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// Copyright (c) 2016 avs333
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <elf.h>
#include <android/log.h>
#include "enhanced_dlfcn.h"
#define TAG_NAME "FastHookManager"
#define log_info(fmt,args...) __android_log_print(ANDROID_LOG_ERROR, TAG_NAME, (const char *) fmt, ##args)
#define log_err(fmt,args...) __android_log_print(ANDROID_LOG_ERROR, TAG_NAME, (const char *) fmt, ##args)
//#ifdef LOG_DBG
#define log_dbg log_info
//#else
//#define log_dbg(...)
//#endif
#ifdef __arm__
#define Elf_Ehdr Elf32_Ehdr
#define Elf_Shdr Elf32_Shdr
#define Elf_Sym Elf32_Sym
#elif defined(__aarch64__)
#define Elf_Ehdr Elf64_Ehdr
#define Elf_Shdr Elf64_Shdr
#define Elf_Sym Elf64_Sym
#else
#error "Arch unknown, please port me"
#endif
struct ctx {
void *load_addr;
void *dynstr;
void *dynsym;
int dynsym_num;
void *strtab;
void *symtab;
int symtab_num;
off_t bias;
};
int enhanced_dlclose(void *handle) {
if (handle) {
struct ctx *ctx = (struct ctx *) handle;
if (ctx->dynsym) free(ctx->dynsym); /* we're saving dynsym and dynstr */
if (ctx->dynstr) free(ctx->dynstr); /* from library file just in case */
if (ctx->symtab) free(ctx->symtab);
if (ctx->strtab) free(ctx->strtab);
free(ctx);
}
return 0;
}
/* flags are ignored */
void *enhanced_dlopen(const char *libpath, int flags) {
FILE *maps;
char buff[256];
struct ctx *ctx = 0;
off_t load_addr, size;
int k, fd = -1, found = 0;
void *shoff;
Elf_Ehdr *elf = (Elf_Ehdr *) MAP_FAILED;
#define fatal(fmt, args...) do { log_err(fmt,##args); goto err_exit; } while(0)
maps = fopen("/proc/self/maps", "r");
if (!maps) fatal("failed to open maps");
while (!found && fgets(buff, sizeof(buff), maps))
if (strstr(buff, "r-xp") && strstr(buff, libpath)) found = 1;
fclose(maps);
if (!found) fatal("%s not found in my userspace", libpath);
if (sscanf(buff, "%lx", &load_addr) != 1)
fatal("failed to read load address for %s", libpath);
log_info("%s loaded in Android at 0x%08lx", libpath, load_addr);
/* Now, mmap the same library once again */
fd = open(libpath, O_RDONLY);
if (fd < 0) fatal("failed to open %s", libpath);
size = lseek(fd, 0, SEEK_END);
if (size <= 0) fatal("lseek() failed for %s", libpath);
elf = (Elf_Ehdr *) mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
close(fd);
fd = -1;
if (elf == MAP_FAILED) fatal("mmap() failed for %s", libpath);
ctx = (struct ctx *) calloc(1, sizeof(struct ctx));
if (!ctx) fatal("no memory for %s", libpath);
ctx->load_addr = (void *) load_addr;
shoff = ((void *) elf) + elf->e_shoff;
Elf_Shdr *shstrtab = (Elf_Shdr *)(shoff + elf->e_shstrndx * elf->e_shentsize);
char * shstr = malloc(shstrtab->sh_size);
memcpy(shstr, ((void *) elf) + shstrtab->sh_offset, shstrtab->sh_size);
for (k = 0; k < elf->e_shnum; k++, shoff += elf->e_shentsize) {
Elf_Shdr *sh = (Elf_Shdr *) shoff;
log_dbg("%s: k=%d shdr=%p type=%d", __func__, k, sh, sh->sh_type);
switch (sh->sh_type) {
case SHT_DYNSYM:
if (ctx->dynsym) fatal("%s: duplicate DYNSYM sections", libpath); /* .dynsym */
ctx->dynsym = malloc(sh->sh_size);
if (!ctx->dynsym) fatal("%s: no memory for .dynsym", libpath);
memcpy(ctx->dynsym, ((void *) elf) + sh->sh_offset, sh->sh_size);
ctx->dynsym_num = (sh->sh_size / sizeof(Elf_Sym));
break;
case SHT_SYMTAB:
if (ctx->symtab) fatal("%s: duplicate SYMTAB sections", libpath); /* .symtab */
ctx->symtab = malloc(sh->sh_size);
if (!ctx->symtab) fatal("%s: no memory for .symtab", libpath);
memcpy(ctx->symtab, ((void *) elf) + sh->sh_offset, sh->sh_size);
ctx->symtab_num = (sh->sh_size / sizeof(Elf_Sym));
break;
case SHT_STRTAB:
if(!strcmp(shstr+sh->sh_name,".dynstr")) {
if (ctx->dynstr) break; /* .dynstr is guaranteed to be the first STRTAB */
ctx->dynstr = malloc(sh->sh_size);
if (!ctx->dynstr) fatal("%s: no memory for .dynstr", libpath);
memcpy(ctx->dynstr, ((void *) elf) + sh->sh_offset, sh->sh_size);
}else if(!strcmp(shstr+sh->sh_name,".strtab")) {
if (ctx->strtab) break;
ctx->strtab = malloc(sh->sh_size);
if (!ctx->strtab) fatal("%s: no memory for .strtab", libpath);
memcpy(ctx->strtab, ((void *) elf) + sh->sh_offset, sh->sh_size);
}
break;
case SHT_PROGBITS:
if (!ctx->dynstr || !ctx->dynsym || ctx->bias) break;
/* won't even bother checking against the section name */
ctx->bias = (off_t) sh->sh_addr - (off_t) sh->sh_offset;
//k = elf->e_shnum; /* exit for */
break;
}
}
munmap(elf, size);
elf = 0;
if (!ctx->dynstr || !ctx->dynsym) fatal("dynamic sections not found in %s", libpath);
#undef fatal
log_dbg("%s: ok, dynsym = %p, dynstr = %p symtab = %p strtab = %p", libpath, ctx->dynsym, ctx->dynstr, ctx->symtab, ctx->strtab);
return ctx;
err_exit:
if (fd >= 0) close(fd);
if (elf != MAP_FAILED) munmap(elf, size);
enhanced_dlclose(ctx);
return 0;
}
void *enhanced_dlsym(void *handle, const char *name) {
int k;
struct ctx *ctx = (struct ctx *) handle;
Elf_Sym *dynsym = (Elf_Sym *) ctx->dynsym;
Elf_Sym *symtab = (Elf_Sym *) ctx->symtab;
char *dynstr = (char *) ctx->dynstr;
char *strtab = (char *) ctx->strtab;
for (k = 0; k < ctx->dynsym_num; k++, dynsym++) {
if (strcmp(dynstr + dynsym->st_name, name) == 0) {
/* NB: sym->st_value is an offset into the section for relocatables,
but a VMA for shared libs or exe files, so we have to subtract the bias */
void *ret = ctx->load_addr + dynsym->st_value - ctx->bias;
log_info("%s found at %p", name, ret);
return ret;
}
}
if(symtab) {
for (k = 0; k < ctx->symtab_num; k++, symtab++) {
//log_info("%s found %u %s at %d", name, sym_tab->st_name,strings + sym_tab->st_name,k);
if (strcmp(strtab + symtab->st_name, name) == 0) {
/* NB: sym->st_value is an offset into the section for relocatables,
but a VMA for shared libs or exe files, so we have to subtract the bias */
void *ret = ctx->load_addr + symtab->st_value - ctx->bias;
log_info("%s found at %p", name, ret);
return ret;
}
}
}
return 0;
}
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