Respect krb5_principal when impersonating #111
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Sigh apparently the latest ubuntu image broke the CI, lemme try to fix it |
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Hi @sesse would you mind rebasing on top of main so we can run the CI (I fixed it). |
When doing impersonation, we need to get initial credentials using some service principal from the given keytab. However, since keytabs have no default principals, libgss just chooses the first one in the file, which generally does not work well when in Active Directory. In particular, in AD, the only valid principal for authenticating is [email protected], whereas e.g. host/[email protected] is just an SPN connected to SERVER$ and not valid for authenticating in its own right. gssd will try SERVER$ first for its own purposes (at least according to the man page), but when impersonating, it will naturally ask for a ticket for a user (e.g. [email protected]) and not the service principal itself. This patch doesn't really make us choose the right principal for AD purposes, but it makes us respect the krb5_principal configuration option when getting a service principal for this purpose, so that an administrator can at least manually select which one to use without having to somehow reorder entries in the keytab (which appears to be hard). Thus, the admin can set "krb5_principal = [email protected]" in the service definition in gssproxy.conf, and it will work. Signed-off-by: Steinar H. Gunderson <[email protected]>
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Thanks for the contribution |
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When doing impersonation, we need to get initial credentials using some service principal from the given keytab. However, since keytabs have no default principals, libgss just chooses the first one in the file, which generally does not work well when in Active Directory.
In particular, in AD, the only valid principal for authenticating is [email protected], whereas e.g. host/[email protected] is just an SPN connected to SERVER$ and not valid for authenticating in its own right. gssd will try SERVER$ first for its own purposes (at least according to the man page), but when impersonating, it will naturally ask for a ticket for a user (e.g. [email protected]) and not the service principal itself.
This patch doesn't really make us choose the right principal for AD purposes, but it makes us respect the krb5_principal configuration option when getting a service principal for this purpose, so that an administrator can at least manually select which one to use without having to somehow reorder entries in the keytab (which appears to be hard). Thus, the admin can set "krb5_principal = [email protected]" in the service definition in gssproxy.conf, and it will work.