Re: error: redefinition of ‘struct rsa_meth_st’

[Shariful Alam <dipto181@xxxxxxxxx>]

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@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@xxxxxxxxxxx> 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@xxxxxxxxxxx
> <mailto:pauli@xxxxxxxxxxx>> 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
>