kuserok.c   [plain text]

/*
 * lib/krb5/os/kuserok.c
 *
 * Copyright 1990,1993 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 * 
 *
 * krb5_kuserok()
 */

#include "k5-int.h"
#if !defined(_WIN32)		/* Not yet for Windows */
#include <stdio.h>
#include <pwd.h>

#if defined(_AIX) && defined(_IBMR2)
#include <sys/access.h>
/* xlc has a bug with "const" */
#define getpwnam(user) getpwnam((char *)user)
#endif

#define MAX_USERNAME 65

#if defined(__APPLE__) && defined(__MACH__)
#include <hfs/hfs_mount.h>	/* XXX */
#define FILE_OWNER_OK(UID)  ((UID) == 0 || (UID) == UNKNOWNUID)
#else
#define FILE_OWNER_OK(UID)  ((UID) == 0)
#endif

/*
 * Given a Kerberos principal "principal", and a local username "luser",
 * determine whether user is authorized to login according to the
 * authorization file ("~luser/.k5login" by default).  Returns TRUE
 * if authorized, FALSE if not authorized.
 *
 * If there is no account for "luser" on the local machine, returns
 * FALSE.  If there is no authorization file, and the given Kerberos
 * name "server" translates to the same name as "luser" (using
 * krb5_aname_to_lname()), returns TRUE.  Otherwise, if the authorization file
 * can't be accessed, returns FALSE.  Otherwise, the file is read for
 * a matching principal name, instance, and realm.  If one is found,
 * returns TRUE, if none is found, returns FALSE.
 *
 * The file entries are in the format produced by krb5_unparse_name(),
 * one entry per line.
 *
 */

krb5_boolean KRB5_CALLCONV
krb5_kuserok(krb5_context context, krb5_principal principal, const char *luser)
{
    struct stat sbuf;
    struct passwd *pwd;
    char pbuf[MAXPATHLEN];
    krb5_boolean isok = FALSE;
    FILE *fp;
    char kuser[MAX_USERNAME];
    char *princname;
    char linebuf[BUFSIZ];
    char *newline;
    int gobble;

    /* no account => no access */
    char pwbuf[BUFSIZ];
    struct passwd pwx;
    if (k5_getpwnam_r(luser, &pwx, pwbuf, sizeof(pwbuf), &pwd) != 0)
	return(FALSE);
    (void) strncpy(pbuf, pwd->pw_dir, sizeof(pbuf) - 1);
    pbuf[sizeof(pbuf) - 1] = '\0';
    (void) strncat(pbuf, "/.k5login", sizeof(pbuf) - 1 - strlen(pbuf));

    if (access(pbuf, F_OK)) {	 /* not accessible */
	/*
	 * if he's trying to log in as himself, and there is no .k5login file,
	 * let him.  To find out, call
	 * krb5_aname_to_localname to convert the principal to a name
	 * which we can string compare. 
	 */
	if (!(krb5_aname_to_localname(context, principal,
				      sizeof(kuser), kuser))
	    && (strcmp(kuser, luser) == 0)) {
	    return(TRUE);
	}
    }
    if (krb5_unparse_name(context, principal, &princname))
	return(FALSE);			/* no hope of matching */

    /* open ~/.k5login */
    if ((fp = fopen(pbuf, "r")) == NULL) {
	free(princname);
	return(FALSE);
    }
    /*
     * For security reasons, the .k5login file must be owned either by
     * the user himself, or by root.  Otherwise, don't grant access.
     */
    if (fstat(fileno(fp), &sbuf)) {
	fclose(fp);
	free(princname);
	return(FALSE);
    }
    if (sbuf.st_uid != pwd->pw_uid && !FILE_OWNER_OK(sbuf.st_uid)) {
	fclose(fp);
	free(princname);
	return(FALSE);
    }

    /* check each line */
    while (!isok && (fgets(linebuf, BUFSIZ, fp) != NULL)) {
	/* null-terminate the input string */
	linebuf[BUFSIZ-1] = '\0';
	newline = NULL;
	/* nuke the newline if it exists */
	if ((newline = strchr(linebuf, '\n')))
	    *newline = '\0';
	if (!strcmp(linebuf, princname)) {
	    isok = TRUE;
	    continue;
	}
	/* clean up the rest of the line if necessary */
	if (!newline)
	    while (((gobble = getc(fp)) != EOF) && gobble != '\n');
    }
    free(princname);
    fclose(fp);
    return(isok);
}

#else /* _WIN32 */

/*
 * If the given Kerberos name "server" translates to the same name as "luser"
 * (using * krb5_aname_to_lname()), returns TRUE.
 */
krb5_boolean KRB5_CALLCONV
krb5_kuserok(context, principal, luser)
    krb5_context context;
    krb5_principal principal;
    const char *luser;
{
    char kuser[50];

    if (krb5_aname_to_localname(context, principal, sizeof(kuser), kuser))
        return FALSE;

    if (strcmp(kuser, luser) == 0)
	    return TRUE;

    return FALSE;
}
#endif /* _WIN32 */