libs/smux/xer_decoder.c

   1 /*
   2  * Copyright (c) 2004-2017 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(const asn_codec_ctx_t *opt_codec_ctx,
  15            const asn_TYPE_descriptor_t *td, void **struct_ptr,
  16            const void *buffer, size_t size) {
  17     asn_codec_ctx_t s_codec_ctx;
  18
  19         /*
  20          * Stack checker requires that the codec context
  21          * must be allocated on the stack.
  22          */
  23         if(opt_codec_ctx) {
  24                 if(opt_codec_ctx->max_stack_size) {
  25                         s_codec_ctx = *opt_codec_ctx;
  26                         opt_codec_ctx = &s_codec_ctx;
  27                 }
  28         } else {
  29                 /* If context is not given, be security-conscious anyway */
  30                 memset(&s_codec_ctx, 0, sizeof(s_codec_ctx));
  31                 s_codec_ctx.max_stack_size = ASN__DEFAULT_STACK_MAX;
  32                 opt_codec_ctx = &s_codec_ctx;
  33         }
  34
  35         /*
  36          * Invoke type-specific decoder.
  37          */
  38         return td->op->xer_decoder(opt_codec_ctx, td, struct_ptr, 0, buffer, size);
  39 }
  40
  41
  42
  43 struct xer__cb_arg {
  44         pxml_chunk_type_e       chunk_type;
  45         size_t                  chunk_size;
  46         const void              *chunk_buf;
  47         int callback_not_invoked;
  48 };
  49
  50 static int
  51 xer__token_cb(pxml_chunk_type_e type, const void *_chunk_data, size_t _chunk_size, void *key) {
  52         struct xer__cb_arg *arg = (struct xer__cb_arg *)key;
  53         arg->chunk_type = type;
  54         arg->chunk_size = _chunk_size;
  55         arg->chunk_buf = _chunk_data;
  56         arg->callback_not_invoked = 0;
  57         return -1;      /* Terminate the XML parsing */
  58 }
  59
  60 /*
  61  * Fetch the next token from the XER/XML stream.
  62  */
  63 ssize_t
  64 xer_next_token(int *stateContext, const void *buffer, size_t size, pxer_chunk_type_e *ch_type) {
  65         struct xer__cb_arg arg;
  66         int new_stateContext = *stateContext;
  67         ssize_t ret;
  68
  69         arg.callback_not_invoked = 1;
  70         ret = pxml_parse(&new_stateContext, buffer, size, xer__token_cb, &arg);
  71         if(ret < 0) return -1;
  72         if(arg.callback_not_invoked) {
  73                 assert(ret == 0);       /* No data was consumed */
  74         *ch_type = PXER_WMORE;
  75                 return 0;               /* Try again with more data */
  76         } else {
  77                 assert(arg.chunk_size);
  78                 assert(arg.chunk_buf == buffer);
  79         }
  80
  81         /*
  82          * Translate the XML chunk types into more convenient ones.
  83          */
  84         switch(arg.chunk_type) {
  85         case PXML_TEXT:
  86                 *ch_type = PXER_TEXT;
  87                 break;
  88         case PXML_TAG:
  89                 *ch_type = PXER_WMORE;
  90                 return 0;       /* Want more */
  91         case PXML_TAG_END:
  92                 *ch_type = PXER_TAG;
  93                 break;
  94         case PXML_COMMENT:
  95         case PXML_COMMENT_END:
  96                 *ch_type = PXER_COMMENT;
  97                 break;
  98         }
  99
 100         *stateContext = new_stateContext;
 101         return arg.chunk_size;
 102 }
 103
 104 #define CSLASH  0x2f    /* '/' */
 105 #define LANGLE  0x3c    /* '<' */
 106 #define RANGLE  0x3e    /* '>' */
 107
 108 xer_check_tag_e
 109 xer_check_tag(const void *buf_ptr, int size, const char *need_tag) {
 110         const char *buf = (const char *)buf_ptr;
 111         const char *end;
 112         xer_check_tag_e ct = XCT_OPENING;
 113
 114         if(size < 2 || buf[0] != LANGLE || buf[size-1] != RANGLE) {
 115                 if(size >= 2)
 116                         ASN_DEBUG("Broken XML tag: \"%c...%c\"",
 117                         buf[0], buf[size - 1]);
 118                 return XCT_BROKEN;
 119         }
 120
 121         /*
 122          * Determine the tag class.
 123          */
 124         if(buf[1] == CSLASH) {
 125                 buf += 2;       /* advance past "</" */
 126                 size -= 3;      /* strip "</" and ">" */
 127                 ct = XCT_CLOSING;
 128                 if(size > 0 && buf[size-1] == CSLASH)
 129                         return XCT_BROKEN;      /* </abc/> */
 130         } else {
 131                 buf++;          /* advance past "<" */
 132                 size -= 2;      /* strip "<" and ">" */
 133                 if(size > 0 && buf[size-1] == CSLASH) {
 134                         ct = XCT_BOTH;
 135                         size--; /* One more, for "/" */
 136                 }
 137         }
 138
 139         /* Sometimes we don't care about the tag */
 140         if(!need_tag || !*need_tag)
 141                 return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 142
 143         /*
 144          * Determine the tag name.
 145          */
 146         for(end = buf + size; buf < end; buf++, need_tag++) {
 147                 int b = *buf, n = *need_tag;
 148                 if(b != n) {
 149                         if(n == 0) {
 150                                 switch(b) {
 151                                 case 0x09: case 0x0a: case 0x0c: case 0x0d:
 152                                 case 0x20:
 153                                         /* "<abc def/>": whitespace is normal */
 154                                         return ct;
 155                                 }
 156                         }
 157                         return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 158                 }
 159                 if(b == 0)
 160                         return XCT_BROKEN;      /* Embedded 0 in buf?! */
 161         }
 162         if(*need_tag)
 163                 return (xer_check_tag_e)(XCT__UNK__MASK | ct);
 164
 165         return ct;
 166 }
 167
 168
 169 #undef  ADVANCE
 170 #define ADVANCE(num_bytes)      do {                            \
 171                 size_t num = (num_bytes);                       \
 172                 buf_ptr = ((const char *)buf_ptr) + num;        \
 173                 size -= num;                                    \
 174                 consumed_myself += num;                         \
 175         } while(0)
 176
 177 #undef  RETURN
 178 #define RETURN(_code)   do {                                    \
 179                 rval.code = _code;                              \
 180                 rval.consumed = consumed_myself;                \
 181                 if(rval.code != RC_OK)                          \
 182                         ASN_DEBUG("Failed with %d", rval.code); \
 183                 return rval;                                    \
 184         } while(0)
 185
 186 #define XER_GOT_BODY(chunk_buf, chunk_size, size)       do {    \
 187                 ssize_t converted_size = body_receiver          \
 188                         (struct_key, chunk_buf, chunk_size,     \
 189                                 (size_t)chunk_size < size);     \
 190                 if(converted_size == -1) RETURN(RC_FAIL);       \
 191                 if(converted_size == 0                          \
 192                         && size == (size_t)chunk_size)          \
 193                         RETURN(RC_WMORE);                       \
 194                 chunk_size = converted_size;                    \
 195         } while(0)
 196 #define XER_GOT_EMPTY() do {                                    \
 197         if(body_receiver(struct_key, 0, 0, size > 0) == -1)     \
 198                         RETURN(RC_FAIL);                        \
 199         } while(0)
 200
 201 /*
 202  * Generalized function for decoding the primitive values.
 203  */
 204 asn_dec_rval_t
 205 xer_decode_general(const asn_codec_ctx_t *opt_codec_ctx,
 206         asn_struct_ctx_t *ctx,  /* Type decoder context */
 207         void *struct_key,
 208         const char *xml_tag,    /* Expected XML tag */
 209         const void *buf_ptr, size_t size,
 210         int (*opt_unexpected_tag_decoder)
 211                 (void *struct_key, const void *chunk_buf, size_t chunk_size),
 212         ssize_t (*body_receiver)
 213                 (void *struct_key, const void *chunk_buf, size_t chunk_size,
 214                         int have_more)
 215         ) {
 216
 217         asn_dec_rval_t rval;
 218         ssize_t consumed_myself = 0;
 219
 220         (void)opt_codec_ctx;
 221
 222         /*
 223          * Phases of XER/XML processing:
 224          * Phase 0: Check that the opening tag matches our expectations.
 225          * Phase 1: Processing body and reacting on closing tag.
 226          */
 227         if(ctx->phase > 1) RETURN(RC_FAIL);
 228         for(;;) {
 229                 pxer_chunk_type_e ch_type;      /* XER chunk type */
 230                 ssize_t ch_size;                /* Chunk size */
 231                 xer_check_tag_e tcv;            /* Tag check value */
 232
 233                 /*
 234                  * Get the next part of the XML stream.
 235                  */
 236                 ch_size = xer_next_token(&ctx->context, buf_ptr, size,
 237                         &ch_type);
 238                 if(ch_size == -1) {
 239             RETURN(RC_FAIL);
 240         } else {
 241                         switch(ch_type) {
 242                         case PXER_WMORE:
 243                 RETURN(RC_WMORE);
 244                         case PXER_COMMENT:              /* Got XML comment */
 245                                 ADVANCE(ch_size);       /* Skip silently */
 246                                 continue;
 247                         case PXER_TEXT:
 248                                 if(ctx->phase == 0) {
 249                                         /*
 250                                          * We have to ignore whitespace here,
 251                                          * but in order to be forward compatible
 252                                          * with EXTENDED-XER (EMBED-VALUES, #25)
 253                                          * any text is just ignored here.
 254                                          */
 255                                 } else {
 256                                         XER_GOT_BODY(buf_ptr, ch_size, size);
 257                                 }
 258                                 ADVANCE(ch_size);
 259                                 continue;
 260                         case PXER_TAG:
 261                                 break;  /* Check the rest down there */
 262                         }
 263                 }
 264
 265                 assert(ch_type == PXER_TAG && size);
 266
 267                 tcv = xer_check_tag(buf_ptr, ch_size, xml_tag);
 268                 /*
 269                  * Phase 0:
 270                  *      Expecting the opening tag
 271                  *      for the type being processed.
 272                  * Phase 1:
 273                  *      Waiting for the closing XML tag.
 274                  */
 275                 switch(tcv) {
 276                 case XCT_BOTH:
 277                         if(ctx->phase) break;
 278                         /* Finished decoding of an empty element */
 279                         XER_GOT_EMPTY();
 280                         ADVANCE(ch_size);
 281                         ctx->phase = 2; /* Phase out */
 282                         RETURN(RC_OK);
 283                 case XCT_OPENING:
 284                         if(ctx->phase) break;
 285                         ADVANCE(ch_size);
 286                         ctx->phase = 1; /* Processing body phase */
 287                         continue;
 288                 case XCT_CLOSING:
 289                         if(!ctx->phase) break;
 290                         ADVANCE(ch_size);
 291                         ctx->phase = 2; /* Phase out */
 292                         RETURN(RC_OK);
 293                 case XCT_UNKNOWN_BO:
 294                         /*
 295                          * Certain tags in the body may be expected.
 296                          */
 297                         if(opt_unexpected_tag_decoder
 298                         && opt_unexpected_tag_decoder(struct_key,
 299                                         buf_ptr, ch_size) >= 0) {
 300                                 /* Tag's processed fine */
 301                                 ADVANCE(ch_size);
 302                                 if(!ctx->phase) {
 303                                         /* We are not expecting
 304                                          * the closing tag anymore. */
 305                                         ctx->phase = 2; /* Phase out */
 306                                         RETURN(RC_OK);
 307                                 }
 308                                 continue;
 309                         }
 310                         /* Fall through */
 311                 default:
 312                         break;          /* Unexpected tag */
 313                 }
 314
 315                 ASN_DEBUG("Unexpected XML tag (expected \"%s\")", xml_tag);
 316                 break;  /* Dark and mysterious things have just happened */
 317         }
 318
 319         RETURN(RC_FAIL);
 320 }
 321
 322
 323 size_t
 324 xer_whitespace_span(const void *chunk_buf, size_t chunk_size) {
 325         const char *p = (const char *)chunk_buf;
 326         const char *pend = p + chunk_size;
 327
 328         for(; p < pend; p++) {
 329                 switch(*p) {
 330                 /* X.693, #8.1.4
 331                  * HORISONTAL TAB (9)
 332                  * LINE FEED (10)
 333                  * CARRIAGE RETURN (13)
 334                  * SPACE (32)
 335                  */
 336                 case 0x09: case 0x0a: case 0x0d: case 0x20:
 337                         continue;
 338                 default:
 339                         break;
 340                 }
 341                 break;
 342         }
 343         return (p - (const char *)chunk_buf);
 344 }
 345
 346 /*
 347  * This is a vastly simplified, non-validating XML tree skipper.
 348  */
 349 int
 350 xer_skip_unknown(xer_check_tag_e tcv, ber_tlv_len_t *depth) {
 351         assert(*depth > 0);
 352         switch(tcv) {
 353         case XCT_BOTH:
 354         case XCT_UNKNOWN_BO:
 355                 /* These negate each other. */
 356                 return 0;
 357         case XCT_OPENING:
 358         case XCT_UNKNOWN_OP:
 359                 ++(*depth);
 360                 return 0;
 361         case XCT_CLOSING:
 362         case XCT_UNKNOWN_CL:
 363                 if(--(*depth) == 0)
 364                         return (tcv == XCT_CLOSING) ? 2 : 1;
 365                 return 0;
 366         default:
 367                 return -1;
 368         }
 369 }