| 1 | /* |
| 2 | * PKCS#5 padding |
| 3 | * |
| 4 | * arguments: block size to pad to, must be power of 2 |
| 5 | * |
| 6 | * encoding: append between 1 and n bytes, all of the same value being |
| 7 | * the number of bytes appended |
| 8 | */ |
| 9 | |
| 10 | #include "forwarder.h" |
| 11 | |
| 12 | struct mechdata { |
| 13 | unsigned mask; |
| 14 | }; |
| 15 | |
| 16 | static unsigned long setup(struct mechdata **md_r) { |
| 17 | struct mechdata *md; |
| 18 | unsigned long blocksize; |
| 19 | |
| 20 | XMALLOC(md); |
| 21 | |
| 22 | blocksize= getarg_ulong(); |
| 23 | md->mask= blocksize - 1; |
| 24 | arg_assert(!md->mask & blocksize); |
| 25 | arg_assert(blocksize <= 255); |
| 26 | |
| 27 | *md_r= md; |
| 28 | return blocksize; |
| 29 | } |
| 30 | |
| 31 | static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
| 32 | unsigned long blocksize; |
| 33 | |
| 34 | blocksize= setup(md_r); |
| 35 | *maxsuffix_io += blocksize + 1; |
| 36 | } |
| 37 | |
| 38 | static void mds_pkcs5(struct mechdata **md_r) { |
| 39 | setup(md_r); |
| 40 | } |
| 41 | |
| 42 | static void menc_pkcs5(struct mechdata *md, struct buffer *buf) { |
| 43 | unsigned char *pad; |
| 44 | int padlen; |
| 45 | |
| 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 */ |
| 51 | |
| 52 | pad= buf_append(buf,padlen); |
| 53 | memset(pad,padlen,padlen); |
| 54 | } |
| 55 | |
| 56 | static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) { |
| 57 | unsigned char *padp; |
| 58 | unsigned padlen; |
| 59 | int i; |
| 60 | |
| 61 | BUF_UNPREPEND(padp,buf,1); |
| 62 | padlen= *padp; |
| 63 | if (!padlen || (padlen & ~md->mask)) return "invalid length"; |
| 64 | |
| 65 | BUF_UNPREPEND(padp,buf,padlen-1); |
| 66 | for (i=0; i<padlen-1; i++) |
| 67 | if (*++padp != padlen) return "corrupted padding"; |
| 68 | |
| 69 | return 0; |
| 70 | } |
| 71 | |
| 72 | STANDARD_MECHANISMLIST("pkcs5",pkcs5) |