"Undefined Reference"

Hello all, when I compile this with gcc on redhat 8, it passes the compilation but gets errors in linking that say:
-------
xxxx.o-undefined reference to BF_set_key
xxxx.o-undefined reference to BF_ecb_encrypt
-------
those two functions are in an include file... do I need to tell the main section that they exist?

Here's the code:

Code:

#include <stdlib.h>
#include <stdio.h>
#include <openssl/blowfish.h>

int main(int argc, char* argv[]) {

  BF_KEY *tkey;
  int ilen;
  char *data;
  unsigned char *in[64],*out[64];

  strncpy(in,"hello",sizeof(in));
  ilen=5;
  strncpy(data,"abcde",sizeof(data));

  BF_set_key(tkey,ilen,data);

  BF_ecb_encrypt(in,out,tkey,BF_ENCRYPT);

  return 0;
}

Thanks All,

Oh, by the way, I'm trying to do blowfish encryption/decryption. If anyone knows of a better way to do this (i would like to be able to use this code for solaris as well), please feel free to suggest them to me.

Thanks again,

Are you linking with the library? I think it's libcrypto:

Code:

gcc blah blah -llibcrypto

gcc -o blowfish blowfish.c -llibcrypto says :"cannot find -llibcrypto"

I also tryed moving "-llibcrypto" around a little in the string, still same thing.

I don't think I need to get the library, the functions are in the blowfish.h, at least that's what "man blowfish" tells me.

thanks

Then you'll need to find out what the library file is called and do -llibrary when linking.

I'm pretty sure the man page said it didnt need a lib but i will look around.

thanks

>I'm pretty sure the man page said it didnt need a lib
The error you're getting basically says that while the declarations for those functions were found (thus allowing you to compile), the definitions weren't found, so the object code couldn't be linked into a binary because it didn't exist.

hm ok. Do you know where the libs are stored so i can look through to find the right one? or do you know another way to do blowfish?

thanks,

>Do you know where the libs are stored so i can look through to find the right one?
I'm afraid I don't. But you could search the OpenSSL documentation to see if it say anything. Also, try -lcrypto.

>or do you know another way to do blowfish?
You could write it yourself. Google should turn up the basica algorithm.

Originally Posted by Prelude

>or do you know another way to do blowfish?
You could write it yourself. Google should turn up the basica algorithm.

Well I don't think I quite have the skills yet to undertake that. I did find three good looking implementations on google, however, i can't get them to work, but's I think it's my fault, and I didn't really want to post that I didn't know how to use it. I was hoping to not be quite THAT noobie-ish.

Thanks,

It should be in libcrypto.so, so you would
gcc -o blah blah.c -lcrypto
That is if you have openssl installed.

when i do a -lcrypto, the "cannot find lcrypto" goes away, but apparently the right stuff isn't in lib crypto, since it still says undefined reference.

first you have to include string.h
You shouldn't pass char *blah[64] to strncpy it should just be char blah[64]. You don't need stdlib.h.
I got to compile the code. But it segfaulted. I wil look into it.

[EDIT] One reason I just noticed is data is a *ptr and you strncpy to it without mallocing it[/EDIT]

Originally Posted by linuxdude

first you have to include string.h

Hm It didn't give me any error on that but sounds true enough.

Originally Posted by linuxdude

You shouldn't pass char *blah[64] to strncpy it should just be char blah[64].

I know, but the man page for the blowfish funcs said that it wanted a pointer, so I defined the variable as such. I have to say I'm not fully comfertable with using pointers as opposed to regular vars.

Originally Posted by linuxdude

You don't need stdlib.h.

I know, but I just set up the header because I knew I would need it later in my program, once I get the basics to work.

Originally Posted by linuxdude

I got to compile the code. But it segfaulted. I wil look into it.

I'm thinking maybe it segfaulted because the func takes a 64-length char array, and I passed it one, thus not leaving a terminating null?

Thanks very much,

did you get it to compile. The reason it didnt' tell you you need to include <string.h> you have to add these two options to your gcc compilation.

Code:

gcc -o test test.c -Wall -pedantic

It would be nice to get into this habit, because it would tell you you undefined reference to strncmp. Let me know how it turned out