source: trunk/athena/bin/discuss/server/acl.c @ 25469

/*
 *
 *      Copyright (C) 1988, 1989 by the Massachusetts Institute of Technology
 *      Developed by the MIT Student Information Processing Board (SIPB).
 *      For copying information, see the file mit-copyright.h in this release.
 *
 */
/*
 *      $Id: acl.c,v 1.18 2006-03-10 07:11:39 ghudson Exp $
 *
 *      Routines for the manipulation of access control lists in core,
 *      along with routines to move them to and from files.
 *
 */

#ifndef __STDC__
#define const
#endif

#ifndef lint
static const char rcsid_acl_c[] =
    "$Id: acl.c,v 1.18 2006-03-10 07:11:39 ghudson Exp $";
#endif /* lint */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <discuss/discuss.h>
#include "internal.h"

char *acl_union(), *acl_intersection(), *acl_subtract();
static void panic ();

bool acl_check(list, principal, modes)
    dsc_acl *list;
    const char *principal;
    const char *modes;
{
        register dsc_acl_entry *ae;
        register int n;
        for (ae = list->acl_entries, n=list->acl_length;
             n;
             ae++, n--) {
                if ((strcmp(principal, ae->principal) == 0) ||
                    (strcmp("*", ae->principal) == 0))
                        return(acl_is_subset(modes, ae->modes));
        }
        return (FALSE);
}

dsc_acl *acl_read(fd)
    int fd;
{
        static char buf[128];
        FILE *f=fdopen(dup(fd), "r");
        register char *cp;
        register int n;
        register dsc_acl_entry *ae;
        register dsc_acl *list;

        if (!f) return NULL;    /* oops. */
        
        list = (dsc_acl *) malloc(sizeof(dsc_acl));
        if (!list) goto punt;
        list->acl_entries = (dsc_acl_entry *)NULL;
        list->acl_length = 0;
        
        if (fgets(buf, 128, f) == NULL) goto punt;
        if (!isdigit((unsigned)buf[0])) goto punt;
        
        n=atoi(buf);
        list->acl_entries =
            (dsc_acl_entry *)malloc((unsigned)(n * sizeof(dsc_acl_entry)));
        if (!list->acl_entries) goto punt;
        
        list->acl_length = 0;
        for (ae=list->acl_entries; n; --n)  {
                buf[0]=0;
                if (fgets(buf, 128, f) == NULL) goto punt;
                if(cp=strchr(buf, '\n')) *cp='\0';
                if(cp=strchr(buf, ':')) {
                        *cp='\0';
                        list->acl_length++;
                        ae->principal = NULL;
                        ae->modes = malloc((unsigned)(strlen(buf)+1));
                        if (!ae->modes) goto punt;
                        (void) strcpy(ae->modes, buf);
                        ae->principal = malloc((unsigned)(strlen(cp+1)+1));
                        if (!ae->principal) goto punt;
                        (void) strcpy(ae->principal, cp+1);
                        ae++;
                } else { /* skip line */
                }
        }
        (void) fclose(f);
        return(list);
punt:
        fclose(f);
        if (list) acl_destroy(list);
        return NULL;
}
/*
 * Attempt to write an access control list to fd.
 * Return FALSE on failure with reason in errno.
 */

bool acl_write(fd, list)
     int fd;
     dsc_acl *list;
{
        FILE *f=fdopen(dup(fd), "w");
        register int n;
        register dsc_acl_entry *ae;
        char buf[BUFSIZ];
        int len;

        (void) sprintf(buf, "%d\n", list->acl_length);
        len = strlen(buf);
        if (fwrite(buf, 1, len, f) != len) goto punt;
        
        for (ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                (void) sprintf(buf, "%s:%.100s\n", ae->modes, ae->principal);
                len = strlen(buf);
                if (fwrite(buf, 1, len, f) != len) goto punt;
        }
        if (fflush(f) == EOF) goto punt;
        if (fsync(fileno(f)) < 0) goto punt;
        if (fclose(f) == EOF) return FALSE;
        return(TRUE);
punt:
        fclose(f);
        return(FALSE);
}

acl_add_access(list, principal, modes)
    dsc_acl *list;
    const char *principal;
    const char *modes;
{
        register int n;
        register dsc_acl_entry *ae;
        char *new_modes;
        for(ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                if (!strcmp(ae->principal, principal)) {
                        new_modes = acl_union(modes, ae->modes);
                        (void) free(ae->modes);
                        ae->modes=new_modes;
                        return;
                }
        }
        /*
         * Whoops.. fell through.
         * Realloc the world - or at least the vector.
         */
        list->acl_length++;
        list->acl_entries =
            (dsc_acl_entry *) realloc((char *)(list->acl_entries),
                                  (unsigned)(list->acl_length
                                             * sizeof(dsc_acl_entry)));
        ae = list->acl_entries + list->acl_length - 2;
        /*
         * Is the last entry "*"?  If so, push it back one.
         */
        if (list -> acl_length > 1) {           /* non-empty acl */
             if (!strcmp(ae->principal, "*")) {
                  if(!strcmp(principal, "*")) 
                          panic("acl broke");
                  *(ae+1) = *ae;
                  --ae;
             }
        }
        ae++;
        ae->principal = malloc((unsigned)(strlen(principal)+1));
        (void) strcpy(ae->principal, principal);
        ae->modes = malloc((unsigned)(strlen(modes)+1));
        (void) strcpy(ae->modes, modes);
}

#ifdef notdef
acl_delete_modes(list, principal, modes)
     dsc_acl *list;
     char *principal;
     char *modes;
{
        register dsc_acl_entry *ae, *ae1;
        register int n;
        char *new_modes;
        for(ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                if (!strcmp(ae->principal, principal)) {
                        new_modes = acl_subtract(modes, ae->modes);
                        (void) free(ae->modes);
                        ae->modes=new_modes;
                        goto cleanup;
                }
        }
        return;
cleanup:
        ae1 = list->acl_entries + list->acl_length - 1;
        if ((strcmp(ae1->principal, "*")!= 0 && strcmp(ae->modes, "")) ||
            (!strcmp(ae1->principal, "*") && !strcmp(ae->modes, ae1->modes))) {
                    (void) free(ae->principal);
                    (void) free(ae->modes);
                for (; ae <ae1; ae++) *ae= *(ae+1);
                list->acl_length--;
                list->acl_entries = (acl_entry *) realloc(list->acl_entries,
                                       list->acl_length * sizeof(dsc_acl_entry));
        }

}              
#endif /* notdef */
acl_replace_access(list, principal, modes)
    dsc_acl *list;
    const char *principal;
    const char *modes;
{
        register dsc_acl_entry *ae;
        register int n;
        for(ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                if (!strcmp(ae->principal, principal)) {
                        (void) free(ae->modes);
                        ae->modes = malloc((unsigned)(strlen(modes)+1));
                        (void) strcpy(ae->modes, modes);
                        return;
                }
        }
        /* Didn't find it.  Insert it.. the easy way. */
        acl_add_access(list, principal, modes);
}

bool
acl_delete_access(list, principal)
        dsc_acl *list;
        const char *principal;
{
        register dsc_acl_entry *ae;
        register int n;
        for(ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                if (!strcmp(ae->principal, principal)) {
                        /* gotcha! */
                        list->acl_length--;
                        while (--n) {
                                *ae= *(ae+1);
                                ae++;
                        }
                        return TRUE;
                }
        }
        return FALSE;
}
/*
 * Return empty ACL
 */

dsc_acl *acl_create()
{
        register dsc_acl *result = (dsc_acl *) malloc(sizeof(dsc_acl));
        result->acl_length=0;
        result->acl_entries=(dsc_acl_entry *) malloc(sizeof(dsc_acl_entry));
        return(result);
}

dsc_acl *acl_copy (old_acl)
    dsc_acl *old_acl;
{
     register dsc_acl *new_acl = (dsc_acl *) malloc (sizeof(dsc_acl));
     register dsc_acl_entry *old_ae,*new_ae;
     register int n;

     new_acl -> acl_length = old_acl -> acl_length;
     new_acl -> acl_entries = (dsc_acl_entry *) malloc ((unsigned)(new_acl -> acl_length * sizeof(dsc_acl_entry)));

     for (old_ae = old_acl->acl_entries, new_ae = new_acl->acl_entries, n=new_acl->acl_length;
          n;
          --n, ++old_ae, ++new_ae) {
               new_ae->principal = malloc (strlen(old_ae->principal)+1);
               strcpy (new_ae->principal,old_ae->principal);
               new_ae->modes = malloc (strlen(old_ae->modes)+1);
               strcpy (new_ae->modes,old_ae->modes);
          }
               
     return (new_acl);
}

const char *acl_get_access(list, principal)
        dsc_acl *list;
        const char *principal;
{
        register dsc_acl_entry *ae;
        register int n;

        for(ae=list->acl_entries, n=list->acl_length; n; --n, ++ae) {
                if (!strcmp(ae->principal, principal) ||
                    !strcmp(ae->principal, "*")) {
                        return(ae->modes);
                }
        }
        return("");
}
/*
 * Destroy an ACL.     
 */

acl_destroy(list)
     dsc_acl *list;
{
        register dsc_acl_entry *ae;
        register int n;
        if(!list) return;
        for (ae=list->acl_entries, n=list->acl_length;
             ae && n;
             --n, ++ae) {
                     if (ae->principal) (void) free(ae->principal);
                     if (ae->modes) (void) free(ae->modes);
        }
        if (ae) (void) free((char *)(list->acl_entries));
        (void) free((char *)list);
}

/*
 * Returns true if every character of s1 occurs in s2.
 */
bool acl_is_subset(s1, s2)
     register const char *s1, *s2;
{
        register char *last;
        while(*s1 && (last = strchr(s2, *s1))) s1++;

        return(last != NULL);
}

/*
 * Returns the intersection of the two strings s1 and s2.
 * This function allocates a new string, which should be freed 
 * when not needed.
 */
char *acl_intersection(s1, s2)
     register const char *s1, *s2;
{
        register char *result=malloc(1);
        register int resp=0;

        while(*s1) {
                if(strchr(s2, *s1)) {
                        result[resp++] = *s1;
                        result=realloc(result, (unsigned)(resp+1));
                }
                s1++;
        }
        result[resp] = '\0';
        return(result);
}

char *acl_union(s1, s2)
     register const char *s1, *s2;
{
        register int resp=strlen(s2);
        register char *result=malloc((unsigned)(resp+1));
        strcpy(result, s2);
        while(*s1) {
                if (!strchr(result, *s1)) {
                        result[resp++]= *s1;
                        result=realloc(result, (unsigned)(resp+1));
                }
                s1++;
        }
        result[resp]='\0';
        return(result);
}

char *acl_subtract(s1, s2)
     register const char *s1, *s2;
{
        register char *result = malloc(1);
        register int len=0;
        for (; *s2; s2++) {
                if (!strchr(s1, *s2)) {
                        result = realloc(result, (unsigned)(len+2));
                        result[len++]= *s2;
                }
        }
        result[len]='\0';
        return(result);
}

/*
 * Canonicalize an acl string; sort the characters of s1 into 
 * the order found in s2, removing duplicates, and returning an error code if 
 * any of them are not in s2.
 * This is a sucky algorithm, but who really gives?
 */

char *acl_canon(s1, s2, code)
        register const char *s1, *s2;
        int *code;
{
        register const char *cp;
        register char *out;
        register int len, maxlen;

        *code = 0;
        for (cp = s1; *cp; cp++) {
                if (*cp != ' ' && !strchr(s2, *cp)) 
                        *code = BAD_MODES;
        }
        maxlen = strlen(s2);
        out = malloc(maxlen + 1); len = 0;
        for (cp = s2; *cp; cp++) {
                len++;
                if (len > maxlen) /* shouldn't happen, but.. */
                        out = realloc(out, (unsigned)len + 1);

                out[len-1] = (strchr(s1, *cp) ? *cp : ' ');
        }
        out[len]='\0';
        return(out);
}

        


#ifdef TESTS
#include <sys/file.h>
main() 
{
        int fd;
        dsc_acl *a;

        printf("%s * %s = %s\n", "eabce", "abcd", 
               acl_intersection("eabce", "abcd"));
        printf("%s + %s = %s\n", "abc", "cbade", acl_union("abc", "cbade"));
        printf("%s < %s = %d\n", "ab", "bcde", acl_is_subset("ab", "bcde"));
        printf("%s < %s = %d\n", "ab", "abcde", acl_is_subset("ab", "abcde"));

        fd = open ("foo.acl", O_RDONLY);
        a=acl_read(fd);
        (void) close(fd);
        printf("a for wesommer: %d\n", acl_check(a, "wesommer", "a"));
        printf("a for foobar: %d\n", acl_check(a, "foobar", "a"));
        printf("a for spook: %d\n", acl_check(a, "spook", "a"));
        printf("g for foobar: %d\n", acl_check(a, "foobar", "g"));
        printf("g for wesommer: %d\n", acl_check(a, "wesommer", "g"));
        printf("g for spook: %d\n", acl_check(a, "spook", "g"));
        printf("d for spook: %d\n", acl_check(a, "spook", "d"));
        printf("d for wesommer: %d\n", acl_check(a, "wesommer", "d"));
        acl_add_access(a, "zot", "qna");
        acl_add_access(a, "spook", "d");
        acl_add_access(a, "*", "w");
        fd = open("bar.acl", O_WRONLY+O_CREAT+O_TRUNC);
        acl_write(fd, a);
        (void) close(fd);
}
#endif /* TESTS */

static void panic(s)
        char *s;
{
        printf("%s\n", s);
        fflush(stdout);
        abort();
}