Script `ssl-dh-params`

Script types: portrule
Categories: vuln, safe
Download: https://svn.nmap.org/nmap/scripts/ssl-dh-params.nse

Script Summary

Weak ephemeral Diffie-Hellman parameter detection for SSL/TLS services.

This script simulates SSL/TLS handshakes using ciphersuites that have ephemeral Diffie-Hellman as the key exchange algorithm.

Diffie-Hellman MODP group parameters are extracted and analyzed for vulnerability to Logjam (CVE 2015-4000) and other weaknesses.

Opportunistic STARTTLS sessions are established on services that support them.

Script Arguments

tls.servername: See the documentation for the tls library.
smbdomain, smbhash, smbnoguest, smbpassword, smbtype, smbusername: See the documentation for the smbauth library.
mssql.domain, mssql.instance-all, mssql.instance-name, mssql.instance-port, mssql.password, mssql.protocol, mssql.scanned-ports-only, mssql.timeout, mssql.username: See the documentation for the mssql library.
smtp.domain: See the documentation for the smtp library.
randomseed, smbbasic, smbport, smbsign: See the documentation for the smb library.
vulns.short, vulns.showall: See the documentation for the vulns library.

Example Usage

nmap --script ssl-dh-params <target>

Script Output

Host script results:
| ssl-dh-params:
|   VULNERABLE:
|   Transport Layer Security (TLS) Protocol DHE_EXPORT Ciphers Downgrade MitM (Logjam)
|     State: VULNERABLE
|     IDs:  BID:74733  CVE:CVE-2015-4000
|       The Transport Layer Security (TLS) protocol contains a flaw that is triggered
|       when handling Diffie-Hellman key exchanges defined with the DHE_EXPORT cipher.
|       This may allow a man-in-the-middle attacker to downgrade the security of a TLS
|       session to 512-bit export-grade cryptography, which is significantly weaker,
|       allowing the attacker to more easily break the encryption and monitor or tamper
|       with the encrypted stream.
|     Disclosure date: 2015-5-19
|     Check results:
|       EXPORT-GRADE DH GROUP 1
|         Ciphersuite: TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
|         Modulus Type: Non-safe prime
|         Modulus Source: sun.security.provider/512-bit DSA group with 160-bit prime order subgroup
|         Modulus Length: 512 bits
|         Generator Length: 512 bits
|         Public Key Length: 512 bits
|     References:
|       https://weakdh.org
|       https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-4000
|       https://www.securityfocus.com/bid/74733
|
|   Diffie-Hellman Key Exchange Insufficient Diffie-Hellman Group Strength
|     State: VULNERABLE
|       Transport Layer Security (TLS) services that use Diffie-Hellman groups of
|       insuffficient strength, especially those using one of a few commonly shared
|       groups, may be susceptible to passive eavesdropping attacks.
|     Check results:
|       WEAK DH GROUP 1
|         Ciphersuite: TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
|         Modulus Type: Safe prime
|         Modulus Source: Unknown/Custom-generated
|         Modulus Length: 512 bits
|         Generator Length: 8 bits
|         Public Key Length: 512 bits
|     References:
|       https://weakdh.org
|
|   Diffie-Hellman Key Exchange Potentially Unsafe Group Parameters
|     State: VULNERABLE
|       This TLS service appears to be using a modulus that is not a safe prime and does
|       not correspond to any well-known DSA group for Diffie-Hellman key exchange.
|       These parameters MAY be secure if:
|       - They were generated according to the procedure described in FIPS 186-4 for
|         DSA Domain Parameter Generation, or
|       - The generator g generates a subgroup of large prime order
|       Additional testing may be required to verify the security of these parameters.
|     Check results:
|       NON-SAFE DH GROUP 1
|         Cipher Suite: TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
|         Modulus Type: Non-safe prime
|         Modulus Source: Unknown/Custom-generated
|         Modulus Length: 1024 bits
|         Generator Length: 1024 bits
|         Public Key Length: 1024 bits
|     References:
|_      https://weakdh.org

Requires

Author:

Jacob Gajek