Synchronet v3.17b-Win32 (install) has been released (Jan-2019).

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faq:tcpip [2019/01/17 16:17]
digital man [FTP NAT] Fixed typos. Removed stale info.
faq:tcpip [2019/04/02 13:51]
digital man Added ssh cipher algo work-around
Line 14: Line 14:
   * [[#​bandwidth|How many nodes/​clients/​users can I support with my Internet connection]]? ​   * [[#​bandwidth|How many nodes/​clients/​users can I support with my Internet connection]]? ​
   * [[#​block_hackers|Can Synchronet automatically block the IP address of hackers]]?   * [[#​block_hackers|Can Synchronet automatically block the IP address of hackers]]?
-  * [[#ssh_kex_algo|Why do some SSH clients fail to connect to my BBS]]?+  * [[#ssh_algo|Why do some SSH clients fail to connect to my BBS]]?
   * [[#​ssh_session_key|How do resolve the SSH error: importing session key to protect private key]]?   * [[#​ssh_session_key|How do resolve the SSH error: importing session key to protect private key]]?
  
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 Yes, see [[howto:​Block-Hackers]] for detailed instructions. Yes, see [[howto:​Block-Hackers]] for detailed instructions.
  
-===== SSH Kex Algo =====+===== SSH Algo =====
 :?: **Question:​**\\ :?: **Question:​**\\
 Why do some SSH clients (e.g. [[http://​www.openssh.com/​|OpenSSH]]) fail to connect to the Synchronet SSH Server? Why do some SSH clients (e.g. [[http://​www.openssh.com/​|OpenSSH]]) fail to connect to the Synchronet SSH Server?
 +
 +:!: **Answer:​**\\
 +SSH supports a variety of cryptographic algorithms for encryption (privacy), integrity (mac) and authentication (key-exchange). As stronger algorithms are introduced, older (less-strong) algorithms are deprecated. As a result, when using a newer version of any SSH client (especially OpenSSH), it may fail to connect to SSH servers which only support less-than-the-strongest (newest) algorithms. There is no permanent solution to this issue as cryptographic algorithms are constantly improving (becoming stronger) and older (weaker) algorithms are going out of favor.
 +
 +
 +==== SSH Cipher Algo ====
 +
 +Example:
 +  $ ssh vert.synchro.net
 +  Unable to negotiate with vert.synchro.net port 22: no matching cipher found. Their offer: aes128-cbc,​3des-cbc
 +  ​
 +Workarounds for OpenSSH:
 +
 +  $ ssh -c aes128-cbc user@yourbbs.com
 +  ​
 +or in the ''​~/​.ssh/​config''​ file (OpenSSH v6):
 +
 +  Host yourbbs.com
 +  Ciphers aes128-cbc
 +  ​
 +==== SSH Kex Algo ====
  
 Example: Example:
   $ ssh vert.synchro.net   $ ssh vert.synchro.net
-  ​Received disconnect from 71.95.196.34:​ 2: Handshake failed+  Received disconnect from 71.95.196.34:​ 2: Handshake failed
   ​   ​
 or: or:
   Unable to negotiate with legacyhost: no matching key exchange method found.   Unable to negotiate with legacyhost: no matching key exchange method found.
   Their offer: diffie-hellman-group1-sha1   Their offer: diffie-hellman-group1-sha1
- 
-:!: **Answer:​**\\ 
- 
-//**NOTE: This has been fixed in CVS now.**// 
- 
-Synchronet uses [[http://​www.cs.auckland.ac.nz/​~pgut001/​cryptlib/​|Cryptlib]],​ a cryptographic library, for SSH and TSL/SSL support in Synchronet. Cryptlib'​s v3.4.2 SSH support uses an older "Key Exchange Algorithm"​. OpenSSH has deprecated support for this older key exchange algorithm. Cryptlib v3.4.4, the currently latest version of Cryptlib now used by Synchronet, does not have this problem. 
  
 From the OpenSSH [[http://​www.openssh.com/​legacy.html|legacy page]]: From the OpenSSH [[http://​www.openssh.com/​legacy.html|legacy page]]:
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 Note: Run ''​ssh -V''​ to see what version of OpenSSH you have. Note: Run ''​ssh -V''​ to see what version of OpenSSH you have.
  
-:!: **Answer:​**\\+==== SSH MAC Algo ==== 
 Another observed problem is with the negotiated Message Authentication Code (MAC) algorithm. Another observed problem is with the negotiated Message Authentication Code (MAC) algorithm.
  

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