Open Sesame (Dlink - CVE-2012-4046)

A couple weeks ago a vulnerability was posted for the dlink DCS-9xx series of cameras. The author of the disclosure found that the setup application that comes with the camera is able to send a specifically crafted request to a camera on the same network and receive its password in plaintext. I figured this was a good chance to do some analysis and figure out exactly how the application carried out this functionality and possibly create a script to pull the password out of a camera.

The basic functionality of the application is as follows:

• Application sends out a UDP broadcast on port 5978
• Camera sees the broadcast on port 5978 and inspects the payload – if it sees that the initial part of the payload contains "FF FF FF FF FF FF" it responds (UDP broadcast port 5978) with an encoded payload with its own MAC address
• Application retrieves the camera's response and creates another UDP broadcast but this time it sets the payload to contain the target camera's MAC address, this encoded value contains the command to send over the password
• Camera sees the broadcast on port 5978 and checks that it is meant for it by inspecting the MAC address that has been specified in the payload, it responds with an encoded payload that contains its password (base64 encoded)

After spending some time with the application in a debugger I found what looked like it was responsible for the decoding of the encoded values that are passed:

super exciting screen shot.

After spending some time documenting the functionality I came up with the following notes (messy wall of text):

	Command	Comments
	.JGE SHORT 0A729D36	; stage1
	./MOV EDX,DWORD PTR SS:[LOCAL.2]	; set EDX to our 1st stage half decoded buffer
	.|MOV ECX,DWORD PTR SS:[LOCAL.4]	; set ECX to our current count/offset
	.|MOV EAX,DWORD PTR SS:[LOCAL.3]	; set EAX to our base64 encoded payload
	.|MOVSX EAX,BYTE PTR DS:[EAX]	; set EAX to the current value in our base64 payload
	.|MOV AL,BYTE PTR DS:[EAX+0A841934]	; set EAX/AL to a hardcoded offset of its value table is at 0a841934
	.|MOV BYTE PTR DS:[ECX+EDX],AL	; ECX = Offset, EDX = start of our half-decoded buffer, write our current byte there
	.|INC DWORD PTR SS:[LOCAL.4]	; increment our offset/count
	.|INC DWORD PTR SS:[LOCAL.3]	; increment our base64 buffer to next value
	.|MOV EDX,DWORD PTR SS:[LOCAL.4]	; set EDX to our counter
	.|CMP EDX,DWORD PTR SS:[ARG.2]	; compare EDX (counter) to our total size
	.\JL SHORT 0A729D13	; jump back if we have not finished half decoding our input value
	.MOV ECX,DWORD PTR SS:[ARG.3]	; Looks like this will point at our decoded buffer
	.MOV DWORD PTR SS:[LOCAL.5],ECX	; set Arg5 to our decoded destination
	.MOV EAX,DWORD PTR SS:[LOCAL.2]	; set EAX to our half-decoded buffer
	.MOV DWORD PTR SS:[LOCAL.3],EAX	; set arg3 to point at our half-decoded buffer
	.MOV EDX,DWORD PTR SS:[ARG.4]	; ???? 1500 decimal
	.XOR ECX,ECX	; clear ECX
	.MOV DWORD PTR DS:[EDX],ECX	; clear out arg4 value
	.XOR EAX,EAX	; clear out EAX
	.MOV DWORD PTR SS:[LOCAL.6],EAX	; clear out local.6
	.JMP SHORT 0A729DAE	; JUMP
	./MOV EDX,DWORD PTR SS:[LOCAL.3]	; move our current half-decoded dword position into EDX
	.|MOV CL,BYTE PTR DS:[EDX]	; move our current byte into ECX (CL) (dword[0])
	.|SHL ECX,2	; shift left 2 dword[0]
	.|MOV EAX,DWORD PTR SS:[LOCAL.3]	; move our current dword position into EAX
	.|MOVSX EDX,BYTE PTR DS:[EAX+1]	; move our current dword position + 1 (dword[1]) into EDX
	.|SAR EDX,4	; shift right 4 dword[1]
	.|ADD CL,DL	; add (shift left 2 dword[0]) + (shift right 4 dword[1])
	.|MOV EAX,DWORD PTR SS:[LOCAL.5]	; set EAX to our current decoded buffer position
	.|MOV BYTE PTR DS:[EAX],CL	; write our decoded (dword[0]) value to or decoded buffer
	.|INC DWORD PTR SS:[LOCAL.5]	; increment our position in the decoded buffer
	.|MOV EDX,DWORD PTR SS:[LOCAL.3]	; set EDX to our current dword position
	.|MOV CL,BYTE PTR DS:[EDX+1]	; set ECX to dword[1]
	.|SHL ECX,4	; left shift 4 dword[1]
	.|MOV EAX,DWORD PTR SS:[LOCAL.3]	; set EAX to our current dword position
	.|MOVSX EDX,BYTE PTR DS:[EAX+2]	; set EDX to dword[2]
	.|SAR EDX,2	; shift right 2 dword[2]
	.|ADD CL,DL	; add (left shift 4 dword[1]) + (right shift 2 dword[2])
	.|MOV EAX,DWORD PTR SS:[LOCAL.5]	; set EAX to our next spot in the decoded buffer
	.|MOV BYTE PTR DS:[EAX],CL	; write our decoded value into our decoded buffer
	.|INC DWORD PTR SS:[LOCAL.5]	; move to the next spot in our decoded buffer
	.|MOV EDX,DWORD PTR SS:[LOCAL.3]	; set EDX to our current half-decoded dword
	.|MOV CL,BYTE PTR DS:[EDX+2]	; set ECX dword[2]
	.|SHL ECX,6	; shift left 6 dword[2]
	.|MOV EAX,DWORD PTR SS:[LOCAL.3]	; set EAX to our current half-decoded dword
	.|ADD CL,BYTE PTR DS:[EAX+3]	; add dword[2] + dword[3]
	.|MOV EDX,DWORD PTR SS:[LOCAL.5]	; set EDX to point at our next spot in our decoded buffer
	.|MOV BYTE PTR DS:[EDX],CL	; write our decoded byte to our decoded buffer
	.|INC DWORD PTR SS:[LOCAL.5]	; move to the next spot in our decoded buffer
	.|ADD DWORD PTR SS:[LOCAL.3],4	; increment our encoded buffer to point at our next dword
	.|MOV ECX,DWORD PTR SS:[ARG.4]	; set ECX to our current offset?
	.|ADD DWORD PTR DS:[ECX],3	; add 3 to our current offset?
	.|ADD DWORD PTR SS:[LOCAL.6],4	; add 4 to our byte counter??
	.|MOV EAX,DWORD PTR SS:[ARG.2]	; move total size into EAX
	.|ADD EAX,-4	; subtract 4 from total size
	.|CMP EAX,DWORD PTR SS:[LOCAL.6]	; compare our total bytes to read bytes
	.\JG SHORT 0A729D50	; jump back if we are not done
	.MOV EDX,DWORD PTR SS:[LOCAL.3]	; set EDX to our last DWORD of encoded buffer
	.MOVSX ECX,BYTE PTR DS:[EDX+3]	; set ECX to dword[3] last byte of our half-decoded dword (dword + 3)
	.INC ECX	; increment the value of dword[3]
	.JE SHORT 0A729E1E
	.MOV EAX,DWORD PTR SS:[LOCAL.3]	; set EAX to our current half-decoded dword
	.MOV DL,BYTE PTR DS:[EAX]	; set EDX (DL) to dword[0]
	.SHL EDX,2	; shift left 2 dword[0]
	.MOV ECX,DWORD PTR SS:[LOCAL.3]	; set ECX to our current encoded dword position
	.MOVSX EAX,BYTE PTR DS:[ECX+1]	; set EAX to dword[1]
	.SAR EAX,4	; shift right 4 dword[1]
	.ADD DL,AL	; add (shifted left 2 dword[0]) + (shifted right 4 dword[1])
	.MOV ECX,DWORD PTR SS:[LOCAL.5]	; set ECX to point at our next spot in our decoded buffer
	.MOV BYTE PTR DS:[ECX],DL	; write our decoded value (EDX/DL) to our decoded buffer
	.INC DWORD PTR SS:[LOCAL.5]	; move to the next spot in our decoded buffer
	.MOV EDX,DWORD PTR SS:[LOCAL.3]	; set EDX to point at our dword
	.MOV AL,BYTE PTR DS:[EDX+1]	; set EAX/AL to dword[1]
	.SHL EAX,4	; shift left 4 dword[1]
	.MOV EDX,DWORD PTR SS:[LOCAL.3]	; set EDX to our current dword
	.MOVSX ECX,BYTE PTR DS:[EDX+2]	; set ECX to dword[2]
	.SAR ECX,2	; shift right 2 dword[2]
	.ADD AL,CL	; add (shifted left 4 dword[1]) + (shifted right 2 dword[2])
	.MOV EDX,DWORD PTR SS:[LOCAL.5]	; set EDX to point at our current spot in our decoded buffer
	.MOV BYTE PTR DS:[EDX],AL	; write our decoded value to the decoded buffer
	.INC DWORD PTR SS:[LOCAL.5]	; move to the next spot in our decoded buffer
	.MOV EAX,DWORD PTR SS:[LOCAL.3]	; set EAX to point at our current dword
	.MOV CL,BYTE PTR DS:[EAX+2]	; set ECX/CL to dword[2]
	.SHL ECX,6	; shift left 6 dword[2]
	.MOV EAX,DWORD PTR SS:[LOCAL.3]	; point EAX at our current dword
	.ADD CL,BYTE PTR DS:[EAX+3]	; add dword[3] + (shifted left 6 dword[2])
	.MOV EDX,DWORD PTR SS:[LOCAL.5]	; point EDX at our current decoded buffer
	.MOV BYTE PTR DS:[EDX],CL	; write our decoded value to the decoded buffer
	.INC DWORD PTR SS:[LOCAL.5]	; increment our deocded buffer
	.MOV ECX,DWORD PTR SS:[ARG.4]	; set ECX to our current offset?
	.ADD DWORD PTR DS:[ECX],3	; add 4 for our current byte counter?
	.JMP 0A729EA6	; jump

Translated into english: the application first uses a lookup table to translate every byte in the input string, to do this it uses the value of the current byte as an offset into the table.  After it is done with "stage1" it traverses the translated input buffer a dword at a time and does some bit shifting and addition to fully decode the value. The following roughly shows the "stage2" routine:

(Dword[0] << 2) + (Dword[1] >> 4) = unencoded byte 1 

(Dword[1] << 4) + (Dword[2] >> 2) = unencoded byte 2 

(Dword[2] << 6) + Dword[3] = unencoded byte 3

I then confirmed that this routine worked on an "encoded" value that went over the wire from the application to the camera. After confirming the encoding scheme worked, I recreated the network transaction the application does with the camera to create a stand alone script that will retrieve the password from a camera that is on the same lan as the "attacker". The script can be found here, thanks to Jason Doyle for the original finding (@jasond0yle ).

Continue reading

1. Wifi Hacker Tools For Windows
2. Blackhat Hacker Tools
3. What Are Hacking Tools
4. What Are Hacking Tools
5. Hack And Tools
6. Hacker Tools Hardware
7. Hacker Tools 2019
8. Pentest Tools Url Fuzzer
9. Hacker Security Tools
10. Best Hacking Tools 2019
11. Beginner Hacker Tools
12. Hacking Tools Download
13. Pentest Tools Nmap
14. Pentest Tools List
15. Pentest Reporting Tools
16. Pentest Tools For Ubuntu
17. Hacking Tools For Windows 7
18. Pentest Tools Subdomain
19. Hacking Tools Hardware
20. Tools For Hacker
21. Hack Tools For Windows
22. Bluetooth Hacking Tools Kali
23. Hacker Tools Mac
24. Hacker
25. Hack Tools For Ubuntu
26. Blackhat Hacker Tools
27. Android Hack Tools Github
28. Pentest Reporting Tools
29. Hack App
30. Hacking Tools Pc
31. Pentest Tools Open Source
32. Hacking Tools For Kali Linux
33. Hacker Tool Kit
34. Hackrf Tools
35. Hacking Tools 2019
36. Nsa Hack Tools
37. Easy Hack Tools
38. Android Hack Tools Github
39. Hacker Tools 2019
40. Pentest Tools For Android
41. Pentest Tools Bluekeep
42. Physical Pentest Tools
43. Computer Hacker
44. Hacking Tools Pc
45. Hacking Tools Name
46. Easy Hack Tools
47. Hacks And Tools
48. Hack Tools Mac
49. Pentest Tools Framework
50. Hacker Search Tools
51. Growth Hacker Tools
52. Hacker Tools For Pc
53. Hacking Tools
54. Pentest Tools For Windows
55. Hacking Tools Download
56. Underground Hacker Sites
57. Pentest Tools Open Source
58. Hack And Tools
59. Hacker Tools Free Download
60. New Hacker Tools
61. Hacker Tools 2020
62. Pentest Tools Review
63. Hack Tools
64. Best Hacking Tools 2020
65. Pentest Tools Download
66. Hacking Tools For Windows Free Download
67. Pentest Tools Windows
68. Pentest Tools Bluekeep
69. Hacking Tools For Windows
70. Pentest Box Tools Download
71. Free Pentest Tools For Windows
72. Hack Tools For Mac
73. Game Hacking
74. Usb Pentest Tools
75. Hacking Tools For Windows 7
76. Hack Rom Tools
77. Hacker Tools 2020
78. Hacker Tools Software
79. Hacking Tools Mac
80. Hack Tools Online
81. Hacking Tools And Software
82. Pentest Tools Nmap
83. Hack Tools For Mac
84. Pentest Tools Website Vulnerability
85. Hacking Tools For Windows
86. How To Make Hacking Tools
87. Hacking Tools Kit
88. Hack Tools
89. Nsa Hacker Tools
90. Hacking Tools Hardware
91. Hackrf Tools
92. Hacks And Tools
93. Hack Tools Pc
94. Hacker Tools For Windows
95. Pentest Tools Subdomain
96. Hack Tools For Pc
97. Game Hacking
98. Pentest Tools Subdomain
99. Hacker Tools Hardware
100. What Are Hacking Tools
101. Hacker Tools For Windows
102. Hack Tools For Pc
103. Hack Tools 2019
104. Bluetooth Hacking Tools Kali
105. Install Pentest Tools Ubuntu
106. Pentest Tools Website Vulnerability
107. Underground Hacker Sites
108. Hacker Search Tools
109. Nsa Hacker Tools
110. Hacker Tools 2019
111. Hacking Apps
112. Easy Hack Tools
113. Pentest Tools Framework
114. Hacker Tool Kit
115. Pentest Tools Port Scanner
116. Hacking Tools Kit
117. Hacking Tools Kit
118. Growth Hacker Tools
119. Hacks And Tools
120. Physical Pentest Tools
121. Hacking Tools For Beginners
122. Github Hacking Tools
123. Pentest Tools Free
124. Pentest Tools Open Source
125. Nsa Hacker Tools
126. Pentest Tools Apk
127. Hacker Tools For Pc
128. Hacking Tools For Kali Linux
129. Hacker Tools For Windows
130. Pentest Tools Website Vulnerability
131. Pentest Tools Apk
132. Hacker Tools Hardware
133. Hacker Tools For Mac
134. Hacking Tools Windows
135. Hacking Tools Windows
136. Bluetooth Hacking Tools Kali
137. Usb Pentest Tools
138. Top Pentest Tools
139. Hacker Techniques Tools And Incident Handling
140. Hacking Tools Download
141. Hack Tools Pc
142. Hack Tools Download
143. Top Pentest Tools