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490 lines
13 KiB
490 lines
13 KiB
/*
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* Copyright (C) 2004 aCaB <acab@clamav.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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** petitep.c
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**
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** 09/07/2k4 - Dumped and reversed
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** 10/07/2k4 - Very 1st approach
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** 10/07/2k4 - PE stuff and main loop
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** 11/07/2k4 - Porting finished, tracking my bugs...
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** 12/07/2k4 - ARRRRRGHHH :D
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** 14/07/2k4 - Code cleaned
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** 15/07/2k4 - Securing && ClamAV porting
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** 21/07/2k4 - Unmangled imports now supported
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** 22/07/2k4 - Unstripped .relocs now supported
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**
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*/
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/*
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** Unpacks a buffer containing a petite 2.2 compressed
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** file. Doesn't perform Import Table unmangling. Doesn't
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** fixup call/jumps. Tries to "guess" the original sections
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** structure and entrypoint.
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**
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** Lotta phanx to Micky for patiently bearing my screams :P
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** Greets to Ian Luck: the SEH MOVSB thingy almost got me :O
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** TODO: Cope with level 0 and older petite versions.
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*/
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#if HAVE_CONFIG_H
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#include "clamav-config.h"
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <string.h>
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#include "cltypes.h"
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#include "pe.h"
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#include "rebuildpe.h"
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#include "others.h"
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#if WORDS_BIGENDIAN == 0
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#define EC32(v) (v)
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#else
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static inline uint32_t EC32(uint32_t v)
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{
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return ((v >> 24) | ((v & 0x00FF0000) >> 8) | ((v & 0x0000FF00) << 8) | (v << 24));
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}
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#endif
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static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, int buffersize)
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{
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unsigned char mydl = *mydlptr;
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unsigned char olddl = mydl;
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mydl*=2;
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if ( !(olddl & 0x7f)) {
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if ( *scur < buffer || *scur >= buffer+buffersize-1 )
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return -1;
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olddl = **scur;
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mydl = olddl*2+1;
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*scur=*scur + 1;
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}
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*mydlptr = mydl;
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return (olddl>>7)&1;
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}
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int petite_inflate2x_1to9(char *buf, uint32_t minrva, int bufsz, struct pe_image_section_hdr *sections, int sectcount, uint32_t Imagebase, uint32_t pep, int desc, int version, uint32_t ResRva, uint32_t ResSize)
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{
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char *adjbuf = buf - minrva;
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char *packed = NULL;
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uint32_t thisrva=0, bottom = 0, enc_ep=0, irva=0, workdone=0, grown=0x355, skew=0x35;
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int j = 0, oob, mangled = 0, check4resources=0;
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struct SECTION *usects = NULL;
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void *tmpsct = NULL;
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/*
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-] The real thing [-
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*/
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/* NOTE: (435063->4350a5) Petite kernel32!imports and error strings */
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/* Here we adjust the start of packed blob, the size of petite code,
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* the difference in size if relocs were stripped
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* See below...
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*/
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if ( version == 2 )
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packed = adjbuf + EC32(sections[sectcount-1].VirtualAddress) + 0x1b8;
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if ( version == 1 ) {
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packed = adjbuf + EC32(sections[sectcount-1].VirtualAddress) + 0x178;
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grown=0x323; /* My name is Harry potter */
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skew=0x34;
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}
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while (1) {
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char *ssrc, *ddst;
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uint32_t size, srva;
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int backbytes, oldback, backsize, addsize;
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if ( packed < buf || packed >= buf+bufsz-4) {
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if (usects)
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free(usects);
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return -1;
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}
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srva = cli_readint32(packed);
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if (! srva) {
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/* WERE DONE !!! :D */
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int t, upd = 1;
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if ( j <= 0 ) /* Some non petite compressed files will get here */
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return -1;
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/* Select * from sections order by rva asc; */
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while ( upd ) {
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upd = 0;
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for (t = 0; t < j-1 ; t++) {
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uint32_t trva, trsz, tvsz;
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if ( usects[t].rva <= usects[t+1].rva )
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continue;
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trva = usects[t].rva;
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trsz = usects[t].rsz;
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tvsz = usects[t].vsz;
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usects[t].rva = usects[t+1].rva;
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usects[t].rsz = usects[t+1].rsz;
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usects[t].vsz = usects[t+1].vsz;
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usects[t+1].rva = trva;
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usects[t+1].rsz = trsz;
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usects[t+1].vsz = tvsz;
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upd = 1;
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}
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}
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/* Computes virtualsize... we try to guess, actually :O */
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for (t = 0; t < j-1 ; t++) {
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if ( usects[t].vsz != usects[t+1].rva - usects[t].rva )
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usects[t].vsz = usects[t+1].rva - usects[t].rva;
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}
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/*
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* Our encryption is pathetic and out software is lame but
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* we need to claim it's unbreakable.
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* So why dont we just mangle the imports and encrypt the EP?!
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*/
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/* Decrypts old entrypoint if we got enough clues */
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if (enc_ep) {
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uint32_t virtaddr = pep + 5 + Imagebase, tmpep;
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int rndm = 0, dummy = 1;
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uint32_t *thunk = (uint32_t*)(adjbuf+irva);
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uint32_t *imports;
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if ( version == 2 ) { /* 2.2 onley */
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while ( (char *)thunk >=buf && (char *)thunk<buf+bufsz-4 && dummy ) {
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uint32_t api;
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if (! *thunk ) {
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workdone = 1;
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break;
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}
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imports = (uint32_t *) (adjbuf + EC32(*thunk++));
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dummy = 0;
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while ( (char *)imports >=buf && (char *)imports<buf+bufsz-4 ) {
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dummy = 0;
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if ( ! (api = EC32(*imports++)) ) {
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dummy = 1;
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break;
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}
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if ( (api != (api | 0x80000000)) && mangled && --rndm < 0) {
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api = virtaddr;
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virtaddr +=5; /* EB + 1 double */
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rndm = virtaddr & 7;
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} else {
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api = 0xbff01337; /* KERNEL32!leet */
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}
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if (EC32(sections[sectcount-1].VirtualAddress)+Imagebase < api )
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enc_ep--;
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if ( api < virtaddr )
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enc_ep--;
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tmpep = (enc_ep & 0xfffffff8)>>3 & 0x1fffffff;
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enc_ep = (enc_ep & 7)<<29 | tmpep;
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}
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}
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} else
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workdone = 1;
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enc_ep = pep+5+enc_ep;
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if ( workdone == 1 )
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cli_dbgmsg("Petite: Old EP: %x\n", enc_ep);
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else
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cli_dbgmsg("Petite: In troubles while attempting to decrypt old EP\n");
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}
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/* Let's compact data */
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for (t = 0; t < j ; t++) {
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usects[t].raw = (usects[t-1].raw + usects[t-1].rsz)*(t>0);
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if (usects[t].rsz != 0)
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memmove(buf + usects[t].raw, adjbuf + usects[t].rva, usects[t].rsz);
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}
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/* Showtime!!! */
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cli_dbgmsg("Petite: Sections dump:\n");
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for (t = 0; t < j ; t++)
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cli_dbgmsg("Petite: .SECT%d RVA:%x VSize:%x ROffset: %x, RSize:% x\n", t, usects[t].rva, usects[t].vsz, usects[t].raw, usects[t].rsz);
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if ( (ssrc = rebuildpe(buf, usects, j, Imagebase, enc_ep, ResRva, ResSize)) ) {
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write(desc, ssrc, 0x148+0x80+0x28*j+usects[j-1].raw+usects[j-1].rsz);
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free(ssrc);
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} else
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cli_dbgmsg("Petite: Rebuilding failed\n");
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free(usects);
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return workdone;
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}
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size = srva & 0x7fffffff;
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if ( srva != size ) { /* Test and clear bit 31 */
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check4resources=0;
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/*
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Enumerates each petite data section
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I should get here once ot twice:
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- 1 time for the resource section (if present)
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- 1 time for the all_the_rest section
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*/
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if ( packed < buf || packed >= buf+bufsz-12) {
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if (usects)
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free(usects);
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return -1;
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}
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/* Save the end of current packed section for later use */
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bottom = cli_readint32(packed+8) + 4;
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ssrc = adjbuf + cli_readint32(packed+4) - (size-1)*4;
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ddst = adjbuf + cli_readint32(packed+8) - (size-1)*4;
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if ( ssrc < buf || ssrc + size*4 >= buf + bufsz || ddst < buf || ddst + size*4 >= buf + bufsz ) {
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if (usects)
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free(usects);
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return -1;
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}
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/* Copy packed data to the end of the current packed section */
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memmove(ddst, ssrc, size*4);
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packed += 0x0c;
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} else {
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uint32_t check1, check2;
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uint8_t mydl = 0;
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uint8_t goback;
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/* Unpak each original section in turn */
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if ( packed < buf || packed >= buf+bufsz-16) {
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if (usects)
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free(usects);
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return -1;
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}
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size = cli_readint32(packed+4); /* How many bytes to unpack */
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packed += 0x10;
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thisrva=cli_readint32(packed-8); /* RVA of the original section */
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/* Alloc 1 more struct */
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if ( ! (tmpsct = realloc(usects, sizeof(struct SECTION) * (j+1))) ) {
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if (usects)
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free(usects);
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return -1;
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}
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usects = (struct SECTION *) tmpsct;
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/* Save section spex for later rebuilding */
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usects[j].rva = thisrva;
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usects[j].rsz = size;
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if ( (int)(bottom - thisrva) >0 )
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usects[j].vsz = bottom - thisrva;
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else
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usects[j].vsz = size;
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usects[j].raw = 0; /* Cheaper than memset */
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if (!size) { /* That's a ghost section! reloc any1? :P */
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j++;
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continue;
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}
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ssrc = adjbuf + srva;
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ddst = adjbuf + thisrva;
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/* Last petite section (unpacked 1st) could contain unpacked data
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* (eg the icon): let's fix the rva
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*/
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if (!check4resources) {
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int q;
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for ( q = 0 ; q < sectcount ; q++ ) {
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if ( thisrva <= EC32(sections[q].VirtualAddress) || thisrva >= EC32(sections[q].VirtualAddress) + EC32(sections[q].VirtualSize))
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continue;
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usects[j].rva = EC32(sections[q].VirtualAddress);
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usects[j].rsz = thisrva - EC32(sections[q].VirtualAddress) + size;
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break;
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}
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}
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/* Increase count of unpacked sections */
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j++;
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/* Setup some crap for later checks */
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if ( size < 0x10000 ) {
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check1 = 0x0FFFFC060;
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check2 = 0x0FFFFFC60;
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goback = 5;
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} else if ( size < 0x40000 ) {
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check1 = 0x0FFFF8180;
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check2 = 0x0FFFFF980;
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goback = 7;
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} else {
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check1 = 0x0FFFF8300;
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check2 = 0x0FFFFFB00;
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goback = 8;
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}
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/*
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* NOTE: on last loop we get esi=edi=ImageBase (which is not writeable)
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* The movsb on the next line causes the iat_rebuild_and_decrypt_oldEP()
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* func to get called instead... ehehe very smart ;)
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*/
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if ( ddst < buf || ddst >= buf+bufsz-1 || ssrc < buf || ssrc >= buf+bufsz-1 ) {
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free(usects);
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return -1;
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}
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size--;
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*ddst++=*ssrc++; /* eheh u C gurus gotta luv these monsters :P */
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backbytes=0;
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oldback = 0;
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/* No surprises here... NRV any1??? ;) */
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while (size > 0) {
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oob = doubledl(&ssrc, &mydl, buf, bufsz);
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if ( oob == -1 ) {
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free(usects);
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return -1;
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}
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if (!oob) {
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if ( ddst < buf || ddst >= buf+bufsz-1 || ssrc < buf || ssrc >= buf+bufsz-1 ) {
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free(usects);
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return -1;
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}
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*ddst++ = (char)((*ssrc++)^(size & 0xff));
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size--;
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} else {
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addsize = 0;
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backbytes++;
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while (1) {
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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backbytes = backbytes*2 + oob;
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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if (!oob)
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break;
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}
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backbytes -= 3;
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if ( backbytes >= 0 ) {
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backsize = goback;
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do {
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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backbytes = backbytes*2 + oob;
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backsize--;
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} while (backsize);
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backbytes^=0xffffffff;
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addsize += 1 + ( backbytes < check2 ) + ( backbytes < check1 );
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oldback = backbytes;
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} else {
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backsize = backbytes+1;
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backbytes = oldback;
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}
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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backsize = backsize*2 + oob;
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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backsize = backsize*2 + oob;
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if (!backsize) {
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backsize++;
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while (1) {
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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backsize = backsize*2 + oob;
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if ( (oob = doubledl(&ssrc, &mydl, buf, bufsz)) == -1 ) {
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free(usects);
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return -1;
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}
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if (!oob)
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break;
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}
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backsize+=2;
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}
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backsize+=addsize;
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size-=backsize;
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if ( ddst<buf || ddst+backsize>=buf+bufsz || ddst+backbytes<buf || ddst+backbytes+backsize>=buf+bufsz ) {
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free(usects);
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return -1;
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}
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while(backsize--) {
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*ddst=*(ddst+backbytes);
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ddst++;
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}
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backbytes=0;
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backsize=0;
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} /* else */
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} /* while(ebx) */
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/* Any lame petite code here? If so let's strip it
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* We've done version adjustments already, see above
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*/
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if ( j &&
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( /* LONG MAGIC = 33C05E64 8B188B1B 8D63D65D */
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( (usects[j-1].rsz > grown ) &&
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cli_readint32(ddst-grown+5+0x4f) == 0x645ec033 &&
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cli_readint32(ddst-grown+5+0x4f+4) == 0x1b8b188b )
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||
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/* This crap is ugly! Gotta make it all pretty one day or another */
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( (usects[j-1].rsz > grown+skew ) &&
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cli_readint32(ddst-grown+5+0x4f-skew) == 0x645ec033 &&
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cli_readint32(ddst-grown+5+0x4f+4-skew) == 0x1b8b188b )
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)
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)
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{
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uint32_t test1, test2;
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/* If the original exe had a .reloc were skewed */
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int reloc = skew*(cli_readint32(ddst-grown+5+0x4f-skew) == 0x645ec033);
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/* REMINDER: DON'T BPX IN HERE U DUMBASS!!!!!!!!!!!!!!!!!!!!!!!! */
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test1 = cli_readint32(ddst-grown+0x0f-8-reloc)^0x9d6661aa;
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test2 = cli_readint32(ddst-grown+0x0f-4-reloc)^0xe908c483;
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cli_dbgmsg("Petite: Found petite code in sect%d(%x). Let's strip it.\n", j-1, usects[j-1].rva);
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if (test1 == test2) {
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irva = cli_readint32(ddst-grown+0x121-reloc);
|
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enc_ep = cli_readint32(ddst-grown+0x0f-reloc)^test1;
|
|
mangled = (cli_readint32(ddst-grown+0x1c0-reloc) != 0x90909090); /* FIXME: Magic's too short??? */
|
|
cli_dbgmsg("Petite: Encrypted EP: %x | Array of imports: %x\n",enc_ep, irva);
|
|
}
|
|
usects[j-1].rsz -= grown+reloc;
|
|
|
|
}
|
|
check4resources++;
|
|
} /* outer else */
|
|
} /* while true */
|
|
}
|
|
|