Description
Amcrest IPM-721S V2.420.AC00.16.R.20160909 devices have default credentials that are hardcoded in the firmware and can be extracted by anyone who reverses the firmware to identify them. 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_3DB2FC in IDA pro is identified to be setting up the values at address 0x003DB5A6. The sub_5C057C then sets this value and adds it to the Configuration files in /mnt/mtd/Config/Account1 file.