[TASK] Enforce read-only semantics for EXAMINE-selected mailboxes

[Aravinda-HWK]

What needs to be done?

Description

The current IMAP implementation does not enforce read-only semantics when a mailbox is selected using the EXAMINE command.

According to the IMAP specification, a mailbox opened with EXAMINE must be treated as read-only, meaning that any mutating operations should be restricted.

However, the current implementation allows state-changing commands such as EXPUNGE and CLOSE to proceed even when the mailbox is in read-only mode. This behavior is explicitly noted as a gap in:

• selection.go (CLOSE handling)
• message.go (EXPUNGE handling)

---

Expected Behavior

When a mailbox is selected using EXAMINE:

• The session must be marked as read-only
• The following commands must be restricted:

🔴 EXPUNGE

• Must fail in read-only mode
• Should return an appropriate tagged response (e.g., NO)

🔴 CLOSE

• Must not remove messages
• Should behave safely without altering mailbox state

🔴 Other mutating commands (if applicable)

• Commands like STORE, APPEND, COPY, etc., should also be reviewed and restricted if they modify mailbox state

---

Current Behavior

• EXPUNGE executes even in read-only mode
• CLOSE may remove messages despite EXAMINE
• No consistent enforcement of read-only state across command handlers

---

Scope of Work

• Introduce a read-only flag in the session/mailbox state when EXAMINE is used
• Update command handlers to check this flag before performing mutations
• Ensure all mutating commands respect read-only mode
• Return proper IMAP responses for restricted operations

---

Suggested Approach

1. Update mailbox/session state:

session.readOnly = true // when EXAMINE is used

2. Add guard checks in mutating commands:

if session.readOnly {
    return NO response (e.g., "Mailbox is read-only")
}

3. Audit all commands that modify mailbox state:

Command	Action Required
EXPUNGE	Return NO in read-only mode
CLOSE	Skip expunge step; do not alter state
STORE	Return NO in read-only mode
APPEND	Return NO in read-only mode
COPY	Review and restrict if state is modified

---

Acceptance Criteria

• Mailbox opened via EXAMINE is strictly read-only
• EXPUNGE fails with appropriate NO response
• CLOSE does not remove messages
• No state mutation occurs in read-only mode
• Behavior aligns with IMAP RFC expectations
• Existing functionality for SELECT (read-write) remains unchanged

---

Additional Notes

• This change is important for protocol compliance and client compatibility
• Many IMAP clients rely on correct read-only enforcement for safe operations
• The implementation should be consistent across all command handlers

---

References

• selection.go:223 — CLOSE handling gap noted
• message.go:1575 — EXPUNGE handling gap noted
• RFC 3501 — IMAP4rev1, Section 6.3.2 (EXAMINE Command)

# [TASK] Enforce read-only semantics for EXAMINE-selected mailboxes

Description

The current IMAP implementation does not enforce read-only semantics when a mailbox is selected using the EXAMINE command.

According to the IMAP specification, a mailbox opened with EXAMINE must be treated as read-only, meaning that any mutating operations should be restricted.

However, the current implementation allows state-changing commands such as EXPUNGE and CLOSE to proceed even when the mailbox is in read-only mode. This behavior is explicitly noted as a gap in:

• selection.go:223 (CLOSE handling)
• message.go:1575 (EXPUNGE handling)

---

Expected Behavior

When a mailbox is selected using EXAMINE:

• The session must be marked as read-only
• The following commands must be restricted:

🔴 EXPUNGE

• Must fail in read-only mode
• Should return an appropriate tagged response (e.g., NO)

🔴 CLOSE

• Must not remove messages
• Should behave safely without altering mailbox state

🔴 Other mutating commands (if applicable)

• Commands like STORE, APPEND, COPY, etc., should also be reviewed and restricted if they modify mailbox state

---

Current Behavior

• EXPUNGE executes even in read-only mode
• CLOSE may remove messages despite EXAMINE
• No consistent enforcement of read-only state across command handlers

---

Scope of Work

• Introduce a read-only flag in the session/mailbox state when EXAMINE is used
• Update command handlers to check this flag before performing mutations
• Ensure all mutating commands respect read-only mode
• Return proper IMAP responses for restricted operations

---

Suggested Approach

1. Update mailbox/session state:

session.readOnly = true // when EXAMINE is used

2. Add guard checks in mutating commands:

if session.readOnly {
    return NO response (e.g., "Mailbox is read-only")
}

3. Audit all commands that modify mailbox state:

Command	Action Required
EXPUNGE	Return NO in read-only mode
CLOSE	Skip expunge step; do not alter state
STORE	Return NO in read-only mode
APPEND	Return NO in read-only mode
COPY	Review and restrict if state is modified

---

Acceptance Criteria

• Mailbox opened via EXAMINE is strictly read-only
• EXPUNGE fails with appropriate NO response
• CLOSE does not remove messages
• No state mutation occurs in read-only mode
• Behavior aligns with IMAP RFC expectations
• Existing functionality for SELECT (read-write) remains unchanged

---

Additional Notes

• This change is important for protocol compliance and client compatibility
• Many IMAP clients rely on correct read-only enforcement for safe operations
• The implementation should be consistent across all command handlers

---

References

• selection.go — CLOSE handling gap noted
• message.go — EXPUNGE handling gap noted
• [RFC 3501 — IMAP4rev1, Section 6.3.2 (EXAMINE Command)](https://datatracker.ietf.org/doc/html/rfc3501#section-6.3.2)