Amcrest IPM-721S V2.420.AC00.16.R.20160909 devices allow an unauthenticated attacker to download the administrative credentials. If the firmware version V2.420.AC00.16.R 9/9/2016 is dissected using binwalk tool, one obtains a _user-x.squashfs.img.extracted archive which contains the filesystem set up on the device that many of the binaries in the /usr folder. The binary "sonia" is the one that has the vulnerable function that sets up the default credentials on the device. If one opens this binary in IDA-pro one will notice that this follows a ARM little endian format. The function sub_436D6 in IDA pro is identified to be setting up the configuration for the device. If one scrolls to the address 0x000437C2 then one can see that /current_config is being set as an ALIAS for /mnt/mtd/Config folder on the device. If one TELNETs into the device and navigates to /mnt/mtd/Config folder, one can observe that it contains various files such as Account1, Account2, SHAACcount1, etc. This means that if one navigates to http://[IPofcamera]/current_config/Sha1Account1 then one should be able to view the content of the files. The security researchers assumed that this was only possible only after authentication to the device. However, when unauthenticated access tests were performed for the same URL as provided above, it was observed that the device file could be downloaded without any authentication.
published: 3. 7. 2019