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yara/libyara/modules/elf/elf.c
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HoundThe 19ac2efeb8 Integrate tlshc library, calculate telfhash and import hash in ELF module (#1624) 
* Add simple_str string implementation

* Integrate tlshc library, calculate telfhash and import hash in the ELF module.

* Hide usage of MD5 into #ifdef crypto
2022-06-20 12:25:33 +02:00

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/*
Copyright (c) 2014. The YARA Authors. All Rights Reserved.
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <tlshc/tlsh.h>
#include <yara/elf.h>
#include <yara/elf_utils.h>
#include <yara/endian.h>
#include <yara/mem.h>
#include <yara/modules.h>
#include <yara/simple_str.h>
#include <yara/utils.h>
#include "../crypto.h"
#define MODULE_NAME elf
#define CLASS_DATA(c, d) ((c << 8) | d)
static int sort_strcmp(const void* a, const void* b)
{
return strcmp(*(const char**) a, *(const char**) b);
}
define_function(telfhash)
{
YR_OBJECT* obj = module();
ELF* elf = (ELF*) obj->data;
if (elf == NULL)
return_string(YR_UNDEFINED);
if (elf->telfhash)
return_string(elf->telfhash);
/* We prefer dynsym if possible */
ELF_SYMBOL_LIST* list = elf->dynsym ? elf->dynsym : elf->symtab;
if (!list)
return_string(YR_UNDEFINED);
/* exclusions are based on the original implementation
https://github.com/trendmicro/telfhash/blob/master/telfhash/telfhash.py */
char* exclude_strings[] = {
"__libc_start_main",
"main",
"abort",
"cachectl",
"cacheflush",
"puts",
"atol",
"malloc_trim"};
SIMPLE_STR* sstr = NULL;
int symbol_count = 0;
char** clean_names = yr_malloc(list->count * sizeof(*clean_names));
if (!clean_names)
return_string(YR_UNDEFINED);
for (ELF_SYMBOL* i = list->symbols; i != NULL; i = i->next)
{
char* name = i->name;
if (!name)
continue;
/* Use only global code symbols */
if (i->bind != ELF_STB_GLOBAL || i->type != ELF_STT_FUNC ||
i->visibility != ELF_STV_DEFAULT)
continue;
/* ignore:
x86-64 specific functions
string functions (str.* and mem.*), gcc changes them depending on arch
symbols starting with . or _ */
bool is_bad_prefix = name[0] == '.' || name[0] == '_';
bool is_x86_64 = name[0] == '.' || name[0] == '_';
bool is_mem_or_str = strncmp(name, "str", 3) == 0 ||
strncmp(name, "mem", 3) == 0;
if (is_bad_prefix || is_x86_64 || is_mem_or_str)
continue;
/* Exclude any symbols that match the excluded ones */
bool is_excluded = false;
for (int i = 0; i < sizeof(exclude_strings) / sizeof(*exclude_strings); i++)
{
if (strcmp(name, exclude_strings[i]) == 0)
{
is_excluded = true;
break;
}
}
if (is_excluded)
continue;
clean_names[symbol_count] = yr_malloc(strlen(name) + 1);
if (!clean_names[symbol_count])
goto cleanup;
/* Convert it to lowercase */
int j;
for (j = 0; name[j]; j++) clean_names[symbol_count][j] = tolower(name[j]);
clean_names[symbol_count][j] = '\0';
symbol_count++;
}
if (!symbol_count)
goto cleanup;
/* Now we have all the valid symbols, sort them, concat them */
qsort(clean_names, symbol_count, sizeof(*clean_names), &sort_strcmp);
sstr = sstr_newf("%s", clean_names[0]);
if (!sstr)
goto cleanup;
/* We've already written first symbol, start at 1 */
for (int i = 1; i < symbol_count; ++i)
{
if (!sstr_appendf(sstr, ",%s", clean_names[i]))
goto cleanup;
}
Tlsh* tlsh = tlsh_new();
if (!tlsh)
goto cleanup;
tlsh_final(tlsh, (const unsigned char*) sstr->str, sstr->len, 0);
const char* telfhash = tlsh_get_hash(tlsh, true);
elf->telfhash = yr_strdup(telfhash); // cache it
if (!elf->telfhash)
goto cleanup;
for (int i = 0; i < symbol_count; ++i) yr_free(clean_names[i]);
yr_free(clean_names);
sstr_free(sstr);
tlsh_free(tlsh);
return_string(elf->telfhash);
cleanup:
for (int i = 0; i < symbol_count; ++i) yr_free(clean_names[i]);
yr_free(clean_names);
sstr_free(sstr);
return_string(YR_UNDEFINED);
}
#if defined(HAVE_LIBCRYPTO) || defined(HAVE_WINCRYPT_H) || \
defined(HAVE_COMMONCRYPTO_COMMONCRYPTO_H)
define_function(import_md5)
{
YR_OBJECT* obj = module();
ELF* elf = (ELF*) obj->data;
if (elf == NULL)
return_string(YR_UNDEFINED);
if (elf->import_hash)
return_string(elf->import_hash);
ELF_SYMBOL_LIST* list = elf->dynsym ? elf->dynsym : elf->symtab;
if (!list)
return_string(YR_UNDEFINED);
SIMPLE_STR* sstr = NULL;
int symbol_count = 0;
char** clean_names = yr_malloc(list->count * sizeof(*clean_names));
if (!clean_names)
return_string(YR_UNDEFINED);
for (ELF_SYMBOL* i = list->symbols; i != NULL; i = i->next)
{
char* name = i->name;
if (!name)
continue;
if (i->shndx != ELF_SHN_UNDEF)
continue;
// skip empty names
if (strlen(i->name) == 0)
continue;
clean_names[symbol_count] = yr_malloc(strlen(name) + 1);
if (!clean_names[symbol_count])
goto cleanup;
/* Convert it to lowercase */
int j;
for (j = 0; name[j]; j++) clean_names[symbol_count][j] = tolower(name[j]);
clean_names[symbol_count][j] = '\0';
symbol_count++;
}
if (!symbol_count)
goto cleanup;
/* Now we have all the valid symbols, sort them, concat them */
qsort(clean_names, symbol_count, sizeof(*clean_names), &sort_strcmp);
sstr = sstr_newf("%s", clean_names[0]);
if (!sstr)
goto cleanup;
/* We've already written first symbol, start at 1 */
for (int i = 1; i < symbol_count; ++i)
{
if (!sstr_appendf(sstr, ",%s", clean_names[i]))
goto cleanup;
}
unsigned char hash[YR_MD5_LEN];
yr_md5_ctx ctx;
yr_md5_init(&ctx);
yr_md5_update(&ctx, sstr->str, sstr->len);
yr_md5_final(hash, &ctx);
elf->import_hash = yr_malloc(YR_MD5_LEN * 2 + 1);
if (!elf->import_hash)
goto cleanup;
for (int i = 0; i < YR_MD5_LEN; ++i)
sprintf(elf->import_hash + (i * 2), "%02x", hash[i]);
for (int i = 0; i < symbol_count; ++i) yr_free(clean_names[i]);
yr_free(clean_names);
sstr_free(sstr);
return_string(elf->import_hash);
cleanup:
for (int i = 0; i < symbol_count; ++i) yr_free(clean_names[i]);
yr_free(clean_names);
sstr_free(sstr);
return_string(YR_UNDEFINED);
}
#endif // defined(HAVE_LIBCRYPTO) || defined(HAVE_WINCRYPT_H)
int get_elf_class_data(const uint8_t* buffer, size_t buffer_length)
{
elf_ident_t* elf_ident;
if (buffer_length < sizeof(elf_ident_t))
return 0;
elf_ident = (elf_ident_t*) buffer;
if (yr_le32toh(elf_ident->magic) == ELF_MAGIC)
{
return CLASS_DATA(elf_ident->_class, elf_ident->data);
}
else
{
return 0;
}
}
static bool is_valid_ptr(
const void* base,
size_t size,
const void* ptr,
uint64_t ptr_size) // ptr_size can be 64bit even in 32bit systems.
{
return ptr >= base && ptr_size <= size &&
((char*) ptr) + ptr_size <= ((char*) base) + size;
}
#define IS_VALID_PTR(base, size, ptr) \
is_valid_ptr(base, size, ptr, sizeof(*ptr))
//
// Returns a string table entry for the index or NULL if the entry is out
// of bounds. A non-null return value will be a null-terminated C string.
//
static const char* str_table_entry(
const char* str_table_base,
const char* str_table_limit,
int index)
{
size_t len;
const char* str_entry;
if (str_table_base >= str_table_limit)
return NULL;
// The first entry in the string table must be a null character, if not the
// string table is probably corrupted.
if (*str_table_base != '\0')
return NULL;
if (index < 0)
return NULL;
str_entry = str_table_base + index;
if (str_entry >= str_table_limit)
return NULL;
len = strnlen(str_entry, str_table_limit - str_entry);
// Entry is clamped by extent of string table, not null-terminated.
if (str_entry + len == str_table_limit)
return NULL;
return str_entry;
}
#define ELF_SIZE_OF_SECTION_TABLE(bits, bo, h) \
(sizeof(elf##bits##_section_header_t) * yr_##bo##16toh(h->sh_entry_count))
#define ELF_SIZE_OF_PROGRAM_TABLE(bits, bo, h) \
(sizeof(elf##bits##_program_header_t) * yr_##bo##16toh(h->ph_entry_count))
#define ELF_RVA_TO_OFFSET(bits, bo) \
uint64_t elf_rva_to_offset_##bits##_##bo( \
elf##bits##_header_t* elf_header, uint64_t rva, size_t elf_size) \
{ \
if (yr_##bo##16toh(elf_header->type) == ELF_ET_EXEC) \
{ \
int i; \
\
elf##bits##_program_header_t* program; \
\
/* check that ph_offset doesn't wrap when added to SIZE_OF_PROGRAM_TABLE \
*/ \
\
if (ULONG_MAX - yr_##bo##bits##toh(elf_header->ph_offset) < \
ELF_SIZE_OF_PROGRAM_TABLE(bits, bo, elf_header)) \
{ \
return YR_UNDEFINED; \
} \
\
if (yr_##bo##bits##toh(elf_header->ph_offset) == 0 || \
yr_##bo##bits##toh(elf_header->ph_offset) > elf_size || \
yr_##bo##bits##toh(elf_header->ph_offset) + \
ELF_SIZE_OF_PROGRAM_TABLE(bits, bo, elf_header) > \
elf_size || \
yr_##bo##16toh(elf_header->ph_entry_count) == 0) \
{ \
return YR_UNDEFINED; \
} \
\
program = (elf##bits##_program_header_t*) \
((uint8_t*) elf_header + yr_##bo##bits##toh(elf_header->ph_offset)); \
\
for (i = 0; i < yr_##bo##16toh(elf_header->ph_entry_count); i++) \
{ \
if (rva >= yr_##bo##bits##toh(program->virt_addr) && \
rva < yr_##bo##bits##toh(program->virt_addr) + \
yr_##bo##bits##toh(program->mem_size)) \
{ \
return yr_##bo##bits##toh(program->offset) + \
(rva - yr_##bo##bits##toh(program->virt_addr)); \
} \
\
program++; \
} \
} \
else \
{ \
int i; \
\
elf##bits##_section_header_t* section; \
\
/* check that sh_offset doesn't wrap when added to SIZE_OF_SECTION_TABLE \
*/ \
\
if (ULONG_MAX - yr_##bo##bits##toh(elf_header->sh_offset) < \
ELF_SIZE_OF_SECTION_TABLE(bits, bo, elf_header)) \
{ \
return YR_UNDEFINED; \
} \
\
if (yr_##bo##bits##toh(elf_header->sh_offset) == 0 || \
yr_##bo##bits##toh(elf_header->sh_offset) > elf_size || \
yr_##bo##bits##toh(elf_header->sh_offset) + \
ELF_SIZE_OF_SECTION_TABLE(bits, bo, elf_header) > \
elf_size || \
yr_##bo##16toh(elf_header->sh_entry_count) == 0) \
{ \
return YR_UNDEFINED; \
} \
\
section = (elf##bits##_section_header_t*) \
((uint8_t*) elf_header + yr_##bo##bits##toh(elf_header->sh_offset)); \
\
for (i = 0; i < yr_##bo##16toh(elf_header->sh_entry_count); i++) \
{ \
if (yr_##bo##32toh(section->type) != ELF_SHT_NULL && \
yr_##bo##32toh(section->type) != ELF_SHT_NOBITS && \
rva >= yr_##bo##bits##toh(section->addr) && \
rva < yr_##bo##bits##toh(section->addr) + \
yr_##bo##bits##toh(section->size)) \
{ \
return yr_##bo##bits##toh(section->offset) + \
(rva - yr_##bo##bits##toh(section->addr)); \
} \
\
section++; \
} \
} \
return YR_UNDEFINED; \
}
#define PARSE_ELF_HEADER(bits, bo) \
int parse_elf_header_##bits##_##bo( \
ELF* elf_data, \
elf##bits##_header_t* elf, \
uint64_t base_address, \
size_t elf_size, \
int flags, \
YR_OBJECT* elf_obj) \
{ \
unsigned int i, j, m; \
const char* elf_raw = (const char*) elf; \
uint16_t str_table_index = yr_##bo##16toh(elf->sh_str_table_index); \
\
const char* sym_table = NULL; \
const char* sym_str_table = NULL; \
const char* dyn_sym_table = NULL; \
const char* dyn_sym_str_table = NULL; \
\
uint##bits##_t sym_table_size = 0; \
uint##bits##_t sym_str_table_size = 0; \
uint##bits##_t dyn_sym_table_size = 0; \
uint##bits##_t dyn_sym_str_table_size = 0; \
\
elf_data->symtab = elf_data->dynsym = NULL; \
\
elf##bits##_section_header_t* section_table; \
elf##bits##_section_header_t* section; \
elf##bits##_program_header_t* segment; \
\
set_integer(yr_##bo##16toh(elf->type), elf_obj, "type"); \
set_integer(yr_##bo##16toh(elf->machine), elf_obj, "machine"); \
set_integer(yr_##bo##bits##toh(elf->sh_offset), elf_obj, "sh_offset"); \
set_integer(yr_##bo##16toh(elf->sh_entry_size), elf_obj, "sh_entry_size"); \
set_integer( \
yr_##bo##16toh(elf->sh_entry_count), elf_obj, "number_of_sections"); \
set_integer(yr_##bo##bits##toh(elf->ph_offset), elf_obj, "ph_offset"); \
set_integer(yr_##bo##16toh(elf->ph_entry_size), elf_obj, "ph_entry_size"); \
set_integer( \
yr_##bo##16toh(elf->ph_entry_count), elf_obj, "number_of_segments"); \
\
if (yr_##bo##bits##toh(elf->entry) != 0) \
{ \
set_integer( \
flags& SCAN_FLAGS_PROCESS_MEMORY \
? base_address + yr_##bo##bits##toh(elf->entry) \
: elf_rva_to_offset_##bits##_##bo( \
elf, yr_##bo##bits##toh(elf->entry), elf_size), \
elf_obj, \
"entry_point"); \
} \
\
if (yr_##bo##16toh(elf->sh_entry_count) < ELF_SHN_LORESERVE && \
str_table_index < yr_##bo##16toh(elf->sh_entry_count) && \
yr_##bo##bits##toh(elf->sh_offset) < elf_size && \
yr_##bo##bits##toh(elf->sh_offset) + \
yr_##bo##16toh(elf->sh_entry_count) * \
sizeof(elf##bits##_section_header_t) <= \
elf_size) \
{ \
const char* str_table = NULL; \
\
section_table = \
(elf##bits##_section_header_t*) (elf_raw + yr_##bo##bits##toh(elf->sh_offset)); \
\
if (yr_##bo##bits##toh(section_table[str_table_index].offset) < \
elf_size) \
{ \
str_table = elf_raw + \
yr_##bo##bits##toh(section_table[str_table_index].offset); \
} \
\
section = section_table; \
\
for (i = 0; i < yr_##bo##16toh(elf->sh_entry_count); i++, section++) \
{ \
set_integer( \
yr_##bo##32toh(section->type), elf_obj, "sections[%i].type", i); \
set_integer( \
yr_##bo##bits##toh(section->flags), \
elf_obj, \
"sections[%i].flags", \
i); \
set_integer( \
yr_##bo##bits##toh(section->addr), \
elf_obj, \
"sections[%i].address", \
i); \
set_integer( \
yr_##bo##bits##toh(section->size), \
elf_obj, \
"sections[%i].size", \
i); \
set_integer( \
yr_##bo##bits##toh(section->offset), \
elf_obj, \
"sections[%i].offset", \
i); \
\
if (yr_##bo##32toh(section->name) < elf_size && str_table > elf_raw) \
{ \
const char* section_name = str_table_entry( \
str_table, elf_raw + elf_size, yr_##bo##32toh(section->name)); \
\
if (section_name) \
set_string(section_name, elf_obj, "sections[%i].name", i); \
} \
\
if (yr_##bo##32toh(section->type) == ELF_SHT_SYMTAB && \
yr_##bo##32toh(section->link) < elf->sh_entry_count) \
{ \
elf##bits##_section_header_t* string_section = section_table + \
yr_##bo##32toh( \
section->link); \
\
if (IS_VALID_PTR(elf, elf_size, string_section) && \
yr_##bo##32toh(string_section->type) == ELF_SHT_STRTAB) \
{ \
sym_table = elf_raw + yr_##bo##bits##toh(section->offset); \
sym_str_table = elf_raw + \
yr_##bo##bits##toh(string_section->offset); \
sym_table_size = yr_##bo##bits##toh(section->size); \
sym_str_table_size = yr_##bo##bits##toh(string_section->size); \
} \
} \
\
if (yr_##bo##32toh(section->type) == ELF_SHT_DYNSYM && \
yr_##bo##32toh(section->link) < elf->sh_entry_count) \
{ \
elf##bits##_section_header_t* dynstr_section = section_table + \
yr_##bo##32toh( \
section->link); \
\
if (IS_VALID_PTR(elf, elf_size, dynstr_section) && \
yr_##bo##32toh(dynstr_section->type) == ELF_SHT_STRTAB) \
{ \
dyn_sym_table = elf_raw + yr_##bo##bits##toh(section->offset); \
dyn_sym_str_table = elf_raw + \
yr_##bo##bits##toh(dynstr_section->offset); \
dyn_sym_table_size = yr_##bo##bits##toh(section->size); \
dyn_sym_str_table_size = yr_##bo##bits##toh(dynstr_section->size); \
} \
} \
} \
\
if (is_valid_ptr(elf, elf_size, sym_str_table, sym_str_table_size) && \
is_valid_ptr(elf, elf_size, sym_table, sym_table_size)) \
{ \
elf##bits##_sym_t* sym = (elf##bits##_sym_t*) sym_table; \
elf_data->symtab = (ELF_SYMBOL_LIST*) yr_malloc( \
sizeof(ELF_SYMBOL_LIST)); \
\
if (elf_data->symtab == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
ELF_SYMBOL** symbol = &(elf_data->symtab->symbols); \
*symbol = NULL; \
\
for (j = 0; j < sym_table_size / sizeof(elf##bits##_sym_t); \
j++, sym++) \
{ \
*symbol = (ELF_SYMBOL*) yr_malloc(sizeof(ELF_SYMBOL)); \
if (*symbol == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
(*symbol)->name = NULL; \
(*symbol)->next = NULL; \
\
const char* sym_name = str_table_entry( \
sym_str_table, \
sym_str_table + sym_str_table_size, \
yr_##bo##32toh(sym->name)); \
\
if (sym_name) \
{ \
set_string(sym_name, elf_obj, "symtab[%i].name", j); \
(*symbol)->name = (char*) yr_malloc(strlen(sym_name) + 1); \
if ((*symbol)->name == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
strcpy((*symbol)->name, sym_name); \
} \
\
int bind = sym->info >> 4; \
(*symbol)->bind = bind; \
set_integer(bind, elf_obj, "symtab[%i].bind", j); \
\
int type = sym->info & 0xf; \
(*symbol)->type = type; \
set_integer(type, elf_obj, "symtab[%i].type", j); \
\
int shndx = yr_##bo##16toh(sym->shndx); \
(*symbol)->shndx = shndx; \
set_integer(shndx, elf_obj, "symtab[%i].shndx", j); \
\
int value = yr_##bo##bits##toh(sym->value); \
(*symbol)->value = value; \
set_integer( \
yr_##bo##bits##toh(sym->value), elf_obj, "symtab[%i].value", j); \
\
int size = yr_##bo##bits##toh(sym->size); \
(*symbol)->size = size; \
set_integer( \
yr_##bo##bits##toh(sym->size), elf_obj, "symtab[%i].size", j); \
\
int other = yr_##bo##bits##toh(sym->other); \
(*symbol)->visibility = other & 0x3; \
\
symbol = &((*symbol)->next); \
} \
\
elf_data->symtab->count = j; \
set_integer(j, elf_obj, "symtab_entries"); \
} \
\
if (is_valid_ptr( \
elf, elf_size, dyn_sym_str_table, dyn_sym_str_table_size) && \
is_valid_ptr(elf, elf_size, dyn_sym_table, dyn_sym_table_size)) \
{ \
elf##bits##_sym_t* dynsym = (elf##bits##_sym_t*) dyn_sym_table; \
\
elf_data->dynsym = (ELF_SYMBOL_LIST*) yr_malloc( \
sizeof(ELF_SYMBOL_LIST)); \
\
if (elf_data->dynsym == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
ELF_SYMBOL** symbol = &(elf_data->dynsym->symbols); \
*symbol = NULL; \
\
for (m = 0; m < dyn_sym_table_size / sizeof(elf##bits##_sym_t); \
m++, dynsym++) \
{ \
*symbol = (ELF_SYMBOL*) yr_malloc(sizeof(ELF_SYMBOL)); \
if (*symbol == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
(*symbol)->name = NULL; \
(*symbol)->next = NULL; \
\
const char* dynsym_name = str_table_entry( \
dyn_sym_str_table, \
dyn_sym_str_table + dyn_sym_str_table_size, \
yr_##bo##32toh(dynsym->name)); \
\
if (dynsym_name) \
{ \
set_string(dynsym_name, elf_obj, "dynsym[%i].name", m); \
(*symbol)->name = (char*) yr_malloc(strlen(dynsym_name) + 1); \
if ((*symbol)->name == NULL) \
return ERROR_INSUFFICIENT_MEMORY; \
\
strcpy((*symbol)->name, dynsym_name); \
} \
\
int bind = dynsym->info >> 4; \
(*symbol)->bind = bind; \
set_integer(dynsym->info >> 4, elf_obj, "dynsym[%i].bind", m); \
\
int type = dynsym->info & 0xf; \
(*symbol)->type = type; \
set_integer(dynsym->info & 0xf, elf_obj, "dynsym[%i].type", m); \
\
int shndx = yr_##bo##16toh(dynsym->shndx); \
(*symbol)->shndx = shndx; \
set_integer( \
yr_##bo##16toh(dynsym->shndx), elf_obj, "dynsym[%i].shndx", m); \
\
int value = yr_##bo##bits##toh(dynsym->value); \
(*symbol)->value = value; \
set_integer( \
yr_##bo##bits##toh(dynsym->value), \
elf_obj, \
"dynsym[%i].value", \
m); \
\
int size = yr_##bo##bits##toh(dynsym->size); \
(*symbol)->size = size; \
set_integer( \
yr_##bo##bits##toh(dynsym->size), \
elf_obj, \
"dynsym[%i].size", \
m); \
\
int other = yr_##bo##bits##toh(dynsym->other); \
(*symbol)->visibility = other & 0x3; \
\
symbol = &((*symbol)->next); \
} \
\
elf_data->dynsym->count = m; \
set_integer(m, elf_obj, "dynsym_entries"); \
} \
} \
\
if (yr_##bo##16toh(elf->ph_entry_count) > 0 && \
yr_##bo##16toh(elf->ph_entry_count) < ELF_PN_XNUM && \
yr_##bo##bits##toh(elf->ph_offset) < elf_size && \
yr_##bo##bits##toh(elf->ph_offset) + \
yr_##bo##16toh(elf->ph_entry_count) * \
sizeof(elf##bits##_program_header_t) <= \
elf_size) \
{ \
segment = \
(elf##bits##_program_header_t*) (elf_raw + yr_##bo##bits##toh(elf->ph_offset)); \
\
for (i = 0; i < yr_##bo##16toh(elf->ph_entry_count); i++, segment++) \
{ \
set_integer( \
yr_##bo##32toh(segment->type), elf_obj, "segments[%i].type", i); \
set_integer( \
yr_##bo##32toh(segment->flags), elf_obj, "segments[%i].flags", i); \
set_integer( \
yr_##bo##bits##toh(segment->offset), \
elf_obj, \
"segments[%i].offset", \
i); \
set_integer( \
yr_##bo##bits##toh(segment->virt_addr), \
elf_obj, \
"segments[%i].virtual_address", \
i); \
set_integer( \
yr_##bo##bits##toh(segment->phys_addr), \
elf_obj, \
"segments[%i].physical_address", \
i); \
set_integer( \
yr_##bo##bits##toh(segment->file_size), \
elf_obj, \
"segments[%i].file_size", \
i); \
set_integer( \
yr_##bo##bits##toh(segment->mem_size), \
elf_obj, \
"segments[%i].memory_size", \
i); \
set_integer( \
yr_##bo##bits##toh(segment->alignment), \
elf_obj, \
"segments[%i].alignment", \
i); \
\
if (yr_##bo##32toh(segment->type) == ELF_PT_DYNAMIC) \
{ \
elf##bits##_dyn_t* dyn = \
(elf##bits##_dyn_t*) (elf_raw + yr_##bo##bits##toh(segment->offset)); \
\
for (j = 0; IS_VALID_PTR(elf, elf_size, dyn); dyn++, j++) \
{ \
set_integer( \
yr_##bo##bits##toh(dyn->tag), elf_obj, "dynamic[%i].type", j); \
set_integer( \
yr_##bo##bits##toh(dyn->val), elf_obj, "dynamic[%i].val", j); \
\
if (dyn->tag == ELF_DT_NULL) \
{ \
j++; \
break; \
} \
} \
set_integer(j, elf_obj, "dynamic_section_entries"); \
} \
} \
} \
return ERROR_SUCCESS; \
}
ELF_RVA_TO_OFFSET(32, le);
ELF_RVA_TO_OFFSET(64, le);
ELF_RVA_TO_OFFSET(32, be);
ELF_RVA_TO_OFFSET(64, be);
PARSE_ELF_HEADER(32, le);
PARSE_ELF_HEADER(64, le);
PARSE_ELF_HEADER(32, be);
PARSE_ELF_HEADER(64, be);
begin_declarations
declare_integer("ET_NONE");
declare_integer("ET_REL");
declare_integer("ET_EXEC");
declare_integer("ET_DYN");
declare_integer("ET_CORE");
declare_integer("EM_NONE");
declare_integer("EM_M32");
declare_integer("EM_SPARC");
declare_integer("EM_386");
declare_integer("EM_68K");
declare_integer("EM_88K");
declare_integer("EM_860");
declare_integer("EM_MIPS");
declare_integer("EM_MIPS_RS3_LE");
declare_integer("EM_PPC");
declare_integer("EM_PPC64");
declare_integer("EM_ARM");
declare_integer("EM_X86_64");
declare_integer("EM_AARCH64");
declare_integer("SHT_NULL");
declare_integer("SHT_PROGBITS");
declare_integer("SHT_SYMTAB");
declare_integer("SHT_STRTAB");
declare_integer("SHT_RELA");
declare_integer("SHT_HASH");
declare_integer("SHT_DYNAMIC");
declare_integer("SHT_NOTE");
declare_integer("SHT_NOBITS");
declare_integer("SHT_REL");
declare_integer("SHT_SHLIB");
declare_integer("SHT_DYNSYM");
declare_integer("SHF_WRITE");
declare_integer("SHF_ALLOC");
declare_integer("SHF_EXECINSTR");
declare_integer("type");
declare_integer("machine");
declare_integer("entry_point");
declare_integer("number_of_sections");
declare_integer("sh_offset");
declare_integer("sh_entry_size");
declare_integer("number_of_segments");
declare_integer("ph_offset");
declare_integer("ph_entry_size");
begin_struct_array("sections")
declare_integer("type");
declare_integer("flags");
declare_integer("address");
declare_string("name");
declare_integer("size");
declare_integer("offset");
end_struct_array("sections")
declare_integer("PT_NULL");
declare_integer("PT_LOAD");
declare_integer("PT_DYNAMIC");
declare_integer("PT_INTERP");
declare_integer("PT_NOTE");
declare_integer("PT_SHLIB");
declare_integer("PT_PHDR");
declare_integer("PT_TLS");
declare_integer("PT_GNU_EH_FRAME");
declare_integer("PT_GNU_STACK");
declare_integer("DT_NULL");
declare_integer("DT_NEEDED");
declare_integer("DT_PLTRELSZ");
declare_integer("DT_PLTGOT");
declare_integer("DT_HASH");
declare_integer("DT_STRTAB");
declare_integer("DT_SYMTAB");
declare_integer("DT_RELA");
declare_integer("DT_RELASZ");
declare_integer("DT_RELAENT");
declare_integer("DT_STRSZ");
declare_integer("DT_SYMENT");
declare_integer("DT_INIT");
declare_integer("DT_FINI");
declare_integer("DT_SONAME");
declare_integer("DT_RPATH");
declare_integer("DT_SYMBOLIC");
declare_integer("DT_REL");
declare_integer("DT_RELSZ");
declare_integer("DT_RELENT");
declare_integer("DT_PLTREL");
declare_integer("DT_DEBUG");
declare_integer("DT_TEXTREL");
declare_integer("DT_JMPREL");
declare_integer("DT_BIND_NOW");
declare_integer("DT_INIT_ARRAY");
declare_integer("DT_FINI_ARRAY");
declare_integer("DT_INIT_ARRAYSZ");
declare_integer("DT_FINI_ARRAYSZ");
declare_integer("DT_RUNPATH");
declare_integer("DT_FLAGS");
declare_integer("DT_ENCODING");
declare_integer("STT_NOTYPE");
declare_integer("STT_OBJECT");
declare_integer("STT_FUNC");
declare_integer("STT_SECTION");
declare_integer("STT_FILE");
declare_integer("STT_COMMON");
declare_integer("STT_TLS");
declare_integer("STB_LOCAL");
declare_integer("STB_GLOBAL");
declare_integer("STB_WEAK");
declare_integer("PF_X");
declare_integer("PF_W");
declare_integer("PF_R");
begin_struct_array("segments")
declare_integer("type");
declare_integer("flags");
declare_integer("offset");
declare_integer("virtual_address");
declare_integer("physical_address");
declare_integer("file_size");
declare_integer("memory_size");
declare_integer("alignment");
end_struct_array("segments")
declare_integer("dynamic_section_entries");
begin_struct_array("dynamic")
declare_integer("type");
declare_integer("val");
end_struct_array("dynamic")
declare_integer("symtab_entries");
begin_struct_array("symtab")
declare_string("name");
declare_integer("value");
declare_integer("size");
declare_integer("type");
declare_integer("bind");
declare_integer("shndx");
end_struct_array("symtab")
declare_integer("dynsym_entries");
begin_struct_array("dynsym")
declare_string("name");
declare_integer("value");
declare_integer("size");
declare_integer("type");
declare_integer("bind");
declare_integer("shndx");
end_struct_array("dynsym")
declare_function("telfhash", "", "s", telfhash);
#if defined(HAVE_LIBCRYPTO) || defined(HAVE_WINCRYPT_H) || \
defined(HAVE_COMMONCRYPTO_COMMONCRYPTO_H)
declare_function("import_md5", "", "s", import_md5);
#endif // defined(HAVE_LIBCRYPTO) || defined(HAVE_WINCRYPT_H)
end_declarations
int module_initialize(YR_MODULE* module)
{
return ERROR_SUCCESS;
}
int module_finalize(YR_MODULE* module)
{
return ERROR_SUCCESS;
}
int module_load(
YR_SCAN_CONTEXT* context,
YR_OBJECT* module_object,
void* module_data,
size_t module_data_size)
{
YR_MEMORY_BLOCK* block;
YR_MEMORY_BLOCK_ITERATOR* iterator = context->iterator;
elf32_header_t* elf_header32;
elf64_header_t* elf_header64;
set_integer(ELF_ET_NONE, module_object, "ET_NONE");
set_integer(ELF_ET_REL, module_object, "ET_REL");
set_integer(ELF_ET_EXEC, module_object, "ET_EXEC");
set_integer(ELF_ET_DYN, module_object, "ET_DYN");
set_integer(ELF_ET_CORE, module_object, "ET_CORE");
set_integer(ELF_EM_NONE, module_object, "EM_NONE");
set_integer(ELF_EM_M32, module_object, "EM_M32");
set_integer(ELF_EM_SPARC, module_object, "EM_SPARC");
set_integer(ELF_EM_386, module_object, "EM_386");
set_integer(ELF_EM_68K, module_object, "EM_68K");
set_integer(ELF_EM_88K, module_object, "EM_88K");
set_integer(ELF_EM_860, module_object, "EM_860");
set_integer(ELF_EM_MIPS, module_object, "EM_MIPS");
set_integer(ELF_EM_MIPS_RS3_LE, module_object, "EM_MIPS_RS3_LE");
set_integer(ELF_EM_PPC, module_object, "EM_PPC");
set_integer(ELF_EM_PPC64, module_object, "EM_PPC64");
set_integer(ELF_EM_ARM, module_object, "EM_ARM");
set_integer(ELF_EM_X86_64, module_object, "EM_X86_64");
set_integer(ELF_EM_AARCH64, module_object, "EM_AARCH64");
set_integer(ELF_SHT_NULL, module_object, "SHT_NULL");
set_integer(ELF_SHT_PROGBITS, module_object, "SHT_PROGBITS");
set_integer(ELF_SHT_SYMTAB, module_object, "SHT_SYMTAB");
set_integer(ELF_SHT_STRTAB, module_object, "SHT_STRTAB");
set_integer(ELF_SHT_RELA, module_object, "SHT_RELA");
set_integer(ELF_SHT_HASH, module_object, "SHT_HASH");
set_integer(ELF_SHT_DYNAMIC, module_object, "SHT_DYNAMIC");
set_integer(ELF_SHT_NOTE, module_object, "SHT_NOTE");
set_integer(ELF_SHT_NOBITS, module_object, "SHT_NOBITS");
set_integer(ELF_SHT_REL, module_object, "SHT_REL");
set_integer(ELF_SHT_SHLIB, module_object, "SHT_SHLIB");
set_integer(ELF_SHT_DYNSYM, module_object, "SHT_DYNSYM");
set_integer(ELF_SHF_WRITE, module_object, "SHF_WRITE");
set_integer(ELF_SHF_ALLOC, module_object, "SHF_ALLOC");
set_integer(ELF_SHF_EXECINSTR, module_object, "SHF_EXECINSTR");
set_integer(ELF_PT_NULL, module_object, "PT_NULL");
set_integer(ELF_PT_LOAD, module_object, "PT_LOAD");
set_integer(ELF_PT_DYNAMIC, module_object, "PT_DYNAMIC");
set_integer(ELF_PT_INTERP, module_object, "PT_INTERP");
set_integer(ELF_PT_NOTE, module_object, "PT_NOTE");
set_integer(ELF_PT_SHLIB, module_object, "PT_SHLIB");
set_integer(ELF_PT_PHDR, module_object, "PT_PHDR");
set_integer(ELF_PT_TLS, module_object, "PT_TLS");
set_integer(ELF_PT_GNU_EH_FRAME, module_object, "PT_GNU_EH_FRAME");
set_integer(ELF_PT_GNU_STACK, module_object, "PT_GNU_STACK");
set_integer(ELF_DT_NULL, module_object, "DT_NULL");
set_integer(ELF_DT_NEEDED, module_object, "DT_NEEDED");
set_integer(ELF_DT_PLTRELSZ, module_object, "DT_PLTRELSZ");
set_integer(ELF_DT_PLTGOT, module_object, "DT_PLTGOT");
set_integer(ELF_DT_HASH, module_object, "DT_HASH");
set_integer(ELF_DT_STRTAB, module_object, "DT_STRTAB");
set_integer(ELF_DT_SYMTAB, module_object, "DT_SYMTAB");
set_integer(ELF_DT_RELA, module_object, "DT_RELA");
set_integer(ELF_DT_RELASZ, module_object, "DT_RELASZ");
set_integer(ELF_DT_RELAENT, module_object, "DT_RELAENT");
set_integer(ELF_DT_STRSZ, module_object, "DT_STRSZ");
set_integer(ELF_DT_SYMENT, module_object, "DT_SYMENT");
set_integer(ELF_DT_INIT, module_object, "DT_INIT");
set_integer(ELF_DT_FINI, module_object, "DT_FINI");
set_integer(ELF_DT_SONAME, module_object, "DT_SONAME");
set_integer(ELF_DT_RPATH, module_object, "DT_RPATH");
set_integer(ELF_DT_SYMBOLIC, module_object, "DT_SYMBOLIC");
set_integer(ELF_DT_REL, module_object, "DT_REL");
set_integer(ELF_DT_RELSZ, module_object, "DT_RELSZ");
set_integer(ELF_DT_RELENT, module_object, "DT_RELENT");
set_integer(ELF_DT_PLTREL, module_object, "DT_PLTREL");
set_integer(ELF_DT_DEBUG, module_object, "DT_DEBUG");
set_integer(ELF_DT_TEXTREL, module_object, "DT_TEXTREL");
set_integer(ELF_DT_JMPREL, module_object, "DT_JMPREL");
set_integer(ELF_DT_BIND_NOW, module_object, "DT_BIND_NOW");
set_integer(ELF_DT_INIT_ARRAY, module_object, "DT_INIT_ARRAY");
set_integer(ELF_DT_FINI_ARRAY, module_object, "DT_FINI_ARRAY");
set_integer(ELF_DT_INIT_ARRAYSZ, module_object, "DT_INIT_ARRAYSZ");
set_integer(ELF_DT_FINI_ARRAYSZ, module_object, "DT_FINI_ARRAYSZ");
set_integer(ELF_DT_RUNPATH, module_object, "DT_RUNPATH");
set_integer(ELF_DT_FLAGS, module_object, "DT_FLAGS");
set_integer(ELF_DT_ENCODING, module_object, "DT_ENCODING");
set_integer(ELF_STT_NOTYPE, module_object, "STT_NOTYPE");
set_integer(ELF_STT_OBJECT, module_object, "STT_OBJECT");
set_integer(ELF_STT_FUNC, module_object, "STT_FUNC");
set_integer(ELF_STT_SECTION, module_object, "STT_SECTION");
set_integer(ELF_STT_FILE, module_object, "STT_FILE");
set_integer(ELF_STT_COMMON, module_object, "STT_COMMON");
set_integer(ELF_STT_TLS, module_object, "STT_TLS");
set_integer(ELF_STB_LOCAL, module_object, "STB_LOCAL");
set_integer(ELF_STB_GLOBAL, module_object, "STB_GLOBAL");
set_integer(ELF_STB_WEAK, module_object, "STB_WEAK");
set_integer(ELF_PF_X, module_object, "PF_X");
set_integer(ELF_PF_W, module_object, "PF_W");
set_integer(ELF_PF_R, module_object, "PF_R");
uint64_t parse_result = ERROR_SUCCESS;
foreach_memory_block(iterator, block)
{
const uint8_t* block_data = block->fetch_data(block);
if (block_data == NULL)
continue;
ELF* elf = (ELF*) yr_calloc(1, sizeof(ELF));
if (elf == NULL)
return ERROR_INSUFFICIENT_MEMORY;
module_object->data = elf;
switch (get_elf_class_data(block_data, block->size))
{
case CLASS_DATA(ELF_CLASS_32, ELF_DATA_2LSB):
if (block->size > sizeof(elf32_header_t))
{
elf_header32 = (elf32_header_t*) block_data;
if (!(context->flags & SCAN_FLAGS_PROCESS_MEMORY) ||
yr_le16toh(elf_header32->type) == ELF_ET_EXEC)
{
parse_result = parse_elf_header_32_le(
elf,
elf_header32,
block->base,
block->size,
context->flags,
module_object);
}
}
break;
case CLASS_DATA(ELF_CLASS_32, ELF_DATA_2MSB):
if (block->size > sizeof(elf32_header_t))
{
elf_header32 = (elf32_header_t*) block_data;
if (!(context->flags & SCAN_FLAGS_PROCESS_MEMORY) ||
yr_be16toh(elf_header32->type) == ELF_ET_EXEC)
{
parse_result = parse_elf_header_32_be(
elf,
elf_header32,
block->base,
block->size,
context->flags,
module_object);
}
}
break;
case CLASS_DATA(ELF_CLASS_64, ELF_DATA_2LSB):
if (block->size > sizeof(elf64_header_t))
{
elf_header64 = (elf64_header_t*) block_data;
if (!(context->flags & SCAN_FLAGS_PROCESS_MEMORY) ||
yr_le16toh(elf_header64->type) == ELF_ET_EXEC)
{
parse_result = parse_elf_header_64_le(
elf,
elf_header64,
block->base,
block->size,
context->flags,
module_object);
}
}
break;
case CLASS_DATA(ELF_CLASS_64, ELF_DATA_2MSB):
if (block->size > sizeof(elf64_header_t))
{
elf_header64 = (elf64_header_t*) block_data;
if (!(context->flags & SCAN_FLAGS_PROCESS_MEMORY) ||
yr_be16toh(elf_header64->type) == ELF_ET_EXEC)
{
parse_result = parse_elf_header_64_be(
elf,
elf_header64,
block->base,
block->size,
context->flags,
module_object);
}
}
break;
}
}
return parse_result;
}
int module_unload(YR_OBJECT* module_object)
{
ELF* elf = (ELF*) module_object->data;
if (elf == NULL)
return ERROR_SUCCESS;
if (elf->symtab != NULL)
{
ELF_SYMBOL *act = NULL, *next = NULL;
for (act = elf->symtab->symbols; act != NULL; act = next)
{
next = act->next;
if (act->name != NULL)
yr_free(act->name);
yr_free(act);
}
yr_free(elf->symtab);
}
if (elf->dynsym != NULL)
{
ELF_SYMBOL *act = NULL, *next = NULL;
for (act = elf->dynsym->symbols; act != NULL; act = next)
{
next = act->next;
if (act->name != NULL)
yr_free(act->name);
yr_free(act);
}
yr_free(elf->dynsym);
}
yr_free(elf->telfhash);
yr_free(elf->import_hash);
yr_free(elf);
module_object->data = NULL;
return ERROR_SUCCESS;
}
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