The commands here provide a better analysis of memory segments and the registers.
elf-info
elf-info (elf for short) provides basic information about the ELF file. This is most useful for viewing memory segments, the entry point, and the ELF header.
Copy gef➤ elf-info
Magic : 7f 45 4c 46
Class : 0x1 - ELF_32_BITS
Endianness : 0x1 - LITTLE_ENDIAN
Version : 0x1
OS ABI : 0x0 - SYSTEMV
ABI Version : 0x0
Type : 0x2 - ET_EXEC
Machine : 0x3 - X86_32
Program Header Table : 0x00000034
Section Header Table : 0x00003628
Header Table : 0x00000034
ELF Version : 0x1
Header size : 52 (0x34)
Entry point : 0x08049090
──────────────────────────────────────────────── Program Header ────────────────────────────────────────────────
[ #] Type Offset Virtaddr Physaddr FileSiz MemSiz Flags Align
[ 0] PT_PHDR 0x34 0x8048034 0x8048034 0x160 0x160 PF_R 0x4
[ 1] PT_INTERP 0x194 0x8048194 0x8048194 0x13 0x13 PF_R 0x1
[ 2] PT_LOAD 0x0 0x8048000 0x8048000 0x388 0x388 PF_R 0x1000
[ 3] PT_LOAD 0x1000 0x8049000 0x8049000 0x270 0x270 None 0x1000
[ 4] PT_LOAD 0x2000 0x804a000 0x804a000 0x160 0x160 PF_R 0x1000
[ 5] PT_LOAD 0x2f08 0x804bf08 0x804bf08 0x120 0x124 None 0x1000
[ 6] PT_DYNAMIC 0x2f10 0x804bf10 0x804bf10 0xe8 0xe8 None 0x4
[ 7] PT_NOTE 0x1a8 0x80481a8 0x80481a8 0x44 0x44 PF_R 0x4
[ 8] PT_GNU_EH_FRAME 0x2038 0x804a038 0x804a038 0x44 0x44 PF_R 0x4
[ 9] PT_GNU_STACK 0x0 0x0 0x0 0x0 0x0 None 0x10
[10] PT_GNU_RELRO 0x2f08 0x804bf08 0x804bf08 0xf8 0xf8 PF_R 0x1
──────────────────────────────────────────────── Section Header ────────────────────────────────────────────────
[ #] Name Type Address Offset Size EntSiz Flags Link Info Align
[ 0] UNKN 0x0 0x0 0x0 0x0 UNKNOWN_FLAG 0x0 0x0 0x0
[ 1] .interp SHT_PROGBITS 0x8048194 0x194 0x13 0x0 ALLOC 0x0 0x0 0x1
[ 2] .note.gnu.build-id SHT_NOTE 0x80481a8 0x1a8 0x24 0x0 ALLOC 0x0 0x0 0x4
[ 3] .note.ABI-tag SHT_NOTE 0x80481cc 0x1cc 0x20 0x0 ALLOC 0x0 0x0 0x4
[ 4] .gnu.hash SHT_GNU_HASH 0x80481ec 0x1ec 0x20 0x4 ALLOC 0x5 0x0 0x4
[ 5] .dynsym SHT_DYNSYM 0x804820c 0x20c 0x90 0x10 ALLOC 0x6 0x1 0x4
[ 6] .dynstr SHT_STRTAB 0x804829c 0x29c 0x6f 0x0 ALLOC 0x0 0x0 0x1
[ 7] .gnu.version SHT_GNU_versym 0x804830c 0x30c 0x12 0x2 ALLOC 0x5 0x0 0x2
[ 8] .gnu.version_r SHT_GNU_verneed 0x8048320 0x320 0x30 0x0 ALLOC 0x6 0x1 0x4
[ 9] .rel.dyn SHT_REL 0x8048350 0x350 0x10 0x8 ALLOC 0x5 0x0 0x4
[10] .rel.plt SHT_REL 0x8048360 0x360 0x28 0x8 UNKNOWN_FLAG 0x5 0x16 0x4
[11] .init SHT_PROGBITS 0x8049000 0x1000 0x24 0x0 UNKNOWN_FLAG 0x0 0x0 0x4
[12] .plt SHT_PROGBITS 0x8049030 0x1030 0x60 0x4 UNKNOWN_FLAG 0x0 0x0 0x10
[13] .text SHT_PROGBITS 0x8049090 0x1090 0x1c8 0x0 UNKNOWN_FLAG 0x0 0x0 0x10
[14] .fini SHT_PROGBITS 0x8049258 0x1258 0x18 0x0 UNKNOWN_FLAG 0x0 0x0 0x4
[15] .rodata SHT_PROGBITS 0x804a000 0x2000 0x37 0x0 ALLOC 0x0 0x0 0x4
[16] .eh_frame_hdr SHT_PROGBITS 0x804a038 0x2038 0x44 0x0 ALLOC 0x0 0x0 0x4
[17] .eh_frame SHT_PROGBITS 0x804a07c 0x207c 0xe4 0x0 ALLOC 0x0 0x0 0x4
[18] .init_array SHT_INIT_ARRAY 0x804bf08 0x2f08 0x4 0x4 UNKNOWN_FLAG 0x0 0x0 0x4
[19] .fini_array SHT_FINI_ARRAY 0x804bf0c 0x2f0c 0x4 0x4 UNKNOWN_FLAG 0x0 0x0 0x4
[20] .dynamic SHT_DYNAMIC 0x804bf10 0x2f10 0xe8 0x8 UNKNOWN_FLAG 0x6 0x0 0x4
[21] .got SHT_PROGBITS 0x804bff8 0x2ff8 0x8 0x4 UNKNOWN_FLAG 0x0 0x0 0x4
[22] .got.plt SHT_PROGBITS 0x804c000 0x3000 0x20 0x4 UNKNOWN_FLAG 0x0 0x0 0x4
[23] .data SHT_PROGBITS 0x804c020 0x3020 0x8 0x0 UNKNOWN_FLAG 0x0 0x0 0x4
[24] .bss SHT_NOBITS 0x804c028 0x3028 0x4 0x0 UNKNOWN_FLAG 0x0 0x0 0x1
[25] .comment SHT_PROGBITS 0x0 0x3028 0x2d 0x1 UNKNOWN_FLAG 0x0 0x0 0x1
[26] .symtab SHT_SYMTAB 0x0 0x3058 0x2b0 0x10 UNKNOWN_FLAG 0x1b 0x12 0x4
[27] .strtab SHT_STRTAB 0x0 0x3308 0x21f 0x0 UNKNOWN_FLAG 0x0 0x0 0x1
[28] .shstrtab SHT_STRTAB 0x0 0x3527 0x101 0x0 UNKNOWN_FLAG 0x0 0x0 0x1 got
The got command prints the GOT table.
Copy gef➤ got
GOT protection: Partial RelRO | GOT functions: 5
[0x804c00c] __libc_start_main@GLIBC_2.34 → 0xf7c21560
[0x804c010] fflush@GLIBC_2.0 → 0xf7c71410
[0x804c014] gets@GLIBC_2.0 → 0x8049066
[0x804c018] puts@GLIBC_2.0 → 0xf7c732a0
[0x804c01c] system@GLIBC_2.0 → 0x8049086 got can apply filters to the output. You can filter by symbol name and can also use more than one filter.
Copy gef➤ got puts
GOT protection: Partial RelRO | GOT functions: 5
[0x804c018] puts@GLIBC_2.0 → 0xf7c732a0
gef➤ got puts system
GOT protection: Partial RelRO | GOT functions: 5
[0x804c018] puts@GLIBC_2.0 → 0xf7c732a0
[0x804c01c] system@GLIBC_2.0 → 0x8049086 The GOT table is resolved at runtime. Therefore, you can only use got at runtime.
heap
The heap command provides information on the heap chunks.
Use heap arenas to view the heap arenas.
Copy gef➤ heap arenas
Arena(base=0x7ffff7e19c80, top=0x5555555596d0, last_remainder=0x0, next=0x7ffff7e19c80) Use heap chunks to view the heap chunks.
Copy gef➤ heap chunks
Chunk(addr=0x555555559010, size=0x290, flags=PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA)
[0x0000555555559010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................]
Chunk(addr=0x5555555592a0, size=0x30, flags=PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA)
[0x00005555555592a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................]
Chunk(addr=0x5555555592d0, size=0x410, flags=PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA)
[0x00005555555592d0 45 6e 74 65 72 20 74 68 65 20 66 6c 61 67 20 68 Enter the flag h]
Chunk(addr=0x5555555596e0, size=0x20930, flags=PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA) ← top chunk Since this guide doesn't cover heap exploits, I won't go into detail about the heap commands.
...yet.
dereference
The dereference (deref for short) command provides similar output to the Stack section of context. It takes three optional arguments:
A start address, symbol, or register (by default, $sp)
The number of consecutive addresses to reference
The base location for offset (by default, the start address)
Copy gef➤ deref
0xffffd640│+0x0000: 0xffffd658 → 0xf7c184be → "_dl_audit_preinit" ← $esp
0xffffd644│+0x0004: 0x00000000
0xffffd648│+0x0008: 0x01000000
0xffffd64c│+0x000c: 0x080491fb → <read_in+12> add ebx, 0x2e05
0xffffd650│+0x0010: 0xf7fc4540 → <__kernel_vsyscall+0> push ecx
0xffffd654│+0x0014: 0x00000000
0xffffd658│+0x0018: 0xf7c184be → "_dl_audit_preinit"
0xffffd65c│+0x001c: 0xf7e2a054 → 0xf7fdde10 → <_dl_audit_preinit+0> endbr32
0xffffd660│+0x0020: 0xf7fbe4a0 → 0xf7c00000 → 0x464c457f
0xffffd664│+0x0024: 0xf7fd6f90 → mov edi, eax With arguments:
Copy gef➤ deref $esp -l 7 -r $ebp
0xffffd640│-0x0048: 0xffffd658 → 0xf7c184be → "_dl_audit_preinit" ← $esp
0xffffd644│-0x0044: 0x00000000
0xffffd648│-0x0040: 0x01000000
0xffffd64c│-0x003c: 0x080491fb → <read_in+12> add ebx, 0x2e05
0xffffd650│-0x0038: 0xf7fc4540 → <__kernel_vsyscall+0> push ecx
0xffffd654│-0x0034: 0x00000000
0xffffd658│-0x0030: 0xf7c184be → "_dl_audit_preinit" registers
The registers command is a wrapper for info registers. It shows the current state of the registers in the same format it is printed in context.
Copy gef➤ registers
$eax : 0xffffd228 → 0xf7c184be → "_dl_audit_preinit"
$ebx : 0x0804c000 → 0x0804bf10 → <_DYNAMIC+0> add DWORD PTR [eax], eax
$ecx : 0x6c0
$edx : 0xf7e2b9b4 → 0x00000000
$esp : 0xffffd210 → 0xffffd228 → 0xf7c184be → "_dl_audit_preinit"
$ebp : 0xffffd258 → 0xffffd268 → 0xf7ffd020 → 0xf7ffda40 → 0x00000000
$esi : 0xffffd324 → 0xffffd4ea → "/home/joybuzzer/args"
$edi : 0xf7ffcb80 → 0x00000000
$eip : 0x0804922e → 0xfffe2de8 → 0x00000000
$eflags: [zero carry PARITY ADJUST SIGN trap INTERRUPT direction overflow resume virtualx86 identification]
$cs: 0x23 $ss: 0x2b $ds: 0x2b $es: 0x2b $fs: 0x00 $gs: 0x63 Like info registers, you can filter by register.
Copy gef➤ registers $eip $esi
$eip : 0x0804922e → 0xfffe2de8 → 0x00000000
$esi : 0xffffd324 → 0xffffd4ea → "/home/joybuzzer/args" vmmap
vmmap performs an extended function to info proc mappings. It shows all loaded memory segments.
Copy gef➤ vmmap
[ Legend: Code | Heap | Stack ]
Start End Offset Perm Path
0x08048000 0x08049000 0x00000000 r-- /home/joybuzzer/args
0x08049000 0x0804a000 0x00001000 r-x /home/joybuzzer/args
0x0804a000 0x0804b000 0x00002000 r-- /home/joybuzzer/args
0x0804b000 0x0804c000 0x00002000 r-- /home/joybuzzer/args
0x0804c000 0x0804d000 0x00003000 rw- /home/joybuzzer/args
0xf7c00000 0xf7c20000 0x00000000 r-- /usr/lib/i386-linux-gnu/libc.so.6
0xf7c20000 0xf7da2000 0x00020000 r-x /usr/lib/i386-linux-gnu/libc.so.6
0xf7da2000 0xf7e27000 0x001a2000 r-- /usr/lib/i386-linux-gnu/libc.so.6
0xf7e27000 0xf7e28000 0x00227000 --- /usr/lib/i386-linux-gnu/libc.so.6
0xf7e28000 0xf7e2a000 0x00227000 r-- /usr/lib/i386-linux-gnu/libc.so.6
0xf7e2a000 0xf7e2b000 0x00229000 rw- /usr/lib/i386-linux-gnu/libc.so.6
0xf7e2b000 0xf7e35000 0x00000000 rw-
0xf7fbe000 0xf7fc0000 0x00000000 rw-
0xf7fc0000 0xf7fc4000 0x00000000 r-- [vvar]
0xf7fc4000 0xf7fc6000 0x00000000 r-x [vdso]
0xf7fc6000 0xf7fc7000 0x00000000 r-- /usr/lib/i386-linux-gnu/ld-linux.so.2
0xf7fc7000 0xf7fec000 0x00001000 r-x /usr/lib/i386-linux-gnu/ld-linux.so.2
0xf7fec000 0xf7ffb000 0x00026000 r-- /usr/lib/i386-linux-gnu/ld-linux.so.2
0xf7ffb000 0xf7ffd000 0x00034000 r-- /usr/lib/i386-linux-gnu/ld-linux.so.2
0xf7ffd000 0xf7ffe000 0x00036000 rw- /usr/lib/i386-linux-gnu/ld-linux.so.2
0xfffdd000 0xffffe000 0x00000000 rwx [stack] vmmap also takes an optional argument. It takes an address and will resolve that address to a certain memory segment.
Copy gef➤ x/wx $ebp-0x30
0xffffd228: 0xf7c18400
gef➤ vmmap 0xffffd228
[ Legend: Code | Heap | Stack ]
Start End Offset Perm Path
0xfffdd000 0xffffe000 0x00000000 rwx [stack] scan
scan searches for addresses of one memory region inside another region. This is also known as needle-in-haystack scanning .
Copy gef➤ scan stack libc
[+] Searching for addresses in 'stack' that point to 'libc'
[stack]: 0x00007fffffffd6a8│+0x1f6a8: 0x00007ffff77cf482 → "__tunable_get_val"
[stack]: 0x00007fffffffd6b0│+0x1f6b0: 0x00007ffff77bff78 → 0x0000001200001ab2
[stack]: 0x00007fffffffd758│+0x1f758: 0x00007ffff77cd9d0 → 0x6c5f755f72647800
[stack]: 0x00007fffffffd778│+0x1f778: 0x00007ffff77bda6c → 0x0000090900000907
[stack]: 0x00007fffffffd7d8│+0x1f7d8: 0x00007ffff77cd9d0 → 0x6c5f755f72647800
[...] You can check mappings without a path associated using an address range.
Copy gef➤ scan 0x555555554000-0x555555555000 libc
[+] Searching for addresses in '0x555555554000-0x555555555000' that point to 'libc' 