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Diffstat (limited to 'stdlib/tst-arc4random-fork.c')
| -rw-r--r-- | stdlib/tst-arc4random-fork.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/stdlib/tst-arc4random-fork.c b/stdlib/tst-arc4random-fork.c new file mode 100644 index 0000000000..019c0a99de --- /dev/null +++ b/stdlib/tst-arc4random-fork.c @@ -0,0 +1,198 @@ +/* Test that subprocesses generate distinct streams of randomness. + Copyright (C) 2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +/* Collect random data from subprocesses and check that all the + results are unique. */ + +#include <array_length.h> +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <support/check.h> +#include <support/support.h> +#include <support/xthread.h> +#include <support/xunistd.h> +#include <unistd.h> + +/* Perform multiple runs. The subsequent runs start with an + already-initialized random number generator. (The number 1500 was + seen to reproduce failures reliable in case of a race condition in + the fork detection code.) */ +enum { runs = 1500 }; + +/* One hundred processes in total. This should be high enough to + expose any issues, but low enough not to tax the overall system too + much. */ +enum { subprocesses = 49 }; + +/* The total number of processes. */ +enum { processes = subprocesses + 1 }; + +/* Number of bytes of randomness to generate per process. Large + enough to make false positive duplicates extremely unlikely. */ +enum { random_size = 16 }; + +/* Generated bytes of randomness. */ +struct result +{ + unsigned char bytes[random_size]; +}; + +/* Shared across all processes. */ +static struct shared_data +{ + pthread_barrier_t barrier; + struct result results[runs][processes]; +} *shared_data; + +static void +generate_arc4random (unsigned char *bytes) +{ + for (int i = 0; i < random_size / sizeof (uint32_t); i++) + { + uint32_t x = arc4random (); + memcpy (&bytes[4 * i], &x, sizeof x); + } +} + +static void +generate_arc4random_buf (unsigned char *bytes) +{ + arc4random_buf (bytes, random_size); +} + +static void +generate_arc4random_uniform (unsigned char *bytes) +{ + for (int i = 0; i < random_size; i++) + bytes[i] = arc4random_uniform (256); +} + +/* Invoked to collect data from a subprocess. */ +static void +subprocess (int run, int process_index, void (*func)(unsigned char *)) +{ + xpthread_barrier_wait (&shared_data->barrier); + func (shared_data->results[run][process_index].bytes); +} + +/* Used to sort the results. */ +struct index +{ + int run; + int process_index; +}; + +/* Used to sort an array of struct index values. */ +static int +index_compare (const void *left1, const void *right1) +{ + const struct index *left = left1; + const struct index *right = right1; + + return memcmp (shared_data->results[left->run][left->process_index].bytes, + shared_data->results[right->run][right->process_index].bytes, + random_size); +} + +static int +do_test_func (void (*func)(unsigned char *bytes)) +{ + /* Collect random data. */ + for (int run = 0; run < runs; ++run) + { + pid_t pids[subprocesses]; + for (int process_index = 0; process_index < subprocesses; + ++process_index) + { + pids[process_index] = xfork (); + if (pids[process_index] == 0) + { + subprocess (run, process_index, func); + _exit (0); + } + } + + /* Trigger all subprocesses. Also add data from the parent + process. */ + subprocess (run, subprocesses, func); + + for (int process_index = 0; process_index < subprocesses; + ++process_index) + { + int status; + xwaitpid (pids[process_index], &status, 0); + if (status != 0) + FAIL_EXIT1 ("subprocess index %d (PID %d) exit status %d\n", + process_index, (int) pids[process_index], status); + } + } + + /* Check for duplicates. */ + struct index indexes[runs * processes]; + for (int run = 0; run < runs; ++run) + for (int process_index = 0; process_index < processes; ++process_index) + indexes[run * processes + process_index] + = (struct index) { .run = run, .process_index = process_index }; + qsort (indexes, array_length (indexes), sizeof (indexes[0]), index_compare); + for (size_t i = 1; i < array_length (indexes); ++i) + { + if (index_compare (indexes + i - 1, indexes + i) == 0) + { + support_record_failure (); + unsigned char *bytes + = shared_data->results[indexes[i].run] + [indexes[i].process_index].bytes; + char *quoted = support_quote_blob (bytes, random_size); + printf ("error: duplicate randomness data: \"%s\"\n" + " run %d, subprocess %d\n" + " run %d, subprocess %d\n", + quoted, indexes[i - 1].run, indexes[i - 1].process_index, + indexes[i].run, indexes[i].process_index); + free (quoted); + } + } + + return 0; +} + +static int +do_test (void) +{ + shared_data = support_shared_allocate (sizeof (*shared_data)); + { + pthread_barrierattr_t attr; + xpthread_barrierattr_init (&attr); + xpthread_barrierattr_setpshared (&attr, PTHREAD_PROCESS_SHARED); + xpthread_barrier_init (&shared_data->barrier, &attr, processes); + xpthread_barrierattr_destroy (&attr); + } + + do_test_func (generate_arc4random); + do_test_func (generate_arc4random_buf); + do_test_func (generate_arc4random_uniform); + + xpthread_barrier_destroy (&shared_data->barrier); + support_shared_free (shared_data); + shared_data = NULL; + + return 0; +} + +#define TIMEOUT 40 +#include <support/test-driver.c> |