Accessing gssapi/kerberos principal

Dan Peterson petesea at
Tue Mar 7 11:31:01 EST 2006

I'm attempting to add authorized_keys functionality to gssapi/kerberos 
authorized connections, mainly to support forced command capability, but 
would like to confirm the best way to determine the gssapi/kerberos 
principal and the best place to check authorized_keys.

To determine the principal, currently I'm indirectly accessing 
gss-serv.c:gssapi_client.displayname.value (more detail below).  This 
seems to work, but I'd just like to know if there's a better/more 
appropriate way to determine the principal?

I'm also not 100% sure WHERE I should be testing for the existence of the 
user in authorized_keys.  Currently the check is done in 
auth2-gss.c:input_gssapi_token() (more detail below).  This seems to work, 
but again is this the best/most appropriate place to check?


To determine the current principal, I created a one-line function in 

   char *ssh_gssapi_displayname(void)

which simply returns (char *)gssapi_client.displayname.value.

This is called from auth2-gss.c:input_gssapi_token() and assigned to a 
"Key" pointer which is passed into auth2-pubkey.c:user_key_allowed().

In auth2-gss.c:input_gssapi_token(), I check for the existence of the user 
in authorized_keys.  I first tried to mimic the pubkey behavior and check 
in userauth_gssapi(), but found out gss-serv.c:gssapi_client wasn't 
defined until AFTER userauth_gssapi() had been called.

The new code is inside the "else" clause, just after "if (send_tok.length 
!= 0)", but before "if (maj_status == GSS_S_COMPLETE)".  My check may 
fail, and if it does, I "goto done", which is just before 
"gss_release_buffer()" at the end of the function.  I can give more 
details if necessary and I will supply a complete patch for review, I just 
hoped to get as close to correct as possible before submitting the patch.

PS. One other note... as I mentioned earlier, I'm calling 
auth2-pubkey.c:user_key_allowed() to parse authorized_keys and search for 
the appropriate key.  I had to make one small change to 
user_key_allowed2() so the new "ssh-gss" type wouldn't try to
call key_fingerprint() with the principal, but other then that, the 
function is the same.

This all works, but auth2-pubkey.c no longer seems like the most 
appropriate place for user_key_allowed() and user_key_allowed2(), since 
they're used for more then just "pubkey".  Would it be better to move 
these to a separate file (eg. authorized_keys.c) or maybe move then to 

Assuming a NEW file (authorized_keys.c) would be best... would it also be 
a good idea to move the other authorized_keys related functions to the 
same file... so in other words, the following 4 functions would be moved 
to authorized_keys.c:


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