211c4d35f2
The error handling was a mess, resulting in an infinite loop (and a test timeout) if you actually took the /dev/urandom fallback. I'm also unconvinced that the getrandom(2) path was correct because of the various reasons why we might get a short count back (http://man7.org/linux/man-pages/man2/getrandom.2.html). In this version, the two paths look very similar except for the getrandom(2) failure case, where it's now much clearer that we just give up so that we can boot (http://b/33059407). Bug: http://b/33059407 Bug: http://b/67015565 Test: ran tests on hikey and a ICS Galaxy Nexus Change-Id: Ie715d59b46f7a70bae66943c316168838787b40d
80 lines
2.9 KiB
C++
80 lines
2.9 KiB
C++
/*
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* Copyright (C) 2018 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 <errno.h>
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#include <fcntl.h>
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#include <sys/random.h>
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#include <unistd.h>
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static int getentropy_urandom(void* buffer, size_t buffer_size, int saved_errno) {
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int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY | O_NOFOLLOW | O_CLOEXEC, 0));
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if (fd == -1) return -1;
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size_t collected = 0;
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while (collected < buffer_size) {
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ssize_t count = TEMP_FAILURE_RETRY(read(fd, static_cast<char*>(buffer) + collected,
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buffer_size - collected));
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if (count == -1) {
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close(fd);
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return -1;
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}
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collected += count;
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}
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close(fd);
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errno = saved_errno;
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return 0;
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}
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int getentropy(void* buffer, size_t buffer_size) {
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if (buffer_size > 256) {
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errno = EIO;
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return -1;
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}
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int saved_errno = errno;
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size_t collected = 0;
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while (collected < buffer_size) {
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long count = TEMP_FAILURE_RETRY(getrandom(static_cast<char*>(buffer) + collected,
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buffer_size - collected, GRND_NONBLOCK));
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if (count == -1) {
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// EAGAIN: there isn't enough entropy right now.
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// ENOSYS/EINVAL: getrandom(2) or GRND_NONBLOCK isn't supported.
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// EFAULT: `buffer` is invalid.
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// Try /dev/urandom regardless because it can't hurt,
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// and we don't need to optimize the EFAULT case.
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// See http://b/33059407 and http://b/67015565.
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return getentropy_urandom(buffer, buffer_size, saved_errno);
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}
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collected += count;
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}
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errno = saved_errno;
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return 0;
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}
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