prestodb/presto · error · HashedPasswordException

Hashing algorithm of password cannot be determined

Error message

Hashing algorithm of password cannot be determined

What it means

PasswordStore.getHashedPassword throws HashedPasswordException("Hashing algorithm of password cannot be determined") when a stored password entry does not match a recognized hash format. getHashingAlgorithm() recognizes bcrypt ($2a$/$2b$/$2y$ prefixes) and PBKDF2-WITHHMACSHAx entries; anything else (plaintext, crypt, malformed line) is rejected at load time.

Source

Thrown at presto-password-authenticators/src/main/java/com/facebook/presto/password/file/PasswordStore.java:122

    private static List<String> readPasswordFile(File file)
    {
        try {
            return Files.readAllLines(file.toPath());
        }
        catch (IOException e) {
            throw new PrestoException(CONFIGURATION_UNAVAILABLE, "Failed to read password file: " + file, e);
        }
    }

    private static HashedPassword getHashedPassword(String hashedPassword)
    {
        switch (getHashingAlgorithm(hashedPassword)) {
            case BCRYPT:
                return password -> doesBCryptPasswordMatch(password, hashedPassword);
            case PBKDF2:
                return password -> doesPBKDF2PasswordMatch(password, hashedPassword);
        }
        throw new HashedPasswordException("Hashing algorithm of password cannot be determined");
    }

    public interface HashedPassword
    {
        boolean matches(String password);
    }
}

View on GitHub (pinned to 55bb57d202)

Solutions

1. Rehash the offending entry with bcrypt or PBKDF2-WORKOUT/S (e.g. htpasswd -bnBC 10) so the line has a recognizable $2x$ or PBKDF2-WITHHMACSHAx prefix
2. Audit every line of the password file for plaintext, crypt, or malformed entries and fix or remove them
3. Ensure no comment/blank/garbage lines; each line must be user:validhash
4. Regenerate the file entirely with supported hash tooling if many entries are invalid

Example fix

// before (password file)
alice:plainpassword
// after
alice:$2y$10$DwtS8Zk0KqQXyVZ8m9nZQeJ7O1z0K0xZ4qZ8hGxWq2nKq1eK2ZKfG

// Validate each password-file line before loading:
Pattern ok = Pattern.compile("^\\$2[aby]\\$.*|^PBKDF2-WITHHMACSHA.*");
for (String line : Files.readAllLines(Paths.get(passwordFile))) {
    String hash = line.split(":", 2)[1];
    if (!ok.matcher(hash).matches()) {
        throw new IllegalStateException("Unsupported hash for entry: " + line.split(":", 2)[0]);
    }
}

try {
    store = new FilePasswordStore(config);
} catch (PrestoException e) {
    if (e.getCause() instanceof HashedPasswordException) {
        log.error("Unrecognized hash format in password file: %s", e.getCause().getMessage());
    }
    throw e;
}

When it happens

Trigger: loadPasswordFile() parses each line via getHashedPassword(); a line whose prefix does not identify BCRYPT or PBKDF2 (plaintext password, crypt hash, truncated/malformed hash) triggers the exception while loading the password file.

Common situations: Password file generated by a tool writing plaintext or crypt-style hashes; hand-edited file with a truncated hash; migration from another system (htpasswd crypt, LDAP) without rehashing; stray comment or blank lines confusing the parser.

Related errors

• ACCUMULO_TABLE_EXISTS
• UNEXPECTED_ACCUMULO_ERROR
• NOT_SUPPORTED
• ARROW_INTERNAL_ERROR
• JDBC_ERROR

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/6d40e8675659445f. Report an issue: GitHub.