pgpassword

Overview ¶

Package pgpassword implements the PostgreSQL "md5" password verifier (hashcat mode 12): the value stored in pg_authid.rolpassword (pg_shadow.passwd) when a role uses md5 authentication. It is an offline credential primitive — compute the stored value for a candidate password, or verify a candidate against a value captured from a pg_authid / pg_dumpall --globals dump. It completes the database-credential pair with mysql_password (the MySQL/MariaDB sibling) and fits the credential toolkit's compute/verify pattern (nt_hash, ldap_password, md5crypt). Pure offline compute from operator-supplied strings; no network or device.

Algorithm ¶

PostgreSQL's pg_md5_encrypt (src/common/md5_common.c) salts the password with the role name before a single MD5:

"md5" + hex( MD5( password ‖ username ) )

The stored value is the literal "md5" followed by 32 lowercase hex digits. The salt is the role name, so the same password under two different roles yields different stored values — verification therefore requires the username as well as the candidate password.

Wrap-vs-native judgement ¶

Native. The verifier is a single crypto/md5 over password+username plus hex — there is nothing to wrap; the only third-party option would be a PostgreSQL client/driver, unwarranted for a pure hash. Consistent with internal/mysqlpw, internal/nthash, and internal/ldappw owning their crypto in-tree.

Verifiable / no confidently-wrong output ¶

Strongest verification class — the construction is unambiguous (a single salted MD5, no rounds) and is exactly PostgreSQL's documented pg_md5_encrypt, gated against the stdlib-hashlib oracle ("md5"+md5(password+rolname)). A malformed stored value (missing "md5" prefix / wrong length / non-hex) is rejected with an error, never silently "verified". Out of scope: SCRAM-SHA-256 (the PostgreSQL 10+ default, hashcat 28600 — salted + iterated PBKDF2/HMAC, a different primitive) and the obsolete pre-7.2 plain-MD5 form.