I'm trying to compile this code which call func from "libcfmapi.so" to decrypt "cfg" file
#include <stdlib.h>
#include <stdio.h>
int restorebackup(const char *tmp_cfg_name,const char *xml_cfg_name);
int ATP_CFM_ExtCustomImportEncryptedUserCfgFile(const char *tmp_cfg_name);
int main(int argc, char **argv)
{
int ret;
if(argc < 3)
{
printf("specify temp config file name.\n");
exit(1);
}
ret=restorebackup(argv[1],argv[2]);
return ret;
}
int restorebackup(const char *tmp_cfg_name,const char *xml_cfg_name)
{
int ret=0;
//ret = ATP_CFM_ExtDigVerifyFile(tmp_cfg_name,tmp_cfg_name);
if(ret != 0)
{
printf("Verify File failed.\n");
return ret;
}
ret = ATP_CFM_ExtCustomImportEncryptedUserCfgFile(tmp_cfg_name);
return ret;
}
but got error regarding func type declare
root#kali:~/debian-qemu# gcc h.c -o demo
/tmp/ccVbt5NT.o: In function `restorebackup':
h.c:(.text+0x8c): undefined reference to `ATP_CFM_ExtCustomImportEncryptedUserCfgFile'
collect2: error: ld returned 1 exit status
any help appreciated
The reason you're getting this error is because you're not linking against the required library, libcfmapi.so.
This is not a library you would expect to find in your Debian system as it is unique to the BT device you're trying to hack.
In short - get the lib from your device, cross compile to the device architecture against the lib you extracted from the device and you should be fine.
More information based on Ishay Peled answer:
readelf -s <pulled library> | grep ATP_CFM_ExtCustomImportEncryptedUserCfgFile
I suspect the problem isn't that function you call doesn't exist but rather there are no functions being displayed it is most likely empty just like nm result:
nm: libcfmapi.so: no symbols
do the command without piping to grep, my bet is your output is:
readelf -s libcfmapi.so
Dynamic symbol information is not available for displaying symbols.
If someone knows the way of getting the headers from the file, i believe then you can find your function you require then link and run (i too am trying to use libcfmapi.so, but lack the programming/reversing knowledge required).
when using a library, then must:
include that library in the link statement via
-l cfmapi
include the header file for that library in the source code:
#include <cfmapi.h>
Related
I am using dlsym to look up symbols in my program, but it always returns NULL, which I am not expecting. According to the manpage, dlsym may return NULL if there was an error somehow, or if the symbol indeed is NULL. In my case, I am getting an error. I will show you the MCVE I have made this evening.
Here is the contents of instr.c:
#include <stdio.h>
void * testing(int i) {
printf("You called testing(%d)\n", i);
return 0;
}
A very simple thing containing only an unremarkable example function.
Here is the contents of test.c:
#include <dlfcn.h>
#include <stdlib.h>
#include <stdio.h>
typedef void * (*dltest)(int);
int main(int argc, char ** argv) {
/* Declare and set a pointer to a function in the executable */
void * handle = dlopen(NULL, RTLD_NOW | RTLD_GLOBAL);
dlerror();
dltest fn = dlsym(handle, "testing");
if(fn == NULL) {
printf("%s\n", dlerror());
dlclose(handle);
return 1;
}
dlclose(handle);
return 0;
}
As I step through the code with the debugger, I see the dlopen is returning a handle. According to the manpage, If filename is NULL, then the returned handle is for the main program. So if I link a symbol called testing into the main program, dlsym should find it, right?
Here is the way that I am compiling and linking the program:
all: test
instr.o: instr.c
gcc -ggdb -Wall -c instr.c
test.o: test.c
gcc -ggdb -Wall -c test.c
test: test.o instr.o
gcc -ldl -o test test.o instr.o
clean:
rm -f *.o test
And when I build this program, and then do objdump -t test | grep testing, I see that the symbol testing is indeed there:
08048632 g F .text 00000020 testing
Yet the output of my program is the error:
./test: undefined symbol: testing
I am not sure what I am doing wrong. I would appreciate if someone could shed some light on this problem.
I don't think you can do that, dlsym works on exported symbols. Because you're doing dlsym on NULL (current image), even though the symbols are present in the executable ELF image, they're not exported (since it's not a shared library).
Why not call it directly and let the linker take care of it? There's no point in using dlsym to get symbols from the same image as your dlsym call. If your testing symbol was in a shared library that you either linked against or loaded using dlopen then you would be able to retrieve it.
I believe there's also a way of exporting symbols when building executables (-Wl,--export-dynamic as mentioned in a comment by Brandon) but I'm not sure why you'd want to do that.
I faced the similar issue in my code.
I did the following to export symbols
#ifndef EXPORT_API
#define EXPORT_API __attribute__ ((visibility("default")))
#endif
Now for each of the function definition I used the above attribute.
For example the earlier code was
int func() { printf(" I am a func %s ", __FUNCTION__ ) ;
I changed to
EXPORT_API int func() { printf(" I am a func %s ", __FUNCTION__ ) ;
Now it works.
dlsym gives no issues after this.
Hope this works for you as well.
I am exploring some adventurous ideas.
TL:DR; gnumake is able to use loadable modules, I am trying to use that C barrier to use OCaml but have trouble with the OCaml runtime initializing.
I have this OCaml code:
(* This is speak_ocaml.ml *)
let do_speak () =
print_endline "This called from OCaml!!";
flush stdout;
"Some return value from OCaml"
let () =
Callback.register "speak" do_speak
and I also have this C code: (Yes, needs to use extra CAML macros but not relevant here)
#include <stdlib.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <gnumake.h>
#include <caml/mlvalues.h>
#include <caml/callback.h>
#include <caml/memory.h>
#include <caml/alloc.h>
int plugin_is_GPL_compatible;
char *ocaml_speaker(const char *func_name, int argc, char **argv)
{
char *answer =
String_val(caml_callback(*caml_named_value("speak"), Val_unit));
printf("Speaking and got: %s\n", answer);
char *buf = gmk_alloc(strlen(answer) + 1);
strcpy(buf, answer);
/* receive_arg */
return buf;
}
int do_speak_gmk_setup()
{
printf("Getting Called by Make\n");
// This is pretty critical, will explain below
char **argv = {"/home/Edgar/foo", NULL};
caml_startup(argv);
printf("Called caml_startup\n");
gmk_add_function("speak", ocaml_speaker, 1, (unsigned int)1, 1);
return 1;
}
and I'm compiling it with this Makefile
all:
ocamlopt -c speak_ocaml.ml
ocamlopt -output-obj -o caml_code.o speak_ocaml.cmx
clang -I`ocamlc -where` -c do_speak.c -o do_speak.o
clang -shared -undefined dynamic_lookup -fPIC -L`ocamlc -where` -ldl \
-lasmrun do_speak.o caml_code.o -o do_speak.so
show_off:
echo "Speaker?"
${speak 123}
clean:
#rm -rf *.{cmi,cmt,cmi,cmx,o,cmo,so}
And my problem is that only printf("Getting Called by Make\n"); is going off when I add the appropriate load do_speak.so in the Makefile, caml_startup is not going off correctly. Now I am calling caml_startup because if I don't then I get an error of
Makefile:9: dlopen(do_speak.so, 9): Symbol not found: _caml_atom_table
Referenced from: do_speak.so
Expected in: flat namespace
in do_speak.so
Makefile:9: *** do_speak.so: failed to load. Stop.
And this is because of the way that clang on OS X does linking, see here for more details: http://psellos.com/2014/10/2014.10.atom-table-undef.html
I am kind of out of ideas... I need to create a C shared library out of OCaml code which then needs to be part of another C shared library from which I obviously don't have the original argv pointers that caml_startup wants. As my code sample show, I've tried faking it out, and also used caml_startup(NULL) and char **argv = {NULL}; caml_startup(argv) with similar lack of success. I don't know how else to initialize the runtime correctly.
I actually can't tell very well what you're asking. However, here's a comment on this part of your question:
I've tried faking it out, and also used caml_startup(NULL) and char **argv = {NULL}; caml_startup(argv) with similar lack of success. I don't know how else to initialize the runtime correctly.
As far as I know, the only reason for the argv argument of caml_startup is to establish the command-line arguments (for Sys.argv). If you don't need command-line arguments it should be OK to call like this:
char *arg = NULL;
caml_startup(&arg);
Technically argv is supposed to contain at least one string (the name of the program). So maybe it would be better to call like this:
char *argv[] = { "program", NULL };
caml_startup(argv);
I'm trying to use libusb for a project but i'm unable to get the library working properly. Here is some source code i'm trying to compile. It doesn't do anything special. It's just a dummy program that gets the USB driver list then frees it.
#include <stdio.h>
#include <usb.h>
#include <stdlib.h>
int main(int argc, char *argv[]){
struct libusb_device **devs;
struct libusb_context *context = NULL;
size_t list;
size_t i;
int ret;
ret = libusb_init(&context);
if(ret < 0)
{
perror("libusb_init");
exit(1);
}
list = libusb_get_device_list(context, &devs);
if(list < 0)
{
fprintf(stderr, "error in getting device list\n");
libusb_free_device_list(devs, 1);
libusb_exit(context);
exit(1);
}
libusb_free_device_list(devs, 1);
libusb_exit(context);
return 0;
}
I compile with
gcc -o test test.c -lusb
I get the error
/tmp/cc2hwzii.o: in function 'main:
test.c:(.text+0x24): undefined reference to 'libusb_init'
test.c:(.text+0x59): undefined reference to 'libusb_get_device_list'
test.c:(.text+0x8e): undefined reference to 'libusb_free_device_list'
test.c:(.text+0x9f): undefined reference to 'libusb_exit'
collect2: error: ld returned 1 exit status
I'm running ubuntu 14.04.3
I've installed libusb by sudo apt-get install libusb-dev
I've searched for my header file and it is called usb.h
I've looked to make sure I have the correct flag and it's -lusb
any ideas? I'd appreciate the help. If any more information is needed just ask.
those libusb_init are included in libusb-1.0.
you have to install libusb-1.0-0-dev
$ sudo apt-get install libusb-1.0-0-dev
$ gcc -o test test.c -lusb-1.0
/usr/lib/x86_64-linux-gnu/pkgconfig/libusb.pc which is included in libusb-dev says that the version is 0.1.12
and
/usr/lib/x86_64-linux-gnu/pkgconfig/libusb-1.0.pc which is included in libusb-1.0-0-dev says that the version is 1.0.17.
http://www.libusb.org/ says that 0.1 is legacy, and seems that API is different from 1.0.
You forgot to include the file that defines the functions, such as libusb_init. Have you tried including libusb.h?
Here is some code from Ben Straub's (link blog) that I am basing this on:
static int do_clone(const char *url, const char *path)
{
git_repository *repo = NULL;
int ret = git_clone(&repo, url, path, NULL);
git_repository_free(repo);
return ret;
}
And here is my code:
#include <git2.h>
int main(void) {
git_repository *out = NULL;
git_clone(&out, "https://github.com/lehitoskin/racketball", "/home/maxwell", NULL);
return 0;
}
I am very inexperienced with C, so I apologize for having such elementary problems. Anyway, here is the error my compiler gives me:
maxwell#max-pc ~ $ gcc -I libgit2/include gitfun.c
/tmp/ccB64nPh.o: In function `main':
gitfun.c:(.text+0x31): undefined reference to `git_clone'
collect2: error: ld returned 1 exit status
Why can't I call git_clone this way?
It looks like you didn't link to the library. Add -lgit2 if libgit2 is the lib name.
gcc -I libgit2/include gitfun.c -L<path to lib> -l<libname minus the "lib" part>
IOW, you compile fine but when the linker goes looking for git_clone it can't find it because you haven't specified the library that it is in.
I am working from a book: TCP/IP Sockets in C and its website code.
I am trying to build a client and server based on those files. My make gives lots of
error related to not being able to find functions from DieWithMessage.c
Here it is:
#include <stdio.h>
#include <stdlib.h>
#include "Practical.h"
void DieWithUserMessage(const char *msg, const char *detail) {
fputs(msg, stderr);
fputs(": ", stderr);
fputs(detail, stderr);
fputc('\n', stderr);
exit(1);
}
void DieWithSystemMessage(const char *msg) {
perror(msg);
exit(1);
}
When I do gcc DieWithMessage.c, I get the following error:
/usr/lib/i386-linux-gnu/gcc/i686-linux-gnu/4.5.2/../../../crt1.o: In function _start':
(.text+0x18): undefined reference tomain'
collect2: ld returned 1 exit status
How do I compile this by itself so that the errors will stop happening when using the makefile?
Thanks for any help.
Your C code needs a main function if you're going to try an link/run it. This is a requirement for hosted C applications under the standard.
That error message indicates what's wrong. The C runtime/startup code (CRT) has an entry point of start which sets up the environment then calls your main. Since you haven't provided a main, it complains.
If you only want to generate an object file for later linking with a main (see here for one description of the process), use something like:
gcc -c -o DieWithMessage.o DieWithMessage.c
(-c is the "compile but don't link" flag). You can then link it later with your main program with something like (although there are other options):
gcc -o myProg myProg.c DieWithMessage.o
If you want a placeholder main to update later with a real one, you can add the following to your code:
int main (void) { return 0; }