2086699b70
Only in developer mode, ofc. Notes: 1. We have to move the initialization before the lightningd main trace_start, since that uses pseudorand(). 2. To make the results stable, we need to use per-caller values to randbytes(). Otherwise external timing changes the call order. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
63 lines
1.4 KiB
C
63 lines
1.4 KiB
C
#include "config.h"
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#include <assert.h>
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#include <ccan/crypto/siphash24/siphash24.h>
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#include <ccan/endian/endian.h>
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#include <ccan/tal/tal.h>
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#include <common/memleak.h>
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#include <common/pseudorand.h>
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#include <common/randbytes.h>
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#include <common/utils.h>
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#include <sodium/randombytes.h>
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#include <stdlib.h>
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#include <unistd.h>
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static bool used = false;
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static u64 dev_seed = 0;
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bool randbytes_overridden(void)
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{
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return dev_seed != 0;
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}
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void randbytes_(void *bytes, size_t num_bytes, u64 *offset)
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{
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static u64 offset_init;
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be64 pattern;
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used = true;
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if (!randbytes_overridden()) {
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randombytes_buf(bytes, num_bytes); /* discouraged: use randbytes() */
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return;
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}
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/* First time, start callers at different offsets */
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if (*offset == 0) {
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*offset = offset_init;
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offset_init += 1000;
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}
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/* Somewhat recognizable pattern */
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pattern = cpu_to_be64(dev_seed + (*offset)++);
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for (size_t i = 0; i < num_bytes; i += sizeof(pattern)) {
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size_t copy = num_bytes - i;
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if (copy > sizeof(pattern))
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copy = sizeof(pattern);
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memcpy((u8 *)bytes + i, &pattern, copy);
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}
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}
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/* We want different seeds for each plugin (hence argv0), and for each
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* lightmingd instance, (hence seed from environment) */
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void dev_override_randbytes(const char *argv0, long int seed)
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{
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struct siphash_seed hashseed;
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assert(!used);
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hashseed.u.u64[0] = seed;
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hashseed.u.u64[1] = 0;
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dev_seed = siphash24(&hashseed, argv0, strlen(argv0));
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assert(randbytes_overridden());
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}
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