RSM/asn1codec/e2ap_engine/der_encoder.c

   1
   2 /*-
   3  * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
   4  * Redistribution and modifications are permitted subject to BSD license.
   5  */
   6 #include <asn_internal.h>
   7 #include <errno.h>
   8
   9 static ssize_t der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
  10         asn_app_consume_bytes_f *cb, void *app_key, int constructed);
  11
  12 /*
  13  * The DER encoder of any type.
  14  */
  15 asn_enc_rval_t
  16 der_encode(const asn_TYPE_descriptor_t *type_descriptor, const void *struct_ptr,
  17            asn_app_consume_bytes_f *consume_bytes, void *app_key) {
  18     ASN_DEBUG("DER encoder invoked for %s",
  19                 type_descriptor->name);
  20
  21         /*
  22          * Invoke type-specific encoder.
  23          */
  24     return type_descriptor->op->der_encoder(
  25         type_descriptor, struct_ptr, /* Pointer to the destination structure */
  26         0, 0, consume_bytes, app_key);
  27 }
  28
  29 /*
  30  * Argument type and callback necessary for der_encode_to_buffer().
  31  */
  32 typedef struct enc_to_buf_arg {
  33         void *buffer;
  34         size_t left;
  35 } enc_to_buf_arg;
  36 static int encode_to_buffer_cb(const void *buffer, size_t size, void *key) {
  37         enc_to_buf_arg *arg = (enc_to_buf_arg *)key;
  38
  39         if(arg->left < size)
  40                 return -1;      /* Data exceeds the available buffer size */
  41
  42         memcpy(arg->buffer, buffer, size);
  43         arg->buffer = ((char *)arg->buffer) + size;
  44         arg->left -= size;
  45
  46         return 0;
  47 }
  48
  49 /*
  50  * A variant of the der_encode() which encodes the data into the provided buffer
  51  */
  52 asn_enc_rval_t
  53 der_encode_to_buffer(const asn_TYPE_descriptor_t *type_descriptor,
  54                      const void *struct_ptr, void *buffer, size_t buffer_size) {
  55     enc_to_buf_arg arg;
  56         asn_enc_rval_t ec;
  57
  58         arg.buffer = buffer;
  59         arg.left = buffer_size;
  60
  61         ec = type_descriptor->op->der_encoder(type_descriptor,
  62                 struct_ptr,     /* Pointer to the destination structure */
  63                 0, 0, encode_to_buffer_cb, &arg);
  64         if(ec.encoded != -1) {
  65                 assert(ec.encoded == (ssize_t)(buffer_size - arg.left));
  66                 /* Return the encoded contents size */
  67         }
  68         return ec;
  69 }
  70
  71
  72 /*
  73  * Write out leading TL[v] sequence according to the type definition.
  74  */
  75 ssize_t
  76 der_write_tags(const asn_TYPE_descriptor_t *sd, size_t struct_length,
  77                int tag_mode, int last_tag_form,
  78                ber_tlv_tag_t tag, /* EXPLICIT or IMPLICIT tag */
  79                asn_app_consume_bytes_f *cb, void *app_key) {
  80 #define ASN1_DER_MAX_TAGS_COUNT 4
  81     ber_tlv_tag_t
  82         tags_buf_scratch[ASN1_DER_MAX_TAGS_COUNT * sizeof(ber_tlv_tag_t)];
  83     ssize_t lens[ASN1_DER_MAX_TAGS_COUNT * sizeof(ssize_t)];
  84     const ber_tlv_tag_t *tags; /* Copy of tags stream */
  85     int tags_count;            /* Number of tags */
  86     size_t overall_length;
  87     int i;
  88
  89     ASN_DEBUG("Writing tags (%s, tm=%d, tc=%d, tag=%s, mtc=%d)",
  90                 sd->name, tag_mode, sd->tags_count,
  91                 ber_tlv_tag_string(tag),
  92                 tag_mode
  93                         ?(sd->tags_count+1
  94                                 -((tag_mode == -1) && sd->tags_count))
  95                         :sd->tags_count
  96         );
  97
  98     if(sd->tags_count + 1 > ASN1_DER_MAX_TAGS_COUNT) {
  99         ASN_DEBUG("System limit %d on tags count", ASN1_DER_MAX_TAGS_COUNT);
 100         return -1;
 101     }
 102
 103         if(tag_mode) {
 104                 /*
 105                  * Instead of doing shaman dance like we do in ber_check_tags(),
 106                  * allocate a small array on the stack
 107                  * and initialize it appropriately.
 108                  */
 109                 int stag_offset;
 110                 ber_tlv_tag_t *tags_buf = tags_buf_scratch;
 111                 tags_count = sd->tags_count
 112                         + 1     /* EXPLICIT or IMPLICIT tag is given */
 113                         - ((tag_mode == -1) && sd->tags_count);
 114                 /* Copy tags over */
 115                 tags_buf[0] = tag;
 116                 stag_offset = -1 + ((tag_mode == -1) && sd->tags_count);
 117                 for(i = 1; i < tags_count; i++)
 118                         tags_buf[i] = sd->tags[i + stag_offset];
 119                 tags = tags_buf;
 120         } else {
 121                 tags = sd->tags;
 122                 tags_count = sd->tags_count;
 123         }
 124
 125         /* No tags to write */
 126         if(tags_count == 0)
 127                 return 0;
 128
 129         /*
 130          * Array of tags is initialized.
 131          * Now, compute the size of the TLV pairs, from right to left.
 132          */
 133         overall_length = struct_length;
 134         for(i = tags_count - 1; i >= 0; --i) {
 135                 lens[i] = der_write_TL(tags[i], overall_length, 0, 0, 0);
 136                 if(lens[i] == -1) return -1;
 137                 overall_length += lens[i];
 138                 lens[i] = overall_length - lens[i];
 139         }
 140
 141         if(!cb) return overall_length - struct_length;
 142
 143         ASN_DEBUG("Encoding %s TL sequence (%d elements)", sd->name,
 144                   tags_count);
 145
 146         /*
 147          * Encode the TL sequence for real.
 148          */
 149         for(i = 0; i < tags_count; i++) {
 150                 ssize_t len;
 151                 int _constr;
 152
 153                 /* Check if this tag happens to be constructed */
 154                 _constr = (last_tag_form || i < (tags_count - 1));
 155
 156                 len = der_write_TL(tags[i], lens[i], cb, app_key, _constr);
 157                 if(len == -1) return -1;
 158         }
 159
 160         return overall_length - struct_length;
 161 }
 162
 163 static ssize_t
 164 der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len,
 165                 asn_app_consume_bytes_f *cb, void *app_key,
 166                 int constructed) {
 167         uint8_t buf[32];
 168         size_t size = 0;
 169         int buf_size = cb?sizeof(buf):0;
 170         ssize_t tmp;
 171
 172         /* Serialize tag (T from TLV) into possibly zero-length buffer */
 173         tmp = ber_tlv_tag_serialize(tag, buf, buf_size);
 174         if(tmp == -1 || tmp > (ssize_t)sizeof(buf)) return -1;
 175         size += tmp;
 176
 177         /* Serialize length (L from TLV) into possibly zero-length buffer */
 178         tmp = der_tlv_length_serialize(len, buf+size, buf_size?buf_size-size:0);
 179         if(tmp == -1) return -1;
 180         size += tmp;
 181
 182         if(size > sizeof(buf))
 183                 return -1;
 184
 185         /*
 186          * If callback is specified, invoke it, and check its return value.
 187          */
 188         if(cb) {
 189                 if(constructed) *buf |= 0x20;
 190                 if(cb(buf, size, app_key) < 0)
 191                         return -1;
 192         }
 193
 194         return size;
 195 }