mirror of
https://github.com/nganhkhoa/CTF-All-In-One.git
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137 lines
5.8 KiB
Markdown
137 lines
5.8 KiB
Markdown
# 6.1.25 pwn HCTF2017 babyprintf
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- [题目复现](#题目复现)
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- [题目解析](#题目解析)
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- [漏洞利用](#漏洞利用)
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- [参考资料](#参考资料)
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[下载文件](../src/writeup/6.1.25_pwn_hctf2017_babyprintf)
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## 题目复现
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```
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$ file babyprintf
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babyprintf: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=5652f65b98094d8ab456eb0a54d37d9b09b4f3f6, stripped
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$ checksec -f babyprintf
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RELRO STACK CANARY NX PIE RPATH RUNPATH FORTIFY Fortified Fortifiable FILE
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Partial RELRO Canary found NX enabled No PIE No RPATH No RUNPATH Yes 1 2 babyprintf
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$ strings libc-2.24.so | grep "GNU C"
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GNU C Library (Ubuntu GLIBC 2.24-9ubuntu2.2) stable release version 2.24, by Roland McGrath et al.
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Compiled by GNU CC version 6.3.0 20170406.
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```
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64 位程序，开启了 canary 和 NX，默认开启 ASLR。
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## 题目解析
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#### main
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```
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[0x00400850]> pdf @ main
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;-- section..text:
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/ (fcn) main 130
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| main ();
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| ; DATA XREF from 0x0040086d (entry0)
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| 0x004007c0 push rbx ; [14] -r-x section size 706 named .text
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| 0x004007c1 xor eax, eax
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| 0x004007c3 call sub.setbuf_950 ; void setbuf(FILE *stream,
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| ,=< 0x004007c8 jmp 0x400815
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| 0x004007ca nop word [rax + rax]
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| | ; JMP XREF from 0x00400832 (main)
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| .--> 0x004007d0 mov edi, eax
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| :| 0x004007d2 call sym.imp.malloc ; void *malloc(size_t size)
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| :| 0x004007d7 mov esi, str.string: ; 0x400aa4 ; "string: "
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| :| 0x004007dc mov rbx, rax
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| :| 0x004007df mov edi, 1
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| :| 0x004007e4 xor eax, eax
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| :| 0x004007e6 call sym.imp.__printf_chk
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| :| 0x004007eb mov rdi, rbx
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| :| 0x004007ee xor eax, eax
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| :| 0x004007f0 call sym.imp.gets ; char*gets(char *s)
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| :| 0x004007f5 mov esi, str.result: ; 0x400aad ; "result: "
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| :| 0x004007fa mov edi, 1
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| :| 0x004007ff xor eax, eax
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| :| 0x00400801 call sym.imp.__printf_chk
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| :| 0x00400806 mov rsi, rbx
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| :| 0x00400809 mov edi, 1
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| :| 0x0040080e xor eax, eax
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| :| 0x00400810 call sym.imp.__printf_chk
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| :| ; JMP XREF from 0x004007c8 (main)
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| :`-> 0x00400815 mov esi, str.size: ; 0x400a94 ; "size: "
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| : 0x0040081a mov edi, 1
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| : 0x0040081f xor eax, eax
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| : 0x00400821 call sym.imp.__printf_chk
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| : 0x00400826 xor eax, eax
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| : 0x00400828 call sub._IO_getc_990
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| : 0x0040082d cmp eax, 0x1000
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| `==< 0x00400832 jbe 0x4007d0
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| 0x00400834 mov edi, str.too_long ; 0x400a9b ; "too long"
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| 0x00400839 call sym.imp.puts ; int puts(const char *s)
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| 0x0040083e mov edi, 1
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\ 0x00400843 call sym.imp.exit ; void exit(int status)
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```
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#### read
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```
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[0x00400850]> pdf @ sub._IO_getc_990
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/ (fcn) sub._IO_getc_990 122
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| sub._IO_getc_990 ();
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| ; CALL XREF from 0x00400828 (main)
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| 0x00400990 push rbp
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| 0x00400991 push rbx
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| 0x00400992 xor ebx, ebx
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| 0x00400994 sub rsp, 0x28 ; '('
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| 0x00400998 mov rax, qword fs:[0x28] ; [0x28:8]=-1 ; '(' ; 40
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| 0x004009a1 mov qword [rsp + 0x18], rax
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| 0x004009a6 xor eax, eax
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| 0x004009a8 nop dword [rax + rax]
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| ; JMP XREF from 0x004009ce (sub._IO_getc_990)
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| .-> 0x004009b0 mov rdi, qword [obj.stdin] ; [0x601090:8]=0
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| : 0x004009b7 movsxd rbp, ebx
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| : 0x004009ba call sym.imp._IO_getc
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| : 0x004009bf cmp al, 0xa ; 10
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| : 0x004009c1 mov byte [rsp + rbx], al
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| ,==< 0x004009c4 je 0x400a05
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| |: 0x004009c6 add rbx, 1
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| |: 0x004009ca cmp rbx, 9 ; 9
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| |`=< 0x004009ce jne 0x4009b0
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| | 0x004009d0 cmp byte [rsp + 9], 0xa ; [0xa:1]=255 ; 10
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| |,=< 0x004009d5 je 0x400a00
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| || ; JMP XREF from 0x00400a09 (sub._IO_getc_990)
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| .---> 0x004009d7 xor edx, edx
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| :|| 0x004009d9 xor esi, esi
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| :|| 0x004009db mov rdi, rsp
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| :|| 0x004009de call sym.imp.strtoul ; long strtoul(const char *str, char**endptr, int base)
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| :|| 0x004009e3 mov rcx, qword [rsp + 0x18] ; [0x18:8]=-1 ; 24
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| :|| 0x004009e8 xor rcx, qword fs:[0x28]
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| ,====< 0x004009f1 jne 0x400a0b
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| |:|| 0x004009f3 add rsp, 0x28 ; '('
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| |:|| 0x004009f7 pop rbx
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| |:|| 0x004009f8 pop rbp
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| |:|| 0x004009f9 ret
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|:|| 0x004009fa nop word [rax + rax]
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| |:|| ; JMP XREF from 0x004009d5 (sub._IO_getc_990)
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| |:|`-> 0x00400a00 mov ebp, 9
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| |:| ; JMP XREF from 0x004009c4 (sub._IO_getc_990)
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| |:`--> 0x00400a05 mov byte [rsp + rbp], 0
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| |`===< 0x00400a09 jmp 0x4009d7
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| | ; JMP XREF from 0x004009f1 (sub._IO_getc_990)
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\ `----> 0x00400a0b call sym.imp.__stack_chk_fail ; void __stack_chk_fail(void)
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```
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## 漏洞利用
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开启 ASLR，Bingo!!!
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```
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```
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#### exploit
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完整 exp 如下：
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```python
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```
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## 参考资料
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- https://github.com/spineee/hctf/tree/master/2017/babyprintf
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