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packer.cpp
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packer.cpp
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#include "packer.h"
#include "elf_utils.h"
#include <cassert>
#include <fcntl.h>
#include <unordered_set>
#include <string.h>
#include <string_view>
#include <sys/mman.h>
#include <sys/stat.h>
#include <elf.h>
int Packer::run()
{
if (entry_ - BASE_ADDRESS == 0)
{
return -1;
}
using Fun = int(*)(void);
Fun f = (Fun)(entry_);
printf("Jumping to entry %p (%p)...\n", (void*)(entry_ - BASE_ADDRESS), (void*)entry_);
int ret = f();
printf("After jump\n");
return ret;
}
int Packer::load_elf_file(std::string_view file_path)
{
int fd = open(file_path.data(), O_RDONLY);
if (fd < 0) return fd;
// Map full elf file into memory
struct stat s;
fstat(fd, &s);
int size = s.st_size;
file_data_ = (char*)mmap(0, size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
close(fd);
return 0;
}
int Packer::parse_program_headers()
{
assert(sizeof(elf64_phdr) == main_header_.e_phentsize);
phdrs_.resize(main_header_.e_phnum);
for (int i = 0; i < main_header_.e_phnum; ++i)
{
phdrs_[i] = *((elf64_phdr*)(file_data_ + main_header_.e_phoff + main_header_.e_phentsize * i));
}
return 0;
}
int Packer::parse_elf_header()
{
memcpy(&main_header_, file_data_, sizeof(elf64_hdr));
entry_ = BASE_ADDRESS + main_header_.e_entry;
return 0;
}
int Packer::handle_program_headers()
{
int ret = 0;
for (int i = 0; i < phdrs_.size(); ++i)
{
ret |= handle_program_header(phdrs_[i]);
}
return ret;
}
int Packer::handle_program_header(elf64_phdr const & header)
{
switch (header.p_type)
{
case PT_NULL:
break;
case PT_LOAD:
return handle_load_phdr(header);
case PT_DYNAMIC:
return retrieve_dynamic_phdrs(header);
break;
case PT_INTERP:
case PT_NOTE:
case PT_SHLIB:
case PT_PHDR:
case PT_TLS:
case PT_LOOS:
case PT_HIOS:
case PT_LOPROC:
case PT_HIPROC:
case PT_GNU_EH_FRAME:
default:
printf("Unrecognized header type %d\n", header.p_type);
}
return 0;
}
int Packer::handle_dynamic_entries()
{
int ret = 0;
for (int i = 0; i < dynamic_entries_.size(); ++i)
{
ret |= handle_dynamic_entry(dynamic_entries_[i]);
}
resolve_dependencies_names();
return ret;
}
int Packer::handle_relocation_entries()
{
if (rela_section_header_ == nullptr || relocation_table_size_ == 0)
{
printf("No relocation.\n");
return 0;
}
const elf64_rela * rel_array = (elf64_rela*)(file_data_ + rela_section_header_->d_un.d_ptr);
for (size_t i = 0; i < relocation_table_size_; ++i)
{
relocate(rel_array[i]);
}
return 0;
}
int Packer::retrieve_symtab_(elf64_dyn const & header)
{
printf("Retrieving symtab...\n");
const elf64_shdr * sht_dynsym = get_sht_dynsym();
if (sht_dynsym == nullptr) return -1;
int size = sht_dynsym->sh_size / sht_dynsym->sh_entsize;
const elf64_sym * sym_runner = (const elf64_sym*)(file_data_ + sht_dynsym->sh_offset);
for (int i = 0; i < size; ++i)
{
symtab_.push_back(&sym_runner[i]);
}
printf("Retrived %d dyn syms\n", size);
print_dynsyms();
return 0;
}
int Packer::handle_dynamic_entry(elf64_dyn const & header)
{
switch (header.d_tag)
{
case Null:
break;
case NEEDED:
{
dependencies_.emplace_back(Dependency{header.d_un.d_ptr, nullptr, {}});
break;
}
case PLTRELSZ:
break;
case PLTGOT:
break;
case HASH:
break;
case STRTAB:
if (dynstr_ == nullptr)
{
dynstr_ = file_data_ + header.d_un.d_ptr;
}
break;
case SYMTAB:
retrieve_symtab_(header);
break;
case RELA:
rela_section_header_ = &header;
break;
case RELASZ:
relocation_table_size_ = header.d_un.d_val;
break;
case RELAENT:
relocation_table_size_ /= header.d_un.d_val;
printf("Setting relocation_table_size_ to %lu\n", relocation_table_size_);
break;
case RPATH:
case RUNPATH:
rpath_ = (char*)header.d_un.d_ptr;
break;
case STRSZ:
case SYMENT:
case INIT:
case FINI:
case SONAME:
break;
case SYMBOLIC:
case REL:
case RELSZ:
case RELENT:
case PLTREL:
case DEBUG:
case TEXTREL:
case JMPREL:
case BINDNOW:
case INITARRAY:
case FINIARRAY:
case INITARRAYSZ:
case FINIARRAYSZ:
case LOOS:
case HIOS:
case LOPROC:
case HIPROC:
case GNUHASH:
case FLAGS1:
case RELACOUNT:
default:
break;
}
// printf("Unrecognized dynamic tag %s\n", dynamic_tag_to_str(DynamicTag(header.d_tag)));
return 0;
}
int Packer::handle_load_phdr(elf64_phdr const & phdr)
{
printf("Mapping header @ 0x%lx ..... 0x%lx | %s%s%s\n",
BASE_ADDRESS + phdr.p_vaddr,
BASE_ADDRESS + phdr.p_vaddr + phdr.p_filesz,
(phdr.p_flags & PF_R) ? "R" : ".",
(phdr.p_flags & PF_W) ? "W" : ".",
(phdr.p_flags & PF_X) ? "X" : "."
);
if (phdr.p_filesz == 0) return 0;
// Length needs to account for page overflow
size_t length = phdr.p_filesz + phdr.p_vaddr % sysconf(_SC_PAGE_SIZE);
MappedZone mapped_zone;
// Mapping to p_vaddr
int ret = mapped_zone.map((void*)phdr.p_vaddr, length);
if (ret == -1)
{
printf("Error mapping zone\n");
return -1;
}
mapped_zone.length = length;
mapped_zone.flags = phdr.p_flags;
mapped_zones_.emplace_back(std::move(mapped_zone));
// Copy data from elf base file to virtual memory
memcpy((void*)(BASE_ADDRESS + (uintptr_t)phdr.p_vaddr), file_data_ + phdr.p_offset, phdr.p_filesz);
return 0;
}
int Packer::retrieve_dynamic_phdrs(elf64_phdr const & header)
{
printf("Handling dynamic header\n");
elf64_dyn *dyn_entries = ((elf64_dyn*)(file_data_ + header.p_offset));
for (int i = 0; i < header.p_filesz / sizeof(elf64_dyn); ++i)
{
if (dyn_entries[i].d_tag == 0) break;
dynamic_entries_.push_back(dyn_entries[i]);
}
return 0;
}
void Packer::print_main_header()
{
print_elf_header(main_header_);
}
void Packer::print_program_headers()
{
for (int i = 0 ; i < main_header_.e_phnum; ++i)
{
printf("============ Program Header %d =========\n", i);
print_program_header(phdrs_[i]);
printf("\n");
}
}
void Packer::print_dynamic_entries()
{
printf("Dynamic Entries:\n");
for (int i = 0 ; i < dynamic_entries_.size(); ++i)
{
printf("\t- Dynamic Entry { tag: %s, addr: %.8lx }\n", dynamic_tag_to_str((DynamicTag)dynamic_entries_[i].d_tag), (long int)(dynamic_entries_[i].d_un.d_val));
}
}
void Packer::print_section_headers()
{
printf("Section Headers:\n");
for (int i = 0 ; i < section_headers_.size(); ++i)
{
printf("{\n");
print_section_header(*section_headers_[i]);
printf("}\n");
}
}
int Packer::relocate(const elf64_rela & rel)
{
printf("Relocation...\n");
print_rela(rel);
RelaType type = (RelaType)(rel.r_info & 0x00000000FFFFFFFF);
switch (type)
{
case RELATIVE:
{
printf("Relative relocating 8-byte word %p to %p\n", (void*)(BASE_ADDRESS + rel.r_addend),(void*)(BASE_ADDRESS + rel.r_offset));
uint64_t to_relocate = BASE_ADDRESS + rel.r_addend;
memcpy((void*)(BASE_ADDRESS + rel.r_offset), (void*)(&to_relocate), 8);
break;
}
case _64:
// return sixtyfour_relocation(rel);
case COPY:
// return copy_relocation(rel);
default:
printf("Cannot handle relocation type '%s'\n", rela_type_to_str(type));
return 0;
}
return 0;
}
int Packer::parse_section_headers()
{
const elf64_shdr * runner = (elf64_shdr *)(file_data_ + (uintptr_t)main_header_.e_shoff);
for (int i = 0; i < main_header_.e_shnum; i++)
{
section_headers_.push_back(&runner[i]);
}
return 0;
}
int Packer::sixtyfour_relocation(const elf64_rela & rel)
{
return 1;
}
int Packer::copy_relocation(const elf64_rela & rel)
{
return 1;
}
void Packer::print_dynsyms()
{
printf("Dynamic symbols:\n");
for (int i = 0; i < symtab_.size(); ++i)
{
const elf64_sym & sym = *symtab_[i];
printf("\t- %d - { st_name: '%s' (%u), st_info: %d, st_other: %d, st_shndx: %d, st_value: 0x%lx, st_size: 0x%lx }\n"
, i, dynstr_ + sym.st_name, sym.st_name, sym.st_info ,sym.st_other ,sym.st_shndx, sym.st_value, sym.st_size);
}
}
int Packer::get_dependency_graph()
{
std::vector<Dependency> ordered_dependencies;
std::unordered_set<std::string> deja_vu;
std::vector<std::string> process_queue;
// Init queue in reverse order
for (int i = dependencies_.size() - 1; i >= 0; --i)
{
process_queue.push_back(dependencies_[i].name);
deja_vu.emplace(dependencies_[i].name);
}
while (process_queue.size() > 0)
{
const std::string & current = process_queue.back();
process_queue.pop_back();
}
return 0;
}