Re: [Bug-wget] bug / security concern

[Tim Rühsen]

Hi,

thanks for the report. Is that still an issue on a recent version of
Wget ? The version 1.17.1 you are using is very outdated.

We don't directly support windows binaries, but here is an unofficial
website that provides for binary downloads:

https://eternallybored.org/misc/wget/

If you find possible security issues, please do not make them public by
writing to this mailing list. Instead open an issue at
  https://savannah.gnu.org/bugs/?func=additem&group=wget
and set 'Privacy' to 'private'.

Regards, Tim

On 10/14/19 8:15 PM, A.K. Zidani wrote:
> Hello there,
> 
> I'm a security researcher and I think I found something interesting when
> using wget to download a file under Windows's BASH environment.
> 
> here is a quick poc I created:
> https://addaxsoft.com/poc/AAAAAAAAA%bb%e4%b8%ad%e7AAAAAAAAAAAAAAAA
> when you wget that file; wget will crash at:
> 
> Program received signal SIGSEGV, Segmentation fault.
> __memset_avx2 () at ../sysdeps/x86_64/multiarch/memset-avx2.S:161
> 
>    0x00007ffffe202ae6 <+374>:   sub    rax,rdx
>    0x00007ffffe202ae9 <+377>:   vzeroupper
>    0x00007ffffe202aec <+380>:   ret
>    0x00007ffffe202aed <+381>:   nop    DWORD PTR [rax]
>    0x00007ffffe202af0 <+384>:   sub    rcx,0xffffffffffffff80
>    0x00007ffffe202af4 <+388>:   vmovd  eax,xmm0
> => 0x00007ffffe202af8 <+392>:   rep stos BYTE PTR es:[rdi],al
>    0x00007ffffe202afa <+394>:   mov    rax,rsi
>    0x00007ffffe202afd <+397>:   sub    rax,rdx
>    0x00007ffffe202b00 <+400>:   vzeroupper
>    0x00007ffffe202b03 <+403>:   ret
> 
> registers:
> (gdb) info registers
> rax            0x20202020       538976288
> rbx            0xffffffffffffffff       -1
> rcx            0xffffffffffff5387       -44153
> rdx            0xffffffffffffffff       -1
> rsi            0x84b1387        139137927
> rdi            0x84bc000        139182080
> rbp            0x84b1140        0x84b1140
> rsp            0x7ffffffed558   0x7ffffffed558
> r8             0x0      0
> r9             0x1      1
> r10            0x7ffffffed4a8   140737488278696
> r11            0x8279880        136812672
> r12            0x7      7
> r13            0x7      7
> r14            0x82798f0        136812784
> r15            0x84b1388        139137928
> rip            0x7ffffe202af8   0x7ffffe202af8 <__memset_avx2+392>
> eflags         0x10287  [ CF PF SF IF RF ]
> cs             0x33     51
> ss             0x2b     43
> ds             0x0      0
> es             0x0      0
> fs             0x0      0
> gs             0x0      0
> 
> rdi is accessing inaccessible memory which the cause of the crash:
> (gdb) x $rdi
> 0x84bc000:      Cannot access memory at address 0x84bc000
> 
> here is my wget -V output:
> root@PC:~# wget -V
> GNU Wget 1.17.1 built on linux-gnu.
> 
> +digest -gpgme +https +ipv6 +iri +large-file -metalink +nls +ntlm
> +opie -psl +ssl/openssl
> 
> Wgetrc:
>     /etc/wgetrc (system)
> Locale:
>     /usr/share/locale
> Compile:
>     gcc -DHAVE_CONFIG_H -DSYSTEM_WGETRC="/etc/wgetrc"
>     -DLOCALEDIR="/usr/share/locale" -I. -I../../src -I../lib
>     -I../../lib -Wdate-time -D_FORTIFY_SOURCE=2 -I/usr/include
>     -DHAVE_LIBSSL -DNDEBUG -g -O2 -fPIE -fstack-protector-strong
>     -Wformat -Werror=format-security -DNO_SSLv2 -D_FILE_OFFSET_BITS=64
>     -g -Wall
> Link:
>     gcc -DHAVE_LIBSSL -DNDEBUG -g -O2 -fPIE -fstack-protector-strong
>     -Wformat -Werror=format-security -DNO_SSLv2 -D_FILE_OFFSET_BITS=64
>     -g -Wall -Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z,relro
>     -Wl,-z,now -L/usr/lib -lpcre -luuid -lssl -lcrypto -lz -lidn
>     ftp-opie.o openssl.o http-ntlm.o ../lib/libgnu.a
> 
> Copyright (C) 2015 Free Software Foundation, Inc.
> Licence GPLv3+: GNU GPL version 3 or later
> <http://www.gnu.org/licenses/gpl.html>.
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> 
> Originally written by Hrvoje Niksic <address@hidden>.
> Please send bug reports and questions to <address@hidden>.
> 
> 
> 
> 
> 
> I didn't look into this further, but potentially I can have a memory write
> if I get control of rdi and rax at some point in the code path, which may
> lead to code execution as well.
> 
> NOTE: this only crashes wget running in bash in a Windows environment.
> not sure if this is the same as CVE-2019-5953, but I would like to
> investigate further.
> 
> 
> 
>

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