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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 | |
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12 | #include "forwarder.h" |
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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[]= { |
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62 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
63 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
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64 | { 0 } |
65 | }; |