PBXZ "extractor" from 'Mac OS X Internals - To The Apple's Core' by Jonathan Levin

pbxz.c

/*
 *  From 'Mac OS X Internals - To The Apple's Core' by Jonathan Levin
 *
 *  http://www.newosxbook.com/articles/OTA.html
 *  http://www.newosxbook.com/src.jl?tree=listings&file=pbzx.c
 *
 */

#include <stdio.h> // for printf
#include <string.h> // for strncmp
#include <fcntl.h>  // for O_RDONLY
#include <unistd.h> // everything else 
#include <stdlib.h> // malloc

typedef unsigned long long uint64_t;


int main(int argc, const char * argv[])
{

    char buffer[1024];
    int fd = 0;

    if (argc < 2) { fd  = 0 ;}
    else { fd = open (argv[1], O_RDONLY);
           if (fd < 0) { perror (argv[1]); exit(5); }
         }


    read (fd, buffer, 4);
    if (strncmp(buffer, "pbzx", 4)) { fprintf(stderr, "Can't find pbzx magic\n"); exit(0);}

    // Now, if it IS a pbzx

    uint64_t length = 0;
    uint64_t flags = 0;

    read (fd, &flags, sizeof (uint64_t));
    flags = __builtin_bswap64(flags);

    fprintf(stderr,"Flags: 0x%llx\n", flags);

    int i = 0;

    while (flags &  0x01000000) {  // have more chunks
    i++;
    read (fd, &flags, sizeof (uint64_t));
    flags = __builtin_bswap64(flags);
    read (fd, &length, sizeof (uint64_t));
    length = __builtin_bswap64(length);

    fprintf(stderr,"Chunk #%d (flags: %llx, length: %lld bytes)\n",i, flags,length);
     
    // Let's ignore the fact I'm allocating based on user input, etc..
    char *buf = malloc (length);
    read (fd, buf, length);

    // We want the XZ header/footer if it's the payload, but prepare_payload doesn't have that, 
    // so just warn.

    if (strncmp(buf, "\xfd""7zXZ\0", 6))  { fprintf (stderr, "Warning: Can't find XZ header. This is likely not XZ data\n"); }
    else // if we have the header, there had better be a footer, too
    if (strncmp(buf + length -2, "YZ", 2)) { fprintf (stderr, "Warning: Can't find XZ footer. This is probably bad.\n"); }

    write (1, buf, length);

    }

    return 0;
}