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DEX: Replace remaining calls to read_uleb128() #1951

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Aug 18, 2023
Merged

DEX: Replace remaining calls to read_uleb128() #1951

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59 changes: 37 additions & 22 deletions libyara/modules/dex/dex.c
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Original file line number Diff line number Diff line change
Expand Up @@ -434,13 +434,6 @@ static int32_t read_uleb128_bounded(
}


static int32_t read_uleb128(const uint8_t* pStream, uint32_t* size)
{
bool error;
return read_uleb128_bounded(pStream, (const uint8_t*) SIZE_MAX, size, &error);
}


static int64_t dex_get_integer(
YR_OBJECT* object,
const char* pattern,
Expand Down Expand Up @@ -592,18 +585,26 @@ uint32_t load_encoded_field(
printf("[DEX] Parse encoded field start_offset:0x%zx\n", start_offset);
#endif

const uint8_t* data_cur_start = dex->data + start_offset;
if (!fits_in_dex(dex, dex->data + start_offset, sizeof(uint32_t) * 2))
return 0;

const uint8_t* data_end = dex->data + dex->data_size;
uint32_t current_size = 0;

bool error = false;
encoded_field_t encoded_field;

encoded_field.field_idx_diff = (uint32_t) read_uleb128(
(dex->data + start_offset + current_size), &current_size);
encoded_field.field_idx_diff =
(uint32_t) read_uleb128_bounded((dex->data + start_offset + current_size),
data_end, &current_size, &error);
if (error)
return 0;

encoded_field.access_flags = (uint32_t) read_uleb128(
(dex->data + start_offset + current_size), &current_size);
encoded_field.access_flags =
(uint32_t) read_uleb128_bounded((dex->data + start_offset + current_size),
data_end, &current_size, &error);
if (error)
return 0;

yr_set_integer(
encoded_field.field_idx_diff,
Expand Down Expand Up @@ -946,6 +947,8 @@ void dex_parse(DEX* dex, uint64_t base_address)
uint32_t index_encoded_method = 0;
uint32_t index_encoded_field = 0;

const uint8_t* data_end = dex->data + dex->data_size;

if (!struct_fits_in_dex(dex, dex->data, dex_header_t))
return;

Expand Down Expand Up @@ -981,9 +984,12 @@ void dex_parse(DEX* dex, uint64_t base_address)
sizeof(uint32_t)))
continue;

uint32_t value = (uint32_t) read_uleb128(
bool error = false;
uint32_t value = (uint32_t) read_uleb128_bounded(
(dex->data + yr_le32toh(string_id_item->string_data_offset)),
&uleb128_size);
data_end, &uleb128_size, &error);
if (error)
continue;

#ifdef DEBUG_DEX_MODULE
printf("[DEX] STRING ID item size:0x%x\n", value);
Expand Down Expand Up @@ -1271,25 +1277,34 @@ void dex_parse(DEX* dex, uint64_t base_address)
return;

uleb128_size = 0;
bool error = false;

class_data_item.static_fields_size = (uint32_t) read_uleb128(
class_data_item.static_fields_size = (uint32_t) read_uleb128_bounded(
(dex->data + yr_le32toh(class_id_item->class_data_offset)),
&uleb128_size);
data_end, &uleb128_size, &error);
if (error)
return;

class_data_item.instance_fields_size = (uint32_t) read_uleb128(
class_data_item.instance_fields_size = (uint32_t) read_uleb128_bounded(
(dex->data + yr_le32toh(class_id_item->class_data_offset) +
uleb128_size),
&uleb128_size);
data_end, &uleb128_size, &error);
if (error)
return;

class_data_item.direct_methods_size = (uint32_t) read_uleb128(
class_data_item.direct_methods_size = (uint32_t) read_uleb128_bounded(
(dex->data + yr_le32toh(class_id_item->class_data_offset) +
uleb128_size),
&uleb128_size);
data_end, &uleb128_size, &error);
if (error)
return;

class_data_item.virtual_methods_size = (uint32_t) read_uleb128(
class_data_item.virtual_methods_size = (uint32_t) read_uleb128_bounded(
(dex->data + yr_le32toh(class_id_item->class_data_offset) +
uleb128_size),
&uleb128_size);
data_end, &uleb128_size, &error);
if (error)
return;

yr_set_integer(
class_data_item.static_fields_size,
Expand Down
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