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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Permission is hereby granted, free of charge, to any person
      5  * obtaining a copy of this software and associated documentation
      6  * files (the "Software"), to deal in the Software without
      7  * restriction, including without limitation the rights to use, copy,
      8  * modify, merge, publish, distribute, sublicense, and/or sell copies
      9  * of the Software, and to permit persons to whom the Software is
     10  * furnished to do so, subject to the following conditions:
     11  *
     12  * The above copyright notice and this permission notice shall be
     13  * included in all copies or substantial portions of the Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     22  * SOFTWARE.
     23  */
     24 
     25 #include "avb_property_descriptor.h"
     26 #include "avb_util.h"
     27 
     28 bool avb_property_descriptor_validate_and_byteswap(
     29     const AvbPropertyDescriptor* src, AvbPropertyDescriptor* dest) {
     30   uint64_t expected_size;
     31 
     32   avb_memcpy(dest, src, sizeof(AvbPropertyDescriptor));
     33 
     34   if (!avb_descriptor_validate_and_byteswap((const AvbDescriptor*)src,
     35                                             (AvbDescriptor*)dest))
     36     return false;
     37 
     38   if (dest->parent_descriptor.tag != AVB_DESCRIPTOR_TAG_PROPERTY) {
     39     avb_error("Invalid tag for property descriptor.\n");
     40     return false;
     41   }
     42 
     43   dest->key_num_bytes = avb_be64toh(dest->key_num_bytes);
     44   dest->value_num_bytes = avb_be64toh(dest->value_num_bytes);
     45 
     46   /* Check that key and value are fully contained. */
     47   expected_size = sizeof(AvbPropertyDescriptor) - sizeof(AvbDescriptor) + 2;
     48   if (!avb_safe_add_to(&expected_size, dest->key_num_bytes) ||
     49       !avb_safe_add_to(&expected_size, dest->value_num_bytes)) {
     50     avb_error("Overflow while adding up sizes.\n");
     51     return false;
     52   }
     53   if (expected_size > dest->parent_descriptor.num_bytes_following) {
     54     avb_error("Descriptor payload size overflow.\n");
     55     return false;
     56   }
     57 
     58   return true;
     59 }
     60 
     61 typedef struct {
     62   const char* key;
     63   size_t key_size;
     64   const char* ret_value;
     65   size_t ret_value_size;
     66 } PropertyIteratorData;
     67 
     68 static bool property_lookup_desc_foreach(const AvbDescriptor* header,
     69                                          void* user_data) {
     70   PropertyIteratorData* data = (PropertyIteratorData*)user_data;
     71   AvbPropertyDescriptor prop_desc;
     72   const uint8_t* p;
     73   bool ret = true;
     74 
     75   if (header->tag != AVB_DESCRIPTOR_TAG_PROPERTY) {
     76     goto out;
     77   }
     78 
     79   if (!avb_property_descriptor_validate_and_byteswap(
     80           (const AvbPropertyDescriptor*)header, &prop_desc)) {
     81     goto out;
     82   }
     83 
     84   p = (const uint8_t*)header;
     85   if (p[sizeof(AvbPropertyDescriptor) + prop_desc.key_num_bytes] != 0) {
     86     avb_error("No terminating NUL byte in key.\n");
     87     goto out;
     88   }
     89 
     90   if (data->key_size == prop_desc.key_num_bytes) {
     91     if (avb_memcmp(p + sizeof(AvbPropertyDescriptor),
     92                    data->key,
     93                    data->key_size) == 0) {
     94       data->ret_value = (const char*)(p + sizeof(AvbPropertyDescriptor) +
     95                                       prop_desc.key_num_bytes + 1);
     96       data->ret_value_size = prop_desc.value_num_bytes;
     97       /* Stop iterating. */
     98       ret = false;
     99       goto out;
    100     }
    101   }
    102 
    103 out:
    104   return ret;
    105 }
    106 
    107 const char* avb_property_lookup(const uint8_t* image_data,
    108                                 size_t image_size,
    109                                 const char* key,
    110                                 size_t key_size,
    111                                 size_t* out_value_size) {
    112   PropertyIteratorData data;
    113 
    114   if (key_size == 0) {
    115     key_size = avb_strlen(key);
    116   }
    117 
    118   data.key = key;
    119   data.key_size = key_size;
    120 
    121   if (avb_descriptor_foreach(
    122           image_data, image_size, property_lookup_desc_foreach, &data) == 0) {
    123     if (out_value_size != NULL) {
    124       *out_value_size = data.ret_value_size;
    125     }
    126     return data.ret_value;
    127   }
    128 
    129   if (out_value_size != NULL) {
    130     *out_value_size = 0;
    131   }
    132   return NULL;
    133 }
    134 
    135 bool avb_property_lookup_uint64(const uint8_t* image_data,
    136                                 size_t image_size,
    137                                 const char* key,
    138                                 size_t key_size,
    139                                 uint64_t* out_value) {
    140   const char* value;
    141   bool ret = false;
    142   uint64_t parsed_val;
    143   int base;
    144   int n;
    145 
    146   value = avb_property_lookup(image_data, image_size, key, key_size, NULL);
    147   if (value == NULL) {
    148     goto out;
    149   }
    150 
    151   base = 10;
    152   if (avb_memcmp(value, "0x", 2) == 0) {
    153     base = 16;
    154     value += 2;
    155   }
    156 
    157   parsed_val = 0;
    158   for (n = 0; value[n] != '\0'; n++) {
    159     int c = value[n];
    160     int digit;
    161 
    162     parsed_val *= base;
    163 
    164     if (c >= '0' && c <= '9') {
    165       digit = c - '0';
    166     } else if (base == 16 && c >= 'a' && c <= 'f') {
    167       digit = c - 'a' + 10;
    168     } else if (base == 16 && c >= 'A' && c <= 'F') {
    169       digit = c - 'A' + 10;
    170     } else {
    171       avb_error("Invalid digit.\n");
    172       goto out;
    173     }
    174 
    175     parsed_val += digit;
    176   }
    177 
    178   ret = true;
    179   if (out_value != NULL) {
    180     *out_value = parsed_val;
    181   }
    182 
    183 out:
    184   return ret;
    185 }
    186