ExportedUserRecord.password_hash returns the redacted placeholder instead of None #1007

Describe your environment

• Operating System version: macOS 26 (also expected on any platform)
• Firebase SDK version: firebase-admin 7.8.0 (main at 740b9ee)
• Firebase Product: auth
• Python version: 3.11

Describe the problem

When the service account is not allowed to read password hashes, the Auth backend returns base64("REDACTED"), i.e. the JSON string "UkVEQUNURUQ=", in the passwordHash field of accounts:batchGet. PR #352 added code so that ExportedUserRecord.password_hash returns None in that case, and the docstring says: "If no password is set, or if the service account doesn't have permission to read the password, then this is None."

This does not work. The marker is defined as B64_REDACTED = base64.b64encode(b'REDACTED'), which is a bytes object (b'UkVEQUNURUQ='). The value from the decoded JSON response is a str, and in Python 3 'UkVEQUNURUQ=' == b'UkVEQUNURUQ=' is False. So password_hash returns 'UkVEQUNURUQ=', which looks like a real base64 hash. The existing unit test passes a bytes value into ExportedUserRecord, so it never covers the real JSON path.

The Node.js SDK compares against a string: const B64_REDACTED = Buffer.from('REDACTED').toString('base64'); and then response.passwordHash === B64_REDACTED.

Impact: code that follows the docs and checks user.password_hash is None to skip accounts without a readable hash (for example, when exporting users for import_users()) instead gets the placeholder, and may import the literal bytes REDACTED as the password hash.

Steps to reproduce:

import base64
from firebase_admin import auth

user = auth.ExportedUserRecord({
    'localId': 'user',
    'passwordHash': base64.b64encode(b'REDACTED').decode(),  # what the JSON response contains
})
print(repr(user.password_hash))  # 'UkVEQUNURUQ=', expected None

The same happens end to end through auth.list_users() when the mocked HTTP response body contains "passwordHash": "UkVEQUNURUQ=". A real hash such as "aGFzaA==" is returned unchanged, as expected.

Relevant Code:

firebase_admin/_user_mgt.py:

B64_REDACTED = base64.b64encode(b'REDACTED')
...
        if password_hash == B64_REDACTED:
            return None

This change was drafted with Claude Code (claude-opus-5-5); the test results above are from the runs described.