| 1 | /* |
| 2 | * Sequence number / nonce mechanism |
| 3 | * |
| 4 | * arguments: none |
| 5 | * |
| 6 | * encoding: prepend 4 bytes of sequence arithmetic serial number |
| 7 | * decoding: check increasingness, or ignore |
| 8 | */ |
| 9 | |
| 10 | #include <netinet/in.h> |
| 11 | |
| 12 | #include "forwarder.h" |
| 13 | |
| 14 | struct mechdata { |
| 15 | uint32_t number; |
| 16 | int anyseen; /* decode only */ |
| 17 | }; |
| 18 | |
| 19 | static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
| 20 | struct mechdata *md; |
| 21 | |
| 22 | XMALLOC(md); |
| 23 | get_random(&md->number,sizeof(md->number)); |
| 24 | *maxprefix_io += 4; |
| 25 | *md_r= md; |
| 26 | } |
| 27 | |
| 28 | static void mds_sequence(struct mechdata **md_r) { |
| 29 | struct mechdata *md; |
| 30 | XMALLOC(md); |
| 31 | md->anyseen= 0; |
| 32 | *md_r= md; |
| 33 | } |
| 34 | |
| 35 | static void menc_sequence(struct mechdata *md, struct buffer *buf) { |
| 36 | md->number++; |
| 37 | *(uint32_t*)buf_prepend(buf,4)= htonl(md->number); |
| 38 | } |
| 39 | |
| 40 | static const char *mdec_check(struct mechdata *md, struct buffer *buf) { |
| 41 | uint32_t *sp, sequence; |
| 42 | |
| 43 | BUF_UNPREPEND(sp,buf,4); |
| 44 | sequence= ntohl(*sp); |
| 45 | |
| 46 | if (md->anyseen) |
| 47 | if (sequence - md->number >= 0x800000UL) return "out of order packet"; |
| 48 | |
| 49 | md->number= sequence; |
| 50 | md->anyseen= 1; |
| 51 | |
| 52 | return 0; |
| 53 | } |
| 54 | |
| 55 | static const char *mdec_skip(struct mechdata *md, struct buffer *buf) { |
| 56 | uint32_t *sp; |
| 57 | BUF_UNPREPEND(sp,buf,4); |
| 58 | return 0; |
| 59 | } |
| 60 | |
| 61 | const struct mechanism mechlist_sequence[]= { |
| 62 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
| 63 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
| 64 | { 0 } |
| 65 | }; |