sha1pass

sha1pass [PASSWORD]

sha1pass is a utility designed to generate a SHA1 cryptographic hash of a given password. This hash is typically used in password files (like /etc/shadow) for user authentication on Unix-like operating systems. While sha1pass provides a quick way to create these hashes, it's crucial to understand that SHA1 is now considered cryptographically weak and susceptible to collision attacks, making it unsuitable for new deployments requiring robust security.

The command can accept the password directly as a command-line argument or read it securely from standard input if no argument is provided. Upon successful execution, it outputs the SHA1 hash string to standard output, often formatted with a prefix (e.g., {SHA} or $sha1$) for compatibility with system password databases. Its primary use case today is maintaining compatibility with older systems or applications that still rely on SHA1 for password storage, rather than for secure new implementations.

Security Risk: SHA1 is cryptographically broken and vulnerable to collision attacks. It should not be used for new password hashing implementations. Stronger algorithms like bcrypt, scrypt, or Argon2 are highly recommended.
Legacy Use: sha1pass is primarily for compatibility with older systems or applications that still rely on SHA1 hashes.
No Salt: Unlike modern password hashing algorithms, sha1pass often produces unsalted SHA1 hashes, making them more susceptible to rainbow table attacks if not explicitly combined with a salt by the system using it.

The output is the SHA1 hash string, usually prefixed with {SHA} or $sha1$ for use in /etc/shadow files. For example, a password 'test' might produce '{SHA}A94A8FE5CCB19BA61C4C0873D391E987982FAACF'.

If no password argument is provided, sha1pass reads the password from standard input, typically in a non-echoing manner, improving security by preventing the password from appearing in shell history or being visible.

The sha1pass utility emerged as part of the evolving landscape of password management in Unix-like systems, particularly as SHA1 gained prominence as a cryptographic hash function in the late 1990s and early 2000s. It was integrated into utilities often associated with the shadow-utils package, which manages secure user account information including hashed passwords in files like /etc/shadow. Its introduction marked a move towards more secure hashing than older methods (like DES-based crypt(3)), albeit one that has since been superseded. Over time, as SHA1's cryptographic weaknesses became apparent, its use for new password storage has diminished significantly, but sha1pass remains available for backward compatibility with existing systems or legacy applications that still employ SHA1.

passwd(1), useradd(8), crypt(3), mkpasswd(1), openssl(1)