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acceptable_password(3) Library Functions Manual acceptable_password(3) NAME acceptable_password - Determines if a password meets deduction require- ments (Enhanced Security) LIBRARY Security Library (libsecurity.a) SYNOPSIS int acceptable_password( char *word, FILE *stream); PARAMETERS Points to the suggested password. Points to the stream to write diag- nostics into. DESCRIPTION The acceptable_password() function determines if the given password is difficult to deduce from well known, password-guessing heuristics. The cleartext (plaintext) password is passed as the first argument, and the file pointer of the stream that is used to report failure reasons is the second argument. If this checking is to be silent, the second ar- gument should be a null file pointer. When the acceptable_password() function returns a value of 1, the pass- word provided meets all the tests listed in the following text. When it returns a value of 0 (zero), the password failed to meet at least one of the tests. The selectivity criteria for the password include but cannot be limited to the following four tests: This test passes if the word is not a palindrome. (A palindrome is a word that is spelled the same backwards as it is forwards.) Examples of palindromes that fail this test are mom, dad, noon, redivider, radar. Palindromes do not make good pass- words because they reduce an n character password to n/2 + 1 charac- ters. A penetrator knowing that palindromes were legal could use heuristics that could deduce the password much more quickly than if they were excluded. This test passes if the password is not a deriva- tive of a login name for the system. Many insecure systems allow pass- words to be the login name itself. This is a fact known by many pene- trators. All login names are excluded because a user that is the owner of several pseudouser accounts can elect to use the login name of one account as the password for all accounts. Similar to the login name issue, this test passes if the password is not a group name derivative. This test passes if the spell program determines that the password is not an English word. A penetrator then could not search the online dictionary to find the password. The spell program also has some built-in rules that go beyond the actual online dictionary in determin- ing what is a proper word, and this routine takes advantage of that. NOTES Programs that use this routine must be compiled with -lsecurity. FILES System password file. System group file. RELATED INFORMATION Functions: getpwent(3), getgrent(3). Commands: spell(1). delim off acceptable_password(3)