129 lines
5.2 KiB
Plaintext
129 lines
5.2 KiB
Plaintext
NOTE: the Sudo auth API is subject to change
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Purpose: to provide a simple API for authentication methods that
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encapsulates things nicely without turning into a maze
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of #ifdef's
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The sudo_auth struct looks like this:
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typedef struct sudo_auth {
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short flags; /* various flags, see below */
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short status; /* status from verify routine */
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char *name; /* name of the method in string form */
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void *data; /* method-specific data pointer */
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int (*init) __P((struct passwd *pw, char **prompt, sudo_auth *auth));
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int (*setup) __P((struct passwd *pw, char **prompt, sudo_auth *auth));
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int (*verify) __P((struct passwd *pw, char *p, sudo_auth *auth));
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int (*cleanup) __P((struct passwd *pw, sudo_auth *auth));
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} sudo_auth;
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The variables in the struct are as follows:
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flags Bitwise binary flags, see below.
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status Contains the return value from the last run of
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the "verify" function. Starts out as AUTH_FAILURE.
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name The name of the authentication method as a C string.
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data A pointer to method-specific data. This is passed to
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all the functions of an auth method and is usually
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initialized in the "init" or "setup" routines.
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Possible values of sudo_auth.flags:
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FLAG_USER Whether or not the auth functions should run with
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the euid of the invoking user instead of 0.
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FLAG_CONFIGURED If set then the auth method is assumed to have been
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configured successfully. All auth methods start out
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with this set. If an "init" or "setup" function
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fails, this bit is cleared.
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FLAG_ONEANDONLY If set, this indicates that the method is the
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only one in use. Can be used by auth functions
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to determine whether to return a fatal or nonfatal
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error.
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The member functions can return the following values:
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AUTH_SUCCESS Function succeeded. For a ``verify'' function
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this means the user correctly authenticated.
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AUTH_FAILURE Function failed. If this is an ``init'' or
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``setup'' routine, the auth method will be
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marked as !configured.
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AUTH_FATAL A fatal error occurred. The routine should have
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written an error message to stderr and optionally
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sent mail to the administrator. (If log_error()
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is called to do this, the NO_EXIT flag must be used.)
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When verify_user() gets AUTH_FATAL from an auth
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function it does an exit(1).
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The functions in the struct are as follows:
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int init(struct passwd *pw, char **prompt, sudo_auth *auth)
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Function to do any one-time initialization for the auth
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method. All of the "init" functions are run before anything
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else. A pointer to the prompt string may be used to add
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method-specific info to the prompt.
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int setup(struct passwd *pw, char **prompt, sudo_auth *auth)
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Function to do method-specific setup. All the "setup"
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routines are run before any of the "verify" routines. A
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pointer to the prompt string may be used to add method-specific
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info to the prompt.
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int verify(struct passwd *pw, char *p, sudo_auth *auth)
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Function to do user verification for this auth method. For
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standalone auth methods ``p'' is the prompt string. For
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normal auth methods, ``p'' is the password the user entered.
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Note that standalone auth methods are responsible for
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rerading the password themselves.
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int cleanup(struct passwd *pw, sudo_auth *auth)
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Function to do per-auth method cleanup. This is only run
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at the end of the authentication process, after the user
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has completely failed or succeeded to authenticate.
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The ``auth->status'' variable contains the result of the
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last authentication attempt which may be interesting.
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A note about standalone methods. Some authentication methods can't
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coexist with any others. This may be because they encapsulate other
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methods (pam, sia) or because they have a special way of interacting
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with the user (securid).
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Adding a new authentication method:
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Each method should live in its own file. Add prototypes for the functions
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in sudo_auth.h.
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If this is a standalone method, add it to the standalone #if cascade
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in sudo_auth.h. For instance, for a method, ``fooauth'', add:
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#elif defined(HAVE_FOOAUTH)
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# define AUTH_STANDALONE \
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AUTH_ENTRY(0, "foo", \
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foo_init, foo_setup, foo_verify, foo_cleanup)
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If the method needs to run as the user, not root, replace the first
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parameter to AUTH_ENTRY (0) with FLAG_USER. If you don't have a
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init/setup/cleanup routine, just use a NULL for that field.
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For a normal authentication method, add it to the ``auth_switch'' in
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sudo_auth.c. If ``fooauth'' is a normal auth method, its entry
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would look like:
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# ifdef HAVE_FOOAUTH
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AUTH_ENTRY(0, "foo", foo_init, foo_setup, foo_verify, foo_cleanup)
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# endif
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Again, if the method doesn't need to run as root, replace the 0 with
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FLAG_USER. Likewise, if you don't have a init/setup/cleanup routine,
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just use a NULL for that field.
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NOTE: You should not make a method both ``standalone'' and
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``normal''. Just use the --without-passwd configure argument
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to disable passwd/shadow file checking and then have your
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auth routines check the FLAG_ONEANDONLY flag to see if
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they are running standalone and act accordingly.
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