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