As others said, it’s important that your users can enter their password on all devices they would want to use.
Because of that, outlawing the likes of line feed, carriage return and backspace (raw input on a tty will store those in passwords, but good luck entering them in a web form) makes sense, as does normalizing Unicode input (typing ‘é’ on their phone may produce a byte sequence that’s different from typing ‘é’ on their PC)
Apart from that, it should not be necessary. If, however, you don’t trust your programmers to do the right thing, you may want to rule out characters that are related to security incidents such as single quotes, and also may want to prevent users from entering strings that might get decoded to such strings such as ‘"’.
That path can be endless, though. If you forbid ‘&’, because your programmers might accidentally html-decode it, should you guard against double html-decoding? URI-decoding and then uudecoding? Getting programmers you can trust to do the right thing and giving them the time to do so is the better option.
Comments
As others said, it’s important that your users can enter their password on all devices they would want to use.
Because of that, outlawing the likes of line feed, carriage return and backspace (raw input on a tty will store those in passwords, but good luck entering them in a web form) makes sense, as does normalizing Unicode input (typing ‘é’ on their phone may produce a byte sequence that’s different from typing ‘é’ on their PC)
Apart from that, it should not be necessary. If, however, you don’t trust your programmers to do the right thing, you may want to rule out characters that are related to security incidents such as single quotes, and also may want to prevent users from entering strings that might get decoded to such strings such as ‘"’.
That path can be endless, though. If you forbid ‘&’, because your programmers might accidentally html-decode it, should you guard against double html-decoding? URI-decoding and then uudecoding? Getting programmers you can trust to do the right thing and giving them the time to do so is the better option.