4 * arguments: block size to pad to, must be power of 2
6 * encoding: append between 1 and n bytes, all of the same value being
7 * the number of bytes appended
10 #include "forwarder.h"
16 static unsigned long setup(struct mechdata
**md_r
) {
18 unsigned long blocksize
;
22 blocksize
= getarg_ulong();
23 md
->mask
= blocksize
- 1;
24 arg_assert(!(md
->mask
& blocksize
));
25 arg_assert(blocksize
<= 255);
31 static void mes_pkcs5(struct mechdata
**md_r
, int *maxprefix_io
, int *maxsuffix_io
) {
32 unsigned long blocksize
;
34 blocksize
= setup(md_r
);
35 *maxsuffix_io
+= blocksize
+ 1;
38 static void mds_pkcs5(struct mechdata
**md_r
) {
42 static void menc_pkcs5(struct mechdata
*md
, struct buffer
*buf
) {
46 /* eg with blocksize=4 mask=3 mask+2=5 */
47 /* msgsize 20 21 22 23 24 */
48 padlen
= md
->mask
- buf
->size
; /* -17 -18 -19 -16 -17 */
49 padlen
&= md
->mask
; /* 3 2 1 0 3 */
50 padlen
++; /* 4 3 2 1 4 */
52 pad
= buf_append(buf
,padlen
);
53 memset(pad
,padlen
,padlen
);
56 static const char *mdec_pkcs5(struct mechdata
*md
, struct buffer
*buf
) {
61 BUF_UNPREPEND(padp
,buf
,1);
63 if (!padlen
|| (padlen
& ~md
->mask
)) return "invalid length";
65 BUF_UNPREPEND(padp
,buf
,padlen
-1);
66 for (i
=0; i
<padlen
-1; i
++)
67 if (*++padp
!= padlen
) return "corrupted padding";
72 STANDARD_MECHANISMLIST("pkcs5",pkcs5
)