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/*
Mode Muncher -- modemuncher.c
961110 Claudio Terra
munch vb
[ME monchen, perh. influenced by MF mangier to eat --more at MANGER]
:to chew with a crunching sound: eat with relish
:to chew food with a crunching sound: eat food with relish
--munch-er n
The NeXT Digital Edition of Webster's Ninth New Collegiate Dictionary
and Webster's Collegiate Thesaurus
*/
/* struct for rwx <-> POSIX constant lookup tables */
struct modeLookup
{
char rwx;
mode_t bits;
};
typedef struct modeLookup modeLookup;
static modeLookup modesel[] =
{
/* RWX char Posix Constant */
{'r', S_IRUSR},
{'w', S_IWUSR},
{'x', S_IXUSR},
{'r', S_IRGRP},
{'w', S_IWGRP},
{'x', S_IXGRP},
{'r', S_IROTH},
{'w', S_IWOTH},
{'x', S_IXOTH},
{'\0', (mode_t)-1} /* do not delete this line */
};
static int rwxrwxrwx(mode_t *mode, const char *p)
{
int count;
mode_t tmp_mode = *mode;
tmp_mode &= ~(S_ISUID | S_ISGID); /* turn off suid and sgid flags */
for (count=0; count<9; count ++)
{
if (*p == modesel[count].rwx) tmp_mode |= modesel[count].bits; /* set a bit */
else if (*p == '-') tmp_mode &= ~modesel[count].bits; /* clear a bit */
else if (*p=='s') switch(count)
{
case 2: /* turn on suid flag */
tmp_mode |= S_ISUID | S_IXUSR;
break;
case 5: /* turn on sgid flag */
tmp_mode |= S_ISGID | S_IXGRP;
break;
default:
return -4; /* failed! -- bad rwxrwxrwx mode change */
break;
}
p++;
}
*mode = tmp_mode;
return 0;
}
static void modechopper(mode_t mode, char *p)
{
/* requires char p[10] */
int count;
char *pp;
pp=p;
for (count=0; count<9; count ++)
{
if (mode & modesel[count].bits) *p = modesel[count].rwx;
else *p='-';
p++;
}
*p=0; /* to finish the string */
/* dealing with suid and sgid flags */
if (mode & S_ISUID) pp[2] = (mode & S_IXUSR) ? 's' : 'S';
if (mode & S_ISGID) pp[5] = (mode & S_IXGRP) ? 's' : 'S';
}
static int mode_munch(mode_t *mode, const char* p)
{
char op=0;
mode_t affected_bits, ch_mode;
int doneFlag = 0;
#ifdef DEBUG
char tmp[10];
#endif
#ifdef DEBUG
modechopper(*mode, tmp);
printf("modemuncher: got base mode = %s\n", tmp);
#endif
while (!doneFlag)
{
/* step 0 -- clear temporary variables */
affected_bits=0;
ch_mode=0;
/* step 1 -- who's affected? */
#ifdef DEBUG
printf("modemuncher step 1\n");
#endif
/* mode string given in rwxrwxrwx format */
if (*p== 'r' || *p == '-') return rwxrwxrwx(mode, p);
/* mode string given in 0644 format */
if (*p >= '0' && *p <= '7') {
char *e;
mode_t tmp_mode = strtol(p, &e, 8);
if (*p == 0 || *e != 0)
return -5;
*mode = tmp_mode;
return 0;
}
/* mode string given in ugoa+-=rwx format */
for ( ; ; p++)
switch (*p)
{
case 'u':
affected_bits |= 04700;
break;
case 'g':
affected_bits |= 02070;
break;
case 'o':
affected_bits |= 01007;
break;
case 'a':
affected_bits |= 07777;
break;
/* ignore spaces */
case ' ':
break;
default:
goto no_more_affected;
}
no_more_affected:
/* If none specified, affect all bits. */
if (affected_bits == 0) affected_bits = 07777;
/* step 2 -- how is it changed? */
#ifdef DEBUG
printf("modemuncher step 2 (*p='%c')\n", *p);
#endif
switch (*p)
{
case '+':
case '-':
case '=':
op = *p;
break;
/* ignore spaces */
case ' ':
break;
default:
return -1; /* failed! -- bad operator */
}
/* step 3 -- what are the changes? */
#ifdef DEBUG
printf("modemuncher step 3\n");
#endif
for (p++ ; *p!=0 ; p++)
switch (*p)
{
case 'r':
ch_mode |= 00444;
break;
case 'w':
ch_mode |= 00222;
break;
case 'x':
ch_mode |= 00111;
break;
case 's':
/* Set the setuid/gid bits if `u' or `g' is selected. */
ch_mode |= 06000;
break;
/* ignore spaces */
case ' ':
break;
default:
goto specs_done;
}
specs_done:
/* step 4 -- apply the changes */
#ifdef DEBUG
printf("modemuncher step 4\n");
#endif
if (*p != ',') doneFlag = 1;
if (*p != 0 && *p != ' ' && *p != ',')
{
#ifdef DEBUG
printf("modemuncher: comma error!\n");
printf("modemuncher: doneflag = %u\n", doneFlag);
#endif
return -2; /* failed! -- bad mode change */
}
p++;
/*if (!ch_mode) return -2;*/ /* failed! -- bad mode change */
if (ch_mode) switch (op)
{
case '+':
*mode |= ch_mode & affected_bits;
break;
case '-':
*mode &= ~(ch_mode & affected_bits);
break;
case '=':
*mode = ch_mode & affected_bits;
break;
default:
return -3; /* failed! -- unknown error */
}
}
#ifdef DEBUG
modechopper(*mode, tmp);
printf("modemuncher: returning mode = %s\n", tmp);
#endif
return 0; /* successful call */
}
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