#include <string.h>

       #include <openssl/x509.h>

       #include <openssl/rsa.h>

      

       int    main()

       {

              X509_REQ            *req;

              int                         ret;

              long               version;

              X509_NAME         *name;

              EVP_PKEY            *pkey;

              RSA                      *rsa;

              X509_NAME_ENTRY   *entry=NULL;

              char               bytes[100],mdout[20];

              int                         len,mdlen;

              int                         bits=512;

              unsigned long  e=RSA_3;

              unsigned char*der,*p;

              FILE                     *fp;

              const EVP_MD      *md;

              X509                    *x509;

              BIO                      *b;

              STACK_OF(X509_EXTENSION) *exts;

             

              req=X509_REQ_new();

              version=1;

              ret=X509_REQ_set_version(req,version);

              name=X509_NAME_new();

              strcpy(bytes,"openssl");

              len=strlen(bytes);

              entry=X509_NAME_ENTRY_create_by_txt(&entry,"commonName",V_ASN1_UTF8STRING,(unsigned char *)bytes,len);

              X509_NAME_add_entry(name,entry,0,-1);

              strcpy(bytes,"bj");

              len=strlen(bytes);

              entry=X509_NAME_ENTRY_create_by_txt(&entry,"countryName",V_ASN1_UTF8STRING,bytes,len);

              X509_NAME_add_entry(name,entry,1,-1);

      

              /* subject name */

              ret=X509_REQ_set_subject_name(req,name);

              /* pub key */

              pkey=EVP_PKEY_new();

              rsa=RSA_generate_key(bits,e,NULL,NULL);

              EVP_PKEY_assign_RSA(pkey,rsa);

              ret=X509_REQ_set_pubkey(req,pkey);

              /* attribute */

              strcpy(bytes,"test");

              len=strlen(bytes);

              ret=X509_REQ_add1_attr_by_txt(req,"organizationName",V_ASN1_UTF8STRING,bytes,len);

              strcpy(bytes,"ttt");

              len=strlen(bytes);

              ret=X509_REQ_add1_attr_by_txt(req,"organizationalUnitName",V_ASN1_UTF8STRING,bytes,len);

              md=EVP_sha1();

              ret=X509_REQ_digest(req,md,mdout,&mdlen);

              ret=X509_REQ_sign(req,pkey,md);

              if(!ret)

              {

                     printf("sign err!\n");

                     X509_REQ_free(req);

                     return -1;

              }

              /* 写入文件PEM格式 */

              b=BIO_new_file("certreq.txt","w");

              PEM_write_bio_X509_REQ(b,req,NULL,NULL);

              BIO_free(b);

              /* DER编码 */

              len=i2d_X509_REQ(req,NULL);

              der=malloc(len);

              p=der;

              len=i2d_X509_REQ(req,&p);

              OpenSSL_add_all_algorithms();

              ret=X509_REQ_verify(req,pkey);

              if(ret<0)

              {

                     printf("verify err.\n");

              }

              fp=fopen("certreq2.txt","wb");

              fwrite(der,1,len,fp);

              fclose(fp);

              free(der);

              X509_REQ_free(req);

              return 0;

       }

       本例用于生成一个证书请求文件，并测试了X509_REQ_verify和X509_REQ_digest等函数。