I have 2 separate programs (spliced together below). The first generates开发者_开发百科 the key pair and saves to files (works fine). The second opens the private key, decrypting with a pass phrase and then I need it to sign a string of text. The code below fails on the PEM_read_PrivateKey() (last) call (can't see why). Can anyone point me at what I am doing wrong and then what openssl calls I should make to use the private key to sign some 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 some text using the private key....
// FREE
RSA_free(rsa);
return 0;
}
Have you initialised pkey
to NULL
before you pass &pkey
to PEM_read_PrivateKey()
? If not, it will attempt to re-use the EVP_PKEY
structure that pkey
points to - and if pkey
is uninitialised, it will be looking at a random spot in memory.
You can use ERR_print_errors_fp(stderr);
to dump the OpenSSL error stack to stderr
when an error occurs - this is often helpful in finding the problem.
Thanks @caf for your help. By trial and error I fixed PEM_read_PrivateKey() error by adding the following to the start:
if (EVP_get_cipherbyname("aes-256-cbc") == NULL)
OpenSSL_add_all_algorithms();
However, I'm still looking for the best (practice) way of generating the keys and then using the private key for signing. From my limited understanding, I am looking for openssl methods that adhere to RSA's "PKCS #1 v2.0: RSA Cryptography Standard"
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