diff options
| -rw-r--r-- | libc/bionic/bionic_arc4random.cpp | 15 | ||||
| -rw-r--r-- | libc/private/bionic_arc4random.h | 17 |
2 files changed, 10 insertions, 22 deletions
diff --git a/libc/bionic/bionic_arc4random.cpp b/libc/bionic/bionic_arc4random.cpp index 391eb0c68..fa2617f0d 100644 --- a/libc/bionic/bionic_arc4random.cpp +++ b/libc/bionic/bionic_arc4random.cpp @@ -28,8 +28,6 @@ #include "private/bionic_arc4random.h" -#include <errno.h> -#include <stdatomic.h> #include <stdlib.h> #include <string.h> #include <sys/auxv.h> @@ -39,15 +37,12 @@ #include "private/KernelArgumentBlock.h" -bool __libc_arc4random_has_unlimited_entropy() { - static bool have_urandom = access("/dev/urandom", R_OK) == 0; - return have_urandom; -} - void __libc_safe_arc4random_buf(void* buf, size_t n, KernelArgumentBlock& args) { - // Only call arc4random_buf once we `have_urandom', since in getentropy_getrandom we may fallback - // to use /dev/urandom, if the kernel entropy pool hasn't been initialized or not enough bytes - if (__libc_arc4random_has_unlimited_entropy()) { + // Only call arc4random_buf once we have `/dev/urandom` because getentropy(3) + // will fall back to using `/dev/urandom` if getrandom(2) fails, and abort if + // if can't use `/dev/urandom`. + static bool have_urandom = access("/dev/urandom", R_OK) == 0; + if (have_urandom) { arc4random_buf(buf, n); return; } diff --git a/libc/private/bionic_arc4random.h b/libc/private/bionic_arc4random.h index b51f818d8..0e9376e9e 100644 --- a/libc/private/bionic_arc4random.h +++ b/libc/private/bionic_arc4random.h @@ -33,18 +33,11 @@ #include "private/KernelArgumentBlock.h" -/* - * arc4random aborts if it's unable to fetch entropy, which is always the case - * for init on devices without getrandom(2), since /dev/random hasn't been - * created yet. Provide a wrapper function that falls back to AT_RANDOM if - * we don't have getrandom and /dev/urandom is missing. - */ +// arc4random(3) aborts if it's unable to fetch entropy, which is always +// the case for init on devices. GCE kernels have a workaround to ensure +// sufficient entropy during early boot, but no device kernels do. This +// wrapper falls back to AT_RANDOM if the kernel doesn't have enough +// entropy for getrandom(2) or /dev/urandom. void __libc_safe_arc4random_buf(void* buf, size_t n, KernelArgumentBlock& args); -/* - * Return true if libc has an unlimited entropy source (something other than - * AT_RANDOM), and arc4random* calls will always succeed. - */ -bool __libc_arc4random_has_unlimited_entropy(); - #endif |