I am writing a plugins subsystem and one of the ideas is to iterate through a dylib (or at least current global scope) exported functions. I know there are other ways, just really want to give this one a try.
What I am wondering, is there a way to get a list of functions exported by a dylib or available in global scope through OS X and iOS API?
Thanks in advance!
You can use a command 'nm' for getting an information from a dynamic library.
See additionally system manual for this command on Mac.
If you are looking to do that from code, you could use this method.
std::vector<std::string> load_mach_o(std::string file_name)
{
/*
Parse the Mach-O structure to find all the exported symbols
Mach-O structure:
mach_header_64
cmd
...
cmd
data
...
data
*/
std::vector<std::string> methods;
off_t offset = sizeof(struct mach_header_64);
BYTE * bytes = load_bytes(file_name.c_str());
if (bytes == NULL)
{
return methods;
}
struct mach_header_64 *header = (struct mach_header_64 *)bytes;
//Get the load commands
struct load_command *cmd = (struct load_command *)(bytes + offset);
for (uint32_t i = 0U; i < header->ncmds; i++)
{
if (cmd->cmd == LC_SYMTAB)
{
struct symtab_command * symtab = (struct symtab_command *)cmd;
off_t string_start = 0;
const char* strings = (const char *)(bytes + symtab->stroff + 1);
for (uint32_t i = 0 ; i < symtab->strsize ; i++)
{
if (strings[i] == '\0')
{
i++;
size_t size = sizeof(char) * (i - string_start);
if (size == 1)
{
string_start = i+1;
continue;
}
methods.push_back(std::string((const char *)(strings + string_start)));
string_start = i+1;
}
}
}
offset += cmd->cmdsize;
//load next command
cmd = (struct load_command *)(bytes + offset);
}
free(bytes);
return methods;
}
This function read the file and parses the structure till mach-O strings section, then, parses each string and store it in a vector containing all the exposed functions.
Best regards.
Related
I want to mount a filesystem on Linux using Lua, but I haven't found any capability in the lua 5.4 manual or the LuaFileSytem library. Is there some way to mount a filesystem in Lua or with an existing library?
Like most platform-dependent syscall, Lua won't provide such mapping out of the box.
So you'll need some C-API module that does the trick.
Looks like https://github.com/justincormack/ljsyscall is generic "but" focused on LuaJIT and https://luaposix.github.io/luaposix/ doesn't provide mount.
I recently had similar needs, and I ended doing the C module:
static int l_mount(lua_State* L)
{
int res = 0;
// TODO add more checks on args!
const char *source = luaL_checkstring(L, 1);
const char *target = luaL_checkstring(L, 2);
const char *type = luaL_checkstring(L, 3);
lua_Integer flags = luaL_checkinteger(L, 4);
const char *data = luaL_checkstring(L, 5);
res = mount(source, target, type, flags, data);
if ( res != 0)
{
int err = errno;
lua_pushnil(L);
lua_pushfstring(L, "mount failed: errno[%s]", strerror(err));
return 2;
}
else
{
lua_pushfstring(L, "ok");
return 1;
}
}
#define register_constant(s)\
lua_pushinteger(L, s);\
lua_setfield(L, -2, #s);
// Module functions
static const luaL_Reg R[] =
{
{ "mount", l_mount },
{ NULL, NULL }
};
int luaopen_sysutils(lua_State* L)
{
luaL_newlib(L, R);
// do more mount defines mapping, maybe in some table.
register_constant(MS_RDONLY);
//...
return 1;
}
Compile this as a C Lua module, and don't forget that you need CAP_SYS_ADMIN to call mount syscall.
I'm trying to get .text segment size of Mach-O executable of my iOS app.
size_t size_of_image(struct mach_header *header) {
size_t sz = sizeof(*header); // Size of the header
sz += header->sizeofcmds; // Size of the load commands
struct load_command *lc = (struct load_command *) (header + 1);
for (uint32_t i = 0; i < header->ncmds; i++) {
if (lc->cmd == LC_SEGMENT_64) {
sz += ((struct segment_command *) lc)->vmsize; // Size of segments
}
lc = (struct load_command *) ((char *) lc + lc->cmdsize);
}
return sz;
}
and i call this function from main
int main(int argc, char * argv[]) {
const struct mach_header * header;
Dl_info dlinfo;
//
if (dladdr(main, &dlinfo) == 0 || dlinfo.dli_fbase == NULL)
return 0; // Can't find symbol for main
//
header = dlinfo.dli_fbase; // Pointer on the Mach-O header
size_of_image(header);
#autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}
Problem is lc->cmd is always 0, and i never get LC_SEGMENT_64 command.
I've tried LC_SEGMENT - same result
Running iOS 12 on iPhone 6.
I need to get the .text segment of the executable for reverse - engineering protection functions.
It seems my ** mach_header *header** is wrongly field by dladdr function.
Any ideas what is wrong?
The culprit is in struct mach_header *header.
Replace it with struct mach_header_64 *header instead.
Keep using LC_SEGMENT_64 for modern binaries.
I just want to use GNOME glib functions to simply write and read a file. I think my syntaxes are wrong in calling the functions. I tried to open a file with g_fopen("filenam.txt", "w"); but it didnt create any file. I also used g_file_set_contents and I am trying to save my Gstring s into a file file.txt with code as
static void events_handler(const uint8_t *pdu, uint16_t len, gpointer user_data)
{
uint8_t *opdu;
uint16_t handle, i, olen;
size_t plen;
//GString *s;
const gchar *s;
gssize length;
length = 100;
handle = get_le16(&pdu[1]);
switch (pdu[0]) {
case ATT_OP_HANDLE_NOTIFY:
s = g_string_new(NULL);
//g_string_printf(s, "Movement data = 0x%04x value: ",handle);
g_file_set_contents("file.txt", s, 100, NULL);
break;
case ATT_OP_HANDLE_IND:
s = g_string_new(NULL);
g_string_printf(s, "Indication handle = 0x%04x value: ",handle);
break;
default:
error("Invalid opcode\n");
return;
}
for (i = 3; i < len; i++)
g_string_append_printf(s, "%02x ", pdu[i]);
rl_printf("%s\n", s->str);
g_string_free(s, TRUE);
if (pdu[0] == ATT_OP_HANDLE_NOTIFY)
return;
opdu = g_attrib_get_buffer(attrib, &plen);
olen = enc_confirmation(opdu, plen);
if (olen > 0)
g_attrib_send(attrib, 0, opdu, olen, NULL, NULL, NULL);
}
You're conflating GString* and gchar*. The g_string_*() functions expect a GString*, and g_file_set_contents() expects gchar*. If you want the raw data, use the str field.
Also, I suggest turning on some more warnings on your compiler, since it really should be complaining during development if you try to do this. Passing -Wall should do the trick…
I am new in communications programming. Basically, I need to get the hex equivalent of the CRC output. I have a hex string which is the parameter -
EE0000000015202020202020202020202020323134373030353935
This is concatenation of two strings. The output I need is E6EB in hex or 59115 in ushort. I tried different approaches based on what I found in the web but to no avail. The polynomial that I should be using is 0x8408, which is [CRC-16-CCITT][1], http://en.wikipedia.org/wiki/Polynomial_representations_of_cyclic_redundancy_checks.
I tried this approach, CRC_CCITT Kermit 16 in C#, but the output is incorrect. I also tried the bitwise ~ operator as some suggested for reverse computation, but still failed.
Any help is very much appreciated.
RevEng reports:
% ./reveng -s -w 16 EE0000000015202020202020202020202020323134373030353935e6eb
width=16 poly=0x1021 init=0xffff refin=true refout=true xorout=0xffff check=0x906e name="X-25"
So there's your CRC. Note that the CRC is reflected, where 0x8408 is 0x1021 reflected.
I found a solution and I'll post them in case someone will encounter the same.
private ushort CCITT_CRC16(string strInput)
{
ushort data;
ushort crc = 0xFFFF;
byte[] bytes = GetBytesFromHexString(strInput);
for (int j = 0; j < bytes.Length; j++)
{
crc = (ushort)(crc ^ bytes[j]);
for (int i = 0; i < 8; i++)
{
if ((crc & 0x0001) == 1)
crc = (ushort)((crc >> 1) ^ 0x8408);
else
crc >>= 1;
}
}
crc = (ushort)~crc;
data = crc;
crc = (ushort)((crc << 8) ^ (data >> 8 & 0xFF));
return crc;
}
private byte[] GetBytesFromHexString(string strInput)
{
Byte[] bytArOutput = new Byte[] { };
if (!string.IsNullOrEmpty(strInput) && strInput.Length % 2 == 0)
{
SoapHexBinary hexBinary = null;
try
{
hexBinary = SoapHexBinary.Parse(strInput);
if (hexBinary != null)
{
bytArOutput = hexBinary.Value;
}
}
catch (Exception ex)
{
throw ex;
}
}
return bytArOutput;
}
import System.Runtime.Remoting.Metadata.W3cXsd2001 for SoapHexBinary.
I am trying madvise() to mark allocated memory as mergeable so that two applications having same pages can be merged.
While using the madvise() function it shows "invalid argument".
#include<stdio.h>
#include<sys/mman.h>
#include<stdlib.h>
#include<errno.h>
#define ADDR 0xf900f000
int main()
{
int *var1=NULL,*var2=NULL;
size_t size=0;
size = 1000*sizeof(int);
var1 = (int*)malloc(size);
var2 = (int *)malloc(size);
int i=0;
for(i=0;i<999;i++)
{
var1[i] = 1;
}
for(i=0;i<999;i++)
{
var2[i] = 1;
}
i = -1;
while(i<0)
{
i = madvise((void *)var1, size, MADV_MERGEABLE); //to declare mergeable
printf("%d %p\n", i, var1); //to print the output value
err(1,NULL); //to print the generated error
i = madvise((void *)var2, size, MADV_MERGEABLE); //to declare mergeable
printf("%d\n", i);
}
return 0;
}
Error:
a.out: Invalid argument
Please help me.
Thank You.
You can only merge whole pages. You can't merge arbitrary chunks of data.