64 lines
1.6 KiB
Plaintext
64 lines
1.6 KiB
Plaintext
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#!/bin/sh
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set -e
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# util-linux creates random UUIDs when uuid_generate_random is called
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# Use LD_PRELOAD to replace uuid_generate_random with a less random version
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# Don't run if gcc is not installed
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if [ ! -e /usr/bin/cc ];
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then
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exit 0
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fi
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cat > unrandomize_uuid_generate_random.c << END_OF_SOURCE
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#include <stdlib.h>
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#include <stdio.h>
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#define SEQUENCE_FILENAME "/var/cache/unrandomize_uuid_generate_random.sequence_number"
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/* https://tools.ietf.org/html/rfc4122 */
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typedef unsigned char uuid_t[16];
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/* Our pseudo-random version */
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void uuid_generate_random(uuid_t out)
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{
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/* Nil UUID */
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for (int i=0;i<16;i++) {
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out[i] = 0x00;
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}
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out[6]=0x40; /* UUID version 4 means randomly generated */
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out[8]=0x80; /* bit7=1,bit6=0 */
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/* The file doesn't need to exist yet */
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FILE *f = fopen(SEQUENCE_FILENAME, "rb");
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if (f) {
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fread(out+12, 4, 1, f);
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fclose(f);
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}
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/* Use the next number. Endianness is not important */
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(*(unsigned long*)(out+12))++;
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unsigned long long epoch;
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/* Use SOURCE_DATE_EPOCH when provided */
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char *date = getenv("SOURCE_DATE_EPOCH");
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if (date) {
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epoch = strtoll(date, NULL, 10);
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} else {
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epoch = 0ll;
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}
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out[0] = (epoch & 0xFF000000) >> 24;
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out[1] = (epoch & 0x00FF0000) >> 16;
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out[2] = (epoch & 0x0000FF00) >> 8;
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out[3] = (epoch & 0x000000FF);
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/* Write the sequence number */
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f = fopen(SEQUENCE_FILENAME, "wb");
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if (f) {
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fwrite(out+12, 4, 1, f);
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fclose(f);
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}
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}
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END_OF_SOURCE
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/usr/bin/cc -shared -fPIC unrandomize_uuid_generate_random.c -Wall --pedantic -o /usr/lib/unrandomize_uuid_generate_random.so
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rm -f unrandomize_uuid_generate_random.c
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