libs/smux/xer_decoder.c

   1 /*
   2  * Copyright (c) 2004, 2005 Lev Walkin <vlm@lionet.info>. All rights reserved.
   3  * Redistribution and modifications are permitted subject to BSD license.
   4  */
   5 #include <asn_application.h>
   6 #include <asn_internal.h>
   7 #include <xer_support.h>                /* XER/XML parsing support */
   8
   9
  10 /*
  11  * Decode the XER encoding of a given type.
  12  */
  13 asn_dec_rval_t
  14 xer_decode(asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td,
  15                 void **struct_ptr, const void *buffer, size_t size) {
  16         asn_codec_ctx_t s_codec_ctx;
  17
  18         /*
  19          * Stack checker requires that the codec context
  20          * must be allocated on the stack.
  21          */
  22         if(opt_codec_ctx) {
  23                 if(opt_codec_ctx->max_stack_size) {
  24                         s_codec_ctx = *opt_codec_ctx;
  25                         opt_codec_ctx = &s_codec_ctx;
  26                 }
  27         } else {
  28                 /* If context is not given, be security-conscious anyway */
  29                 memset(&s_codec_ctx, 0, sizeof(s_codec_ctx));
  30                 s_codec_ctx.max_stack_size = ASN__DEFAULT_STACK_MAX;
  31                 opt_codec_ctx = &s_codec_ctx;
  32         }
  33
  34         /*
  35          * Invoke type-specific decoder.
  36          */
  37         return td->xer_decoder(opt_codec_ctx, td, struct_ptr, 0, buffer, size);
  38 }
  39
  40
  41
  42 struct xer__cb_arg {
  43         pxml_chunk_type_e       chunk_type;
  44         size_t                  chunk_size;
  45         const void              *chunk_buf;
  46         int callback_not_invoked;
  47 };
  48
  49 static int
  50 xer__token_cb(pxml_chunk_type_e type, const void *_chunk_data, size_t _chunk_size, void *key) {
  51         struct xer__cb_arg *arg = (struct xer__cb_arg *)key;
  52         arg->chunk_type = type;
  53         arg->chunk_size = _chunk_size;
  54         arg->chunk_buf = _chunk_data;
  55         arg->callback_not_invoked = 0;
  56         return -1;      /* Terminate the XML parsing */
  57 }
  58
  59 /*
  60  * Fetch the next token from the XER/XML stream.
  61  */
  62 ssize_t
  63 xer_next_token(int *stateContext, const void *buffer, size_t size, pxer_chunk_type_e *ch_type) {
  64         struct xer__cb_arg arg;
  65         int new_stateContext = *stateContext;
  66         ssize_t ret;
  67
  68         arg.callback_not_invoked = 1;
  69         ret = pxml_parse(&new_stateContext, buffer, size, xer__token_cb, &arg);
  70         if(ret < 0) return -1;
  71         if(arg.callback_not_invoked) {
  72                 assert(ret == 0);       /* No data was consumed */
  73         *ch_type = PXER_WMORE;
  74                 return 0;               /* Try again with more data */
  75         } else {
  76                 assert(arg.chunk_size);
  77                 assert(arg.chunk_buf == buffer);
  78         }
  79
  80         /*
  81          * Translate the XML chunk types into more convenient ones.
  82          */
  83         switch(arg.chunk_type) {
  84         case PXML_TEXT:
  85                 *ch_type = PXER_TEXT;
  86                 break;
  87         case PXML_TAG:
  88         *ch_type = PXER_WMORE;
  89         return 0;       /* Want more */
  90         case PXML_TAG_END:
  91                 *ch_type = PXER_TAG;
  92                 break;
  93         case PXML_COMMENT:
  94         case PXML_COMMENT_END:
  95                 *ch_type = PXER_COMMENT;
  96                 break;
  97         }
  98
  99         *stateContext = new_stateContext;
 100         return arg.chunk_size;
 101 }
 102
 103 #define CSLASH  0x2f    /* '/' */
 104 #define LANGLE  0x3c    /* '<' */
 105 #define RANGLE  0x3e    /* '>' */
 106
 107 xer_check_tag_e
 108 xer_check_tag(const void *buf_ptr, int size, const char *need_tag) {
 109         const char *buf = (const char *)buf_ptr;
 110         const char *end;
 111         xer_check_tag_e ct = XCT_OPENING;
 112
 113         if(size < 2 || buf[0] != LANGLE || buf[size-1] != RANGLE) {
 114                 if(size >= 2)
 115                         ASN_DEBUG("Broken XML tag: \"%c...%c\"",
 116                         buf[0], buf[size - 1]);
 117                 return XCT_BROKEN;
 118         }
 119
 120         /*
 121          * Determine the tag class.
 122          */
 123         if(buf[1] == CSLASH) {
 124                 buf += 2;       /* advance past "</" */
 125                 size -= 3;      /* strip "</" and ">" */
 126                 ct = XCT_CLOSING;
 127                 if(size > 0 && buf[size-1] == CSLASH)
 128                         return XCT_BROKEN;      /* </abc/> */
 129         } else {
 130                 buf++;          /* advance past "<" */
 131                 size -= 2;      /* strip "<" and ">" */
 132                 if(size > 0 && buf[size-1] == CSLASH) {
 133                         ct = XCT_BOTH;
 134                         size--; /* One more, for "/" */
 135                 }
 136         }
 137
 138         /* Sometimes we don't care about the tag */
 139         if(!need_tag || !*need_tag)
 140                 return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 141
 142         /*
 143          * Determine the tag name.
 144          */
 145         for(end = buf + size; buf < end; buf++, need_tag++) {
 146                 int b = *buf, n = *need_tag;
 147                 if(b != n) {
 148                         if(n == 0) {
 149                                 switch(b) {
 150                                 case 0x09: case 0x0a: case 0x0c: case 0x0d:
 151                                 case 0x20:
 152                                         /* "<abc def/>": whitespace is normal */
 153                                         return ct;
 154                                 }
 155                         }
 156                         return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 157                 }
 158                 if(b == 0)
 159                         return XCT_BROKEN;      /* Embedded 0 in buf?! */
 160         }
 161         if(*need_tag)
 162                 return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 163
 164         return ct;
 165 }
 166
 167
 168 #undef  ADVANCE
 169 #define ADVANCE(num_bytes)      do {                            \
 170                 size_t num = (num_bytes);                       \
 171                 buf_ptr = ((const char *)buf_ptr) + num;        \
 172                 size -= num;                                    \
 173                 consumed_myself += num;                         \
 174         } while(0)
 175
 176 #undef  RETURN
 177 #define RETURN(_code)   do {                                    \
 178                 rval.code = _code;                              \
 179                 rval.consumed = consumed_myself;                \
 180                 if(rval.code != RC_OK)                          \
 181                         ASN_DEBUG("Failed with %d", rval.code); \
 182                 return rval;                                    \
 183         } while(0)
 184
 185 #define XER_GOT_BODY(chunk_buf, chunk_size, size)       do {    \
 186                 ssize_t converted_size = body_receiver          \
 187                         (struct_key, chunk_buf, chunk_size,     \
 188                                 (size_t)chunk_size < size);     \
 189                 if(converted_size == -1) RETURN(RC_FAIL);       \
 190                 if(converted_size == 0                          \
 191                         && size == (size_t)chunk_size)          \
 192                         RETURN(RC_WMORE);                       \
 193                 chunk_size = converted_size;                    \
 194         } while(0)
 195 #define XER_GOT_EMPTY() do {                                    \
 196         if(body_receiver(struct_key, 0, 0, size > 0) == -1)     \
 197                         RETURN(RC_FAIL);                        \
 198         } while(0)
 199
 200 /*
 201  * Generalized function for decoding the primitive values.
 202  */
 203 asn_dec_rval_t
 204 xer_decode_general(asn_codec_ctx_t *opt_codec_ctx,
 205         asn_struct_ctx_t *ctx,  /* Type decoder context */
 206         void *struct_key,
 207         const char *xml_tag,    /* Expected XML tag */
 208         const void *buf_ptr, size_t size,
 209         int (*opt_unexpected_tag_decoder)
 210                 (void *struct_key, const void *chunk_buf, size_t chunk_size),
 211         ssize_t (*body_receiver)
 212                 (void *struct_key, const void *chunk_buf, size_t chunk_size,
 213                         int have_more)
 214         ) {
 215
 216         asn_dec_rval_t rval;
 217         ssize_t consumed_myself = 0;
 218
 219         (void)opt_codec_ctx;
 220
 221         /*
 222          * Phases of XER/XML processing:
 223          * Phase 0: Check that the opening tag matches our expectations.
 224          * Phase 1: Processing body and reacting on closing tag.
 225          */
 226         if(ctx->phase > 1) RETURN(RC_FAIL);
 227         for(;;) {
 228                 pxer_chunk_type_e ch_type;      /* XER chunk type */
 229                 ssize_t ch_size;                /* Chunk size */
 230                 xer_check_tag_e tcv;            /* Tag check value */
 231
 232                 /*
 233                  * Get the next part of the XML stream.
 234                  */
 235                 ch_size = xer_next_token(&ctx->context, buf_ptr, size,
 236                         &ch_type);
 237                 if(ch_size == -1) {
 238             RETURN(RC_FAIL);
 239         } else {
 240                         switch(ch_type) {
 241                         case PXER_WMORE:
 242                 RETURN(RC_WMORE);
 243                         case PXER_COMMENT:              /* Got XML comment */
 244                                 ADVANCE(ch_size);       /* Skip silently */
 245                                 continue;
 246                         case PXER_TEXT:
 247                                 if(ctx->phase == 0) {
 248                                         /*
 249                                          * We have to ignore whitespace here,
 250                                          * but in order to be forward compatible
 251                                          * with EXTENDED-XER (EMBED-VALUES, #25)
 252                                          * any text is just ignored here.
 253                                          */
 254                                 } else {
 255                                         XER_GOT_BODY(buf_ptr, ch_size, size);
 256                                 }
 257                                 ADVANCE(ch_size);
 258                                 continue;
 259                         case PXER_TAG:
 260                                 break;  /* Check the rest down there */
 261                         }
 262                 }
 263
 264                 assert(ch_type == PXER_TAG && size);
 265
 266                 tcv = xer_check_tag(buf_ptr, ch_size, xml_tag);
 267                 /*
 268                  * Phase 0:
 269                  *      Expecting the opening tag
 270                  *      for the type being processed.
 271                  * Phase 1:
 272                  *      Waiting for the closing XML tag.
 273                  */
 274                 switch(tcv) {
 275                 case XCT_BOTH:
 276                         if(ctx->phase) break;
 277                         /* Finished decoding of an empty element */
 278                         XER_GOT_EMPTY();
 279                         ADVANCE(ch_size);
 280                         ctx->phase = 2; /* Phase out */
 281                         RETURN(RC_OK);
 282                 case XCT_OPENING:
 283                         if(ctx->phase) break;
 284                         ADVANCE(ch_size);
 285                         ctx->phase = 1; /* Processing body phase */
 286                         continue;
 287                 case XCT_CLOSING:
 288                         if(!ctx->phase) break;
 289                         ADVANCE(ch_size);
 290                         ctx->phase = 2; /* Phase out */
 291                         RETURN(RC_OK);
 292                 case XCT_UNKNOWN_BO:
 293                         /*
 294                          * Certain tags in the body may be expected.
 295                          */
 296                         if(opt_unexpected_tag_decoder
 297                         && opt_unexpected_tag_decoder(struct_key,
 298                                         buf_ptr, ch_size) >= 0) {
 299                                 /* Tag's processed fine */
 300                                 ADVANCE(ch_size);
 301                                 if(!ctx->phase) {
 302                                         /* We are not expecting
 303                                          * the closing tag anymore. */
 304                                         ctx->phase = 2; /* Phase out */
 305                                         RETURN(RC_OK);
 306                                 }
 307                                 continue;
 308                         }
 309                         /* Fall through */
 310                 default:
 311                         break;          /* Unexpected tag */
 312                 }
 313
 314                 ASN_DEBUG("Unexpected XML tag (expected \"%s\")", xml_tag);
 315                 break;  /* Dark and mysterious things have just happened */
 316         }
 317
 318         RETURN(RC_FAIL);
 319 }
 320
 321
 322 size_t
 323 xer_whitespace_span(const void *chunk_buf, size_t chunk_size) {
 324         const char *p = (const char *)chunk_buf;
 325         const char *pend = p + chunk_size;
 326
 327         for(; p < pend; p++) {
 328                 switch(*p) {
 329                 /* X.693, #8.1.4
 330                  * HORISONTAL TAB (9)
 331                  * LINE FEED (10)
 332                  * CARRIAGE RETURN (13)
 333                  * SPACE (32)
 334                  */
 335                 case 0x09: case 0x0a: case 0x0d: case 0x20:
 336                         continue;
 337                 default:
 338                         break;
 339                 }
 340                 break;
 341         }
 342         return (p - (const char *)chunk_buf);
 343 }
 344
 345 /*
 346  * This is a vastly simplified, non-validating XML tree skipper.
 347  */
 348 int
 349 xer_skip_unknown(xer_check_tag_e tcv, ber_tlv_len_t *depth) {
 350         assert(*depth > 0);
 351         switch(tcv) {
 352         case XCT_BOTH:
 353         case XCT_UNKNOWN_BO:
 354                 /* These negate each other. */
 355                 return 0;
 356         case XCT_OPENING:
 357         case XCT_UNKNOWN_OP:
 358                 ++(*depth);
 359                 return 0;
 360         case XCT_CLOSING:
 361         case XCT_UNKNOWN_CL:
 362                 if(--(*depth) == 0)
 363                         return (tcv == XCT_CLOSING) ? 2 : 1;
 364                 return 0;
 365         default:
 366                 return -1;
 367         }
 368 }