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