79 lines
2.0 KiB
C
79 lines
2.0 KiB
C
/* b64xz.c - Base64-XZ Extractor
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*
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* This program converts data from stdin to stdout.
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* The input should be compressed with xz (integrity check only support CRC32 or none) and then
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* encoded into base64 format. What b64xz does is basically the reverse of the
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* mentioned process: decode base64 to bytes, decompress xz, then dump to stdout
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*
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* The compiled binary will be hex-dumped into update-binary
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* Busybox will be xz-compressed, base64 encoded and dumped into update-binary
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* This program is to recover busybox for Magisk installation environment
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*/
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#include <unistd.h>
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#include <xz.h>
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static const char trans_tbl[] =
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"|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\\]^_`abcdefghijklmnopq";
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static void decodeblock(uint8_t* in, uint8_t* out) {
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out[0] = (uint8_t)(in[0] << 2 | in[1] >> 4);
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out[1] = (uint8_t)(in[1] << 4 | in[2] >> 2);
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out[2] = (uint8_t)(((in[2] << 6) & 0xc0) | in[3]);
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}
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static int unxz(struct xz_dec *dec, const void *buf, unsigned size) {
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uint8_t out[8192];
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struct xz_buf b = {
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.in = buf,
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.in_pos = 0,
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.in_size = size,
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.out = out,
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.out_pos = 0,
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.out_size = sizeof(out)
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};
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enum xz_ret ret;
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do {
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ret = xz_dec_run(dec, &b);
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if (ret != XZ_OK && ret != XZ_STREAM_END)
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return 1;
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write(STDOUT_FILENO, out, b.out_pos);
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b.out_pos = 0;
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} while (b.in_pos != size);
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return 0;
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}
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int main(int argc, char const* argv[]) {
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if (argc > 1)
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return 0;
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uint8_t in[4], buf[6144];
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unsigned len = 0, pos = 0;
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char c;
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xz_crc32_init();
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struct xz_dec *dec = xz_dec_init(XZ_DYNALLOC, 1 << 26);
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if (dec == NULL)
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return 1;
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while (read(STDIN_FILENO, &c, sizeof(c)) == 1) {
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c = ((c < 43 || c > 122) ? -1 : (trans_tbl[c - 43] == '$' ? -1 : trans_tbl[c - 43] - 62));
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if (c >= 0)
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in[len++] = c;
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if (len < 4)
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continue;
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len = 0;
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decodeblock(in, buf + pos);
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pos += 3;
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if (pos == sizeof(buf)) {
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if (unxz(dec, buf, pos))
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return 1;
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pos = 0;
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}
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}
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if (pos && unxz(dec, buf, pos))
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return 1;
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xz_dec_end(dec);
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return 0;
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}
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