66extern crate std;
77
88use crate :: Error ;
9- use core:: mem:: MaybeUninit ;
9+ use core:: {
10+ mem:: MaybeUninit ,
11+ sync:: atomic:: { AtomicU8 , Ordering } ,
12+ } ;
1013#[ cfg( feature = "std" ) ]
1114use std:: thread_local;
1215
@@ -15,35 +18,71 @@ pub use crate::util::{inner_u32, inner_u64};
1518#[ cfg( not( all( target_arch = "wasm32" , any( target_os = "unknown" , target_os = "none" ) ) ) ) ]
1619compile_error ! ( "`wasm_js` backend can be enabled only for OS-less WASM targets!" ) ;
1720
18- use js_sys:: Uint8Array ;
19- use wasm_bindgen:: { prelude:: wasm_bindgen, JsValue } ;
21+ use js_sys:: { SharedArrayBuffer , Uint8Array , WebAssembly :: Memory } ;
22+ use wasm_bindgen:: { prelude:: wasm_bindgen, JsCast , JsValue } ;
2023
2124// Size of our temporary Uint8Array buffer used with WebCrypto methods
2225// Maximum is 65536 bytes see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
2326const CRYPTO_BUFFER_SIZE : u16 = 256 ;
2427
28+ const MEMORY_KIND_UNINIT : u8 = 0 ;
29+ const MEMORY_KIND_NOT_SHARED : u8 = 1 ;
30+ const MEMORY_KIND_SHARED : u8 = 2 ;
31+
32+ static MEMORY_KIND : AtomicU8 = AtomicU8 :: new ( 0 ) ;
33+
2534pub fn fill_inner ( dest : & mut [ MaybeUninit < u8 > ] ) -> Result < ( ) , Error > {
2635 CRYPTO . with ( |crypto| {
2736 let crypto = crypto. as_ref ( ) . ok_or ( Error :: WEB_CRYPTO ) ?;
2837
29- // getRandomValues does not work with all types of WASM memory,
30- // so we initially write to browser memory to avoid exceptions.
31- let buf = Uint8Array :: new_with_length ( CRYPTO_BUFFER_SIZE . into ( ) ) ;
32- for chunk in dest. chunks_mut ( CRYPTO_BUFFER_SIZE . into ( ) ) {
33- let chunk_len: u32 = chunk
34- . len ( )
35- . try_into ( )
36- . expect ( "chunk length is bounded by CRYPTO_BUFFER_SIZE" ) ;
37- // The chunk can be smaller than buf's length, so we call to
38- // JS to create a smaller view of buf without allocation.
39- let sub_buf = buf. subarray ( 0 , chunk_len) ;
40-
41- if crypto. get_random_values ( & sub_buf) . is_err ( ) {
42- return Err ( Error :: WEB_GET_RANDOM_VALUES ) ;
43- }
38+ let shared = loop {
39+ break match MEMORY_KIND . load ( Ordering :: Relaxed ) {
40+ MEMORY_KIND_NOT_SHARED => false ,
41+ MEMORY_KIND_SHARED => true ,
42+ MEMORY_KIND_UNINIT => {
43+ let memory: Memory = wasm_bindgen:: memory ( ) . unchecked_into ( ) ;
44+ let val = if memory. buffer ( ) . is_instance_of :: < SharedArrayBuffer > ( ) {
45+ MEMORY_KIND_SHARED
46+ } else {
47+ MEMORY_KIND_NOT_SHARED
48+ } ;
49+ MEMORY_KIND . store ( val, Ordering :: Relaxed ) ;
50+ continue ;
51+ }
52+ _ => unreachable ! ( ) ,
53+ } ;
54+ } ;
55+
56+ if shared {
57+ // getRandomValues does not work with all types of WASM memory,
58+ // so we initially write to browser memory to avoid exceptions.
59+ let buf = Uint8Array :: new_with_length ( CRYPTO_BUFFER_SIZE . into ( ) ) ;
60+ for chunk in dest. chunks_mut ( CRYPTO_BUFFER_SIZE . into ( ) ) {
61+ let chunk_len: u32 = chunk
62+ . len ( )
63+ . try_into ( )
64+ . expect ( "chunk length is bounded by CRYPTO_BUFFER_SIZE" ) ;
65+ // The chunk can be smaller than buf's length, so we call to
66+ // JS to create a smaller view of buf without allocation.
67+ let sub_buf = buf. subarray ( 0 , chunk_len) ;
4468
45- // SAFETY: `sub_buf`'s length is the same length as `chunk`
46- unsafe { sub_buf. raw_copy_to_ptr ( chunk. as_mut_ptr ( ) . cast :: < u8 > ( ) ) } ;
69+ if crypto. get_random_values ( & sub_buf) . is_err ( ) {
70+ return Err ( Error :: WEB_GET_RANDOM_VALUES ) ;
71+ }
72+
73+ // SAFETY: `sub_buf`'s length is the same length as `chunk`
74+ unsafe { sub_buf. raw_copy_to_ptr ( chunk. as_mut_ptr ( ) . cast :: < u8 > ( ) ) } ;
75+ }
76+ } else {
77+ for chunk in dest. chunks_mut ( CRYPTO_BUFFER_SIZE . into ( ) ) {
78+ // SAFETY: this is only safe because on Wasm the issues with unitialized data don't exist
79+ let buf = unsafe {
80+ core:: slice:: from_raw_parts_mut ( chunk. as_mut_ptr ( ) . cast :: < u8 > ( ) , chunk. len ( ) )
81+ } ;
82+ if crypto. get_random_values_ref ( buf) . is_err ( ) {
83+ return Err ( Error :: WEB_GET_RANDOM_VALUES ) ;
84+ }
85+ }
4786 }
4887 Ok ( ( ) )
4988 } )
@@ -59,4 +98,6 @@ extern "C" {
5998 // Crypto.getRandomValues()
6099 #[ wasm_bindgen( method, js_name = getRandomValues, catch) ]
61100 fn get_random_values ( this : & Crypto , buf : & Uint8Array ) -> Result < ( ) , JsValue > ;
101+ #[ wasm_bindgen( method, js_name = getRandomValues, catch) ]
102+ fn get_random_values_ref ( this : & Crypto , buf : & mut [ u8 ] ) -> Result < ( ) , JsValue > ;
62103}
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