/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ #undef NDEBUG #include <assert.h> #include <cstring> #include <cstdlib> #include <cstdio> #include "elfxx.h" #define ver "0" #define elfhack_data ".elfhack.data.v" ver #define elfhack_text ".elfhack.text.v" ver #ifndef R_ARM_V4BX #define R_ARM_V4BX 0x28 #endif #ifndef R_ARM_CALL #define R_ARM_CALL 0x1c #endif #ifndef R_ARM_JUMP24 #define R_ARM_JUMP24 0x1d #endif #ifndef R_ARM_THM_JUMP24 #define R_ARM_THM_JUMP24 0x1e #endif char *rundir = nullptr; template <typename T> struct wrapped { T value; }; class Elf_Addr_Traits { public: typedef wrapped<Elf32_Addr> Type32; typedef wrapped<Elf64_Addr> Type64; template <class endian, typename R, typename T> static inline void swap(T &t, R &r) { r.value = endian::swap(t.value); } }; typedef serializable<Elf_Addr_Traits> Elf_Addr; class Elf_RelHack_Traits { public: typedef Elf32_Rel Type32; typedef Elf32_Rel Type64; template <class endian, typename R, typename T> static inline void swap(T &t, R &r) { r.r_offset = endian::swap(t.r_offset); r.r_info = endian::swap(t.r_info); } }; typedef serializable<Elf_RelHack_Traits> Elf_RelHack; class ElfRelHack_Section: public ElfSection { public: ElfRelHack_Section(Elf_Shdr &s) : ElfSection(s, nullptr, nullptr) { name = elfhack_data; }; void serialize(std::ofstream &file, char ei_class, char ei_data) { for (std::vector<Elf_RelHack>::iterator i = rels.begin(); i != rels.end(); ++i) (*i).serialize(file, ei_class, ei_data); } bool isRelocatable() { return true; } void push_back(Elf_RelHack &r) { rels.push_back(r); shdr.sh_size = rels.size() * shdr.sh_entsize; } private: std::vector<Elf_RelHack> rels; }; class ElfRelHackCode_Section: public ElfSection { public: ElfRelHackCode_Section(Elf_Shdr &s, Elf &e, unsigned int init) : ElfSection(s, nullptr, nullptr), parent(e), init(init) { std::string file(rundir); file += "/inject/"; switch (parent.getMachine()) { case EM_386: file += "x86"; break; case EM_X86_64: file += "x86_64"; break; case EM_ARM: file += "arm"; break; default: throw std::runtime_error("unsupported architecture"); } file += ".o"; std::ifstream inject(file.c_str(), std::ios::in|std::ios::binary); elf = new Elf(inject); if (elf->getType() != ET_REL) throw std::runtime_error("object for injected code is not ET_REL"); if (elf->getMachine() != parent.getMachine()) throw std::runtime_error("architecture of object for injected code doesn't match"); ElfSymtab_Section *symtab = nullptr; // Find the symbol table. for (ElfSection *section = elf->getSection(1); section != nullptr; section = section->getNext()) { if (section->getType() == SHT_SYMTAB) symtab = (ElfSymtab_Section *) section; } if (symtab == nullptr) throw std::runtime_error("Couldn't find a symbol table for the injected code"); // Find the init symbol entry_point = -1; Elf_SymValue *sym = symtab->lookup(init ? "init" : "init_noinit"); if (!sym) throw std::runtime_error("Couldn't find an 'init' symbol in the injected code"); entry_point = sym->value.getValue(); // Get all relevant sections from the injected code object. add_code_section(sym->value.getSection()); // Adjust code sections offsets according to their size std::vector<ElfSection *>::iterator c = code.begin(); (*c)->getShdr().sh_addr = 0; for(ElfSection *last = *(c++); c != code.end(); c++) { unsigned int addr = last->getShdr().sh_addr + last->getSize(); if (addr & ((*c)->getAddrAlign() - 1)) addr = (addr | ((*c)->getAddrAlign() - 1)) + 1; (*c)->getShdr().sh_addr = addr; // We need to align this section depending on the greater // alignment required by code sections. if (shdr.sh_addralign < (*c)->getAddrAlign()) shdr.sh_addralign = (*c)->getAddrAlign(); } shdr.sh_size = code.back()->getAddr() + code.back()->getSize(); data = new char[shdr.sh_size]; char *buf = data; for (c = code.begin(); c != code.end(); c++) { memcpy(buf, (*c)->getData(), (*c)->getSize()); buf += (*c)->getSize(); } name = elfhack_text; } ~ElfRelHackCode_Section() { delete elf; } void serialize(std::ofstream &file, char ei_class, char ei_data) { // Readjust code offsets for (std::vector<ElfSection *>::iterator c = code.begin(); c != code.end(); c++) (*c)->getShdr().sh_addr += getAddr(); // Apply relocations for (std::vector<ElfSection *>::iterator c = code.begin(); c != code.end(); c++) { for (ElfSection *rel = elf->getSection(1); rel != nullptr; rel = rel->getNext()) if (((rel->getType() == SHT_REL) || (rel->getType() == SHT_RELA)) && (rel->getInfo().section == *c)) { if (rel->getType() == SHT_REL) apply_relocations((ElfRel_Section<Elf_Rel> *)rel, *c); else apply_relocations((ElfRel_Section<Elf_Rela> *)rel, *c); } } ElfSection::serialize(file, ei_class, ei_data); } bool isRelocatable() { return true; } unsigned int getEntryPoint() { return entry_point; } private: void add_code_section(ElfSection *section) { if (section) { /* Don't add section if it's already been added in the past */ for (auto s = code.begin(); s != code.end(); ++s) { if (section == *s) return; } code.push_back(section); find_code(section); } } /* Look at the relocations associated to the given section to find other * sections that it requires */ void find_code(ElfSection *section) { for (ElfSection *s = elf->getSection(1); s != nullptr; s = s->getNext()) { if (((s->getType() == SHT_REL) || (s->getType() == SHT_RELA)) && (s->getInfo().section == section)) { if (s->getType() == SHT_REL) scan_relocs_for_code((ElfRel_Section<Elf_Rel> *)s); else scan_relocs_for_code((ElfRel_Section<Elf_Rela> *)s); } } } template <typename Rel_Type> void scan_relocs_for_code(ElfRel_Section<Rel_Type> *rel) { ElfSymtab_Section *symtab = (ElfSymtab_Section *)rel->getLink(); for (auto r = rel->rels.begin(); r != rel->rels.end(); r++) { ElfSection *section = symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection(); add_code_section(section); } } class pc32_relocation { public: Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset, Elf32_Word addend, unsigned int addr) { return addr + addend - offset - base_addr; } }; class arm_plt32_relocation { public: Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset, Elf32_Word addend, unsigned int addr) { // We don't care about sign_extend because the only case where this is // going to be used only jumps forward. Elf32_Addr tmp = (Elf32_Addr) (addr - offset - base_addr) >> 2; tmp = (addend + tmp) & 0x00ffffff; return (addend & 0xff000000) | tmp; } }; class arm_thm_jump24_relocation { public: Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset, Elf32_Word addend, unsigned int addr) { /* Follows description of b.w and bl instructions as per ARM Architecture Reference Manual ARMĀ® v7-A and ARMĀ® v7-R edition, A8.6.16 We limit ourselves to Encoding T4 of b.w and Encoding T1 of bl. We don't care about sign_extend because the only case where this is going to be used only jumps forward. */ Elf32_Addr tmp = (Elf32_Addr) (addr - offset - base_addr); unsigned int word0 = addend & 0xffff, word1 = addend >> 16; /* Encoding T4 of B.W is 10x1 ; Encoding T1 of BL is 11x1. */ unsigned int type = (word1 & 0xd000) >> 12; if (((word0 & 0xf800) != 0xf000) || ((type & 0x9) != 0x9)) throw std::runtime_error("R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for B.W <label> and BL <label>"); /* When the target address points to ARM code, switch a BL to a * BLX. This however can't be done with a B.W without adding a * trampoline, which is not supported as of now. */ if ((addr & 0x1) == 0) { if (type == 0x9) throw std::runtime_error("R_ARM_THM_JUMP24/R_ARM_THM_CALL relocation only supported for BL <label> when label points to ARM code"); /* The address of the target is always relative to a 4-bytes * aligned address, so if the address of the BL instruction is * not 4-bytes aligned, adjust for it. */ if ((base_addr + offset) & 0x2) tmp += 2; /* Encoding T2 of BLX is 11x0. */ type = 0xc; } unsigned int s = (word0 & (1 << 10)) >> 10; unsigned int j1 = (word1 & (1 << 13)) >> 13; unsigned int j2 = (word1 & (1 << 11)) >> 11; unsigned int i1 = j1 ^ s ? 0 : 1; unsigned int i2 = j2 ^ s ? 0 : 1; tmp += ((s << 24) | (i1 << 23) | (i2 << 22) | ((word0 & 0x3ff) << 12) | ((word1 & 0x7ff) << 1)); s = (tmp & (1 << 24)) >> 24; j1 = ((tmp & (1 << 23)) >> 23) ^ !s; j2 = ((tmp & (1 << 22)) >> 22) ^ !s; return 0xf000 | (s << 10) | ((tmp & (0x3ff << 12)) >> 12) | (type << 28) | (j1 << 29) | (j2 << 27) | ((tmp & 0xffe) << 15); } }; class gotoff_relocation { public: Elf32_Addr operator()(unsigned int base_addr, Elf32_Off offset, Elf32_Word addend, unsigned int addr) { return addr + addend; } }; template <class relocation_type> void apply_relocation(ElfSection *the_code, char *base, Elf_Rel *r, unsigned int addr) { relocation_type relocation; Elf32_Addr value; memcpy(&value, base + r->r_offset, 4); value = relocation(the_code->getAddr(), r->r_offset, value, addr); memcpy(base + r->r_offset, &value, 4); } template <class relocation_type> void apply_relocation(ElfSection *the_code, char *base, Elf_Rela *r, unsigned int addr) { relocation_type relocation; Elf32_Addr value = relocation(the_code->getAddr(), r->r_offset, r->r_addend, addr); memcpy(base + r->r_offset, &value, 4); } template <typename Rel_Type> void apply_relocations(ElfRel_Section<Rel_Type> *rel, ElfSection *the_code) { assert(rel->getType() == Rel_Type::sh_type); char *buf = data + (the_code->getAddr() - code.front()->getAddr()); // TODO: various checks on the sections ElfSymtab_Section *symtab = (ElfSymtab_Section *)rel->getLink(); for (typename std::vector<Rel_Type>::iterator r = rel->rels.begin(); r != rel->rels.end(); r++) { // TODO: various checks on the symbol const char *name = symtab->syms[ELF32_R_SYM(r->r_info)].name; unsigned int addr; if (symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection() == nullptr) { if (strcmp(name, "relhack") == 0) { addr = getNext()->getAddr(); } else if (strcmp(name, "elf_header") == 0) { // TODO: change this ungly hack to something better ElfSection *ehdr = parent.getSection(1)->getPrevious()->getPrevious(); addr = ehdr->getAddr(); } else if (strcmp(name, "original_init") == 0) { addr = init; } else if (strcmp(name, "_GLOBAL_OFFSET_TABLE_") == 0) { // We actually don't need a GOT, but need it as a reference for // GOTOFF relocations. We'll just use the start of the ELF file addr = 0; } else if (strcmp(name, "") == 0) { // This is for R_ARM_V4BX, until we find something better addr = -1; } else { throw std::runtime_error("Unsupported symbol in relocation"); } } else { ElfSection *section = symtab->syms[ELF32_R_SYM(r->r_info)].value.getSection(); assert((section->getType() == SHT_PROGBITS) && (section->getFlags() & SHF_EXECINSTR)); addr = symtab->syms[ELF32_R_SYM(r->r_info)].value.getValue(); } // Do the relocation #define REL(machine, type) (EM_ ## machine | (R_ ## machine ## _ ## type << 8)) switch (elf->getMachine() | (ELF32_R_TYPE(r->r_info) << 8)) { case REL(X86_64, PC32): case REL(386, PC32): case REL(386, GOTPC): case REL(ARM, GOTPC): case REL(ARM, REL32): apply_relocation<pc32_relocation>(the_code, buf, &*r, addr); break; case REL(ARM, CALL): case REL(ARM, JUMP24): case REL(ARM, PLT32): apply_relocation<arm_plt32_relocation>(the_code, buf, &*r, addr); break; case REL(ARM, THM_PC22 /* THM_CALL */): case REL(ARM, THM_JUMP24): apply_relocation<arm_thm_jump24_relocation>(the_code, buf, &*r, addr); break; case REL(386, GOTOFF): case REL(ARM, GOTOFF): apply_relocation<gotoff_relocation>(the_code, buf, &*r, addr); break; case REL(ARM, V4BX): // Ignore R_ARM_V4BX relocations break; default: throw std::runtime_error("Unsupported relocation type"); } } } Elf *elf, &parent; std::vector<ElfSection *> code; unsigned int init; int entry_point; }; unsigned int get_addend(Elf_Rel *rel, Elf *elf) { ElfLocation loc(rel->r_offset, elf); Elf_Addr addr(loc.getBuffer(), Elf_Addr::size(elf->getClass()), elf->getClass(), elf->getData()); return addr.value; } unsigned int get_addend(Elf_Rela *rel, Elf *elf) { return rel->r_addend; } void set_relative_reloc(Elf_Rel *rel, Elf *elf, unsigned int value) { ElfLocation loc(rel->r_offset, elf); Elf_Addr addr; addr.value = value; addr.serialize(const_cast<char *>(loc.getBuffer()), Elf_Addr::size(elf->getClass()), elf->getClass(), elf->getData()); } void set_relative_reloc(Elf_Rela *rel, Elf *elf, unsigned int value) { // ld puts the value of relocated relocations both in the addend and // at r_offset. For consistency, keep it that way. set_relative_reloc((Elf_Rel *)rel, elf, value); rel->r_addend = value; } void maybe_split_segment(Elf *elf, ElfSegment *segment, bool fill) { std::list<ElfSection *>::iterator it = segment->begin(); for (ElfSection *last = *(it++); it != segment->end(); last = *(it++)) { // When two consecutive non-SHT_NOBITS sections are apart by more // than the alignment of the section, the second can be moved closer // to the first, but this requires the segment to be split. if (((*it)->getType() != SHT_NOBITS) && (last->getType() != SHT_NOBITS) && ((*it)->getOffset() - last->getOffset() - last->getSize() > segment->getAlign())) { // Probably very wrong. Elf_Phdr phdr; phdr.p_type = PT_LOAD; phdr.p_vaddr = 0; phdr.p_paddr = phdr.p_vaddr + segment->getVPDiff(); phdr.p_flags = segment->getFlags(); phdr.p_align = segment->getAlign(); phdr.p_filesz = (unsigned int)-1; phdr.p_memsz = (unsigned int)-1; ElfSegment *newSegment = new ElfSegment(&phdr); elf->insertSegmentAfter(segment, newSegment); ElfSection *section = *it; for (; it != segment->end(); ++it) { newSegment->addSection(*it); } for (it = newSegment->begin(); it != newSegment->end(); it++) { segment->removeSection(*it); } // Fill the virtual address space gap left between the two PT_LOADs // with a new PT_LOAD with no permissions. This avoids the linker // (especially bionic's) filling the gap with anonymous memory, // which breakpad doesn't like. // /!\ running strip on a elfhacked binary will break this filler // PT_LOAD. if (!fill) break; // Insert dummy segment to normalize the entire Elf with the header // sizes adjusted, before inserting a filler segment. { memset(&phdr, 0, sizeof(phdr)); ElfSegment dummySegment(&phdr); elf->insertSegmentAfter(segment, &dummySegment); elf->normalize(); elf->removeSegment(&dummySegment); } ElfSection *previous = section->getPrevious(); phdr.p_type = PT_LOAD; phdr.p_vaddr = (previous->getAddr() + previous->getSize() + segment->getAlign() - 1) & ~(segment->getAlign() - 1); phdr.p_paddr = phdr.p_vaddr + segment->getVPDiff(); phdr.p_flags = 0; phdr.p_align = 0; phdr.p_filesz = (section->getAddr() & ~(newSegment->getAlign() - 1)) - phdr.p_vaddr; phdr.p_memsz = phdr.p_filesz; if (phdr.p_filesz) { newSegment = new ElfSegment(&phdr); assert(newSegment->isElfHackFillerSegment()); elf->insertSegmentAfter(segment, newSegment); } else { elf->normalize(); } break; } } } template <typename Rel_Type> int do_relocation_section(Elf *elf, unsigned int rel_type, unsigned int rel_type2, bool force, bool fill) { ElfDynamic_Section *dyn = elf->getDynSection(); if (dyn == nullptr) { fprintf(stderr, "Couldn't find SHT_DYNAMIC section\n"); return -1; } ElfSegment *relro = elf->getSegmentByType(PT_GNU_RELRO); ElfRel_Section<Rel_Type> *section = (ElfRel_Section<Rel_Type> *)dyn->getSectionForType(Rel_Type::d_tag); assert(section->getType() == Rel_Type::sh_type); Elf32_Shdr relhack32_section = { 0, SHT_PROGBITS, SHF_ALLOC, 0, (Elf32_Off)-1, 0, SHN_UNDEF, 0, Elf_RelHack::size(elf->getClass()), Elf_RelHack::size(elf->getClass()) }; // TODO: sh_addralign should be an alignment, not size Elf32_Shdr relhackcode32_section = { 0, SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR, 0, (Elf32_Off)-1, 0, SHN_UNDEF, 0, 1, 0 }; unsigned int entry_sz = Elf_Addr::size(elf->getClass()); // The injected code needs to be executed before any init code in the // binary. There are three possible cases: // - The binary has no init code at all. In this case, we will add a // DT_INIT entry pointing to the injected code. // - The binary has a DT_INIT entry. In this case, we will interpose: // we change DT_INIT to point to the injected code, and have the // injected code call the original DT_INIT entry point. // - The binary has no DT_INIT entry, but has a DT_INIT_ARRAY. In this // case, we interpose as well, by replacing the first entry in the // array to point to the injected code, and have the injected code // call the original first entry. // The binary may have .ctors instead of DT_INIT_ARRAY, for its init // functions, but this falls into the second case above, since .ctors // are actually run by DT_INIT code. ElfValue *value = dyn->getValueForType(DT_INIT); unsigned int original_init = value ? value->getValue() : 0; ElfSection *init_array = nullptr; if (!value || !value->getValue()) { value = dyn->getValueForType(DT_INIT_ARRAYSZ); if (value && value->getValue() >= entry_sz) init_array = dyn->getSectionForType(DT_INIT_ARRAY); } Elf_Shdr relhack_section(relhack32_section); Elf_Shdr relhackcode_section(relhackcode32_section); ElfRelHack_Section *relhack = new ElfRelHack_Section(relhack_section); ElfSymtab_Section *symtab = (ElfSymtab_Section *) section->getLink(); Elf_SymValue *sym = symtab->lookup("__cxa_pure_virtual"); std::vector<Rel_Type> new_rels; Elf_RelHack relhack_entry; relhack_entry.r_offset = relhack_entry.r_info = 0; size_t init_array_reloc = 0; for (typename std::vector<Rel_Type>::iterator i = section->rels.begin(); i != section->rels.end(); i++) { // We don't need to keep R_*_NONE relocations if (!ELF32_R_TYPE(i->r_info)) continue; ElfLocation loc(i->r_offset, elf); // __cxa_pure_virtual is a function used in vtables to point at pure // virtual methods. The __cxa_pure_virtual function usually abort()s. // These functions are however normally never called. In the case // where they would, jumping to the null address instead of calling // __cxa_pure_virtual is going to work just as well. So we can remove // relocations for the __cxa_pure_virtual symbol and null out the // content at the offset pointed by the relocation. if (sym) { if (sym->defined) { // If we are statically linked to libstdc++, the // __cxa_pure_virtual symbol is defined in our lib, and we // have relative relocations (rel_type) for it. if (ELF32_R_TYPE(i->r_info) == rel_type) { Elf_Addr addr(loc.getBuffer(), entry_sz, elf->getClass(), elf->getData()); if (addr.value == sym->value.getValue()) { memset((char *)loc.getBuffer(), 0, entry_sz); continue; } } } else { // If we are dynamically linked to libstdc++, the // __cxa_pure_virtual symbol is undefined in our lib, and we // have absolute relocations (rel_type2) for it. if ((ELF32_R_TYPE(i->r_info) == rel_type2) && (sym == &symtab->syms[ELF32_R_SYM(i->r_info)])) { memset((char *)loc.getBuffer(), 0, entry_sz); continue; } } } // Keep track of the relocation associated with the first init_array entry. if (init_array && i->r_offset == init_array->getAddr()) { if (init_array_reloc) { fprintf(stderr, "Found multiple relocations for the first init_array entry. Skipping\n"); return -1; } new_rels.push_back(*i); init_array_reloc = new_rels.size(); } else if (!(loc.getSection()->getFlags() & SHF_WRITE) || (ELF32_R_TYPE(i->r_info) != rel_type) || (relro && (i->r_offset >= relro->getAddr()) && (i->r_offset < relro->getAddr() + relro->getMemSize()))) { // Don't pack relocations happening in non writable sections. // Our injected code is likely not to be allowed to write there. new_rels.push_back(*i); } else { // TODO: check that i->r_addend == *i->r_offset if (i->r_offset == relhack_entry.r_offset + relhack_entry.r_info * entry_sz) { relhack_entry.r_info++; } else { if (relhack_entry.r_offset) relhack->push_back(relhack_entry); relhack_entry.r_offset = i->r_offset; relhack_entry.r_info = 1; } } } if (relhack_entry.r_offset) relhack->push_back(relhack_entry); // Last entry must be nullptr relhack_entry.r_offset = relhack_entry.r_info = 0; relhack->push_back(relhack_entry); unsigned int old_end = section->getOffset() + section->getSize(); if (init_array) { if (! init_array_reloc) { fprintf(stderr, "Didn't find relocation for DT_INIT_ARRAY's first entry. Skipping\n"); return -1; } Rel_Type *rel = &new_rels[init_array_reloc - 1]; unsigned int addend = get_addend(rel, elf); // Use relocated value of DT_INIT_ARRAY's first entry for the // function to be called by the injected code. if (ELF32_R_TYPE(rel->r_info) == rel_type) { original_init = addend; } else if (ELF32_R_TYPE(rel->r_info) == rel_type2) { ElfSymtab_Section *symtab = (ElfSymtab_Section *)section->getLink(); original_init = symtab->syms[ELF32_R_SYM(rel->r_info)].value.getValue() + addend; } else { fprintf(stderr, "Unsupported relocation type for DT_INIT_ARRAY's first entry. Skipping\n"); return -1; } } section->rels.assign(new_rels.begin(), new_rels.end()); section->shrink(new_rels.size() * section->getEntSize()); ElfRelHackCode_Section *relhackcode = new ElfRelHackCode_Section(relhackcode_section, *elf, original_init); relhackcode->insertBefore(section); relhack->insertAfter(relhackcode); if (section->getOffset() + section->getSize() >= old_end) { fprintf(stderr, "No gain. Skipping\n"); return -1; } // Adjust PT_LOAD segments for (ElfSegment *segment = elf->getSegmentByType(PT_LOAD); segment; segment = elf->getSegmentByType(PT_LOAD, segment)) { maybe_split_segment(elf, segment, fill); } // Ensure Elf sections will be at their final location. elf->normalize(); ElfLocation *init = new ElfLocation(relhackcode, relhackcode->getEntryPoint()); if (init_array) { // Adjust the first DT_INIT_ARRAY entry to point at the injected code // by transforming its relocation into a relative one pointing to the // address of the injected code. Rel_Type *rel = §ion->rels[init_array_reloc - 1]; rel->r_info = ELF32_R_INFO(0, rel_type); // Set as a relative relocation set_relative_reloc(§ion->rels[init_array_reloc - 1], elf, init->getValue()); } else if (!dyn->setValueForType(DT_INIT, init)) { fprintf(stderr, "Can't grow .dynamic section to set DT_INIT. Skipping\n"); return -1; } // TODO: adjust the value according to the remaining number of relative relocations if (dyn->getValueForType(Rel_Type::d_tag_count)) dyn->setValueForType(Rel_Type::d_tag_count, new ElfPlainValue(0)); return 0; } static inline int backup_file(const char *name) { std::string fname(name); fname += ".bak"; return rename(name, fname.c_str()); } void do_file(const char *name, bool backup = false, bool force = false, bool fill = false) { std::ifstream file(name, std::ios::in|std::ios::binary); Elf elf(file); unsigned int size = elf.getSize(); fprintf(stderr, "%s: ", name); if (elf.getType() != ET_DYN) { fprintf(stderr, "Not a shared object. Skipping\n"); return; } for (ElfSection *section = elf.getSection(1); section != nullptr; section = section->getNext()) { if (section->getName() && (strncmp(section->getName(), ".elfhack.", 9) == 0)) { fprintf(stderr, "Already elfhacked. Skipping\n"); return; } } int exit = -1; switch (elf.getMachine()) { case EM_386: exit = do_relocation_section<Elf_Rel>(&elf, R_386_RELATIVE, R_386_32, force, fill); break; case EM_X86_64: exit = do_relocation_section<Elf_Rela>(&elf, R_X86_64_RELATIVE, R_X86_64_64, force, fill); break; case EM_ARM: exit = do_relocation_section<Elf_Rel>(&elf, R_ARM_RELATIVE, R_ARM_ABS32, force, fill); break; } if (exit == 0) { if (!force && (elf.getSize() >= size)) { fprintf(stderr, "No gain. Skipping\n"); } else if (backup && backup_file(name) != 0) { fprintf(stderr, "Couln't create backup file\n"); } else { std::ofstream ofile(name, std::ios::out|std::ios::binary|std::ios::trunc); elf.write(ofile); fprintf(stderr, "Reduced by %d bytes\n", size - elf.getSize()); } } } void undo_file(const char *name, bool backup = false) { std::ifstream file(name, std::ios::in|std::ios::binary); Elf elf(file); unsigned int size = elf.getSize(); fprintf(stderr, "%s: ", name); if (elf.getType() != ET_DYN) { fprintf(stderr, "Not a shared object. Skipping\n"); return; } ElfSection *data = nullptr, *text = nullptr; for (ElfSection *section = elf.getSection(1); section != nullptr; section = section->getNext()) { if (section->getName() && (strcmp(section->getName(), elfhack_data) == 0)) data = section; if (section->getName() && (strcmp(section->getName(), elfhack_text) == 0)) text = section; } if (!data || !text) { fprintf(stderr, "Not elfhacked. Skipping\n"); return; } if (data != text->getNext()) { fprintf(stderr, elfhack_data " section not following " elfhack_text ". Skipping\n"); return; } ElfSegment *first = elf.getSegmentByType(PT_LOAD); ElfSegment *second = elf.getSegmentByType(PT_LOAD, first); ElfSegment *filler = nullptr; // If the second PT_LOAD is a filler from elfhack --fill, check the third. if (second->isElfHackFillerSegment()) { filler = second; second = elf.getSegmentByType(PT_LOAD, filler); } if (second->getFlags() != first->getFlags()) { fprintf(stderr, "Couldn't identify elfhacked PT_LOAD segments. Skipping\n"); return; } // Move sections from the second PT_LOAD to the first, and remove the // second PT_LOAD segment. for (std::list<ElfSection *>::iterator section = second->begin(); section != second->end(); ++section) first->addSection(*section); elf.removeSegment(second); if (filler) elf.removeSegment(filler); if (backup && backup_file(name) != 0) { fprintf(stderr, "Couln't create backup file\n"); } else { std::ofstream ofile(name, std::ios::out|std::ios::binary|std::ios::trunc); elf.write(ofile); fprintf(stderr, "Grown by %d bytes\n", elf.getSize() - size); } } int main(int argc, char *argv[]) { int arg; bool backup = false; bool force = false; bool revert = false; bool fill = false; char *lastSlash = rindex(argv[0], '/'); if (lastSlash != nullptr) rundir = strndup(argv[0], lastSlash - argv[0]); for (arg = 1; arg < argc; arg++) { if (strcmp(argv[arg], "-f") == 0) force = true; else if (strcmp(argv[arg], "-b") == 0) backup = true; else if (strcmp(argv[arg], "-r") == 0) revert = true; else if (strcmp(argv[arg], "--fill") == 0) fill = true; else if (revert) { undo_file(argv[arg], backup); } else do_file(argv[arg], backup, force, fill); } free(rundir); return 0; }