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|  Topic: TLS/SSL sever using commonly used prime numbers |  |  
| Author |  |  
| danielc 
 
 
 Joined: 15 Jul 2022
 Posts: 3
 Location: HK
 
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|  Posted: Mon 03 Oct '22 13:48    Post subject: TLS/SSL sever using commonly used prime numbers |   |  
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| Hello, 
 Our apache server have been audited and the following messages have been given:
 
 
  	  | Quote: |  	  | Vulnerability Type TLS/SSL sever using commonly used prime numbers
 
 Description of Vulnerability
 The server is using a common or default prime number as a parameter during the Diffie-Hellman key exchange. This makes the secure session vulnerable to a precomputation attack.  An attacker may be able to deduce the shared secret for the handshake and decrypt the session.
 
 Suggested Actions
 It is recommended to use a 2048-bit or stronger Diffie-Hellman group.
 
 
 Vulnerability Solution:
 Configure the server to use a randomly generated Diffie-Hellman group. It's recommend that you generate a 2048-bit group. The simplest way of generating a new group is to use OpenSSL:
 openssi dhparam -out dhparams.pem 2048
 To use the DH parameters in newer versions of Apache (2.4.8 and newer) and OpenSSL 1.0.2 or later, you can directly specify your DH params file as follows:
 SSLOpenSSLConfCmd DHParameters "(path to dhparams.pem)*
 If you are using Apache with LibreSSL, or Apache 2.4.7 and OpenSSL 0.9.8a or later, you can append the DHparams you generated
 
 
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 Give that our Apache version is only 2.4.6 currently, what method should we actually use for solving this problem?
 
 Should we use
 SSLDHParametersFile "/PATH/TO/YOUR/CERTIFICATE/FILES/dhparams.pem" or something else?
 
 Thanks
 Daniel
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| danielc 
 
 
 Joined: 15 Jul 2022
 Posts: 3
 Location: HK
 
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|  Posted: Mon 03 Oct '22 13:56    Post subject: |   |  
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| Additionally, It looks like to use SSLDHParametersFile, it needs to be patched 
 https://bz.apache.org/bugzilla/show_bug.cgi?id=49559
 
 But I am not sure if that fix meanss we can use SSLDHParametersFile in 2.4.6, or we should use something else...
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| James Blond Moderator
 
  
 Joined: 19 Jan 2006
 Posts: 7442
 Location: EU, Germany, Next to Hamburg
 
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|  Posted: Tue 04 Oct '22 13:14    Post subject: |   |  
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| use the following 
 
 
  	  | Code: |  	  | SSLOpenSSLConfCmd ECDHParameters secp521r1
 SSLOpenSSLConfCmd Curves sect571r1:sect571k1:secp521r1:sect409k1:sect409r1:secp384r1
 
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