Diffie-Hellman question

[Ohad Rodeh]

Hello,
  I've recently downloaded and installed the OpenSSL toolkit. 
It is really cool!

  What I'm doing now is preparing a binding for the OCaml language,
allowing use of the cryptographic functionality of OpenSSL from OCaml.  
I'm having a bit of trouble with the Diffie-Hellman stuff, specifically,
the d2i_DHparam, and i2d_DHparam functions. Perhaps you can explain
what I'm suppose to be doing.

  I've written a simple program that creates a DH pair, converts it into a
string, and back. It doesn't work properly, and I couldn't figure out
the percise workings of the ASN1 package. 

  Any help appreciated, 
        Ohad.

  


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef WINDOWS
#include "../bio/bss_file.c" 
#endif
#include <openssl/crypto.h>
#include <openssl/bio.h>
#include <openssl/bn.h>

#ifdef NO_DH
int main(int argc, char *argv[])
{
    printf("No DH support\n");
    return(0);
}
#else
#include <openssl/dh.h>

#ifdef WIN16
#define MS_CALLBACK     _far _loadds
#else
#define MS_CALLBACK
#endif

static void MS_CALLBACK cb(int p, int n, char *arg);
#ifdef NO_STDIO
#define APPS_WIN16
#include "bss_file.c"
#endif

BIO *out=NULL;

int main(int argc, char *argv[])
        {
        DH *a,*b;
        char buf[12];
        unsigned char *abuf=NULL,*bbuf=NULL;
        int i,alen,blen,aout,bout,ret=1;

        long len = 0;
        unsigned char *p,**pp;
        int i;
        DH *c = NULL;
        
#ifdef WIN32
        CRYPTO_malloc_init();
#endif

        out=BIO_new(BIO_s_file());
        if (out == NULL) exit(1);
        BIO_set_fp(out,stdout,BIO_NOCLOSE);

        a=DH_generate_parameters(64,DH_GENERATOR_5,cb,(char *)out);
        if (a == NULL) goto err;

        if (!DH_generate_key(a)) goto err;

        
        p = malloc(16);
        pp = &p;
        memset((char*)p,0,16);
        len = i2d_DHparams(a,pp);
        
        c = d2i_DHparams(NULL,pp,16);
        if (c == NULL) {
          printf ("Null return value in DH routines.\n");
        } else {
          BIO_puts(out,"\np    =");
          BN_print(out,c->p);
          BIO_puts(out,"\ng    =");
          BN_print(out,c->g);
          BIO_puts(out,"\n");
        }
        err:
        exit(0)
          }

static void MS_CALLBACK cb(int p, int n, char *arg)
{
        char c='*';

        if (p == 0) c='.';
        if (p == 1) c='+';
        if (p == 2) c='*';
        if (p == 3) c='\n';
        BIO_write((BIO *)arg,&c,1);
        BIO_flush((BIO *)arg);
#ifdef LINT
        p=n;
#endif
        }
#endif





#
# SSLeay/crypto/dh/Makefile
#
#*************************************************************#

INC = ../../include/ 
LIB = ../../lib
CC = gcc

#*************************************************************#
.SUFFIXES: .ml .mli .cmo .cmi .cmx
.mli.cmi:
        ocamlc -c $< -o $@
.ml.cmo:
        ocamlc -c $< -o $@
.ml.cmx:
        ocamlopt -c $< -o $@
#*************************************************************#


.SUFFIXES: .o .c
.c.o.:
        gcc  -g -o $@ -c -I$(INC) $< 

all : check_this #dh


check_this.o : check_this.c
        gcc -g -o check_this.o -c -I$(INC) check_this.c

check_this : check_this.o
        gcc -g -o check_this check_this.o  -L$(LIB) -lcrypto 

dhtest.o : dhtest.c
        gcc -g -o dhtest.o -c -I$(INC) dhtest.c

dhtest : dhtest.o 
        gcc -g -o dhtest dhtest.o -L$(LIB) -lcrypto

t : t.o $(LIBOBJ)
        gcc -o t t.o -L$(LIB) -lcrypto


times.o : times.c
        gcc -O2 -o times.o -c -I$(INC) times.c

times : times.o 
        gcc -O2 -o times times.o -L$(LIB) -lcrypto


dh_c.o : dh_c.c
        gcc -O2 -o dh_c.o -c -I$(INC) -I$(CAMLLIB) dh_c.c 

#dh : dh.cmi dh.cmx dh_c.o mltest.cmx
#       ocamlopt -o dh dh_c.o  -cclib -lunix unix.cmxa -cclib ../../lib/libcrypto.a 
dh.cmx mltest.cmx


dh : dh.cmi dh.cmo dh_c.o mltest.cmo
        ocamlc -custom -o dh dh_c.o  -cclib -lunix unix.cma -cclib 
../../lib/libcrypto.a dh.cmo mltest.cmo

clean : 
        rm -f *.o *.cm* dh times dhtest