SG2218 using SHA-1 for SSH key signatures

SG2218 using SHA-1 for SSH key signatures

SG2218 using SHA-1 for SSH key signatures
SG2218 using SHA-1 for SSH key signatures
2 weeks ago - last edited a week ago
Model: TL-SG2218  
Hardware Version: V1
Firmware Version: 1.20.9

I just discovered that my brand new TP-Link SG2218, running firmware released earlier this year, will only use SHA-1 signatures for SSH key-based authentication. SHA-1 was deprecated in 2011, because it is known to be insecure. Sometime in the last few years, Fedora completely disabled SHA-1 in its default system-wide crypto policy. It is literally impossible to SSH to one of these things (if one has any SSH keys set up) without reducing the system-wide crypto level.

 

I don't expect network equipment vendors to move fast, nor do I expect them to keep updating EOL equipment, but that is not what is happening here. This is a brand new managed switch, running its most recent firmware that was released in 2025. There is absolutely no excuse for this level of pure laziness.

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#1
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1 Accepted Solution
Re:SG2218 using SHA-1 for SSH key signatures-Solution
a week ago - last edited a week ago

 Hi @ipilcher , after analysis, we have identified the cause and will fix it as soon as possible in the next software version. Thank you!

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#6
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Re:SG2218 using SHA-1 for SSH key signatures
2 weeks ago

  @ipilcher 

To help assist and streamline the identification of the behavior, we recommend sending an email to forumsupport.usa@tp-link.com with the following information:

Subject: [Forum Escalation][ID] 

Forum Nickname: 

Thread URL: 

Model&Version: 

Description: 

Any Other Relevant Information (Logs, Config Files, Images, etc.): [

Once sent, a ticket will be created in our support system, and a member of the team will follow up to gather more information or troubleshoot a cause.

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#2
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Re:SG2218 using SHA-1 for SSH key signatures
a week ago - last edited a week ago

 Hi @ipilcher , I checked, and it seem already support SHA2, and it supports RSA-SHA2-256 by default, which uses SHA2 as the key signature algorithm. Could you please share us where do you get the information about SHA1 at TL-SG2218 V1 / FW 1.20.9 ? And could you please help to upgrade to the lasted FW and check?

 

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#3
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Re:SG2218 using SHA-1 for SSH key signatures
a week ago

  @Penry.huang 

 

You are correct that the switch supports SHA-2 signatures for host keys.  That's not the issue here.

 

The algorithm in question is the signature algorithm used for user keys (when using key-based, rather than password-based) authentication.

 

For example, when I connect to the switch with ssh -vvv ..., the output includes the following:

 

debug1: kex: host key algorithm: rsa-sha2-256

 

This confirms that the switch does support SHA-256 (SHA-2) for host key signatures.

 

Later in the output, the following appears:

 

debug3: sign_and_send_pubkey: signing using ssh-rsa SHA256:EOg4nSUl05t08gAElH+wvzM1zDHHa0rI6KjL3mS5iDY

 

This can be a misleading, because of the fact that "SHA256" appears in the output.  However, that refers to the algorithm used to create the key fingerprint, not the signature hash algorithm.  The latter algorithm is identified by signing using ssh-rsa, which identifies the signature algorithm (RSA with SHA-1).

 

A connection to a different system, using SHA-256 as the signature algorithm, shows this:

 

debug3: sign_and_send_pubkey: signing using rsa-sha2-256 SHA256:EOg4nSUl05t08gAElH+wvzM1zDHHa0rI6KjL3mS5iDY

 

Hopefully this explains the issue.

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#4
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Re:SG2218 using SHA-1 for SSH key signatures
a week ago

Hi  @ipilcher , we will check.

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#5
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Re:SG2218 using SHA-1 for SSH key signatures-Solution
a week ago - last edited a week ago

 Hi @ipilcher , after analysis, we have identified the cause and will fix it as soon as possible in the next software version. Thank you!

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#6
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