challenge-su | su implementation using Ed25519 signatures

challenge-su is a C library. challenge-su has no bugs, it has no vulnerabilities and it has low support. However challenge-su has a Non-SPDX License. You can download it from GitHub.

copyright 2016 joshua juran. this is an implementation of su that authenticates non-root users by issuing a cryptographic challenge, which must be answered by an ed25519 signature of the challenge using the correct secret key. it’s intended for use with android devices. unlike the typical android su, this one does not solicit confirmation by the user through a superuser app. instead, it issues a cryptographic challenge on stdout, to which it expects a response on stdin. the challenge is a sequence of 32 mostly-random bytes, in hexadecimal form. the response is an ed25519 signature of the challenge. for the benefit of adb shell users, the actual message to be signed consists of the 64 hexadecimal digits (using lowercase letters) followed by lf — 65 bytes in total. the trailing newline is included for