| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
| * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
| * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include "private/bionic_arc4random.h" |
| |
| #include <errno.h> |
| #include <stdatomic.h> |
| #include <stdlib.h> |
| #include <sys/auxv.h> |
| #include <unistd.h> |
| |
| #include <async_safe/log.h> |
| |
| #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()) { |
| arc4random_buf(buf, n); |
| return; |
| } |
| |
| static size_t at_random_bytes_consumed = 0; |
| if (at_random_bytes_consumed + n > 16) { |
| async_safe_fatal("ran out of AT_RANDOM bytes, have %zu, requested %zu", |
| 16 - at_random_bytes_consumed, n); |
| } |
| |
| memcpy(buf, reinterpret_cast<char*>(args.getauxval(AT_RANDOM)) + at_random_bytes_consumed, n); |
| at_random_bytes_consumed += n; |
| return; |
| } |