IMAP/POP3 Pentesting Notes

Protocol Overview

Basic Information

IMAP:

• Port: TCP 143 (default), TCP 993 (IMAPS)

• Protocol Type: Application layer, client-server

• Purpose: Email access and management on server

• Security: Plain text by default, supports SSL/TLS

POP3:

• Port: TCP 110 (default), TCP 995 (POP3S)

• Protocol Type: Application layer, client-server

• Purpose: Email retrieval and deletion

• Security: Plain text by default, supports SSL/TLS

Protocol Differences

Feature	IMAP	POP3
Storage	Server-side	Client-side
Sync	Multi-device sync	Single device
Management	Full email/folder management	Basic retrieval/deletion
Connection	Persistent connection	Connect, download, disconnect

Initial Enumeration

Port Scanning

# Basic scan
nmap -p110,143,993,995 -sV <target>

# Aggressive scan
nmap -p110,143,993,995 -sV -sC -A <target>

# All related scripts
nmap -p110,143,993,995 --script imap* pop3* <target>

Banner Grabbing

# IMAP
nc -nv <target> 143

# POP3
nc -nv <target> 110

# IMAPS
openssl s_client -connect <target>:993

# POP3S
openssl s_client -connect <target>:995

Authentication Testing

IMAP Authentication

# Using netcat
nc -nv <target> 143
a001 LOGIN username password

# Using openssl for IMAPS
openssl s_client -connect <target>:993
a001 LOGIN username password

# Using curl
curl -k 'imaps://<target>' --user username:password

POP3 Authentication

# Using netcat
nc -nv <target> 110
USER username
PASS password

# Using openssl for POP3S
openssl s_client -connect <target>:995
USER username
PASS password

Brute Force Attacks

Using Hydra

# IMAP
hydra -l user -P passwords.txt <target> imap
hydra -L users.txt -P passwords.txt <target> imap

# POP3
hydra -l user -P passwords.txt <target> pop3
hydra -L users.txt -P passwords.txt <target> pop3

Using Metasploit

# IMAP
use auxiliary/scanner/imap/imap_version
use auxiliary/scanner/imap/imap_login

# POP3
use auxiliary/scanner/pop3/pop3_version
use auxiliary/scanner/pop3/pop3_login

Command Reference

IMAP Commands

Command	Description	Example
LOGIN	Authenticate	a001 LOGIN user pass
LIST	List mailboxes	a002 LIST "" "*"
SELECT	Select mailbox	a003 SELECT INBOX
FETCH	Retrieve message	a004 FETCH 1 BODY[]
STORE	Modify flags	a005 STORE 1 +FLAGS (\Deleted)
EXPUNGE	Delete marked messages	a006 EXPUNGE
LOGOUT	End session	a007 LOGOUT

POP3 Commands

Command	Description	Example
USER	Set username	USER username
PASS	Set password	PASS password
STAT	Get mailbox stats	STAT
LIST	List messages	LIST
RETR	Retrieve message	RETR 1
DELE	Delete message	DELE 1
QUIT	End session	QUIT

Common NSE Scripts

# IMAP Scripts
nmap -p143,993 --script imap-capabilities <target>
nmap -p143,993 --script imap-ntlm-info <target>
nmap -p143,993 --script imap-brute <target>

# POP3 Scripts
nmap -p110,995 --script pop3-capabilities <target>
nmap -p110,995 --script pop3-ntlm-info <target>
nmap -p110,995 --script pop3-brute <target>

SSL/TLS Testing

# Test IMAPS
openssl s_client -connect <target>:993 -crlf
nmap -p993 --script ssl-enum-ciphers <target>

# Test POP3S
openssl s_client -connect <target>:995 -crlf
nmap -p995 --script ssl-enum-ciphers <target>

Configuration Files

Server Configuration

• Dovecot: /etc/dovecot/dovecot.conf

• Courier: /etc/courier/imapd, /etc/courier/pop3d

• Cyrus: /etc/imapd.conf, /etc/cyrus.conf

Security Files

• SSL Certificates: Often in /etc/ssl/certs/

• Authentication: Various PAM or SASL configs

Common Vulnerabilities

1. Authentication Issues:

   • Clear text transmission

   • Weak credentials

   • No rate limiting

   • Authentication bypass

2. SSL/TLS Problems:

   • Weak ciphers

   • Outdated protocols

   • Invalid certificates

   • Missing encryption

3. Configuration:

   • Debug logging enabled

   • Anonymous access

   • Unencrypted ports open

   • Excessive information disclosure

Post Exploitation

Information Gathering

• Access email content

• Extract attachments

• Find sensitive data

• Gather internal addresses

• Map email relationships

Privilege Escalation

• Check attachment permissions

• Search for credentials

• Test for command injection

• Access configuration files

Response Codes

IMAP Response Codes

Code	Meaning
OK	Command completed
NO	Command failed
BAD	Invalid command
PREAUTH	Authenticated connection
BYE	Server signing off

POP3 Response Codes

Code	Meaning
+OK	Command successful
-ERR	Command failed

Best Practices for Pentesting

1. Initial Reconnaissance:

   • Version identification

   • SSL/TLS check

   • Capability enumeration

   • Authentication methods

2. Deep Enumeration:

   • Vulnerability scanning

   • User enumeration

   • SSL/TLS analysis

   • Configuration review

3. Documentation:

   • Server details

   • Found vulnerabilities

   • Access methods

   • Sensitive data

4. Risk Assessment:

   • Impact analysis

   • Data sensitivity

   • Attack vectors

   • Mitigation recommendations

Additional Tools

1. swaks:

   swaks --to [email protected] --server <target>

2. evolution:

   evolution --account="imap://<target>"

3. Custom Python Scripts:

   # Basic IMAP connection
   import imaplib
   mail = imaplib.IMAP4("<target>")
   mail.login(user, password)

4. Misc Tools:

   • thunderbird (GUI client)

   • mutt (terminal client)

   • alpine (terminal client)