Re: error: redefinition of ‘struct rsa_meth_st’

Shariful Alam dipto181 at gmail.com
Mon Apr 12 23:56:35 UTC 2021


Mr, Matt,
Thanks for the link. It was helpful. However, I'm encountering some weird
issues while compiling.
I have two machines. In one machine The following code is compiling and
working file whereas in another machine I'm receiving *"warning: implicit
declaration of function ‘RSA_meth_new’" *during compilation. Both of my
machine is running

   - *Linux 4.15.0-140-generic,*
   - *gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609*
   - *OpenSSL 1.1.1c  28 May 2019*


My simple code is below.

//rsa-engine.c
===================================
#include <stdio.h>
#include <string.h>

#include <openssl/engine.h>
#include <openssl/sha.h>
#include <openssl/aes.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/async.h>
#include <openssl/bn.h>
#include <openssl/crypto.h>
#include <openssl/ssl.h>
#include <openssl/modes.h>

/* Engine Id and Name */
static const char *engine_dasync_id = "dasync";
static const char *engine_dasync_name = "Dummy Async engine support";

static int dasync_pub_enc(int flen, const unsigned char *from, unsigned
char *to, RSA *rsa, int padding) {
      printf("dasync_pub_enc\n");
      return 0;
}

static int dasync_pub_dec(int flen, const unsigned char *from, unsigned
char *to, RSA *rsa, int padding) {
      printf("dasync_pub_dec\n");
      return 0;
}

static int dasync_rsa_priv_enc(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding){
    printf("dasync_rsa_priv_enc\n");
    return 0;
}

static int dasync_rsa_priv_dec(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding){
    printf("dasync_rsa_priv_dec\n");
    return 0;
}

static RSA_METHOD *dasync_rsa_method = NULL;
static int bind_dasync(ENGINE *e){
    /* Setup RSA_METHOD */
    if ((dasync_rsa_method = RSA_meth_new("Dummy Async RSA method", 0)) ==
NULL
        || RSA_meth_set_pub_enc(dasync_rsa_method, dasync_pub_enc) == 0
        || RSA_meth_set_pub_dec(dasync_rsa_method, dasync_pub_dec) == 0
        || RSA_meth_set_priv_enc(dasync_rsa_method, dasync_rsa_priv_enc) ==
0
        || RSA_meth_set_priv_dec(dasync_rsa_method, dasync_rsa_priv_dec) ==
0
    ) {
        return 0;
    }

    if (!ENGINE_set_id(e, engine_dasync_id)
        || !ENGINE_set_name(e, engine_dasync_name)
        || !ENGINE_set_RSA(e, dasync_rsa_method)
     ) {
         return 0;
    }
    return 1;
}

static int bind_helper(ENGINE *e, const char *id){
    if (!bind_dasync(e)){
        printf("2_Error: Inside Bind helper\n");
        return 0;
    }
    return 1;
}

IMPLEMENT_DYNAMIC_BIND_FN(bind_helper)
IMPLEMENT_DYNAMIC_CHECK_FN()


===================================

In the machine where this engine is working, I use the following command to
compile my code,

   -
*gcc -fPIC -c rsa-engine.c *
   - *gcc -shared -o librsa_engine.so -lcrypto rsa-engine.o*

And Following command to load my engine,

   - *openssl engine -t -c `pwd`/librsa_engine.so*


The same code on the other machine upon running,  *gcc -fPIC -c
rsa-engine.c, *I get the following warning,

ss at ss:~/Downloads/test_engine$ gcc -fPIC -c rsa-engine.c
rsa-engine.c: In function ‘bind_dasync’:
rsa-engine.c:64:30: warning: implicit declaration of function
‘RSA_meth_new’ [-Wimplicit-function-declaration]
     if ((dasync_rsa_method = RSA_meth_new("Dummy Async RSA method", 0)) ==
NULL
                              ^
rsa-engine.c:64:28: warning: assignment makes pointer from integer without
a cast [-Wint-conversion]
     if ((dasync_rsa_method = RSA_meth_new("Dummy Async RSA method", 0)) ==
NULL
                            ^
rsa-engine.c:65:12: warning: implicit declaration of function
‘RSA_meth_set_pub_enc’ [-Wimplicit-function-declaration]
         || RSA_meth_set_pub_enc(dasync_rsa_method, dasync_pub_enc) == 0
            ^
rsa-engine.c:66:12: warning: implicit declaration of function
‘RSA_meth_set_pub_dec’ [-Wimplicit-function-declaration]
         || RSA_meth_set_pub_dec(dasync_rsa_method, dasync_pub_dec) == 0
            ^
rsa-engine.c:67:12: warning: implicit declaration of function
‘RSA_meth_set_priv_enc’ [-Wimplicit-function-declaration]
         || RSA_meth_set_priv_enc(dasync_rsa_method, dasync_rsa_priv_enc)
== 0
            ^
rsa-engine.c:68:12: warning: implicit declaration of function
‘RSA_meth_set_priv_dec’ [-Wimplicit-function-declaration]
         || RSA_meth_set_priv_dec(dasync_rsa_method, dasync_rsa_priv_dec)
== 0



can you please tell me why the same code is throwing two different results
in different machines?


Regards,
Shariful Alam







On Mon, Apr 12, 2021 at 10:42 AM Matt Caswell <matt at openssl.org> wrote:

> You can look at the dummy async engine which wraps the standard RSA
> functions inside an engine (as well as various other crypto primitives).
> You can see it here:
>
>
> https://github.com/openssl/openssl/blob/OpenSSL_1_1_1-stable/engines/e_dasync.c
>
> Matt
>
> On 12/04/2021 17:32, Shariful Alam wrote:
> > Dr. Pauli,
> > Goodmorning. Thank you for replying. I found the documentation a bit
> > difficult for me to understand. I was wondering if you can direct me to
> > a sample skeleton code for creating a custom RSA engine.
> >
> > Regards,
> > Shariful Alam
> >
> > On Sun, Apr 11, 2021 at 6:00 PM Dr Paul Dale <pauli at openssl.org
> > <mailto:pauli at openssl.org>> wrote:
> >
> >     You shouldn't be accessing the internal of a private structure. That
> >     structure was made private for a reason and duplicating it in your
> >     engine will break when we change the structure's contents.
> >
> >     Your engine should be using the EVP_PKEY_meth_set_* function to do
> >     what you want (for 1.1.1).  For 3.0, you should be writing a
> >     provider instead.
> >
> >
> >     Pauli
> >
> >     On 12/4/21 5:04 am, Shariful Alam wrote:
> >>     Hello,
> >>     Hope you guys are doing well. I'm trying to develop an RSA engine.
> >>     My engine was somewhat working until I try to integrate my engine
> >>     with an apache httpd server. After installing the httpd from the
> >>     source code, it turns out that, I can't compile my engine anymore.
> >>     I get the following error while I try to compile (it was compiling
> >>     before and I did not make any changes to my engine code).
> >>
> >>     ==============================
> >>
> >>     *$gcc -fPIC -c r_engine.c*
> >>     *r_engine.c:29:8: error: redefinition of ‘struct rsa_meth_st’
> >>      struct rsa_meth_st {
> >>             ^
> >>     In file included from /usr/include/openssl/crypto.h:131:0,
> >>                      from r_engine.c:7:
> >>     /usr/include/openssl/ossl_typ.h:147:16: note: originally defined
> here
> >>      typedef struct rsa_meth_st RSA_METHOD;*
> >>
> >>     =============================
> >>
> >>     and my *struct rsa_meth_st *looks like the following,
> >>
> >>
>  ================================================================================
> >>
> >>     *struct rsa_meth_st {
> >>
> >>         const char *name;
> >>         int (*rsa_pub_enc) (int flen, const unsigned char *from,
> >>     unsigned char *to, RSA *rsa, int padding);
> >>         int (*rsa_pub_dec) (int flen, const unsigned char *from,
> >>     unsigned char *to, RSA *rsa, int padding);
> >>         int (*rsa_priv_enc) (int flen, const unsigned char *from,
> >>     unsigned char *to, RSA *rsa, int padding);
> >>         int (*rsa_priv_dec) (int flen, const unsigned char *from,
> >>     unsigned char *to, RSA *rsa, int padding);
> >>
> >>         int (*rsa_mod_exp) (BIGNUM *r0, const BIGNUM *I, RSA *rsa,
> >>     BN_CTX *ctx);
> >>
> >>         int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM
> >>     *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
> >>
> >>         int (*init) (RSA *rsa);
> >>
> >>         int (*finish) (RSA *rsa);
> >>
> >>         int flags;
> >>
> >>         char *app_data;
> >>
> >>         int (*rsa_sign) (int type, const unsigned char *m, unsigned
> >>     int m_length, unsigned char *sigret, unsigned int *siglen, const
> >>     RSA *rsa);
> >>
> >>         int (*rsa_verify) (int dtype, const unsigned char *m, unsigned
> >>     int m_length, const unsigned char *sigbuf, unsigned int siglen,
> >>     const RSA *rsa);
> >>
> >>         int (*rsa_keygen) (RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
> >>
> >>     };
> >>     *
> >>
> >>
>  =================================================================================
> >>
> >>     My sample skeleton code is here https://pastebin.com/uNXYknEA
> >>     <https://pastebin.com/uNXYknEA>
> >>
> >>     Can anyone please tell me what I'm I doing wrong?
> >>
> >>     Regards,
> >>     Shariful Alam
> >
>
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