Remove TLS by using lazy_static (#25)

Author: josephlr

Cargo.toml

@@ -22,6 +22,7 @@ log = { version = "0.4", optional = true }
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2.34"
+lazy_static = "1.3.0"
 
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3.6", features = ["minwindef", "ntsecapi", "winnt"] }
@@ -32,9 +33,13 @@ cloudabi = "0.0.3"
 [target.'cfg(fuchsia)'.dependencies]
 fuchsia-cprng = "0.1"
 
+[target.'cfg(target_os = "redox")'.dependencies]
+lazy_static = "1.3.0"
+
 [target.wasm32-unknown-unknown.dependencies]
 wasm-bindgen = { version = "0.2.29", optional = true }
 stdweb = { version = "0.4.9", optional = true }
+lazy_static = "1.3.0"
 
 [target.wasm32-wasi.dependencies]
 libc = "0.2.54"

src/lib.rs

@@ -132,21 +132,6 @@ macro_rules! error { ($($x:tt)*) => () }
 #[cfg(target_arch = "wasm32")]
 extern crate std;
 
-#[cfg(any(
-    target_os = "android",
-    target_os = "netbsd",
-    target_os = "solaris",
-    target_os = "illumos",
-    target_os = "redox",
-    target_os = "dragonfly",
-    target_os = "haiku",
-    target_os = "linux",
-    all(
-        target_arch = "wasm32", 
-        not(target_os = "wasi")
-    ),
-))]
-mod utils;
 mod error;
 pub use crate::error::Error;
 
@@ -172,6 +157,15 @@ macro_rules! mod_use {
 ))]
 mod error_impls;
 
+// These targets read from a file as a fallback method.
+#[cfg(any(
+    target_os = "android",
+    target_os = "linux",
+    target_os = "solaris",
+    target_os = "illumos",
+))]
+mod use_file;
+
 mod_use!(cfg(target_os = "android"), linux_android);
 mod_use!(cfg(target_os = "bitrig"), openbsd_bitrig);
 mod_use!(cfg(target_os = "cloudabi"), cloudabi);
@@ -233,16 +227,12 @@ mod_use!(
         target_os = "redox",
         target_os = "solaris",
         all(target_arch = "x86_64", target_os = "uefi"),
+        target_os = "wasi",
         target_env = "sgx",
         windows,
         all(
             target_arch = "wasm32",
-            any(
-                target_os = "emscripten",
-                target_os = "wasi",
-                feature = "wasm-bindgen",
-                feature = "stdweb",
-            ),
+            any(feature = "wasm-bindgen", feature = "stdweb"),
         ),
     ))),
     dummy

src/linux_android.rs

@@ -9,24 +9,10 @@
 //! Implementation for Linux / Android
 extern crate std;
 
-use crate::Error;
-use crate::utils::use_init;
-use std::{thread_local, io::{self, Read}, fs::File};
-use core::cell::RefCell;
+use crate::{use_file, Error};
 use core::num::NonZeroU32;
-use core::sync::atomic::{AtomicBool, Ordering};
-
-// This flag tells getrandom() to return EAGAIN instead of blocking.
-static RNG_INIT: AtomicBool = AtomicBool::new(false);
-
-enum RngSource {
-    GetRandom,
-    Device(File),
-}
-
-thread_local!(
-    static RNG_SOURCE: RefCell<Option<RngSource>> = RefCell::new(None);
-);
+use lazy_static::lazy_static;
+use std::io;
 
 fn syscall_getrandom(dest: &mut [u8], block: bool) -> Result<usize, io::Error> {
     let flags = if block { 0 } else { libc::GRND_NONBLOCK };
@@ -45,52 +31,28 @@ fn syscall_getrandom(dest: &mut [u8], block: bool) -> Result<usize, io::Error> {
 }
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
-    RNG_SOURCE.with(|f| {
-        use_init(f,
-        || {
-            let s = if is_getrandom_available() {
-                RngSource::GetRandom
-            } else {
-                // read one byte from "/dev/random" to ensure that
-                // OS RNG has initialized
-                if !RNG_INIT.load(Ordering::Relaxed) {
-                    File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
-                    RNG_INIT.store(true, Ordering::Relaxed)
-                }
-                RngSource::Device(File::open("/dev/urandom")?)
-            };
-            Ok(s)
-        }, |f| {
-            match f {
-                RngSource::GetRandom => {
-                    let mut start = 0;
-                    while start < dest.len() {
-                        start += syscall_getrandom(&mut dest[start..], true)?;
-                    }
-                    Ok(())
-                }
-                RngSource::Device(f) => f.read_exact(dest).map_err(From::from),
+    lazy_static! { static ref HAS_GETRANDOM: bool = is_getrandom_available(); }
+    match *HAS_GETRANDOM {
+        true => {
+            let mut start = 0;
+            while start < dest.len() {
+                start += syscall_getrandom(&mut dest[start..], true)?;
             }
-        })
-    })
+            Ok(())
+        },
+        false => use_file::getrandom_inner(dest),
+    }
 }
 
 fn is_getrandom_available() -> bool {
-    use std::sync::{Once, ONCE_INIT};
-
-    static CHECKER: Once = ONCE_INIT;
-    static AVAILABLE: AtomicBool = AtomicBool::new(false);
-
-    CHECKER.call_once(|| {
-        let mut buf: [u8; 0] = [];
-        let available = match syscall_getrandom(&mut buf, false) {
-            Ok(_) => true,
-            Err(err) => err.raw_os_error() != Some(libc::ENOSYS),
-        };
-        AVAILABLE.store(available, Ordering::Relaxed);
-    });
-
-    AVAILABLE.load(Ordering::Relaxed)
+    match syscall_getrandom(&mut [], false) {
+        Err(err) => match err.raw_os_error() {
+            Some(libc::ENOSYS) => false, // No kernel support
+            Some(libc::EPERM) => false, // Blocked by seccomp
+            _ => true,
+        }
+        Ok(_) => true,
+    }
 }
 
 #[inline(always)]

src/solaris_illumos.rs

@@ -19,26 +19,17 @@
 //! libc::dlsym.
 extern crate std;
 
-use crate::Error;
-use crate::utils::use_init;
-use std::{thread_local, io::{self, Read}, fs::File};
-use core::cell::RefCell;
+use crate::{use_file, Error};
+use core::mem;
 use core::num::NonZeroU32;
+use lazy_static::lazy_static;
+use std::io;
 
 #[cfg(target_os = "illumos")]
 type GetRandomFn = unsafe extern "C" fn(*mut u8, libc::size_t, libc::c_uint) -> libc::ssize_t;
 #[cfg(target_os = "solaris")]
 type GetRandomFn = unsafe extern "C" fn(*mut u8, libc::size_t, libc::c_uint) -> libc::c_int;
 
-enum RngSource {
-    GetRandom(GetRandomFn),
-    Device(File),
-}
-
-thread_local!(
-    static RNG_SOURCE: RefCell<Option<RngSource>> = RefCell::new(None);
-);
-
 fn libc_getrandom(rand: GetRandomFn, dest: &mut [u8]) -> Result<(), Error> {
     let ret = unsafe { rand(dest.as_mut_ptr(), dest.len(), 0) as libc::ssize_t };
 
@@ -51,51 +42,23 @@ fn libc_getrandom(rand: GetRandomFn, dest: &mut [u8]) -> Result<(), Error> {
 }
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
+    lazy_static! { static ref GETRANDOM_FUNC: Option<GetRandomFn> = fetch_getrandom(); }
+
     // 256 bytes is the lowest common denominator across all the Solaris
     // derived platforms for atomically obtaining random data.
-    RNG_SOURCE.with(|f| {
-        use_init(
-            f,
-            || {
-                let s = match fetch_getrandom() {
-                    Some(fptr) => RngSource::GetRandom(fptr),
-                    None => RngSource::Device(File::open("/dev/random")?),
-                };
-                Ok(s)
-            },
-            |f| {
-                match f {
-                    RngSource::GetRandom(rp) => {
-                        for chunk in dest.chunks_mut(256) {
-                            libc_getrandom(*rp, chunk)?
-                        }
-                    }
-                    RngSource::Device(randf) => {
-                        for chunk in dest.chunks_mut(256) {
-                            randf.read_exact(chunk)?
-                        }
-                    }
-                };
-                Ok(())
-            },
-        )
-    })
+    for chunk in dest.chunks_mut(256) {
+        match *GETRANDOM_FUNC {
+            Some(fptr) => libc_getrandom(fptr, chunk)?,
+            None => use_file::getrandom_inner(chunk)?,
+        };
+    }
+    Ok(())
 }
 
 fn fetch_getrandom() -> Option<GetRandomFn> {
-    use std::mem;
-    use std::sync::atomic::{AtomicUsize, Ordering};
-
-    static FPTR: AtomicUsize = AtomicUsize::new(1);
-
-    if FPTR.load(Ordering::SeqCst) == 1 {
-        let name = "getrandom\0";
-        let addr = unsafe { libc::dlsym(libc::RTLD_DEFAULT, name.as_ptr() as *const _) as usize };
-        FPTR.store(addr, Ordering::SeqCst);
-    }
-
-    let ptr = FPTR.load(Ordering::SeqCst);
-    unsafe { mem::transmute::<usize, Option<GetRandomFn>>(ptr) }
+    let name = "getrandom\0";
+    let addr = unsafe { libc::dlsym(libc::RTLD_DEFAULT, name.as_ptr() as *const _) };
+    unsafe { mem::transmute(addr) }
 }
 
 #[inline(always)]

src/use_file.rs

@@ -6,31 +6,35 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Implementation for DragonFly / Haiku
+//! Implementations that just need to read from a file
 extern crate std;
 
 use crate::Error;
-use crate::utils::use_init;
-use std::{thread_local, io::Read, fs::File};
-use core::cell::RefCell;
 use core::num::NonZeroU32;
-
-thread_local!(static RNG_FILE: RefCell<Option<File>> = RefCell::new(None));
+use lazy_static::lazy_static;
+use std::{
+    fs::File,
+    io::Read,
+    os::unix::io::{FromRawFd, IntoRawFd, RawFd},
+};
 
 #[cfg(target_os = "redox")]
 const FILE_PATH: &str = "rand:";
-#[cfg(target_os = "netbsd")]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "netbsd"))]
 const FILE_PATH: &str = "/dev/urandom";
-#[cfg(any(target_os = "dragonfly", target_os = "emscripten", target_os = "haiku"))]
+#[cfg(any(
+    target_os = "dragonfly",
+    target_os = "emscripten",
+    target_os = "haiku",
+    target_os = "solaris",
+    target_os = "illumos"
+))]
 const FILE_PATH: &str = "/dev/random";
 
 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
-    RNG_FILE.with(|f| {
-        use_init(f, || init_file(), |f| use_file(f, dest))
-    })
-}
+    lazy_static! { static ref RNG_FD: Result<RawFd, Error> = init_file(); }
+    let mut f = unsafe { File::from_raw_fd((*RNG_FD)?) };
 
-fn use_file(f: &mut File, dest: &mut [u8]) -> Result<(), Error> {
     if cfg!(target_os = "emscripten") {
         // `Crypto.getRandomValues` documents `dest` should be at most 65536 bytes.
         for chunk in dest.chunks_mut(65536) {
@@ -39,18 +43,17 @@ fn use_file(f: &mut File, dest: &mut [u8]) -> Result<(), Error> {
     } else {
         f.read_exact(dest)?;
     }
-    core::mem::forget(f);
     Ok(())
 }
 
-fn init_file() -> Result<File, Error> {
-    if cfg!(target_os = "netbsd") {
+fn init_file() -> Result<RawFd, Error> {
+    if FILE_PATH == "/dev/urandom" {
         // read one byte from "/dev/random" to ensure that OS RNG has initialized
         File::open("/dev/random")?.read_exact(&mut [0u8; 1])?;
     }
-    let f = File::open(FILE_PATH)?;
-    Ok(f)
+    Ok(File::open(FILE_PATH)?.into_raw_fd())
 }
 
 #[inline(always)]
+#[allow(dead_code)]
 pub fn error_msg_inner(_: NonZeroU32) -> Option<&'static str> { None }