84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
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/* b64xz.c - Base64-XZ Extractor
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*
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* This program expects data from stdin. The data should be compressed with xz and
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* then encoded into base64 format. What b64xz does is basically the reverse of the
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* mentioned process: decode base64 to uint8_ts, 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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* I intentionally removed stdio. This will result in a smaller binary size because
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* all I/O are handled by system calls (read/write) instead of libc wrappers
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*/
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#include <unistd.h>
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#include <lzma.h>
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#define BUFSIZE 8192
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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(lzma_stream *strm, void *buf, size_t size) {
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lzma_ret ret = 0;
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uint8_t out[BUFSIZE];
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strm->next_in = buf;
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strm->avail_in = size;
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do {
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strm->next_out = out;
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strm->avail_out = sizeof(out);
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ret = lzma_code(strm, LZMA_RUN);
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write(STDOUT_FILENO, out, sizeof(out) - strm->avail_out);
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} while (strm->avail_out == 0 && ret == LZMA_OK);
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if (ret != LZMA_OK && ret != LZMA_STREAM_END)
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write(STDERR_FILENO, "LZMA error!\n", 13);
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return ret;
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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[BUFSIZE];
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int len = 0, pos = 0;
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char c;
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// Setup lzma stream
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lzma_stream strm = LZMA_STREAM_INIT;
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if (lzma_auto_decoder(&strm, UINT64_MAX, 0) != LZMA_OK) {
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write(STDERR_FILENO, "Unable to init lzma stream\n", 28);
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return 1;
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}
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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) - 3) {
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// Buffer is full, unxz
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if (unxz(&strm, 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) {
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if (unxz(&strm, buf, pos))
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return 1;
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}
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lzma_end(&strm);
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return 0;
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}
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