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Revert "Use getentropy when possible on all Apple platforms"

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This reverts commit 3fc35b5b93.
This commit is contained in:
BlackHoleFox 2022-10-05 00:48:22 -05:00
parent d8613f792c
commit a955ef2c8c
1 changed files with 38 additions and 56 deletions
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94
library/std/src/sys/unix/rand.rs
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@ -137,9 +137,11 @@ mod imp {
}
}
#[cfg(any(target_os = "macos", target_os = "ios", target_os = "watchos"))]
#[cfg(target_os = "macos")]
mod imp {
use crate::io;
use crate::fs::File;
use crate::io::Read;
use crate::sys::os::errno;
use crate::sys::weak::weak;
use libc::{c_int, c_void, size_t};
@ -153,7 +155,7 @@ mod imp {
for s in v.chunks_mut(256) {
let ret = unsafe { f(s.as_mut_ptr() as *mut c_void, s.len()) };
if ret == -1 {
panic!("unexpected getentropy error: {}", io::Error::last_os_error());
panic!("unexpected getentropy error: {}", errno());
}
}
true
@ -161,64 +163,14 @@ mod imp {
.unwrap_or(false)
}
#[cfg(target_os = "macos")]
fn fallback_fill_bytes(v: &mut [u8]) {
use crate::fs::File;
use crate::io::Read;
let mut file = File::open("/dev/urandom").expect("failed to open /dev/urandom");
file.read_exact(v).expect("failed to read /dev/urandom")
}
// On iOS and MacOS `SecRandomCopyBytes` calls `CCRandomCopyBytes` with
// `kCCRandomDefault`. `CCRandomCopyBytes` manages a CSPRNG which is seeded
// from `/dev/random` and which runs on its own thread accessed via GCD.
//
// This is very heavyweight compared to the alternatives, but they may not be usable:
// - `getentropy` was added in iOS 10, but we support a minimum of iOS 7
// - `/dev/urandom` is not accessible inside the iOS app sandbox.
//
// Therefore `SecRandomCopyBytes` is only used on older iOS versions where no
// better options are present.
#[cfg(target_os = "ios")]
fn fallback_fill_bytes(v: &mut [u8]) {
use crate::ptr;
enum SecRandom {}
#[allow(non_upper_case_globals)]
const kSecRandomDefault: *const SecRandom = ptr::null();
extern "C" {
fn SecRandomCopyBytes(rnd: *const SecRandom, count: size_t, bytes: *mut u8) -> c_int;
}
let ret = unsafe { SecRandomCopyBytes(kSecRandomDefault, v.len(), v.as_mut_ptr()) };
if ret == -1 {
panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
}
}
// All supported versions of watchOS (>= 5) have support for `getentropy`.
#[cfg(target_os = "watchos")]
#[cold]
fn fallback_fill_bytes(_: &mut [u8]) {
unreachable!()
}
pub fn fill_bytes(v: &mut [u8]) {
if getentropy_fill_bytes(v) {
return;
}
// Older macOS versions (< 10.12) don't support `getentropy`. Fallback to
// reading from `/dev/urandom` on these systems.
//
// Older iOS versions (< 10) don't support it either. Fallback to
// `SecRandomCopyBytes` on these systems. On watchOS, this is unreachable
// because the minimum supported version is 5 while `getentropy` became accessible
// in 3.
fallback_fill_bytes(v)
// for older macos which doesn't support getentropy
let mut file = File::open("/dev/urandom").expect("failed to open /dev/urandom");
file.read_exact(v).expect("failed to read /dev/urandom")
}
}
@ -237,6 +189,36 @@ mod imp {
}
}
// On iOS and MacOS `SecRandomCopyBytes` calls `CCRandomCopyBytes` with
// `kCCRandomDefault`. `CCRandomCopyBytes` manages a CSPRNG which is seeded
// from `/dev/random` and which runs on its own thread accessed via GCD.
// This seems needlessly heavyweight for the purposes of generating two u64s
// once per thread in `hashmap_random_keys`. Therefore `SecRandomCopyBytes` is
// only used on iOS where direct access to `/dev/urandom` is blocked by the
// sandbox.
#[cfg(any(target_os = "ios", target_os = "watchos"))]
mod imp {
use crate::io;
use crate::ptr;
use libc::{c_int, size_t};
enum SecRandom {}
#[allow(non_upper_case_globals)]
const kSecRandomDefault: *const SecRandom = ptr::null();
extern "C" {
fn SecRandomCopyBytes(rnd: *const SecRandom, count: size_t, bytes: *mut u8) -> c_int;
}
pub fn fill_bytes(v: &mut [u8]) {
let ret = unsafe { SecRandomCopyBytes(kSecRandomDefault, v.len(), v.as_mut_ptr()) };
if ret == -1 {
panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
}
}
}
#[cfg(any(target_os = "freebsd", target_os = "netbsd"))]
mod imp {
use crate::ptr;