fatal error: openssl/opensslconf.h: No such file or directory

I try to compile a C file which decrypts and executes an rc-4 encryped shellcode with virtual alloc.

Now I get an error:

"In file included from rc-4.c:2: rc4.h:62:11: fatal error: openssl/opensslconf.h: No such file or directory #include <openssl/opensslconf.h>/* OPENSSL_NO_RC4, RC4_INT */"

My compile command is: i586-mingw32msvc-gcc rc-4.c -o test.exe -lcrypto

At first mingw32 gave me the error that rc-4.h could not be found. I fixed this by copying the rc-4.h in my current directory and included it with #include "rc-4.h"

the first two lines of the code

```
#include <windows.h>
#include "rc4.h"
```

how the rc-4 shellcode should be decrypted and executed:

int lpBufSize = sizeof(int) * PAYLOADSIZE;
        LPVOID lpBuf = VirtualAlloc(NULL, lpBufSize, MEM_COMMIT, 0x04);
        memset(lpBuf, '\0', lpBufSize);
        RC4(RC4KEY, payload, (char*) lpBuf, PAYLOADSIZE);
        MessageBox(NULL, (char*) lpBuf, "Test", MB_OK);
        return 0;

the expected output should be the compiled test.exe file

Solution

I'm using MinGW64 because that's what is installed here. I'm aware of the tag "mingw32", hoping it's OK.

1. Compiling

The header file rc4.h lives in the path <path-of-installation>/<version>/mingw64/opt/include, so this has to be given as an argument to -I:

i586-mingw32msvc-gcc -c -I "<path-of-installation>/<version>/mingw64/opt/include" rc-4.c -o rc-4.o

You could as well set CPATH or C_INCLUDE_PATH, see The C Preprocessor: Environment Variables.

2. Linking

Note: Because you didn't provide enough source code I could not try this.

The library file libcrypto.a lives in the path <path-of-installation>/<version>/mingw64/opt/lib, so this has to be given as an argument to -L:

i586-mingw32msvc-gcc -L "<path-of-installation>/<version>/mingw64/opt/lib" rc-4.o -lcrypto -o test.exe