fix: Return HTTP 401 instead of 500 when password exceeds bcrypt maximum length

[kiyeonjeon21]

Summary

• Fixes Incorrect HTTP response code 500 is returned when the password is too long #25679
• When file-based authentication is enabled and a password exceeds bcrypt's 72-byte limit, BCrypt.verifyer().verify() throws an IllegalArgumentException that propagates as an unhandled RuntimeException, resulting in HTTP 500
• Catch IllegalArgumentException in EncryptionUtil.doesBCryptPasswordMatch() and return false, so the normal authentication failure flow (HTTP 401) is used instead

Test plan

• Added TestEncryptionUtil.testBCryptPasswordExceedingMaxLength() to verify bcrypt returns false for oversized passwords
• Added TestPasswordStore.testAuthenticateWithTooLongPassword() to verify end-to-end authentication failure without exception
• All existing tests pass (10/10)

Summary by Sourcery

Handle oversized bcrypt passwords in file-based authentication without throwing server errors.

Bug Fixes:

• Catch IllegalArgumentException in bcrypt password verification and treat it as an authentication failure instead of an unhandled error.

Tests:

• Add unit test to verify bcrypt password verification returns false when the password exceeds the supported length.
• Add integration-style test to confirm authenticating with an oversized password fails cleanly without throwing exceptions.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: kiyeonjeon21 / name: Kiyeon Jeon (22e7e1e, 8b61b0d)

[sourcery-ai]

Reviewer's Guide

Adjusts bcrypt-based password verification to treat excessively long passwords as authentication failures (401) instead of server errors (500), and adds focused unit tests for the utility and end-to-end authentication behavior.

Sequence diagram for handling too-long bcrypt passwords during authentication

sequenceDiagram
    actor User
    participant Client
    participant AuthController
    participant PasswordStore
    participant EncryptionUtil
    participant BCrypt

    User->>Client: Submit login form with too_long_password
    Client->>AuthController: POST /login (username, too_long_password)
    AuthController->>PasswordStore: authenticate(username, too_long_password)
    PasswordStore->>EncryptionUtil: doesBCryptPasswordMatch(too_long_password, storedHash)
    EncryptionUtil->>BCrypt: verify(too_long_password.toCharArray(), storedHash)
    BCrypt-->>EncryptionUtil: throw IllegalArgumentException
    EncryptionUtil-->>PasswordStore: return false
    PasswordStore-->>AuthController: authentication failed
    AuthController-->>Client: HTTP 401 Unauthorized
    Client-->>User: Show authentication failed message

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Class diagram for updated bcrypt password verification flow

classDiagram
    class EncryptionUtil {
        +boolean doesBCryptPasswordMatch(String inputPassword, String hashedPassword)
    }

    class BCryptVerifier {
        +BCryptResult verify(char[] passwordChars, String hashedPassword)
    }

    class BCryptResult {
        +boolean verified
    }

    class PasswordStore {
        +boolean authenticate(String username, String password)
    }

    EncryptionUtil ..> BCryptVerifier : uses
    BCryptVerifier ..> BCryptResult : returns
    PasswordStore ..> EncryptionUtil : uses

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File-Level Changes

Change	Details	Files
Handle bcrypt IllegalArgumentException in password verification and treat oversized passwords as failed authentication instead of propagating an error.	Wrap the bcrypt verify call in a try/catch for IllegalArgumentException in the password verification helper Return false when bcrypt throws IllegalArgumentException so the normal authentication failure flow is used	presto-password-authenticators/src/main/java/com/facebook/presto/password/file/EncryptionUtil.java
Add unit test to ensure bcrypt password verification returns false when the password exceeds bcrypt's maximum length.	Import doesBCryptPasswordMatch and assertFalse for clearer test semantics Create a deterministic oversized password string for the test Assert that doesBCryptPasswordMatch returns false for an oversized password against a known bcrypt hash	presto-password-authenticators/src/test/java/com/facebook/presto/password/file/TestEncryptionUtil.java
Add end-to-end authentication test to verify that too-long passwords fail authentication cleanly without exceptions.	Instantiate a PasswordStore configured with a bcrypt-stored password Use a deterministic overlong password string in the test Assert that store.authenticate returns false for the user with the too-long password	presto-password-authenticators/src/test/java/com/facebook/presto/password/file/TestPasswordStore.java

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#25679	Ensure that when file-based authentication is enabled and the supplied password is too long, the server returns HTTP 401 (normal auth failure) instead of HTTP 500.	✅
#25679	Add automated tests to cover the behavior of too-long passwords in bcrypt-based file authentication to prevent regressions.	✅

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[sourcery-ai]

Hey - I've left some high level feedback:

• Catching all IllegalArgumentException instances in doesBCryptPasswordMatch() may hide unrelated problems (e.g., malformed hash); consider either validating input length/format before calling BCrypt.verifyer() or narrowing the catch to only the expected failure case and at least logging unexpected issues.
• The bcrypt maximum length is effectively a protocol boundary here; consider extracting the limit into a named constant and using it (and perhaps trimming or rejecting inputs above it) so the behavior is clearer and easier to adjust if needed.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Catching all IllegalArgumentException instances in doesBCryptPasswordMatch() may hide unrelated problems (e.g., malformed hash); consider either validating input length/format before calling BCrypt.verifyer() or narrowing the catch to only the expected failure case and at least logging unexpected issues.
- The bcrypt maximum length is effectively a protocol boundary here; consider extracting the limit into a named constant and using it (and perhaps trimming or rejecting inputs above it) so the behavior is clearer and easier to adjust if needed.

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[kiyeonjeon21]

Thanks for the feedback! Updated the implementation to validate password byte length upfront (BCRYPT_MAX_PASSWORD_LENGTH = 72) instead of broadly catching IllegalArgumentException. This avoids hiding unrelated issues like malformed hashes.