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[stg.git] / libs / smux / der_encoder.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 <errno.h>
7
8 static ssize_t der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
9         asn_app_consume_bytes_f *cb, void *app_key, int constructed);
10
11 /*
12  * The DER encoder of any type.
13  */
14 asn_enc_rval_t
15 der_encode(const asn_TYPE_descriptor_t *type_descriptor, const void *struct_ptr,
16            asn_app_consume_bytes_f *consume_bytes, void *app_key) {
17     ASN_DEBUG("DER encoder invoked for %s",
18                 type_descriptor->name);
19
20         /*
21          * Invoke type-specific encoder.
22          */
23     return type_descriptor->op->der_encoder(
24         type_descriptor, struct_ptr, /* Pointer to the destination structure */
25         0, 0, consume_bytes, app_key);
26 }
27
28 /*
29  * Argument type and callback necessary for der_encode_to_buffer().
30  */
31 typedef struct enc_to_buf_arg {
32         void *buffer;
33         size_t left;
34 } enc_to_buf_arg;
35 static int encode_to_buffer_cb(const void *buffer, size_t size, void *key) {
36         enc_to_buf_arg *arg = (enc_to_buf_arg *)key;
37
38         if(arg->left < size)
39                 return -1;      /* Data exceeds the available buffer size */
40
41         memcpy(arg->buffer, buffer, size);
42         arg->buffer = ((char *)arg->buffer) + size;
43         arg->left -= size;
44
45         return 0;
46 }
47
48 /*
49  * A variant of the der_encode() which encodes the data into the provided buffer
50  */
51 asn_enc_rval_t
52 der_encode_to_buffer(const asn_TYPE_descriptor_t *type_descriptor,
53                      const void *struct_ptr, void *buffer, size_t buffer_size) {
54     enc_to_buf_arg arg;
55         asn_enc_rval_t ec;
56
57         arg.buffer = buffer;
58         arg.left = buffer_size;
59
60         ec = type_descriptor->op->der_encoder(type_descriptor,
61                 struct_ptr,     /* Pointer to the destination structure */
62                 0, 0, encode_to_buffer_cb, &arg);
63         if(ec.encoded != -1) {
64                 assert(ec.encoded == (ssize_t)(buffer_size - arg.left));
65                 /* Return the encoded contents size */
66         }
67         return ec;
68 }
69
70
71 /*
72  * Write out leading TL[v] sequence according to the type definition.
73  */
74 ssize_t
75 der_write_tags(const asn_TYPE_descriptor_t *sd, size_t struct_length,
76                int tag_mode, int last_tag_form,
77                ber_tlv_tag_t tag, /* EXPLICIT or IMPLICIT tag */
78                asn_app_consume_bytes_f *cb, void *app_key) {
79 #define ASN1_DER_MAX_TAGS_COUNT 4
80     ber_tlv_tag_t
81         tags_buf_scratch[ASN1_DER_MAX_TAGS_COUNT * sizeof(ber_tlv_tag_t)];
82     ssize_t lens[ASN1_DER_MAX_TAGS_COUNT * sizeof(ssize_t)];
83     const ber_tlv_tag_t *tags; /* Copy of tags stream */
84     int tags_count;            /* Number of tags */
85     size_t overall_length;
86     int i;
87
88     ASN_DEBUG("Writing tags (%s, tm=%d, tc=%d, tag=%s, mtc=%d)",
89                 sd->name, tag_mode, sd->tags_count,
90                 ber_tlv_tag_string(tag),
91                 tag_mode
92                         ?(sd->tags_count+1
93                                 -((tag_mode == -1) && sd->tags_count))
94                         :sd->tags_count
95         );
96
97     if(sd->tags_count + 1 > ASN1_DER_MAX_TAGS_COUNT) {
98         ASN_DEBUG("System limit %d on tags count", ASN1_DER_MAX_TAGS_COUNT);
99         return -1;
100     }
101
102         if(tag_mode) {
103                 /*
104                  * Instead of doing shaman dance like we do in ber_check_tags(),
105                  * allocate a small array on the stack
106                  * and initialize it appropriately.
107                  */
108                 int stag_offset;
109                 ber_tlv_tag_t *tags_buf = tags_buf_scratch;
110                 tags_count = sd->tags_count
111                         + 1     /* EXPLICIT or IMPLICIT tag is given */
112                         - ((tag_mode == -1) && sd->tags_count);
113                 /* Copy tags over */
114                 tags_buf[0] = tag;
115                 stag_offset = -1 + ((tag_mode == -1) && sd->tags_count);
116                 for(i = 1; i < tags_count; i++)
117                         tags_buf[i] = sd->tags[i + stag_offset];
118                 tags = tags_buf;
119         } else {
120                 tags = sd->tags;
121                 tags_count = sd->tags_count;
122         }
123
124         /* No tags to write */
125         if(tags_count == 0)
126                 return 0;
127
128         /*
129          * Array of tags is initialized.
130          * Now, compute the size of the TLV pairs, from right to left.
131          */
132         overall_length = struct_length;
133         for(i = tags_count - 1; i >= 0; --i) {
134                 lens[i] = der_write_TL(tags[i], overall_length, 0, 0, 0);
135                 if(lens[i] == -1) return -1;
136                 overall_length += lens[i];
137                 lens[i] = overall_length - lens[i];
138         }
139
140         if(!cb) return overall_length - struct_length;
141
142         ASN_DEBUG("Encoding %s TL sequence (%d elements)", sd->name,
143                   tags_count);
144
145         /*
146          * Encode the TL sequence for real.
147          */
148         for(i = 0; i < tags_count; i++) {
149                 ssize_t len;
150                 int _constr;
151
152                 /* Check if this tag happens to be constructed */
153                 _constr = (last_tag_form || i < (tags_count - 1));
154
155                 len = der_write_TL(tags[i], lens[i], cb, app_key, _constr);
156                 if(len == -1) return -1;
157         }
158
159         return overall_length - struct_length;
160 }
161
162 static ssize_t
163 der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
164                 asn_app_consume_bytes_f *cb, void *app_key,
165                 int constructed) {
166         uint8_t buf[32];
167         size_t size = 0;
168         int buf_size = cb?sizeof(buf):0;
169         ssize_t tmp;
170
171         /* Serialize tag (T from TLV) into possibly zero-length buffer */
172         tmp = ber_tlv_tag_serialize(tag, buf, buf_size);
173         if(tmp == -1 || tmp > (ssize_t)sizeof(buf)) return -1;
174         size += tmp;
175
176         /* Serialize length (L from TLV) into possibly zero-length buffer */
177         tmp = der_tlv_length_serialize(len, buf+size, buf_size?buf_size-size:0);
178         if(tmp == -1) return -1;
179         size += tmp;
180
181         if(size > sizeof(buf))
182                 return -1;
183
184         /*
185          * If callback is specified, invoke it, and check its return value.
186          */
187         if(cb) {
188                 if(constructed) *buf |= 0x20;
189                 if(cb(buf, size, app_key) < 0)
190                         return -1;
191         }
192
193         return size;
194 }