On linux, running the keytool so that it prompts for a password and entering a 6 character password will reprompt with the message "The password must be at least 6 characters". Similarly any other interactive input is truncated by a character.
The problem is that is assumes the newline terminator is 2 characters, which it is on windows, but not on other platforms.
The problem can be recreated by running:
Enter keystore password: 12345
The password must be at least 6 characters
Also this password length checking is not performed when running the tool non-interactively, e.g. running
target/hdk/jdk/jre/bin/keytool -genkey -keypass 1234 -storepass 1234
doesn't throw any password length errors