amount, newns, addns, login, noworld, auth_proxy, fauth_proxy, auth_allocrpc, auth_freerpc, auth_rpc, auth_getkey, amount_getkey, auth_freeAI, auth_chuid, auth_challenge, auth_response, auth_freechal, auth_respond, auth_userpasswd, auth_getuserpasswd, auth_getinfo – routines for authenticating users


#include <u.h>
#include <libc.h>
#include <auth.h>

int         newns(char *user, char *nsfile);

int         addns(char *user, char *nsfile);

int         amount(int fd, char *old, int flag, char *aname);

int         login(char *user, char *password, char *namespace);

int         noworld(char *user);

AuthInfo*    auth_proxy(int fd, AuthGetkey *getkey, char *fmt, ...);

AuthInfo*    fauth_proxy(int fd, AuthRpc *rpc, AuthGetkey *getkey,
char *params);

AuthRpc*     auth_allocrpc(int afd);

void        auth_freerpc(AuthRpc *rpc);

uint        auth_rpc(AuthRpc *rpc, char *verb, void *a, int n);

int         auth_getkey(char *proto, char *dom);

int         (*amount_getkey)(char*, char*);

void        auth_freeAI(AuthInfo *ai);

int            auth_chuid(AuthInfo *ai, char *ns);

Chalstate* auth_challenge(char *fmt, ...);

AuthInfo*    auth_response(Chalstate*);

void        auth_freechal(Chalstate*);

int            auth_respond(void *chal, uint nchal, char *user, uint nuser, void *resp, uint nresp, AuthGetkey *getkey, char *fmt, ...);

AuthInfo*    auth_userpasswd(char*user, char*password);

UserPasswd*    auth_getuserpasswd(AuthGetkey *getkey, char*fmt, ...);

AuthInfo*    auth_getinfo(int fd);


This library, in concert with factotum(4), is used to authenticate users. It provides the primary interface to factotum.

Newns builds a name space for user. It opens the file nsfile (/lib/namespace is used if nsfile is null), copies the old environment, erases the current name space, sets the environment variables user and home, and interprets the commands in nsfile. The format of nsfile is described in namespace(6).

Addns also interprets and executes the commands in nsfile. Unlike newns it applies the command to the current name space rather than starting from scratch.

Amount is like mount but performs any authentication required. It should be used instead of mount whenever the file server being mounted requires authentication. See bind(2) for a definition of the arguments to mount and amount.

Login changes the user id of the process user and recreates the namespace using the file namespace (default /lib/namespace). It uses auth_userpasswd and auth_chuid.

Noworld returns 1 if the user is in the group noworld in /adm/users. Otherwise, it returns 0. Noworld is used by telnetd and ftpd to provide sandboxed access for some users.

The following routines use the AuthInfo structure returned after a successful authentication by factotum(4).
typedef struct
char    *cuid;       /* caller id */
char    *suid;       /* server id */
char    *cap;        /* capability */
int     nsecret;     /* length of secret */
uchar *secret;     /* secret */
} AuthInfo;

The fields cuid and suid point to the authenticated ids of the client and server. Cap is a capability returned only to the server. It can be passed to the cap(3) device to change the user id of the process. Secret is an nsecret–byte shared secret that can be used by the client and server to create encryption and hashing keys for the rest of the conversation.

Auth_proxy proxies an authentication conversation between a remote server reading and writing fd and a factotum file. The factotum file used is /mnt/factotum/rpc. An sprint (see print(2)) of fmt and the variable arg list yields a key template (see factotum(4)) specifying the key to use. The template must specify at least the protocol ( proto=xxx) and the role (either role=client or role=server). Auth_proxy either returns an allocated AuthInfo structure, or sets the error string and returns nil.

Fauth_proxy can be used instead of auth_proxy if a single connection to factotum will be used for multiple authentications. This is necessary, for example, for newns which must open the factotum file before wiping out the namespace. Fauth_proxy takes as an argument a pointer to an AuthRPC structure which contains an fd for an open connection to factotum in addition to storage and state information for the protocol. An AuthRPC structure is obtained by calling auth_allocrpc with the fd of an open factotum connection. It is freed using auth_freerpc. Individual commands can be sent to factotum(4) by invoking auth_rpc.

Both auth_proxy and fauth_proxy take a pointer to a routine, getkey, to invoke should factotum not posess a key for the authentication. If getkey is nil, the authentication fails. Getkey is called with a key template for the desired key. We have provided a generic routine, auth_getkey, which queries the user for the key information and passes it to factotum. This is the default for the global variable, amount_getkey, which holds a pointer to the key prompting routine used by amount.

Auth_chuid uses the cuid and cap fields of an AuthInfo structure to change the user id of the current process and uses ns, default /lib/namespace, to build it a new name space.

Auth_challenge and auth_response perform challenge/response protocols with factotum. State between the challenge and response phase are kept in the Chalstate structure:
struct Chalstate
char    *user;
char    chal[MAXCHLEN];
int     nchal;
void    *resp;
int     nresp;
/* for implementation only */
int     afd;
AuthRpc    *rpc;
char    userbuf[MAXNAMELEN];
int     userinchal;

Auth_challenge requires a key template generated by an sprint of fmt and the variable arguments. It must contain the protocol (proto=xxx) and depending on the protocol, the user name (user=xxx). P9cr and vnc expect the user specified as an attribute in the key template and apop, cram, and chap expect it in the user field of the arg to auth_response. For all protocols, the response is returned to auth_response in the resp field of the Chalstate. Chalstate.nresp must be the length of the response.

Supply to auth_respond a challenge string and the fmt and args specifying a key, and it will use factotum to return the proper user and response.

Auth_userpasswd verifies a simple user/password pair. Auth_getuserpasswd retrieves a user/password pair from factotum if permitted:
typedef struct UserPasswd {
char    *user;
char    *passwd;
} UserPasswd;

Auth_getinfo reads an AuthInfo message from fd and converts it into a structure. It is only used by the other routines in this library when communicating with factotum.

Auth_freeAI is used to free an AuthInfo structure returned by one of these routines. Similary auth_freechal frees a challenge/response state.


factotum(4), authsrv(2), bind(2)

These routines set errstr.
Copyright © 2024 Plan 9 Foundation. All rights reserved.