unable to create SshPublicKey object from public key string

Question

Hi,

I'm trying to create a SshPublicKey object from a public key string that has been generated using the ssh-keygen command in a cmd. I get an exception that says "Error while decoding key. ---> System.InvalidOperationException: Data too long."

this is the code I'm using:

        var stream = new MemoryStream();
        var writer = new StreamWriter(stream);
        writer.Write(publicKeyString);
        writer.Flush();
        stream.Position = 0;

        return new SshPublicKey(stream);

The public key that was generated is in this format:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDJrQZgKrcqeRsSSpTR4J5w013Ax2ZThIWhIZrSravuRo3XojUxunwDVoTku3PvJGbcL8sxFfCHI70myCk/6S7TK2rwUAmQoEJxV+DGwldBpkRoPRHy8eK31CDLHbkPpCIYJzacoteXZQXztLSKnBDqyhvQ5ILSTlnsYgNrJxoyDPUumXoD3ZAi7ReSOqDOqxOwkT5Nr9I7u1AYv4mDx8kStnWYQBBVbdSNADJJMQ/YG85Rhe4hS3B5zt/8TB+w/EIvej9Fh6+qDTVbgt+J/JrL6TL+EFXP+mtJKVTVYo09Nk5BA30V16ect48CGmvas+NPyn4k/ZYNH4TJRbk4YzvR corp\mattias.andries@PF-MAndries1

However a public key that is in this format does seem to work:

---- BEGIN SSH2 PUBLIC KEY ----
Comment: ""
AAAAB3NzaC1yc2EAAAABJQAAAQEAg8+3TU/U8OSEocpEH/V1s4BvtjrHt1li5uH3
GBU4EzpC4cgVQUBXliWwQhVQcseSpwtBoK6n/WN+LRGqdBzILkl9ahFj1KXi9zW1
dMeSEIElU6R7Tb9wBBVFUng+U0fiYt47QmfiONgEXm70ZrrHXPKKnu/XG3PboCDI
7IzhWSzrbTGcFTj3c/ZkJVIZkiZnOzvMD0SWXEdkD0mKAuoYunBYucSILjYbnL/P
AaftEwZtu8/GdS4hWseNBM3fv8xDBF/7Z5CzNAlDTrGVaKQqThMTlKzxcalsmzvL
gwBvITPypX5VIzrVYAXPHirR0+tAhr+/wbcO23WP662N0GwIHw==
---- END SSH2 PUBLIC KEY ----

Any ideas on why the first key format gets the exception but the second key works fine?

Thanks.

Answer 1

Hi,

The first format is the format of OpenSSH's authenticated_keys file, which is supposed to contain a list of public keys, and can be loaded using SshPublicKey.LoadPublicKeys static method.

Comments

So the reason why I asked is because clients send us their public keys for us to store in a database that we retrieve when they try to log in to check against their private key. We save the public keys as strings.

Would I have to retrieve the public key, save it in a file, then call the SshPublicKey.LoadPublicKeys method? Does this work with the second format as well? Our clients use all kinds of different formats and we should support all of them.

Thanks.

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We can make the SshPublicKey constructor accept this format as well, but then what about authorized_keys with multiple entries? Throw an exception? Only load the first one? None if this looks like a good option... Or perhaps it would be better to make SshPublicKey.LoadPublicKeys accept the other stand-alone key formats as well? We'll consider this for one of the next releases.

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Thanks! We'll work around it for now. Appreciate the help

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Specify an  index parameter to select the key or just support one key at a time.