An issue was discovered on D-Link DCS-1100 and DCS-1130 devices....

Vulnerability Description

An issue was discovered on D-Link DCS-1100 and DCS-1130 devices. The device has a custom telnet daemon as a part of the busybox and retrieves the password from the shadow file using the function getspnam at address 0x00053894. Then performs a crypt operation on the password retrieved from the user at address 0x000538E0 and performs a strcmp at address 0x00053908 to check if the password is correct or incorrect. However, the /etc/shadow file is a part of CRAM-FS filesystem which means that the user cannot change the password and hence a hardcoded hash in /etc/shadow is used to match the credentials provided by the user. This is a salted hash of the string "admin" and hence it acts as a password to the device which cannot be changed as the whole filesystem is read only.

References

• https://seclists.org/bugtraq/2019/Jun/8
• http://packetstormsecurity.com/files/153226/Dlink-DCS-1130-Command-Injection-CSRF-Stack-Overflow.html
• https://github.com/ethanhunnt/IoT_vulnerabilities/blob/master/Dlink_DCS_1130_security.pdf