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Fix symbolic mode parsing in parsemode

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I found quite a lot of bugs, so I ended up pretty much rewriting as I
followed the spec¹.

Now, it works as follows:

- Determine a mask (who) of bits that can be modified for the subsequent
  operations. If none are specified, select all file mode bits.
- In a loop, determine which operation (+, -, =) to apply.
- If the next character is a permcopy (u, g, o), set the new permissions
  (perm) corresponding to the bits set in the user, group or other parts
  of the existing mode.
- Otherwise, set the new permissions by looping through the next r, w,
  x, s, t characters.
- Now, the set of bits we want to add or remove is (who & perm). Set or
  remove these bits according the the operation (first clearing the
  appropriate bits if the operation is =).
- Continue from the top if the next character is a comma, otherwise,
  process the next operation.

I tested this on some made up inputs, and I believe it is working
correctly now:

  parsemode("g+w", 0644, 0),    before: 0606, now: 0664, fixed
  parsemode("u+rx", 0222, 0),   before: 0077, now: 0722, fixed
  parsemode("+x", 0644, 023),   before: 0754, now: 0754, still works
  parsemode("+w", 0444, 022),   before: 0644, now: 0644, still works
  parsemode("+w", 0444, 0),     before: 0666, now: 0666, still works
  parsemode("+s", 0755, 0),     before: 0755, now: 6755, fixed
  parsemode("u+s", 0755, 0),    before: 0055, now: 4755, fixed
  parsemode("g+s", 0755, 0),    before: 0705, now: 2755, fixed
  parsemode("g=u", 0700, 0),    before: 0000, now: 0770, fixed
  parsemode("go=u-w", 0700, 0), before: 0000, now: 0755, fixed
  parsemode("o+u-g", 0641, 0),  before: 0000, now: 0643, fixed
  parsemode("u=rx,o+w,g-r", 0654, 0) before: error, now: 0516, fixed
  parsemode(",", 0654, 0), before: error, now: error, still works

¹ http://pubs.opengroup.org/onlinepubs/9699919799/utilities/chmod.html
This commit is contained in:
Michael Forney 2014-11-02 22:24:52 +00:00 committed by sin
parent 6327290cf2
commit 6164445cce
1 changed files with 96 additions and 35 deletions
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129
util/mode.c
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@ -16,9 +16,9 @@ mode_t
parsemode(const char *str, mode_t mode, mode_t mask)
{
char *end;
const char *p;
int octal, op = '+';
mode_t gmask = 0, m = 0;
const char *p = str;
int octal, op;
mode_t who, perm, clear;
octal = strtol(str, &end, 8);
if(*end == '\0') {
@ -41,61 +41,122 @@ parsemode(const char *str, mode_t mode, mode_t mask)
if(octal & 00001) mode |= S_IXOTH;
return mode;
}
for(p = str; *p; p++) {
next:
/* first, determine which bits we will be modifying */
for(who = 0; *p; p++) {
switch(*p) {
/* masks */
case 'u':
gmask |= S_IRWXU;
break;
who |= S_IRWXU|S_ISUID;
continue;
case 'g':
gmask |= S_IRWXG;
break;
who |= S_IRWXG|S_ISGID;
continue;
case 'o':
gmask |= S_IRWXO;
break;
who |= S_IRWXO;
continue;
case 'a':
gmask |= S_IRWXU|S_IRWXG|S_IRWXO;
who |= S_IRWXU|S_ISUID|S_IRWXG|S_ISGID|S_IRWXO;
continue;
}
break;
}
if(who) {
clear = who;
} else {
clear = S_ISUID|S_ISGID|S_ISVTX|S_IRWXU|S_IRWXG|S_IRWXO;
who = ~mask;
}
while(*p) {
switch(*p) {
/* opers */
case '=':
case '+':
case '-':
op = (int)*p;
break;
/* modes */
case 'r':
m |= S_IRUSR|S_IRGRP|S_IROTH;
break;
case 'w':
m |= S_IWUSR|S_IWGRP|S_IWOTH;
break;
case 'x':
m |= S_IXUSR|S_IXGRP|S_IXOTH;
break;
case 's':
m |= S_ISUID|S_ISGID;
break;
case 't':
m |= S_ISVTX;
break;
default:
eprintf("%s: invalid mode\n", str);
return -1;
}
perm = 0;
switch(*++p) {
/* copy */
case 'u':
if(mode & S_IRUSR)
perm |= S_IRUSR|S_IRGRP|S_IROTH;
if(mode & S_IWUSR)
perm |= S_IWUSR|S_IWGRP|S_IWOTH;
if(mode & S_IXUSR)
perm |= S_IXUSR|S_IXGRP|S_IXOTH;
if(mode & S_ISUID)
perm |= S_ISUID|S_ISGID;
p++;
break;
case 'g':
if(mode & S_IRGRP)
perm |= S_IRUSR|S_IRGRP|S_IROTH;
if(mode & S_IWGRP)
perm |= S_IWUSR|S_IWGRP|S_IWOTH;
if(mode & S_IXGRP)
perm |= S_IXUSR|S_IXGRP|S_IXOTH;
if(mode & S_ISGID)
perm |= S_ISUID|S_ISGID;
p++;
break;
case 'o':
if(mode & S_IROTH)
perm |= S_IRUSR|S_IRGRP|S_IROTH;
if(mode & S_IWOTH)
perm |= S_IWUSR|S_IWGRP|S_IWOTH;
if(mode & S_IXOTH)
perm |= S_IXUSR|S_IXGRP|S_IXOTH;
p++;
break;
default:
for(; *p; p++) {
switch(*p) {
/* modes */
case 'r':
perm |= S_IRUSR|S_IRGRP|S_IROTH;
break;
case 'w':
perm |= S_IWUSR|S_IWGRP|S_IWOTH;
break;
case 'x':
perm |= S_IXUSR|S_IXGRP|S_IXOTH;
break;
case 's':
perm |= S_ISUID|S_ISGID;
break;
case 't':
perm |= S_ISVTX;
break;
default:
goto apply;
}
}
}
apply:
/* apply */
switch(op) {
case '=':
mode &= ~clear;
/* fallthrough */
case '+':
mode |= (m & ((~mask) & 0777));
mode |= perm & who;
break;
case '-':
mode &= (~(m & ((~mask) & 0777)));
break;
case '=':
mode = (m & ((~mask) & 0777));
mode &= ~(perm & who);
break;
}
/* if we hit a comma, move on to the next clause */
if(*p == ',') {
p++;
goto next;
}
}
if(gmask && op != '=')
mode &= ~gmask;
return mode;
}