Re: Data signing (for Git signing)

[Aris Adamantiadis <aris@xxxxxxxxxx>]

Hi,


Thanks for looking at this, this is a great idea.

You're probably seeing nothing because the signature is a byte array and 
not a base64-encoded string, so printf will not show you any content 
after a null byte, which is probably not what you expect. Look around 
how ssh_strings can be managed from your code (however I think most of 
these interfaces are private).

You require a session object not because you need to be connected 
(actually it would work with only session = ssh_new()) but because the 
error management requires a session pointer.


Regards,


Aris

Le 12/12/25 à 00:45, Abdelilah El Aissaoui a écrit :
> Hello!
>
> I've been using libssh for quite a while now for the usual SSH auth 
> for my Git client and it has been great so far.
>
> One feature request I got was to add support signing with SSH keys, as 
> Git CLI does. I've been reading the docs but haven't found anything 
> that could help me to that aside from some methods in "The SSH Public 
> Key Infrastructure" 
> (https://api.libssh.org/stable/group__libssh__pki.html) such as 
> "*ssh_pki_do_sign*"**and "*ssh_pki_do_sign_agent*".
>
> Given that both methods were not part of the public API, I've done 
> some small changes moving them to "*libssh.h*" and used it like it can 
> be seen here:
>
> ```
> int result =0;
> ssh_init();
> ssh_set_log_level(4);
> ssh_session session =ssh_new();
> ssh_options_set(session,SSH_OPTIONS_HOST,"localhost");
> result =ssh_connect(session);
>
> handleResult(result,session);
>
> ssh_buffer buffer =ssh_buffer_new();
> char*text ="Hello world";
> ssh_buffer_add_data(buffer,text,strlen(text));
> ssh_key key =ssh_key_new();
>
> result =ssh_pki_import_privkey_file("/path/to/.ssh/id_rsa","",NULL,NULL, &key);
> handleResult(result,session);
>
> int hash_type =2;
> ssh_string output =ssh_pki_do_sign(session,buffer,key,hash_type);
>
> char*text_signed =ssh_string_to_char(output);
>
> printf("Output is %s",text_signed);
> ```
>
> The output always returns empty unfortunately. Given that both methods require a session I assume I'm doing something wrong. It could also be an issue with my C code given that I'm anything but proficient in the language.
>
> I was wondering if I'm going in the right direction or perhaps I'm completely off, as I'm not sure it's even possible with what LIBSSH currently offers. I would be grateful for any guidance.
>
> Thank you in advance,
> Abde.