cryptography - How do I decrypt a private key file and sign some text using openssl calls in C? -

i have 2 separate programs (spliced below). first generates key pair , saves files (works fine). second opens private key, decrypting pass phrase , need sign string of text. code below fails on pem_read_privatekey() (last) call (can't see why). can point me @ doing wrong , openssl calls should make use private key sign text?

int main (int argc, char *argv[]) {     char *priv_pem = "priv.pem";     char *pub_pem  = "pub.pem";     char *pass     = "password";     file *fp;        int bits = 4096;     unsigned long exp = rsa_f4;      rsa *rsa;     evp_pkey *pkey;      //  generate key     rsa=rsa_generate_key(bits,exp,null,null);     if (rsa_check_key(rsa)!=1)         exit(1,"error whilst checking key","");     pkey = evp_pkey_new();     evp_pkey_assign_rsa(pkey, rsa);      //  write encrypted private key     if (!(fp = fopen(priv_pem, "w")))         exit(2,"error opening pem file",priv_pem);     if (!pem_write_privatekey(fp,pkey,evp_aes_256_cbc(),null,0,null,pass))         exit(3,"error writing pem file",priv_pem);     fclose(fp);      //  write public key     if (!(fp = fopen(pub_pem, "w")))         exit(4,"error opening pem file",pub_pem);     if (!pem_write_pubkey(fp, pkey))         exit(5,"error writing pem file",pub_pem);     fclose(fp);     // ------- end of key generation program -------      // ------- start of text signing program -------     //  read in encrypted private key     if (!(fp = fopen(priv_pem, "r")))         exit(6,"error reading encrypted private key file",priv_pem);     if (!pem_read_privatekey(fp,&pkey,null,pass))         exit(7,"error decrypting private key file",priv_pem);     fclose(fp);      // sign text using private key....      //  free     rsa_free(rsa);       return 0; } 

have initialised pkey null before pass &pkey pem_read_privatekey()? if not, attempt re-use evp_pkey structure pkey points - , if pkey uninitialised, looking @ random spot in memory.

you can use err_print_errors_fp(stderr); dump openssl error stack stderr when error occurs - helpful in finding problem.