mDNSMacOSX/mdns_objects/mdns_tlv.c

   1 /*
   2  * Copyright (c) 2020 Apple Inc. All rights reserved.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     https://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include "mdns_tlv.h"
  18
  19 #include <CoreUtils/CoreUtils.h>
  20
  21 //======================================================================================================================
  22 // MARK: - Type-Length Headers
  23
  24 typedef struct
  25 {
  26         uint8_t type[2];
  27         uint8_t length[2];
  28 } mdns_tl16_t;
  29
  30 check_compile_time(sizeof(mdns_tl16_t) == 4);
  31
  32 //======================================================================================================================
  33 // MARK: - Local Prototypes
  34
  35 static uint16_t
  36 _mdns_tl16_get_type(const mdns_tl16_t *tl);
  37
  38 static uint16_t
  39 _mdns_tl16_get_length(const mdns_tl16_t *tl);
  40
  41 static void
  42 _mdns_tl16_init(mdns_tl16_t *tl, uint16_t type, uint16_t length);
  43
  44 //======================================================================================================================
  45 // MARK: - Public Functions
  46
  47 OSStatus
  48 mdns_tlv16_get_value(const uint8_t * const start, const uint8_t * const end, const uint16_t type,
  49         size_t * const out_length, const uint8_t ** const out_value, const uint8_t ** const out_ptr)
  50 {
  51         OSStatus err;
  52         require_action_quiet(start <= end, exit, err = kRangeErr);
  53
  54         const uint8_t *ptr = start;
  55         while ((end - ptr) > 0) {
  56                 const mdns_tl16_t *tl;
  57                 require_action_quiet((end - ptr) >= (ptrdiff_t)sizeof(*tl), exit, err = kUnderrunErr);
  58
  59                 tl = (const mdns_tl16_t *)ptr;
  60                 const uint16_t                  tlv_type        = _mdns_tl16_get_type(tl);
  61                 const uint16_t                  tlv_length      = _mdns_tl16_get_length(tl);
  62                 const uint8_t * const   tlv_value       = (const uint8_t *)&tl[1];
  63                 require_action_quiet((end - tlv_value) >= tlv_length, exit, err = kUnderrunErr);
  64
  65                 ptr = &tlv_value[tlv_length];
  66                 if (tlv_type == type) {
  67                         if (out_length) {
  68                                 *out_length = tlv_length;
  69                         }
  70                         if (out_value) {
  71                                 *out_value = tlv_value;
  72                         }
  73                         if (out_ptr) {
  74                                 *out_ptr = ptr;
  75                         }
  76                         return kNoErr;
  77                 }
  78         }
  79         err = kNotFoundErr;
  80
  81 exit:
  82         return err;
  83 }
  84
  85 //======================================================================================================================
  86
  87 OSStatus
  88 mdns_tlv16_set(uint8_t * const dst, const uint8_t * const limit, const uint16_t type, const uint16_t length,
  89         const uint8_t * const value, uint8_t ** const out_end)
  90 {
  91         OSStatus err;
  92         mdns_tl16_t *tl;
  93         require_action_quiet(!limit || ((limit - dst) >= (ptrdiff_t)(sizeof(tl) + length)), exit, err = kUnderrunErr);
  94
  95         tl = (mdns_tl16_t *)dst;
  96         _mdns_tl16_init(tl, type, length);
  97         uint8_t * const dst_value = (uint8_t *)&tl[1];
  98         if (length > 0) {
  99                 memcpy(dst_value, value, length);
 100         }
 101         if (out_end) {
 102                 *out_end = &dst_value[length];
 103         }
 104         err = kNoErr;
 105
 106 exit:
 107         return err;
 108 }
 109
 110 //======================================================================================================================
 111
 112 size_t
 113 mdns_tlv16_get_required_length(const uint16_t value_length)
 114 {
 115         return (sizeof(mdns_tl16_t) + value_length);
 116 }
 117
 118 //======================================================================================================================
 119 // MARK: - Private Functions
 120
 121 static uint16_t
 122 _mdns_tl16_get_type(const mdns_tl16_t * const tl)
 123 {
 124         return ReadBig16(tl->type);
 125 }
 126
 127 //======================================================================================================================
 128
 129 static uint16_t
 130 _mdns_tl16_get_length(const mdns_tl16_t * const tl)
 131 {
 132         return ReadBig16(tl->length);
 133 }
 134
 135 //======================================================================================================================
 136
 137 static void
 138 _mdns_tl16_init(mdns_tl16_t * const tl, const uint16_t type, const uint16_t length)
 139 {
 140         WriteBig16(tl->type, type);
 141         WriteBig16(tl->length, length);
 142 }