 8804d1f..8748506 100644
--- a/include/olm/pk.h
+++ b/include/olm/pk.h
@@ -80,7 +80,7 @@ size_t olm_pk_encrypt_random_length(
  * key. Returns olm_error() on failure. If the ciphertext, mac, or
  * ephemeral_key buffers were too small then olm_pk_encryption_last_error()
  * will be "OUTPUT_BUFFER_TOO_SMALL". If there weren't enough random bytes then
- * olm_pk_encryption_last_error() will be "NOT_ENOUGH_RANDOM". */
+ * olm_pk_encryption_last_error() will be "OLM_INPUT_BUFFER_TOO_SMALL". */
 size_t olm_pk_encrypt(
     OlmPkEncryption *encryption,
     void const * plaintext, size_t plaintext_length,
@@ -112,19 +112,24 @@ size_t olm_clear_pk_decryption(
     OlmPkDecryption *decryption
 );
 
-/** The number of random bytes needed to generate a new key. */
-size_t olm_pk_generate_key_random_length(void);
-
-/** Generate a new key pair to use for decrypting messages. The private key is
- * stored in the decryption object, and the associated public key will be
- * written to the pubkey buffer. Returns olm_error() on failure. If the pubkey
- * buffer is too small then olm_pk_decryption_last_error() will be
- * "OUTPUT_BUFFER_TOO_SMALL". If there weren't enough random bytes then
- * olm_pk_decryption_last_error() will be "NOT_ENOUGH_RANDOM". */
-size_t olm_pk_generate_key(
+/** Get the number of bytes required to store an olm private key
+ */
+size_t olm_pk_private_key_length();
+
+/** Initialise the key from the private part of a key as returned by
+ * olm_pk_get_private_key(). The associated public key will be written to the
+ * pubkey buffer. Returns olm_error() on failure. If the pubkey buffer is too
+ * small then olm_pk_decryption_last_error() will be "OUTPUT_BUFFER_TOO_SMALL".
+ * If the private key was not long enough then olm_pk_decryption_last_error()
+ * will be "OLM_INPUT_BUFFER_TOO_SMALL".
+ *
+ * Note that the pubkey is a base64 encoded string, but the private key is
+ * an unencoded byte array
+ */
+size_t olm_pk_key_from_private(
     OlmPkDecryption * decryption,
     void * pubkey, size_t pubkey_length,
-    void * random, size_t random_length
+    void * privkey, size_t privkey_length
 );
 
 /** Returns the number of bytes needed to store a decryption object. */
@@ -177,6 +182,19 @@ size_t olm_pk_decrypt(
     void * plaintext, size_t max_plaintext_length
 );
 
+/**
+ * Get the private key for an OlmDecryption object as an unencoded byte array
+ * private_key must be a pointer to a buffer of at least
+ * olm_pk_private_key_length() bytes and this length must be passed in
+ * private_key_length. If the given buffer is too small, returns olm_error()
+ * and olm_pk_encryption_last_error() will be "OUTPUT_BUFFER_TOO_SMALL".
+ * Returns the number of bytes written.
+ */
+size_t olm_pk_get_private_key(
+    OlmPkDecryption * decryption,
+    void *private_key, size_t private_key_length
+);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/javascript/.gitignore b/javascript/.gitignore
index ec22345..3437f73 100644
--- a/javascript/.gitignore
+++ b/javascript/.gitignore
@@ -2,4 +2,5 @@
 /node_modules
 /npm-debug.log
 /olm.js
+/olm.wasm
 /reports
diff --git a/javascript/externs.js b/javascript/externs.js
new file mode 100644
index 0000000..752e937
--- /dev/null
+++ b/javascript/externs.js
@@ -0,0 +1,4 @@
+var OLM_OPTIONS;
+var olm_exports;
+var onInitSuccess;
+var onInitFail;
diff --git a/javascript/olm_inbound_group_session.js b/javascript/olm_inbound_group_session.js
index 6bc745d..7d9e401 100644
--- a/javascript/olm_inbound_group_session.js
+++ b/javascript/olm_inbound_group_session.js
@@ -1,9 +1,3 @@
-/* The 'length' argument to Pointer_stringify doesn't work if the input includes
- * characters >= 128; we therefore need to add a NULL character to all of our
- * strings. This acts as a symbolic constant to help show what we're doing.
- */
-var NULL_BYTE_PADDING_LENGTH = 1;
-
 function InboundGroupSession() {
     var size = Module['_olm_inbound_group_session_size']();
     this.buf = malloc(size);
@@ -77,14 +71,14 @@ InboundGroupSession.prototype['decrypt'] = restore_stack(function(
 
     try {
         message_buffer = malloc(message.length);
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         var max_plaintext_length = inbound_group_session_method(
             Module['_olm_group_decrypt_max_plaintext_length']
         )(this.ptr, message_buffer, message.length);
 
         // caculating the length destroys the input buffer, so we need to re-copy it.
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
         var message_index = stack(4);
@@ -100,14 +94,14 @@ InboundGroupSession.prototype['decrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
 
         return {
             "plaintext": UTF8ToString(plaintext_buffer),
-            "message_index": Module['getValue'](message_index, "i32")
+            "message_index": getValue(message_index, "i32")
         }
     } finally {
         if (message_buffer !== undefined) {
diff --git a/javascript/olm_outbound_group_session.js b/javascript/olm_outbound_group_session.js
index 24ea644..e232883 100644
--- a/javascript/olm_outbound_group_session.js
+++ b/javascript/olm_outbound_group_session.js
@@ -1,10 +1,3 @@
-/* The 'length' argument to Pointer_stringify doesn't work if the input includes
- * characters >= 128; we therefore need to add a NULL character to all of our
- * strings. This acts as a symbolic constant to help show what we're doing.
- */
-var NULL_BYTE_PADDING_LENGTH = 1;
-
-
 function OutboundGroupSession() {
     var size = Module['_olm_outbound_group_session_size']();
     this.buf = malloc(size);
@@ -66,7 +59,7 @@ OutboundGroupSession.prototype['create'] = restore_stack(function() {
 OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
     var plaintext_buffer, message_buffer, plaintext_length;
     try {
-        plaintext_length = Module['lengthBytesUTF8'](plaintext);
+        plaintext_length = lengthBytesUTF8(plaintext);
 
         var message_length = outbound_group_session_method(
             Module['_olm_group_encrypt_message_length']
@@ -75,7 +68,7 @@ OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
         // need to allow space for the terminator (which stringToUTF8 always
         // writes), hence + 1.
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
 
         message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
         outbound_group_session_method(Module['_olm_group_encrypt'])(
@@ -86,12 +79,12 @@ OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             message_buffer+message_length,
             0, "i8"
         );
 
-        return Module['UTF8ToString'](message_buffer);
+        return UTF8ToString(message_buffer);
     } finally {
         if (plaintext_buffer !== undefined) {
             // don't leave a copy of the plaintext in the heap.
diff --git a/javascript/olm_pk.js b/javascript/olm_pk.js
index 407eaf1..4f730dd 100644
--- a/javascript/olm_pk.js
+++ b/javascript/olm_pk.js
@@ -35,9 +35,9 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
 ) {
     var plaintext_buffer, ciphertext_buffer, plaintext_length;
     try {
-        plaintext_length = Module['lengthBytesUTF8'](plaintext)
+        plaintext_length = lengthBytesUTF8(plaintext)
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
         var random_length = pk_encryption_method(
             Module['_olm_pk_encrypt_random_length']
         )();
@@ -50,7 +50,7 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
             Module['_olm_pk_mac_length']
         )(this.ptr);
         var mac_buffer = stack(mac_length + NULL_BYTE_PADDING_LENGTH);
-        Module['setValue'](
+        setValue(
             mac_buffer + mac_length,
             0, "i8"
         );
@@ -58,7 +58,7 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
             Module['_olm_pk_key_length']
         )();
         var ephemeral_buffer = stack(ephemeral_length + NULL_BYTE_PADDING_LENGTH);
-        Module['setValue'](
+        setValue(
             ephemeral_buffer + ephemeral_length,
             0, "i8"
         );
@@ -72,12 +72,12 @@ PkEncryption.prototype['encrypt'] = restore_stack(function(
         );
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             ciphertext_buffer + ciphertext_length,
             0, "i8"
         );
         return {
-            "ciphertext": Module['UTF8ToString'](ciphertext_buffer),
+            "ciphertext": UTF8ToString(ciphertext_buffer),
             "mac": Pointer_stringify(mac_buffer),
             "ephemeral": Pointer_stringify(ephemeral_buffer)
         };
@@ -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_decryption_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(
@@ -169,9 +197,9 @@ PkDecryption.prototype['decrypt'] = restore_stack(function (
 ) {
     var plaintext_buffer, ciphertext_buffer, plaintext_max_length;
     try {
-        ciphertext_length = Module['lengthBytesUTF8'](ciphertext)
+        var ciphertext_length = lengthBytesUTF8(ciphertext)
         ciphertext_buffer = malloc(ciphertext_length + 1);
-        Module['stringToUTF8'](ciphertext, ciphertext_buffer, ciphertext_length + 1);
+        stringToUTF8(ciphertext, ciphertext_buffer, ciphertext_length + 1);
         var ephemeralkey_array = array_from_string(ephemeral_key);
         var ephemeralkey_buffer = stack(ephemeralkey_array);
         var mac_array = array_from_string(mac);
@@ -190,11 +218,11 @@ PkDecryption.prototype['decrypt'] = restore_stack(function (
         );
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer + plaintext_length,
             0, "i8"
         );
-        return Module['UTF8ToString'](plaintext_buffer);
+        return UTF8ToString(plaintext_buffer);
     } finally {
         if (plaintext_buffer !== undefined) {
             // don't leave a copy of the plaintext in the heap.
diff --git a/javascript/olm_post.js b/javascript/olm_post.js
index 7a1d284..fffffad 100644
--- a/javascript/olm_post.js
+++ b/javascript/olm_post.js
@@ -1,27 +1,17 @@
-var runtime = Module['Runtime'];
 var malloc = Module['_malloc'];
 var free = Module['_free'];
-var Pointer_stringify = Module['Pointer_stringify'];
-var OLM_ERROR = Module['_olm_error']();
-
-/* The 'length' argument to Pointer_stringify doesn't work if the input
- * includes characters >= 128, which makes Pointer_stringify unreliable. We
- * could use it on strings which are known to be ascii, but that seems
- * dangerous. Instead we add a NULL character to all of our strings and just
- * use UTF8ToString.
- */
-var NULL_BYTE_PADDING_LENGTH = 1;
+var OLM_ERROR;
 
 /* allocate a number of bytes of storage on the stack.
  *
  * If size_or_array is a Number, allocates that number of zero-initialised bytes.
  */
 function stack(size_or_array) {
-    return Module['allocate'](size_or_array, 'i8', Module['ALLOC_STACK']);
+    return allocate(size_or_array, 'i8', Module['ALLOC_STACK']);
 }
 
 function array_from_string(string) {
-    return Module['intArrayFromString'](string, true);
+    return intArrayFromString(string, true);
 }
 
 function random_stack(size) {
@@ -33,11 +23,11 @@ function random_stack(size) {
 
 function restore_stack(wrapped) {
     return function() {
-        var sp = runtime.stackSave();
+        var sp = stackSave();
         try {
             return wrapped.apply(this, arguments);
         } finally {
-            runtime.stackRestore(sp);
+            stackRestore(sp);
         }
     }
 }
@@ -315,7 +305,7 @@ Session.prototype['encrypt'] = restore_stack(function(
             Module['_olm_encrypt_message_type']
         )(this.ptr);
 
-        plaintext_length = Module['lengthBytesUTF8'](plaintext);
+        plaintext_length = lengthBytesUTF8(plaintext);
         var message_length = session_method(
             Module['_olm_encrypt_message_length']
         )(this.ptr, plaintext_length);
@@ -325,7 +315,7 @@ Session.prototype['encrypt'] = restore_stack(function(
         // need to allow space for the terminator (which stringToUTF8 always
         // writes), hence + 1.
         plaintext_buffer = malloc(plaintext_length + 1);
-        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+        stringToUTF8(plaintext, plaintext_buffer, plaintext_length + 1);
 
         message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
 
@@ -338,14 +328,14 @@ Session.prototype['encrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             message_buffer+message_length,
             0, "i8"
         );
 
         return {
             "type": message_type,
-            "body": Module['UTF8ToString'](message_buffer),
+            "body": UTF8ToString(message_buffer),
         };
     } finally {
         if (plaintext_buffer !== undefined) {
@@ -366,14 +356,14 @@ Session.prototype['decrypt'] = restore_stack(function(
 
     try {
         message_buffer = malloc(message.length);
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         max_plaintext_length = session_method(
             Module['_olm_decrypt_max_plaintext_length']
         )(this.ptr, message_type, message_buffer, message.length);
 
         // caculating the length destroys the input buffer, so we need to re-copy it.
-        Module['writeAsciiToMemory'](message, message_buffer, true);
+        writeAsciiToMemory(message, message_buffer, true);
 
         plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
 
@@ -385,7 +375,7 @@ Session.prototype['decrypt'] = restore_stack(function(
 
         // UTF8ToString requires a null-terminated argument, so add the
         // null terminator.
-        Module['setValue'](
+        setValue(
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
@@ -474,21 +464,12 @@ olm_exports["get_library_version"] = restore_stack(function() {
     ];
 });
 
-})();
-
-// export the olm functions into the environment.
-//
-// make sure that we do this *after* populating olm_exports, so that we don't
-// get a half-built window.Olm if there is an exception.
-
-if (typeof module !== 'undefined' && module.exports) {
-    // node / browserify
-    module.exports = olm_exports;
-}
+Module['onRuntimeInitialized'] = function() {
+    OLM_ERROR = Module['_olm_error']();
+    olm_exports["PRIVATE_KEY_LENGTH"] = Module['_olm_pk_private_key_length']();
+    if (onInitSuccess) onInitSuccess();
+};
 
-if (typeof(window) !== 'undefined') {
-    // We've been imported directly into a browser. Define the global 'Olm' object.
-    // (we do this even if module.exports was defined, because it's useful to have
-    // Olm in the global scope for browserified and webpacked apps.)
-    window["Olm"] = olm_exports;
-}
+Module['onAbort'] = function(err) {
+    if (onInitFail) onInitFail(err);
+};
diff --git a/javascript/olm_pre.js b/javascript/olm_pre.js
index ae7aba5..4feff97 100644
--- a/javascript/olm_pre.js
+++ b/javascript/olm_pre.js
@@ -1,10 +1,7 @@
-var olm_exports = {};
 var get_random_values;
-var process; // Shadow the process object so that emscripten won't get
-             // confused by browserify
 
 if (typeof(window) !== 'undefined') {
-    // We've in a browser (directly, via browserify, or via webpack).
+    // We're in a browser (directly, via browserify, or via webpack).
     get_random_values = function(buf) {
         window.crypto.getRandomValues(buf);
     };
@@ -12,7 +9,9 @@ if (typeof(window) !== 'undefined') {
     // We're running in node.
     var nodeCrypto = require("crypto");
     get_random_values = function(buf) {
-        var bytes = nodeCrypto.randomBytes(buf.length);
+        // [''] syntax needed here rather than '.' to prevent
+        // closure compiler from mangling the import(!)
+        var bytes = nodeCrypto['randomBytes'](buf.length);
         buf.set(bytes);
     };
     process = global["process"];
@@ -20,14 +19,21 @@ if (typeof(window) !== 'undefined') {
     throw new Error("Cannot find global to attach library to");
 }
 
-(function() {
-    /* applications should define OLM_OPTIONS in the environment to override
-     * emscripten module settings */
-    var Module = {};
-    if (typeof(OLM_OPTIONS) !== 'undefined') {
-        for (var key in OLM_OPTIONS) {
-            if (OLM_OPTIONS.hasOwnProperty(key)) {
-                Module[key] = OLM_OPTIONS[key];
-            }
+/* applications should define OLM_OPTIONS in the environment to override
+ * emscripten module settings
+ */
+if (typeof(OLM_OPTIONS) !== 'undefined') {
+    for (var olm_option_key in OLM_OPTIONS) {
+        if (OLM_OPTIONS.hasOwnProperty(olm_option_key)) {
+            Module[olm_option_key] = OLM_OPTIONS[olm_option_key];
         }
     }
+}
+
+/* The 'length' argument to Pointer_stringify doesn't work if the input
+ * includes characters >= 128, which makes Pointer_stringify unreliable. We
+ * could use it on strings which are known to be ascii, but that seems
+ * dangerous. Instead we add a NULL character to all of our strings and just
+ * use UTF8ToString.
+ */
+var NULL_BYTE_PADDING_LENGTH = 1;
diff --git a/javascript/olm_prefix.js b/javascript/olm_prefix.js
new file mode 100644
index 0000000..b33dfe9
--- /dev/null
+++ b/javascript/olm_prefix.js
@@ -0,0 +1,3 @@
+var olm_exports = {};
+var onInitSuccess;
+var onInitFail;
diff --git a/javascript/olm_suffix.js b/javascript/olm_suffix.js
new file mode 100644
index 0000000..7f19953
--- /dev/null
+++ b/javascript/olm_suffix.js
@@ -0,0 +1,30 @@
+var olmInitPromise;
+
+olm_exports['init'] = function(opts) {
+    if (olmInitPromise) return olmInitPromise;
+
+    if (opts) OLM_OPTIONS = opts;
+
+    olmInitPromise = new Promise(function(resolve, reject) {
+        onInitSuccess = function() {
+            resolve();
+        };
+        onInitFail = function(err) {
+            reject(err);
+        };
+        Module();
+    });
+    return olmInitPromise;
+};
+
+if (typeof(window) !== 'undefined') {
+    // We've been imported directly into a browser. Define the global 'Olm' object.
+    // (we do this even if module.exports was defined, because it's useful to have
+    // Olm in the global scope for browserified and webpacked apps.)
+    window["Olm"] = olm_exports;
+}
+
+// Emscripten sets the module exports to be its module
+// with wrapped c functions. Clobber it with our higher
+// level wrapper class.
+module.exports = olm_exports;
diff --git a/javascript/package.json b/javascript/package.json
index 9cae60e..efe3705 100644
--- a/javascript/package.json
+++ b/javascript/package.json
@@ -5,6 +5,7 @@
   "main": "olm.js",
   "files": [
     "olm.js",
+    "olm.wasm",
     "README.md"
   ],
   "scripts": {
diff --git a/javascript/test/megolm.spec.js b/javascript/test/megolm.spec.js
index 8f9d24a..241d4bd 100644
--- a/javascript/test/megolm.spec.js
+++ b/javascript/test/megolm.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -21,9 +22,13 @@ var Olm = require('../olm');
 describe("megolm", function() {
     var aliceSession, bobSession;
 
-    beforeEach(function() {
-        aliceSession = new Olm.OutboundGroupSession();
-        bobSession = new Olm.InboundGroupSession();
+    beforeEach(function(done) {
+        Olm.init().then(function() {
+            aliceSession = new Olm.OutboundGroupSession();
+            bobSession = new Olm.InboundGroupSession();
+
+            done();
+        });
     });
 
     afterEach(function() {
diff --git a/javascript/test/olm.spec.js b/javascript/test/olm.spec.js
index b7cc3ae..77dd712 100644
--- a/javascript/test/olm.spec.js
+++ b/javascript/test/olm.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2018 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -30,11 +31,18 @@ describe("olm", function() {
     var aliceAccount, bobAccount;
     var aliceSession, bobSession;
 
-    beforeEach(function() {
-        aliceAccount = new Olm.Account();
-        bobAccount = new Olm.Account();
-        aliceSession = new Olm.Session();
-        bobSession = new Olm.Session();
+    beforeEach(function(done) {
+        // This should really be in a beforeAll, but jasmine-node
+        // doesn't support that
+        debugger;
+        Olm.init().then(function() {
+            aliceAccount = new Olm.Account();
+            bobAccount = new Olm.Account();
+            aliceSession = new Olm.Session();
+            bobSession = new Olm.Session();
+
+            done();
+        });
     });
 
     afterEach(function() {
diff --git a/javascript/test/pk.spec.js b/javascript/test/pk.spec.js
index 0b27470..b4b119e 100644
--- a/javascript/test/pk.spec.js
+++ b/javascript/test/pk.spec.js
@@ -21,9 +21,13 @@ var Olm = require('../olm');
 describe("pk", function() {
     var encryption, decryption;
 
-    beforeEach(function() {
-        encryption = new Olm.PkEncryption();
-        decryption = new Olm.PkDecryption();
+    beforeEach(function(done) {
+        Olm.init().then(function() {
+            encryption = new Olm.PkEncryption();
+            decryption = new Olm.PkDecryption();
+
+            done();
+        });
     });
 
     afterEach(function () {
@@ -37,6 +41,20 @@ 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();
diff --git a/src/error.c b/src/error.c
index f541a93..5147b5c 100644
--- a/src/error.c
+++ b/src/error.c
@@ -31,6 +31,7 @@ static const char * ERRORS[] = {
     "UNKNOWN_MESSAGE_INDEX",
     "BAD_LEGACY_ACCOUNT_PICKLE",
     "BAD_SIGNATURE",
+    "OLM_INPUT_BUFFER_TOO_SMALL",
 };
 
 const char * _olm_error_to_string(enum OlmErrorCode error)
diff --git a/src/pk.cpp b/src/pk.cpp
index 4c5f50e..5ee35d9 100644
--- a/src/pk.cpp
+++ b/src/pk.cpp
@@ -187,7 +187,7 @@ size_t olm_clear_pk_decryption(
     return sizeof(OlmPkDecryption);
 }
 
-size_t olm_pk_generate_key_random_length(void) {
+size_t olm_pk_private_key_length(void) {
     return CURVE25519_KEY_LENGTH;
 }
 
@@ -195,23 +195,23 @@ size_t olm_pk_key_length(void) {
     return olm::encode_base64_length(CURVE25519_KEY_LENGTH);
 }
 
-size_t olm_pk_generate_key(
+size_t olm_pk_key_from_private(
     OlmPkDecryption * decryption,
     void * pubkey, size_t pubkey_length,
-    void * random, size_t random_length
+    void * privkey, size_t privkey_length
 ) {
     if (pubkey_length < olm_pk_key_length()) {
         decryption->last_error =
             OlmErrorCode::OLM_OUTPUT_BUFFER_TOO_SMALL;
         return std::size_t(-1);
     }
-    if (random_length < olm_pk_generate_key_random_length()) {
+    if (privkey_length < olm_pk_private_key_length()) {
         decryption->last_error =
-            OlmErrorCode::OLM_NOT_ENOUGH_RANDOM;
+            OlmErrorCode::OLM_INPUT_BUFFER_TOO_SMALL;
         return std::size_t(-1);
     }
 
-    _olm_crypto_curve25519_generate_key((uint8_t *) random, &decryption->key_pair);
+    _olm_crypto_curve25519_generate_key((uint8_t *) privkey, &decryption->key_pair);
     olm::encode_base64(
         (const uint8_t *)decryption->key_pair.public_key.public_key,
         CURVE25519_KEY_LENGTH,
@@ -380,4 +380,21 @@ size_t olm_pk_decrypt(
     }
 }
 
+size_t olm_pk_get_private_key(
+    OlmPkDecryption * decryption,
+    void *private_key, size_t private_key_length
+) {
+    if (private_key_length < olm_pk_private_key_length()) {
+        decryption->last_error =
+            OlmErrorCode::OLM_OUTPUT_BUFFER_TOO_SMALL;
+        return std::size_t(-1);
+    }
+    std::memcpy(
+        private_key,
+        decryption->key_pair.private_key.private_key,
+        olm_pk_private_key_length()
+    );
+    return olm_pk_private_key_length();
+}
+
 }
diff --git a/tests/test_pk.cpp b/tests/test_pk.cpp
index ee12603..42cc8c9 100644
--- a/tests/test_pk.cpp
+++ b/tests/test_pk.cpp
@@ -36,7 +36,7 @@ const std::uint8_t *bob_public = (std::uint8_t *) "3p7bfXt9wbTTW2HC7OQ1Nz+DQ8hbe
 
 std::uint8_t pubkey[::olm_pk_key_length()];
 
-olm_pk_generate_key(
+olm_pk_key_from_private(
     decryption,
     pubkey, sizeof(pubkey),
     alice_private, sizeof(alice_private)
@@ -44,6 +44,11 @@ olm_pk_generate_key(
 
 assert_equals(alice_public, pubkey, olm_pk_key_length());
 
+uint8_t *alice_private_back_out = (uint8_t *)malloc(olm_pk_private_key_length());
+olm_pk_get_private_key(decryption, alice_private_back_out, olm_pk_private_key_length());
+assert_equals(alice_private, alice_private_back_out, olm_pk_private_key_length());
+free(alice_private_back_out);
+
 std::uint8_t encryption_buffer[olm_pk_encryption_size()];
 OlmPkEncryption *encryption = olm_pk_encryption(encryption_buffer);
 
@@ -105,7 +110,7 @@ const std::uint8_t *alice_public = (std::uint8_t *) "hSDwCYkwp1R0i33ctD73Wg2/Og0
 
 std::uint8_t pubkey[olm_pk_key_length()];
 
-olm_pk_generate_key(
+olm_pk_key_from_private(
     decryption,
     pubkey, sizeof(pubkey),
     alice_private, sizeof(alice_private)