...
The
...
rename()
...
function
...
has
...
the
...
following
...
prototype:
| Code Block |
|---|
} int rename(const char *old, const char *new); {code} |
If
...
the
...
file
...
pointed
...
to
...
by
...
new
...
exists
...
prior
...
to
...
a
...
call
...
to
...
rename()
...
,
...
the
...
behavior
...
is
...
implementation-defined.
...
Therefore,
...
care
...
must
...
be
...
taken
...
when
...
using
...
rename()
...
.
Non-Compliant
...
Code
...
Example
...
In
...
the
...
following
...
non-compliant
...
code,
...
a
...
file
...
is
...
renamed
...
to
...
another
...
file
...
using
...
rename()
...
.
| Code Block | ||||
|---|---|---|---|---|
| =
| |||
/* program code */
const char *old = "oldfile.ext";
const char *new = "newfile.ext";
if (rename(old, new) != 0) {
/* Handle rename failure */
}
/* program code */
{null}
|
However,
...
if
...
newfile.ext
...
already
...
existed,
...
the
...
result
...
is
...
undefined.
...
Compliant
...
Solution
...
This
...
compliant
...
solution
...
first
...
checks
...
for
...
the
...
existence
...
of
...
the
...
new
...
file
...
before
...
the
...
call
...
to
...
rename()
...
.
...
Note
...
that
...
this
...
code
...
contains
...
an
...
unavoidable
...
race
...
condition
...
between
...
the
...
call
...
to
...
fopen()
...
and
...
the
...
call
...
to
...
rename()
...
.
| Code Block | ||||
|---|---|---|---|---|
| =
| |||
/* program code */
const char *old = "oldfile.ext";
const char *new = "newfile.ext";
FILE *file = fopen(new, "r");
if (file != NULL) {
fclose(file);
if (rename(old, new) != 0) {
/* Handle remove failure */
}
}
else {
/* handle error condition */
}
/* program code */
{null}
h2. Risk Assessment
Using {{ |
Risk Assessment
Using rename()
...
without
...
caution
...
leads
...
to
...
undefined
...
behavior,
...
possibly
...
resulting
...
in
...
a
...
file
...
being
...
unexpectedly
...
overwritten.
...
Recommendation | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
FIO10-A | 2 (medium) | 2 (probable) | 2 (medium) | P8 | L2 |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
References
| Wiki Markup |
|---|
\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 7.9.4.2, "The {{rename}} function" |