#include "libbb.h" /* uncompress for busybox -- (c) 2002 Robert Griebl * * based on the original compress42.c source * (see disclaimer below) */ /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992. * * Authors: * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas) * Jim McKie (decvax!mcvax!jim) * Steve Davies (decvax!vax135!petsd!peora!srd) * Ken Turkowski (decvax!decwrl!turtlevax!ken) * James A. Woods (decvax!ihnp4!ames!jaw) * Joe Orost (decvax!vax135!petsd!joe) * Dave Mack (csu@alembic.acs.com) * Peter Jannesen, Network Communication Systems * (peter@ncs.nl) * * marc@suse.de : a small security fix for a buffer overflow * * [... History snipped ...] * */ #include <stdio.h> #include <string.h> #include <unistd.h> /* Default input buffer size */ #define IBUFSIZ 2048 /* Default output buffer size */ #define OBUFSIZ 2048 /* Defines for third byte of header */ #define MAGIC_1 (char_type)'\037' /* First byte of compressed file */ #define MAGIC_2 (char_type)'\235' /* Second byte of compressed file */ #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */ /* Masks 0x20 and 0x40 are free. */ /* I think 0x20 should mean that there is */ /* a fourth header byte (for expansion). */ #define BLOCK_MODE 0x80 /* Block compresssion if table is full and */ /* compression rate is dropping flush tables */ /* the next two codes should not be changed lightly, as they must not */ /* lie within the contiguous general code space. */ #define FIRST 257 /* first free entry */ #define CLEAR 256 /* table clear output code */ #define INIT_BITS 9 /* initial number of bits/code */ /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */ #define FAST #define HBITS 17 /* 50% occupancy */ #define HSIZE (1<<HBITS) #define HMASK (HSIZE-1) #define HPRIME 9941 #define BITS 16 #undef MAXSEG_64K #define MAXCODE(n) (1L << (n)) /* Block compress mode -C compatible with 2.0 */ static int block_mode = BLOCK_MODE; /* user settable max # bits/code */ static int maxbits = BITS; /* Input buffer */ static unsigned char inbuf[IBUFSIZ + 64]; /* Output buffer */ static unsigned char outbuf[OBUFSIZ + 2048]; static long int htab[HSIZE]; static unsigned short codetab[HSIZE]; #define htabof(i) htab[i] #define codetabof(i) codetab[i] #define tab_prefixof(i) codetabof(i) #define tab_suffixof(i) ((unsigned char *)(htab))[i] #define de_stack ((unsigned char *)&(htab[HSIZE-1])) #define clear_htab() memset(htab, -1, sizeof(htab)) #define clear_tab_prefixof() memset(codetab, 0, 256); /* * Decompress stdin to stdout. This routine adapts to the codes in the * file building the "string" table on-the-fly; requiring no table to * be stored in the compressed file. The tables used herein are shared * with those of the compress() routine. See the definitions above. */ int uncompress(int fd_in, int fd_out) { unsigned char *stackp; long int code; int finchar; long int oldcode; long int incode; int inbits; int posbits; int outpos; int insize; int bitmask; long int free_ent; long int maxcode; long int maxmaxcode; int n_bits; int rsize = 0; insize = 0; inbuf[0] = bb_xread_char(fd_in); maxbits = inbuf[0] & BIT_MASK; block_mode = inbuf[0] & BLOCK_MODE; maxmaxcode = MAXCODE(maxbits); if (maxbits > BITS) { bb_error_msg("compressed with %d bits, can only handle %d bits", maxbits, BITS); return -1; } maxcode = MAXCODE(n_bits = INIT_BITS) - 1; bitmask = (1 << n_bits) - 1; oldcode = -1; finchar = 0; outpos = 0; posbits = 0 << 3; free_ent = ((block_mode) ? FIRST : 256); /* As above, initialize the first 256 entries in the table. */ clear_tab_prefixof(); for (code = 255; code >= 0; --code) { tab_suffixof(code) = (unsigned char) code; } do { resetbuf:; { int i; int e; int o; e = insize - (o = (posbits >> 3)); for (i = 0; i < e; ++i) inbuf[i] = inbuf[i + o]; insize = e; posbits = 0; } if (insize < (int) sizeof(inbuf) - IBUFSIZ) { rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ); insize += rsize; } inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 : (insize << 3) - (n_bits - 1)); while (inbits > posbits) { if (free_ent > maxcode) { posbits = ((posbits - 1) + ((n_bits << 3) - (posbits - 1 + (n_bits << 3)) % (n_bits << 3))); ++n_bits; if (n_bits == maxbits) { maxcode = maxmaxcode; } else { maxcode = MAXCODE(n_bits) - 1; } bitmask = (1 << n_bits) - 1; goto resetbuf; } { unsigned char *p = &inbuf[posbits >> 3]; code = ((((long) (p[0])) | ((long) (p[1]) << 8) | ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask; } posbits += n_bits; if (oldcode == -1) { outbuf[outpos++] = (unsigned char) (finchar = (int) (oldcode = code)); continue; } if (code == CLEAR && block_mode) { clear_tab_prefixof(); free_ent = FIRST - 1; posbits = ((posbits - 1) + ((n_bits << 3) - (posbits - 1 + (n_bits << 3)) % (n_bits << 3))); maxcode = MAXCODE(n_bits = INIT_BITS) - 1; bitmask = (1 << n_bits) - 1; goto resetbuf; } incode = code; stackp = de_stack; /* Special case for KwKwK string. */ if (code >= free_ent) { if (code > free_ent) { unsigned char *p; posbits -= n_bits; p = &inbuf[posbits >> 3]; bb_error_msg ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)", insize, posbits, p[-1], p[0], p[1], p[2], p[3], (posbits & 07)); bb_error_msg("uncompress: corrupt input"); return -1; } *--stackp = (unsigned char) finchar; code = oldcode; } /* Generate output characters in reverse order */ while ((long int) code >= (long int) 256) { *--stackp = tab_suffixof(code); code = tab_prefixof(code); } *--stackp = (unsigned char) (finchar = tab_suffixof(code)); /* And put them out in forward order */ { int i; if (outpos + (i = (de_stack - stackp)) >= OBUFSIZ) { do { if (i > OBUFSIZ - outpos) { i = OBUFSIZ - outpos; } if (i > 0) { memcpy(outbuf + outpos, stackp, i); outpos += i; } if (outpos >= OBUFSIZ) { write(fd_out, outbuf, outpos); outpos = 0; } stackp += i; } while ((i = (de_stack - stackp)) > 0); } else { memcpy(outbuf + outpos, stackp, i); outpos += i; } } /* Generate the new entry. */ if ((code = free_ent) < maxmaxcode) { tab_prefixof(code) = (unsigned short) oldcode; tab_suffixof(code) = (unsigned char) finchar; free_ent = code + 1; } /* Remember previous code. */ oldcode = incode; } } while (rsize > 0); if (outpos > 0) { write(fd_out, outbuf, outpos); } return 0; }