mirror of https://github.com/dirtbags/moth.git
98 lines
1.8 KiB
C
98 lines
1.8 KiB
C
#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <values.h>
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#ifndef CTF_BASE
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#define CTF_BASE "/var/lib/ctf"
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#endif
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struct arc4_ctx {
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uint8_t S[256];
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uint8_t i;
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uint8_t j;
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};
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#define swap(a, b) do {int _swap=a; a=b, b=_swap;} while (0)
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void
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arc4_init(struct arc4_ctx *ctx, uint8_t const *key, size_t keylen)
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{
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int i;
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int j = 0;
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for (i = 0; i < 256; i += 1) {
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ctx->S[i] = i;
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}
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for (i = 0; i < 256; i += 1) {
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j = (j + ctx->S[i] + key[i % keylen]) % 256;
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swap(ctx->S[i], ctx->S[j]);
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}
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ctx->i = 0;
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ctx->j = 0;
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}
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void
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arc4_crypt(struct arc4_ctx *ctx,
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uint8_t *obuf, uint8_t const *ibuf, size_t buflen)
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{
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int i = ctx->i;
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int j = ctx->j;
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size_t k;
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for (k = 0; k < buflen; k += 1) {
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uint8_t mask;
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i = (i + 1) % 256;
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j = (j + ctx->S[i]) % 256;
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swap(ctx->S[i], ctx->S[j]);
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mask = ctx->S[(ctx->S[i] + ctx->S[j]) % 256];
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obuf[k] = ibuf[k] ^ mask;
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}
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ctx->i = i;
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ctx->j = j;
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}
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void
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arc4_crypt_buffer(uint8_t const *key, size_t keylen,
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uint8_t *buf, size_t buflen)
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{
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struct arc4_ctx ctx;
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arc4_init(&ctx, key, keylen);
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arc4_crypt(&ctx, buf, buf, buflen);
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}
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ssize_t
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read_token(char *name,
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uint8_t const *key, size_t keylen,
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char *buf, size_t buflen)
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{
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char path[PATH_MAX];
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int pathlen;
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int fd;
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ssize_t ret;
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pathlen = snprintf(path, sizeof(path) - 1,
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CTF_BASE "/tokens/%s", name);
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path[pathlen] = '\0';
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fd = open(path, O_RDONLY);
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if (-1 == fd) return -1;
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ret = read(fd, buf, buflen);
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close(fd);
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if (-1 != ret) {
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arc4_crypt_buffer(key, keylen, (uint8_t *)buf, (size_t)ret);
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}
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return ret;
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}
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