sys64738
/
dynamic-dso
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
dynamic-dso/dynso.c

543 lines
16 KiB
C
Raw Permalink Blame History

#define _GNU_SOURCE
#include <stddef.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <elf.h>
#include <dlfcn.h>
#include <link.h>
#include <sys/auxv.h>
#include <sys/stat.h>
#include "dynso.h"
#include "dynso_internal.h"
#define BREAK() asm volatile("int3":::"memory")
/*static void print_link_map(struct link_map* glob) {
printf("[*] link map:\n");
for (size_t i = 0; glob; glob = glob->l_next, ++i) {
printf("- [%zu] %p -> '%s'\n", i, (void*)glob->l_addr, glob->l_name);
}
}*/
static ptrdiff_t get_priv1_priv2_offset(void) {
// the offset between the priv1 and priv2 parts of a link_map is a
// constant but only determinted at runtime, as we don't know with which
// glibc version we're running (nor do we want to hardcode stuff)
// link_map of the main executable always comes first (... I hope)
struct link_map_priv1* exe_map = (struct link_map_priv1*)_r_debug.r_map;
ElfW(Ehdr)* exe_ehdr = (ElfW(Ehdr)*)exe_map->l_addr;
// priv2 contains a field with the entrypoint of an ELF
ElfW(Addr) entry = exe_ehdr->e_entry + exe_map->l_addr;
// time for crimes
const ElfW(Addr)* crimes = (const ElfW(Addr)*)&exe_map->l_info[0];
for (size_t iter = 0;
*crimes != entry && iter < 4096/sizeof(*crimes);
++crimes, ++iter)
;
if (*crimes != entry) {
//printf("[!] E: can't get priv2 offset, bailing out...\n");
return -1;//exit(1);
}
// crimes is now &priv2->l_entry;
ptrdiff_t r = (ptrdiff_t)crimes - (ptrdiff_t)exe_map - offsetof(struct link_map_priv2, l_entry);
//printf("[-] offset of priv2 is %zd\n", r);
return r;
}
static ptrdiff_t get_priv2_priv3_offset(void) {
struct link_map_priv1* exe_map = (struct link_map_priv1*)_r_debug.r_map;
struct link_map_priv2* exe2 = priv1_to_priv2(exe_map);
// priv3 has a 'versyms' field, which we can easily fetch from the dyn
// table for comparison. otherwise, same method as above
ElfW(Versym)* versym_good = NULL;
for (size_t i = 0; _DYNAMIC[i].d_tag != DT_NULL && i < 128; ++i) {
if (_DYNAMIC[i].d_tag == DT_VERSYM) {
versym_good = (ElfW(Versym*))_DYNAMIC[i].d_un.d_ptr;
break;
}
}
if (versym_good == NULL) {
//printf("[!] E: can't find VERSYM, bailing out...\n");
return -1;//exit(1);
}
const ElfW(Versym)** crimes = (const ElfW(Versym)**)&exe2->l_direct_opencount;
for (size_t iter = 0;
*crimes != versym_good && iter < 4096/sizeof(*crimes);
++crimes, ++iter)
;
if (*crimes != versym_good) {
//printf("[!] E: can't get priv3 offset, bailing out...\n");
return -1;//exit(1);
}
// crimes is now &priv3->l_versyms;
ptrdiff_t r = (ptrdiff_t)crimes - (ptrdiff_t)exe2 - offsetof(struct link_map_priv3, l_versyms);
//printf("[-] offset of priv3 is %zd\n", r);
return r;
}
static struct link_map_priv2* priv1_to_priv2(struct link_map_priv1* lm) {
if (!lm) return NULL;
static ptrdiff_t d = -1;
if (d < 0) {
d = get_priv1_priv2_offset();
if (d < 0) return NULL;
}
return (struct link_map_priv2*)((ptrdiff_t)lm + d);
}
static struct link_map_priv3* priv2_to_priv3(struct link_map_priv2* l2) {
if (!l2) return NULL;
static ptrdiff_t d = -1;
if (d < 0) {
d = get_priv2_priv3_offset();
if (d < 0) return NULL;
}
return (struct link_map_priv3*)((ptrdiff_t)l2 + d);
}
static enum dynso_err get_rtld_symtab(struct rtldinfo* ret) {
ElfW(Addr) ldso_base = (ElfW(Addr))getauxval(AT_BASE);
//printf("[-] getauxval(AT_BASE) = %p\n", (void*)ldso_base);
//printf("[-] getauxval(AT_SYSINFO_EHDR) = %p\n", (void*)getauxval(AT_SYSINFO_EHDR));
struct link_map* glob = _r_debug.r_map;
//print_link_map(glob);
for (size_t i = 0; glob; glob = glob->l_next, ++i) {
if (glob->l_addr != ldso_base) continue;
//printf("[*] [%zu] %p:%s is ld.so!\n", i, (void*)glob->l_addr, glob->l_name);
ElfW(Sym)* symtab = NULL;
char* strtab = NULL;
size_t strsz = 0;
size_t shsz = ~(size_t)0;
ptrdiff_t syment = 0;
bool sym_malloc = false, str_malloc = false;
// gives us .dynsym, not .symtab -> kinda useless
ElfW(Dyn)* dyn = glob->l_ld;
for (size_t j = 0; dyn->d_tag != DT_NULL; ++dyn, ++j) {
if (dyn->d_tag == DT_STRTAB) {
strtab = (char*)(/*glob->l_addr +*/ dyn->d_un.d_ptr);
//printf(" - [%zu] strtab\n", j);
}
if (dyn->d_tag == DT_SYMTAB) {
symtab = (ElfW(Sym) *)(/*glob->l_addr +*/ dyn->d_un.d_ptr);
//printf(" - [%zu] symtab\n", j);
}
if (dyn->d_tag == DT_STRSZ) {
strsz = dyn->d_un.d_val;
//printf(" - [%zu] strsz\n", j);
}
if (dyn->d_tag == DT_SYMENT) {
syment = dyn->d_un.d_val;
//printf(" - [%zu] syment\n", j);
}
}
if (!memcmp((const void*)ldso_base, ELFMAG, SELFMAG)) {
//printf("[-] ldso is ELF\n");
FILE* fff = fopen(glob->l_name, "rb"); // TODO: use l_origin instead?
if (!fff) goto nah;
ElfW(Ehdr)* ldso = (ElfW(Ehdr)*)ldso_base;
if (ldso->e_shoff && ldso->e_shnum && ldso->e_shentsize) {
//printf(" - shoff=0x%zx shnum=0x%zx\n", ldso->e_shoff, ldso->e_shnum);
enum dynso_err errr = dynso_ok;
if (fseek(fff, ldso->e_shoff, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
uint8_t shdr_blob[ldso->e_shentsize];
ElfW(Shdr)* shdr = (ElfW(Shdr)*)shdr_blob;
if (fseek(fff, ldso->e_shoff + ldso->e_shstrndx*ldso->e_shentsize, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
if (fread(shdr_blob, 1, sizeof(shdr_blob), fff) < 0) errr = dynso_ldso_ioerr;
char* shstrtab = (char*)malloc(shdr->sh_size);
if (shstrtab == NULL) errr = dynso_oom;
if (fseek(fff, shdr->sh_offset, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
if (fread(shstrtab, 1, shdr->sh_size, fff) < 0) errr = dynso_ldso_ioerr;
for (size_t j = 0; j < ldso->e_shnum; ++j) {
if (fseek(fff, ldso->e_shoff + j*ldso->e_shentsize, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
if (fread(shdr_blob, 1, sizeof(shdr_blob), fff) < 0) errr = dynso_ldso_ioerr;
//printf(" [-] shdr [%zx] -> %p, type=0x%zx\n", j, shdr, shdr->sh_type);
if (shdr->sh_type == SHT_SYMTAB) {
//printf(" [-] using .symtab instead of .dynsym at offset 0x%zx\n", shdr->sh_offset);
////symtab = (ElfW(Sym)*)(ldso_base + shdr->sh_offset); // not mapped in phdrs...
sym_malloc = true;
symtab = (ElfW(Sym)*)malloc(shdr->sh_size);
if (symtab == NULL) errr = dynso_oom;
if (fseek(fff, shdr->sh_offset, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
if (fread(symtab, 1, shdr->sh_size, fff) < 0) errr = dynso_ldso_ioerr;
shsz = shdr->sh_size;
syment = shdr->sh_entsize; // not *technically* needed, but doing this for completeness' sake
}
if (shdr->sh_type == SHT_STRTAB && !strcmp(&shstrtab[shdr->sh_name], ".strtab")) {
//printf(" [-] using .strtab instead of .dynstr at offset 0x%zx\n", shdr->sh_offset);
str_malloc = true;
strtab = (char*)malloc(shdr->sh_size);
if (strtab == NULL) errr = dynso_oom;
if (fseek(fff, shdr->sh_offset, SEEK_SET) < 0) errr = dynso_ldso_ioerr;
if (fread(strtab, 1, shdr->sh_size, fff) < 0) errr = dynso_ldso_ioerr;
strsz = shdr->sh_size;
}
}
free(shstrtab);
if (errr != dynso_ok) {
if (fff) fclose(fff);
if (str_malloc && strtab) free(strtab);
if (sym_malloc && symtab) free(symtab);
return errr;
}
} //else printf("wut\n");
}
nah:
if (symtab == NULL || strtab == NULL) {
return dynso_ldso_stripped;
}
//printf(" [-] symtab=%p\tstrtab=%p\tstrsz=0x%zx\tsyment=0x%zx\n",
// symtab, strtab, strsz, syment);
//printf("[-] resolving hidden needed symbols\n");
ret->base = ldso_base;
ret->symtab = symtab;
ret->strtab = strtab;
ret->strsz = strsz;
ret->shsz = shsz;
ret->syment = syment;
ret->sym_malloc = sym_malloc;
ret->str_malloc = str_malloc;
return dynso_ok;
}
//printf("wtf\n");
return dynso_ldso_not_found;//exit(1);
}
typedef void* (*gnu_ifunc_f)(void);
static void* sym2addr(ElfW(Addr) ldso_base, ElfW(Sym)* sym) {
void* r = (void*)(ldso_base + sym->st_value);
if (ELF64_ST_TYPE(sym->st_info) == STT_GNU_IFUNC) { // sigh
//printf("[-] W: IFUNC. not tested.\n");
return ((gnu_ifunc_f)(r))();
} else return r;
}
static enum dynso_err link_private_rtld_syms(struct dynso_lib* l) {
struct rtldinfo rtldinf;
enum dynso_err r = get_rtld_symtab(&rtldinf);
if (r != dynso_ok) return r;
ElfW(Sym)* sym = rtldinf.symtab;
for (size_t j = 0; j*rtldinf.syment < rtldinf.shsz;
++j, sym = (ElfW(Sym*))((ptrdiff_t)sym + rtldinf.syment)) {
if (ELF64_ST_BIND(sym->st_info) != STB_LOCAL) continue;
if (sym->st_value == 0) continue;
if (sym->st_name >= rtldinf.strsz) continue;
const char* name = &rtldinf.strtab[sym->st_name];
if (!*name) continue;
if (!strcmp(name, "_dl_new_object")) {
//printf("- [%zu] -> info=0x%x other=0x%x value=0x%zx\t'%s'\n", j,
// sym->st_info, sym->st_other, sym->st_value, name);
l->_dl_new_object = (dl_new_object_f)sym2addr(rtldinf.base, sym);
}
if (!strcmp(name, "_dl_add_to_namespace_list")) {
//printf("- [%zu] -> info=0x%x other=0x%x value=0x%zx\t'%s'\n", j,
// sym->st_info, sym->st_other, sym->st_value, name);
l->_dl_add_to_namespace_list = (dl_add_to_namespace_list_f)sym2addr(rtldinf.base, sym);
}
if (!strcmp(name, "_dl_setup_hash")) {
//printf("- [%zu] -> info=0x%x other=0x%x value=0x%zx\t'%s'\n", j,
// sym->st_info, sym->st_other, sym->st_value, name);
l->_dl_setup_hash = (dl_setup_hash_f)sym2addr(rtldinf.base, sym);
}
}
if (rtldinf.sym_malloc) free(rtldinf.symtab);
if (rtldinf.str_malloc) free(rtldinf.strtab);
//printf("[*] _dl_new_object=%p\n", _dl_new_object);
//printf("[*] _dl_add_to_namespace_list=%p\n", _dl_add_to_namespace_list);
//printf("[*] _dl_setup_hash=%p\n", _dl_setup_hash);
if (l->_dl_new_object && l->_dl_add_to_namespace_list && l->_dl_setup_hash)
return dynso_ok;
else return dynso_no_ldso_syms;
}
static enum dynso_err inject_in_scope_of(struct inject_undo_info* r,
struct link_map_priv3* vic3, struct link_map_priv1* add) {
r->alloced = NULL;
struct r_scope_elem* oldscope = vic3->l_scope[0];
struct r_scope_elem* scope = NULL;
scope = (struct r_scope_elem*)calloc(1, sizeof(*scope)
+ sizeof(struct link_map_priv1*)*(oldscope->r_nlist+1));
if (scope == NULL) return dynso_oom;
r->alloced = scope;
struct link_map_priv1** rlist = (struct link_map_priv1**)(
(size_t)scope + sizeof(*scope));
for (size_t i = 0; i < oldscope->r_nlist; ++i)
rlist[i] = oldscope->r_list[i];
rlist[oldscope->r_nlist] = add;
scope->r_list = rlist;
scope->r_nlist = oldscope->r_nlist + 1;
// now apply the new scope
vic3->l_scope[0] = scope;
r->dest = &vic3->l_scope[0];
r->old = oldscope;
//r->rlist = rlist;
return dynso_ok;
}
static void inject_undo(const struct inject_undo_info* inf) {
*inf->dest = inf->old;
if (inf->alloced) free(inf->alloced);
//free(inf->rlist);
}
enum dynso_err dynso_create(struct dynso_lib** ll, size_t address,
char* realname, const char* libname, struct link_map* calling, Lmid_t ns) {
if (!ll) return dynso_argument;
if (calling == NULL) calling = _r_debug.r_map;
struct dynso_lib* r = (struct dynso_lib*)calloc(1, sizeof(struct dynso_lib)
+ 16*sizeof(struct dynso_sym));
if (r == NULL) return dynso_oom;
enum dynso_err e = link_private_rtld_syms(r);
if (e != dynso_ok) { free(r); return e; }
struct link_map_priv1* lm =
r->_dl_new_object(realname, libname, lt_loaded, calling, 0, ns);
if (!lm) { free(r); return dynso_no_newobj; }
struct link_map_priv2* l2 = priv1_to_priv2(lm);
struct link_map_priv3* l3 = priv2_to_priv3(l2);
if (!l2) { free(r); return dynso_no_priv2; }
if (!l3) { free(r); return dynso_no_priv3; }
l2->l_faked = 1;
l2->l_nbuckets = 0; // disables symbol lookup
l2->l_gnu_bitmask = NULL; // disable GNU hashing, use SysV hashing
l3->l_initfini = NULL;
lm->l_addr = address;
r->ns = ns;
r->caller = (struct link_map_priv1*)calling;
r->fake1 = lm;
r->fake2 = l2;
r->fake3 = l3;
r->address = address;
r->syms = (struct dynso_sym*)((ptrdiff_t)r + sizeof(*r));
r->nsyms = 0;
r->syms_cap = 16;
*ll = r;
return dynso_ok;
}
enum dynso_err dynso_add_sym_ex(struct dynso_lib* f, const char* name,
void* value, int type, size_t size) {
if (!f || f->added || f->removed) return dynso_argument;
if (f->nsyms == f->syms_cap) {
f->syms_cap <<= 1;
if (f->alloc_syms) {
f->syms = (struct dynso_sym*)realloc(
f->syms, f->syms_cap * sizeof(struct dynso_sym));
if (f->syms == NULL) return dynso_oom;
} else {
struct dynso_sym* nsym = (struct dynso_sym*)calloc(f->syms_cap, sizeof(struct dynso_sym));
if (nsym == NULL) return dynso_oom;
memcpy(nsym, f->syms, sizeof(struct dynso_sym)*f->nsyms);
f->syms = nsym;
f->alloc_syms = true;
}
}
f->syms[f->nsyms].name = name ;
f->syms[f->nsyms].value = value;
f->syms[f->nsyms].type = type;
f->syms[f->nsyms].size = size;
++f->nsyms;
return dynso_ok;
}
enum dynso_err dynso_bind(struct dynso_lib* l) {
if (!l || l->removed || l->added) return dynso_argument;
struct link_map_priv1* lm = l->fake1;
struct link_map_priv2* l2 = l->fake2;
struct link_map_priv3* l3 = l->fake3;
lm->l_addr = l->address;
size_t strsz = 2; // beginning and ending null terminators
for (size_t i = 0; i < l->nsyms; ++i) {
strsz += strlen(l->syms[i].name) + 1; // include null terminator
}
ElfW(Dyn)* dyn = (ElfW(Dyn)*)calloc(5, sizeof(ElfW(Dyn)));
if (!dyn) return dynso_oom;
Elf_Symndx* idx = (Elf_Symndx*)calloc(l->nsyms + 2, sizeof(Elf_Symndx));
if (!idx) { free(dyn); return dynso_oom; }
ElfW(Sym)* sym = (ElfW(Sym)*)calloc(l->nsyms + 2, sizeof(ElfW(Sym)));
if (!sym) { free(dyn); free(idx); return dynso_oom; }
char* str = (char*)calloc(strsz, 1);
if (!str) { free(dyn); free(idx); free(sym); return dynso_oom; }
// NOTE: should we give it a phdr? seems to work without for now...
str[0] = 0;
//BREAK();
//sym[0] = ((ElfW(Sym)){.st_name=0, .st_info=0, .st_other=0, .st_shndx=0, .st_value=0, .st_size=0};
for (size_t i = 0, strind = 1; i < l->nsyms; ++i) {
int typ = l->syms[i].type & 0xf;
if (typ == 0) typ = STT_FUNC;
sym[i+1].st_name = strind;
sym[i+1].st_info = typ | (STB_GLOBAL << 4);
sym[i+1].st_other = STV_DEFAULT;
sym[i+1].st_shndx = 0;
sym[i+1].st_value = (ElfW(Addr))l->syms[i].value - l->address;
sym[i+1].st_size = 0;
strcpy(&str[strind], l->syms[i].name);
strind += strlen(l->syms[i].name) + 1;
}
//sym[l->nsyms+1] = ((ElfW(Sym)){.st_name=0, .st_info=0, .st_other=0, .st_shndx=0, .st_value=0, .st_size=0};
str[strsz-1] = 0;
for (size_t i = 0; i < l->nsyms; ++i) idx[i] = i + 1;
idx[l->nsyms+0] = STN_UNDEF;
idx[l->nsyms+1] = SHN_UNDEF;
dyn[0].d_tag = DT_SYMTAB;
dyn[0].d_un.d_ptr = (ElfW(Addr))sym;
dyn[1].d_tag = DT_STRTAB;
dyn[1].d_un.d_ptr = (ElfW(Addr))str;
// these two aren't strictly needed, but adding them for completeness' sake
dyn[2].d_tag = DT_STRSZ;
dyn[2].d_un.d_val = strsz;
dyn[3].d_tag = DT_SYMENT;
dyn[3].d_un.d_val = sizeof(ElfW(Sym));
dyn[4].d_tag = DT_NULL;
lm->l_ld = dyn;
size_t ldnum = 0;
for (size_t i = 0; dyn[i].d_tag != DT_NULL; ++i, ++ldnum)
lm->l_info[dyn[i].d_tag] = &dyn[i];
l2->l_ldnum = ldnum;
// lm->l_origin = "something"; // maybe? eh.
l->_dl_setup_hash(lm);
l2->l_relocated = 1;
l3->l_used = 1;
l2->l_global = 1;
l2->l_faked = 1;
//l2->l_type = lt_loaded;
l2->l_nbuckets = 1;
l2->l_buckets = idx; // TODO
l2->l_chain = idx; // TODO
l2->l_gnu_bitmask = NULL; // disable GNU hashing, use SysV legacy hashing (was easier to 'implement' on my end)
l3->l_initfini = NULL;
l->_dl_add_to_namespace_list(l->fake1, l->ns);
enum dynso_err r = inject_in_scope_of(&l->undoinf, priv1_to_priv3(l->caller), lm);
if (r == dynso_ok) {
l->dyn = dyn;
l->sym = sym;
l->idx = idx;
l->str = str;
l->added = true;
return dynso_ok;
}
free(dyn); free(idx); free(sym); free(str);
return r;
}
void dynso_remove(struct dynso_lib* l) {
if (!l) return;
if (l->added) {
inject_undo(&l->undoinf);
for (size_t i = 0; l->dyn[i].d_tag != DT_NULL; ++i)
l->fake1->l_info[l->dyn[i].d_tag] = NULL;
l->fake1->l_ld = NULL;
l->fake2->l_ldnum = 0;
free(l->dyn);
free(l->sym);
free(l->idx);
free(l->str);
}
if (l->alloc_syms) free(l->syms);
// TODO: free dyn, symtab, strtab, idxtab
l->fake2->l_removed = 1;
l->fake3->l_used = 0;
l->fake2->l_global = 0;
l->fake2->l_nbuckets = 0;
l->removed = true;
free(l);
}
Reference in New Issue View Git Blame Copy Permalink