libclamav: include FSG unpacker from aCaB

git-svn: trunk@725

clamav-devel/ChangeLog

@@ -1,3 +1,7 @@
+Thu Aug  5 03:10:32 CEST 2004 (tk)
+----------------------------------
+  * libclamav: include FSG unpacker from aCaB
+
 Wed Aug  4 22:03:56 CEST 2004 (tk)
 ----------------------------------
   * libclamav: pe: improve detection of broken executable files

clamav-devel/libclamav/Makefile.am

@@ -110,6 +110,8 @@ libclamav_la_SOURCES = \
 	rebuildpe.c \
 	rebuildpe.h \
 	petite.c \
-	petite.h
+	petite.h \
+	fsg.c \
+	fsg.h
 
 lib_LTLIBRARIES = libclamav.la

clamav-devel/libclamav/Makefile.in

@@ -79,7 +79,7 @@ am_libclamav_la_OBJECTS = matcher-ac.lo matcher-bm.lo matcher.lo \
 	blob.lo mbox.lo message.lo snprintf.lo strrcpy.lo table.lo \
 	text.lo ole2_extract.lo vba_extract.lo msexpand.lo pe.lo \
 	cabd.lo lzxd.lo mszipd.lo qtmd.lo system.lo upx.lo htmlnorm.lo \
-	chmunpack.lo rebuildpe.lo petite.lo
+	chmunpack.lo rebuildpe.lo petite.lo fsg.lo
 libclamav_la_OBJECTS = $(am_libclamav_la_OBJECTS)
 DEFAULT_INCLUDES = -I. -I$(srcdir) -I$(top_builddir)
 depcomp = $(SHELL) $(top_srcdir)/depcomp
@@ -87,8 +87,8 @@ am__depfiles_maybe = depfiles
 @AMDEP_TRUE@DEP_FILES = ./$(DEPDIR)/blob.Plo ./$(DEPDIR)/cabd.Plo \
 @AMDEP_TRUE@	./$(DEPDIR)/chmunpack.Plo ./$(DEPDIR)/cvd.Plo \
 @AMDEP_TRUE@	./$(DEPDIR)/dsig.Plo ./$(DEPDIR)/filetypes.Plo \
-@AMDEP_TRUE@	./$(DEPDIR)/htmlnorm.Plo ./$(DEPDIR)/lzxd.Plo \
+@AMDEP_TRUE@	./$(DEPDIR)/fsg.Plo ./$(DEPDIR)/htmlnorm.Plo \
-@AMDEP_TRUE@	./$(DEPDIR)/matcher-ac.Plo \
+@AMDEP_TRUE@	./$(DEPDIR)/lzxd.Plo ./$(DEPDIR)/matcher-ac.Plo \
 @AMDEP_TRUE@	./$(DEPDIR)/matcher-bm.Plo ./$(DEPDIR)/matcher.Plo \
 @AMDEP_TRUE@	./$(DEPDIR)/mbox.Plo ./$(DEPDIR)/md5.Plo \
 @AMDEP_TRUE@	./$(DEPDIR)/message.Plo ./$(DEPDIR)/msexpand.Plo \
@@ -319,7 +319,9 @@ libclamav_la_SOURCES = \
 	rebuildpe.c \
 	rebuildpe.h \
 	petite.c \
-	petite.h
+	petite.h \
+	fsg.c \
+	fsg.h
 
 lib_LTLIBRARIES = libclamav.la
 all: all-am
@@ -397,6 +399,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/cvd.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/dsig.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/filetypes.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/fsg.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/htmlnorm.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/lzxd.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/matcher-ac.Plo@am__quote@

clamav-devel/libclamav/fsg.c

@@ -0,0 +1,190 @@
+/*
+ *  Copyright (C) 2004 aCaB <acab@clamav.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/*
+** defsg.c
+** 
+** 02/08/2k4 - Dumped and reversed
+** 02/08/2k4 - Done coding
+** 03/08/2k4 - Cleaning and securing
+** 04/08/2k4 - Done porting
+*/
+
+/*
+** Unpacks an FSG compressed section.
+**
+** Czesc bart, good asm, nice piece of code ;)
+*/
+
+#if HAVE_CONFIG_H
+#include "clamav-config.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "cltypes.h"
+#include "pe.h"
+#include "rebuildpe.h"
+#include "others.h"
+
+
+static int doubledl(char **scur, uint8_t *mydlptr, char *buffer, int buffersize)
+{
+  unsigned char mydl = *mydlptr;
+  unsigned char olddl = mydl;
+
+  mydl*=2;
+  if ( !(olddl & 0x7f)) {
+    if ( *scur < buffer || *scur >= buffer+buffersize-1 )
+      return -1;
+    olddl = **scur;
+    mydl = olddl*2+1;
+    *scur=*scur + 1;
+  }
+  *mydlptr = mydl;
+  return (olddl>>7)&1;
+}
+
+int unfsg(char *source, char *dest, int ssize, int dsize) {
+  uint8_t mydl=0x80;
+  uint32_t backbytes, backsize, oldback;
+  char *csrc = source, *cdst = dest;
+  int oob, lostbit = 1;
+
+  /* I assume buffers size is >0 - No checking! */
+  *cdst++=*csrc++;
+
+  while ( 1 ) {
+    if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
+      if (oob == -1)
+	return -1;
+      /* 164 */
+      backsize = 0;
+      if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
+	if (oob == -1)
+	  return -1;
+	/* 16a */
+	backbytes = 0;
+	if ((oob=doubledl(&csrc, &mydl, source, ssize))) {
+	  if (oob == -1)
+	    return -1;
+	  /* 170 */
+	  lostbit = 1;
+	  backsize++;
+	  backbytes = 0x10;
+	  while ( backbytes < 0x100 ) {
+	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	      return -1;
+	    backbytes = backbytes*2+oob;
+	  }
+	  backbytes &= 0xff;
+	  if ( ! backbytes ) {
+	    if (cdst >= dest+dsize)
+	      return -1;
+	    *cdst++=0x00;
+	    continue;
+	  } else {
+	    /* repne movsb - FIXME dont remove for now */
+	  }
+	} else {
+	  /* 18f */
+	  if (csrc >= source+ssize)
+	    return -1;
+	  backbytes = *(unsigned char*)csrc;
+	  backsize = backsize * 2 + (backbytes & 1);
+	  backbytes = (backbytes & 0xff)>>1;
+	  csrc++;
+	  if (! backbytes)
+	    break;
+	  backsize+=2;
+	  oldback = backbytes;
+	  lostbit = 0;
+	}
+      } else {
+	/* 180 */
+	backsize = 1;
+	do {
+	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	    return -1;
+	  backsize = backsize*2+oob;
+	  if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	    return -1;
+	} while (oob);
+
+	backsize = backsize - 1 - lostbit;
+	if (! backsize) {
+	  /* 18a */
+	  backsize = 1;
+	  do {
+	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	      return -1;
+	    backsize = backsize*2+oob;
+	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	      return -1;
+	  } while (oob);
+
+	  backbytes = oldback;
+	} else {
+	  /* 198 */
+	  if (csrc >= source+ssize)
+	    return -1;
+	  backbytes = *(unsigned char*)csrc;
+	  backbytes += (backsize-1)<<8;
+	  backsize = 1;
+	  csrc++;
+	  do {
+	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	      return -1;
+	    backsize = backsize*2+oob;
+	    if ((oob=doubledl(&csrc, &mydl, source, ssize)) == -1)
+	      return -1;
+	  } while (oob);
+
+          if (backbytes >= 0x7d00)
+            backsize++;
+          if (backbytes >= 0x500)
+            backsize++;
+          if (backbytes <= 0x7f)
+            backsize += 2;
+
+	  oldback = backbytes;
+	}
+	lostbit = 0;
+      }
+      if (cdst-backbytes < dest || cdst+backsize >= dest+dsize)
+	return -1;
+      while(backsize--) {
+	*cdst=*(cdst-backbytes);
+	cdst++;
+      }
+
+    } else {
+      /* 15d */
+      if (cdst < dest || cdst >= dest+dsize || csrc < source || csrc >= source+ssize)
+	return -1;
+      *cdst++=*csrc++;
+      lostbit=1;
+    }
+  }
+  return 0;
+}

clamav-devel/libclamav/fsg.h

@@ -0,0 +1,28 @@
+/*
+ *  Copyright (C) 2004 aCaB <acab@clamav.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __FSG_H
+#define __FSG_H
+
+#include "cltypes.h"
+#include "pe.h"
+
+int unfsg(char *, char *, int, int);
+
+#endif
+

clamav-devel/libclamav/pe.c

@@ -35,6 +35,7 @@
 #include "pe.h"
 #include "upx.h"
 #include "petite.h"
+#include "fsg.h"
 #include "scanners.h"
 
 #define IMAGE_DOS_SIGNATURE	    0x5a4d	    /* MZ */
@@ -168,7 +169,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 	struct pe_image_section_hdr *section_hdr;
 	struct stat sb;
 	char sname[9], buff[256], *tempfile;
-	int i, found, upx_success = 0, broken = 0, min = 0, max = 0;
+	int i, found, upx_success = 0, min = 0, max = 0;
 	int (*upxfn)(char *, int , char *, int) = NULL;
 	char *src, *dest;
 	int ssize, dsize, ndesc;
@@ -385,7 +386,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 
     }
 
-    if((ep = cli_rawaddr(EC32(optional_hdr.AddressOfEntryPoint), section_hdr, nsections)) == -1) {
+    if((ep = EC32(optional_hdr.AddressOfEntryPoint)) >= min && (ep = cli_rawaddr(EC32(optional_hdr.AddressOfEntryPoint), section_hdr, nsections)) == -1) {
 	cli_dbgmsg("Possibly broken PE file\n");
 	free(section_hdr);
 	if(DETECT_BROKEN) {
@@ -398,19 +399,140 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 
     cli_dbgmsg("EntryPoint offset: 0x%x (%d)\n", ep, ep);
 
-    /* UPX support */
+    /* UPX & FSG support */
 
     /* try to find the first section with physical size == 0 */
     found = 0;
     for(i = 0; i < nsections - 1; i++) {
-	if(!section_hdr[i].SizeOfRawData && section_hdr[i].VirtualSize && section_hdr[i+1].SizeOfRawData && section_hdr[i+1].VirtualSize) {
+	if(!section_hdr[i].SizeOfRawData && section_hdr[i].VirtualSize && section_hdr[i + 1].SizeOfRawData && section_hdr[i + 1].VirtualSize) {
 	    found = 1;
-	    cli_dbgmsg("UPX: empty section found - assuming UPX compression\n");
+	    cli_dbgmsg("UPX/FSG: empty section found - assuming compression\n");
+	    break;
+	}
+    }
+
+    if(found) {
+
+	/* Check EP for UPX vs. FSG */
+	if(lseek(desc, ep, SEEK_SET) == -1) {
+	    cli_dbgmsg("UPX/FSG: lseek() failed\n");
+	    free(section_hdr);
+	    return CL_EIO;
+	}
+
+	if(read(desc, buff, 126) != 126) { /* i.e. 0x69 + 13 + 8 */
+	    cli_dbgmsg("UPX/FSG: Can't read 126 bytes at 0x%x (%d)\n", ep, ep);
+            free(section_hdr);
+	    return CL_EIO;
+	}
+
+	if(buff[0]=='\x87' || buff [1]=='\x25') {
+
+	    /* FSG support - thanks to aCaB ! */
+
+	    ssize = EC32(section_hdr[i + 1].SizeOfRawData);
+	    dsize = EC32(section_hdr[i].VirtualSize);
+
+	    while(found) {
+		    uint32_t newesi, newedi, newebx, newedx;
+
+		if(limits && limits->maxfilesize && (ssize > limits->maxfilesize || dsize > limits->maxfilesize)) {
+		    cli_dbgmsg("FSG: Sizes exceeded (ssize: %d, dsize: %d, max: %lu)\n", ssize, dsize , limits->maxfilesize);
+		    free(section_hdr);
+		    return CL_CLEAN;
+		}
+
+		if(ssize <= 0x19 || dsize <= ssize) {
+		    cli_dbgmsg("FSG: Size mismatch (ssize: %d, dsize: %d)\n", ssize, dsize);
+		    free(section_hdr);
+		    return CL_CLEAN;
+		}
+
+		if((newedx = cli_readint32(buff + 2) - EC32(optional_hdr.ImageBase)) < EC32(section_hdr[i + 1].VirtualAddress) || newedx >= EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData) - 4) {
+		    cli_dbgmsg("FSG: xchg out of bounds (%x), giving up\n", newedx);
+		    break;
+		}
+
+		if((src = (char *) cli_malloc(ssize)) == NULL) {
+		    free(section_hdr);
+		    return CL_EMEM;
+		}
+
+		lseek(desc, EC32(section_hdr[i + 1].PointerToRawData), SEEK_SET);
+		if(read(desc, src, ssize) != ssize) {
+		    cli_dbgmsg("Can't read raw data of section %d\n", i);
+		    free(section_hdr);
+		    free(src);
+		    return CL_EIO;
+		}
+
+		if((dest = src + newedx - EC32(section_hdr[i + 1].VirtualAddress)) < src || dest >= src + EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData) - 4) {
+		    cli_dbgmsg("FSG: New ESP out of bounds\n");
+		    free(src);
 		    break;
 		}
+
+		if((newedx = cli_readint32(dest) - EC32(optional_hdr.ImageBase)) <= EC32(section_hdr[i + 1].VirtualAddress) || newedx >= EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData) - 4) {
+		    cli_dbgmsg("FSG: New ESP (%x) is wrong\n", newedx);
+		    free(src);
+		    break;
+		}
+ 
+		if((dest = src + newedx - EC32(section_hdr[i + 1].VirtualAddress)) < src || dest >= src + EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData) - 32) {
+		    cli_dbgmsg("FSG: New stack out of bounds\n");
+		    free(src);
+		    break;
+		}
+
+		newedi = cli_readint32(dest) - EC32(optional_hdr.ImageBase);
+		newesi = cli_readint32(dest + 4) - EC32(optional_hdr.ImageBase);
+		newebx = cli_readint32(dest + 16) - EC32(optional_hdr.ImageBase);
+		newedx = cli_readint32(dest + 20);
+
+		if(newedi != EC32(section_hdr[i].VirtualAddress)) {
+		    cli_dbgmsg("FSG: Bad destination buffer (edi is %x should be %x)\n", newedi, EC32(section_hdr[i].VirtualAddress));
+		    free(src);
+		    break;
+		}
+
+		if(newesi < EC32(section_hdr[i + 1].VirtualAddress) || newesi >= EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData)) {
+		    cli_dbgmsg("FSG: Source buffer out of section bounds\n");
+		    free(src);
+		    break;
+		}
+
+		if(newebx < EC32(section_hdr[i + 1].VirtualAddress) || newebx >= EC32(section_hdr[i + 1].VirtualAddress) + EC32(section_hdr[i + 1].SizeOfRawData) - 16) {
+		    cli_dbgmsg("FSG: Array of functions out of bounds\n");
+		    free(src);
+		    break;
+		}
+
+		/* FIXME: unused atm, needed for pe rebuilding */
+		cli_dbgmsg("FSG: found old EP @%x\n", cli_readint32(newebx + 12 - EC32(section_hdr[i + 1].VirtualAddress) + src) - EC32(optional_hdr.ImageBase));
+
+		if((dest = (char *) cli_calloc(dsize, sizeof(char))) == NULL) {
+		    free(section_hdr);
+		    free(src);
+		    return CL_EMEM;
+		}
+
+		if(unfsg(newesi - EC32(section_hdr[i + 1].VirtualAddress) + src, dest, ssize, dsize) == -1) {
+		    cli_dbgmsg("FSG: Unpacking failed\n");
+		    free(src);
+		    free(dest);
+		    break;
+		}
+
+		found = 0;
+		upx_success = 1;
+		cli_dbgmsg("FSG: Successfully decompressed\n");
+	    }
 	}
 
 	if(found) {
+
+	    /* UPX support */
+
 	    strncpy(sname, section_hdr[i].Name, 8);
 	    sname[8] = 0;
 	    cli_dbgmsg("UPX: Section %d name: %s\n", i, sname);
@@ -488,7 +610,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 	    }
 
 	    if(upxfn) {
-		int skew = cli_readint32(buff + 2) - EC32(optional_hdr.ImageBase) - EC32(section_hdr[i+1].VirtualAddress);
+		    int skew = cli_readint32(buff + 2) - EC32(optional_hdr.ImageBase) - EC32(section_hdr[i + 1].VirtualAddress);
 
 		if(buff[1] != '\xbe' || skew <= 0 || skew > 0xfff ) { /* FIXME: legit skews?? */
 		    skew = 0; 
@@ -517,7 +639,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 	    }
 
 	    if(!upx_success && upxfn != upx_inflate2d) {
-	    if(upx_inflate2d(src, ssize, dest, dsize) && upx_inflate2d(src+0x15, ssize-0x15, dest, dsize) ) {
+		if(upx_inflate2d(src, ssize, dest, dsize) && upx_inflate2d(src + 0x15, ssize - 0x15, dest, dsize) ) {
 		    cli_dbgmsg("UPX: NRV2D decompressor failed\n");
 		} else {
 		    upx_success = 1;
@@ -536,13 +658,18 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 
 	    if(!upx_success) {
 		cli_dbgmsg("UPX: All decompressors failed\n");
-	} else {
+		free(src);
+		free(dest);
+	    }
+	}
+
+	if(upx_success) {
 		int ndesc;
 
 	    if(cli_leavetemps_flag) {
 		tempfile = cli_gentemp(NULL);
 		if((ndesc = open(tempfile, O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU)) < 0) {
-		    cli_dbgmsg("UPX: Can't create file %s\n", tempfile);
+		    cli_dbgmsg("UPX/FSG: Can't create file %s\n", tempfile);
 		    free(tempfile);
 		    free(section_hdr);
 		    free(src);
@@ -551,7 +678,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 		}
 
 		if(write(ndesc, dest, dsize) != dsize) {
-		    cli_dbgmsg("Can't write %d bytes\n", dsize);
+		    cli_dbgmsg("UPX/FSG: Can't write %d bytes\n", dsize);
 		    free(tempfile);
 		    free(section_hdr);
 		    free(src);
@@ -560,7 +687,7 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 		}
 
 		close(ndesc);
-		cli_dbgmsg("UPX: Decompressed data saved in %s\n", tempfile);
+		cli_dbgmsg("UPX/FSG: Decompressed data saved in %s\n", tempfile);
 		free(tempfile);
 	    }
 
@@ -570,11 +697,11 @@ int cli_scanpe(int desc, const char **virname, long int *scanned, const struct c
 		free(dest);
 		return CL_VIRUS;
 	    }
-	}
 
 	    free(src);
 	    free(dest);
 	}
+    }
 
     /* Petite */