]> git.stg.codes - stg.git/blob - stglibs/smux.lib/ber_tlv_length.c
Trailing coma removed
[stg.git] / stglibs / smux.lib / ber_tlv_length.c
1 /*-
2  * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
3  * Redistribution and modifications are permitted subject to BSD license.
4  */
5 #include <asn_internal.h>
6 #include <ber_tlv_length.h>
7 #include <ber_tlv_tag.h>
8
9 ssize_t
10 ber_fetch_length(int _is_constructed, const void *bufptr, size_t size,
11                 ber_tlv_len_t *len_r) {
12         const uint8_t *buf = (const uint8_t *)bufptr;
13         unsigned oct;
14
15         if(size == 0)
16                 return 0;       /* Want more */
17
18         oct = *(const uint8_t *)buf;
19         if((oct & 0x80) == 0) {
20                 /*
21                  * Short definite length.
22                  */
23                 *len_r = oct;   /* & 0x7F */
24                 return 1;
25         } else {
26                 ber_tlv_len_t len;
27                 size_t skipped;
28
29                 if(_is_constructed && oct == 0x80) {
30                         *len_r = -1;    /* Indefinite length */
31                         return 1;
32                 }
33
34                 if(oct == 0xff) {
35                         /* Reserved in standard for future use. */
36                         return -1;
37                 }
38
39                 oct &= 0x7F;    /* Leave only the 7 LS bits */
40                 for(len = 0, buf++, skipped = 1;
41                         oct && (++skipped <= size); buf++, oct--) {
42
43                         len = (len << 8) | *buf;
44                         if(len < 0
45                         || (len >> ((8 * sizeof(len)) - 8) && oct > 1)) {
46                                 /*
47                                  * Too large length value.
48                                  */
49                                 return -1;
50                         }
51                 }
52
53                 if(oct == 0) {
54                         ber_tlv_len_t lenplusepsilon = (size_t)len + 1024;
55                         /*
56                          * Here length may be very close or equal to 2G.
57                          * However, the arithmetics used in some decoders
58                          * may add some (small) quantities to the length,
59                          * to check the resulting value against some limits.
60                          * This may result in integer wrap-around, which
61                          * we try to avoid by checking it earlier here.
62                          */
63                         if(lenplusepsilon < 0) {
64                                 /* Too large length value */
65                                 return -1;
66                         }
67
68                         *len_r = len;
69                         return skipped;
70                 }
71
72                 return 0;       /* Want more */
73         }
74
75 }
76
77 ssize_t
78 ber_skip_length(asn_codec_ctx_t *opt_codec_ctx,
79                 int _is_constructed, const void *ptr, size_t size) {
80         ber_tlv_len_t vlen;     /* Length of V in TLV */
81         ssize_t tl;             /* Length of L in TLV */
82         ssize_t ll;             /* Length of L in TLV */
83         size_t skip;
84
85         /*
86          * Make sure we didn't exceed the maximum stack size.
87          */
88         if(_ASN_STACK_OVERFLOW_CHECK(opt_codec_ctx))
89                 return -1;
90
91         /*
92          * Determine the size of L in TLV.
93          */
94         ll = ber_fetch_length(_is_constructed, ptr, size, &vlen);
95         if(ll <= 0) return ll;
96
97         /*
98          * Definite length.
99          */
100         if(vlen >= 0) {
101                 skip = ll + vlen;
102                 if(skip > size)
103                         return 0;       /* Want more */
104                 return skip;
105         }
106
107         /*
108          * Indefinite length!
109          */
110         ASN_DEBUG("Skipping indefinite length");
111         for(skip = ll, ptr = ((const char *)ptr) + ll, size -= ll;;) {
112                 ber_tlv_tag_t tag;
113
114                 /* Fetch the tag */
115                 tl = ber_fetch_tag(ptr, size, &tag);
116                 if(tl <= 0) return tl;
117
118                 ll = ber_skip_length(opt_codec_ctx,
119                         BER_TLV_CONSTRUCTED(ptr),
120                         ((const char *)ptr) + tl, size - tl);
121                 if(ll <= 0) return ll;
122
123                 skip += tl + ll;
124
125                 /*
126                  * This may be the end of the indefinite length structure,
127                  * two consecutive 0 octets.
128                  * Check if it is true.
129                  */
130                 if(((const uint8_t *)ptr)[0] == 0
131                 && ((const uint8_t *)ptr)[1] == 0)
132                         return skip;
133
134                 ptr = ((const char *)ptr) + tl + ll;
135                 size -= tl + ll;
136         }
137
138         /* UNREACHABLE */
139 }
140
141 size_t
142 der_tlv_length_serialize(ber_tlv_len_t len, void *bufp, size_t size) {
143         size_t required_size;   /* Size of len encoding */
144         uint8_t *buf = (uint8_t *)bufp;
145         uint8_t *end;
146         size_t i;
147
148         if(len <= 127) {
149                 /* Encoded in 1 octet */
150                 if(size) *buf = (uint8_t)len;
151                 return 1;
152         }
153
154         /*
155          * Compute the size of the subsequent bytes.
156          */
157         for(required_size = 1, i = 8; i < 8 * sizeof(len); i += 8) {
158                 if(len >> i)
159                         required_size++;
160                 else
161                         break;
162         }
163
164         if(size <= required_size)
165                 return required_size + 1;
166
167         *buf++ = (uint8_t)(0x80 | required_size);  /* Length of the encoding */
168
169         /*
170          * Produce the len encoding, space permitting.
171          */
172         end = buf + required_size;
173         for(i -= 8; buf < end; i -= 8, buf++)
174                 *buf = (uint8_t)(len >> i);
175
176         return required_size + 1;
177 }
178