64 lines
2.5 KiB
C++
64 lines
2.5 KiB
C++
/*
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* Copyright (C) 2016 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "private/bionic_arc4random.h"
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#include <errno.h>
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#include <stdatomic.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/auxv.h>
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#include <unistd.h>
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#include <async_safe/log.h>
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#include "private/KernelArgumentBlock.h"
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bool __libc_arc4random_has_unlimited_entropy() {
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static bool have_urandom = access("/dev/urandom", R_OK) == 0;
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return have_urandom;
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}
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void __libc_safe_arc4random_buf(void* buf, size_t n, KernelArgumentBlock& args) {
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// Only call arc4random_buf once we `have_urandom', since in getentropy_getrandom we may fallback
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// to use /dev/urandom, if the kernel entropy pool hasn't been initialized or not enough bytes
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if (__libc_arc4random_has_unlimited_entropy()) {
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arc4random_buf(buf, n);
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return;
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}
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static size_t at_random_bytes_consumed = 0;
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if (at_random_bytes_consumed + n > 16) {
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async_safe_fatal("ran out of AT_RANDOM bytes, have %zu, requested %zu",
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16 - at_random_bytes_consumed, n);
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}
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memcpy(buf, reinterpret_cast<char*>(args.getauxval(AT_RANDOM)) + at_random_bytes_consumed, n);
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at_random_bytes_consumed += n;
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return;
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}
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