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[libc] Prevent strndup() from reading beyond the end of the string

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strndup() may be called on a string which is not NUL-terminated.  Use
strnlen() instead of strlen() to ensure that we do not read beyond the
end of such a string.

Add self-tests for strndup(), including a test case with an
unterminated string.

Originally-fixed-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2014-05-18 21:05:39 +01:00
parent 5249368950
commit 2b4be69eee
2 changed files with 21 additions and 3 deletions
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4
src/core/string.c
View File

@ -337,11 +337,9 @@ void * memchr(const void *s, int c, size_t n)
char * strndup(const char *s, size_t n)
{
size_t len = strlen(s);
size_t len = strnlen(s,n);
char *new;
if (len>n)
len = n;
new = malloc(len+1);
if (new) {
new[len] = '\0';

20
src/tests/string_test.c
View File

@ -134,6 +134,26 @@ static void string_test_exec ( void ) {
ok ( strcmp ( dup, orig ) == 0 );
free ( dup );
}
/* Test strndup() */
{
const char *normal = "testing testing";
const char unterminated[6] = { 'h', 'e', 'l', 'l', 'o', '!' };
char *dup;
dup = strndup ( normal, 32 );
ok ( dup != NULL );
ok ( dup != normal );
ok ( strcmp ( dup, normal ) == 0 );
free ( dup );
dup = strndup ( normal, 4 );
ok ( dup != NULL );
ok ( strcmp ( dup, "test" ) == 0 );
free ( dup );
dup = strndup ( unterminated, 5 );
ok ( dup != NULL );
ok ( strcmp ( dup, "hello" ) == 0 );
free ( dup );
}
}
/** String self-test */