How to fix RSA Deprecation [duplicate] - c

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This question already has answers here:
How to generate RSA private key using OpenSSL?
(3 answers)
Closed 3 years ago.
I have a program to test the throughput of RSA, but the RSA_key is deprecated and I'm not sure how to switch the code over to the new RSA_key.
The program throws the warning:
rsa2.c:29:5: warning: ‘RSA_generate_key’ is deprecated [-Wdeprecated-declarations]
rsa2.c:29 is:
RSA *keypair = RSA_generate_key(KEY_LENGTH, PUB_EXP, NULL, NULL);
I know that I need to switch the RSA_generate_key to:
int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
but because the new RSA_key is an int I'm not sure how to set RSA *keypair = int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);.
My code is:
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#define KEY_LENGTH 768
#define PUB_EXP 65537
#define PRINT_KEYS
#define WRITE_TO_FILE
int main(void) {
size_t pri_len; // Length of private key
size_t pub_len; // Length of public key
char *pri_key; // Private key
char *pub_key; // Public key
char msg[KEY_LENGTH/8] = "hello"; // Message to encrypt
char *encrypt = NULL; // Encrypted message
char *decrypt = NULL; // Decrypted message
char *err; // Buffer for any error messages
clock_t begin, end;
double time_spent; begin = clock();
// Generate key pair
printf("Generating RSA (%d bits) keypair...", KEY_LENGTH);
fflush(stdout);
RSA *keypair = RSA_generate_key(KEY_LENGTH, PUB_EXP, NULL, NULL);
// To get the C-string PEM form:
BIO *pri = BIO_new(BIO_s_mem());
BIO *pub = BIO_new(BIO_s_mem());
PEM_write_bio_RSAPrivateKey(pri, keypair, NULL, NULL, 0, NULL, NULL);
PEM_write_bio_RSAPublicKey(pub, keypair);
pri_len = BIO_pending(pri);
pub_len = BIO_pending(pub);
pri_key = malloc(pri_len + 1);
pub_key = malloc(pub_len + 1);
BIO_read(pri, pri_key, pri_len);
BIO_read(pub, pub_key, pub_len);
pri_key[pri_len] = '\0';
pub_key[pub_len] = '\0';
#ifdef PRINT_KEYS
printf("\n%s\n%s\n", pri_key, pub_key);
#endif
printf("done.\n");
encrypt = malloc(RSA_size(keypair));
int encrypt_len;
err = malloc(130);
if((encrypt_len = RSA_public_encrypt(strlen(msg)+1, (unsigned char*)msg, (unsigned char*)encrypt,
keypair, RSA_PKCS1_OAEP_PADDING)) == -1) {
ERR_load_crypto_strings();
ERR_error_string(ERR_get_error(), err);
fprintf(stderr, "Error encrypting message: %s\n", err);
goto free_stuff;
}
#ifdef WRITE_TO_FILE
// Write the encrypted message to a file
FILE *out = fopen("out.bin", "w");
fwrite(encrypt, sizeof(*encrypt), RSA_size(keypair), out);
fclose(out);
printf("Encrypted message written to file.\n");
free(encrypt);
encrypt = NULL;
// Read it back
printf("Reading back encrypted message and attempting decryption...\n");
encrypt = malloc(RSA_size(keypair));
out = fopen("out.bin", "r");
fread(encrypt, sizeof(*encrypt), RSA_size(keypair), out);
fclose(out);
#endif
// Decrypt it
decrypt = malloc(encrypt_len);
if(RSA_private_decrypt(encrypt_len, (unsigned char*)encrypt, (unsigned char*)decrypt,
keypair, RSA_PKCS1_OAEP_PADDING) == -1) {
ERR_load_crypto_strings();
ERR_error_string(ERR_get_error(), err);
fprintf(stderr, "Error decrypting message: %s\n", err);
goto free_stuff;
}
printf("Decrypted message: %s\n", decrypt);
end = clock();
time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
printf("time spent %f\n", time_spent);
free_stuff:
RSA_free(keypair);
BIO_free_all(pub);
BIO_free_all(pri);
free(pri_key);
free(pub_key);
free(encrypt);
free(decrypt);
free(err);
return 0;
}

Answer 1

Maybe this could work for you (adapted using this link):
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#define KEY_LENGTH 768
#define PUB_EXP 65537
#define PRINT_KEYS
#define WRITE_TO_FILE
int main(void) {
size_t pri_len; // Length of private key
size_t pub_len; // Length of public key
char *pri_key; // Private key
char *pub_key; // Public key
char msg[KEY_LENGTH/8] = "hello"; // Message to encrypt
char *encrypt = NULL; // Encrypted message
char *decrypt = NULL; // Decrypted message
char *err; // Buffer for any error messages
clock_t begin, end;
RSA *r = NULL;
BIGNUM *bne = NULL;
int ret;
double time_spent; begin = clock();
// Generate key pair
printf("Generating RSA (%d bits) keypair...", KEY_LENGTH);
fflush(stdout);
// RSA *keypair = RSA_generate_key(KEY_LENGTH, PUB_EXP, NULL, NULL);
// 1. generate rsa key
bne = BN_new();
ret = BN_set_word(bne, PUB_EXP);
if(ret != 1){
goto free_stuff;
}
r = RSA_new();
ret = RSA_generate_key_ex(r, KEY_LENGTH, bne, NULL);
if(ret != 1){
goto free_stuff;
}
// To get the C-string PEM form:
BIO *pri = BIO_new(BIO_s_mem());
BIO *pub = BIO_new(BIO_s_mem());
PEM_write_bio_RSAPrivateKey(pri, keypair, NULL, NULL, 0, NULL, NULL);
PEM_write_bio_RSAPublicKey(pub, keypair);
pri_len = BIO_pending(pri);
pub_len = BIO_pending(pub);
pri_key = malloc(pri_len + 1);
pub_key = malloc(pub_len + 1);
BIO_read(pri, pri_key, pri_len);
BIO_read(pub, pub_key, pub_len);
pri_key[pri_len] = '\0';
pub_key[pub_len] = '\0';
#ifdef PRINT_KEYS
printf("\n%s\n%s\n", pri_key, pub_key);
#endif
printf("done.\n");
// Get the message to encrypt
// printf("Message to encrypt: ");
// fgets(msg, KEY_LENGTH-1, stdin);
// msg[strlen(msg)-1] = '\0';
// Encrypt the message
encrypt = malloc(RSA_size(keypair));
int encrypt_len;
err = malloc(130);
if((encrypt_len = RSA_public_encrypt(strlen(msg)+1, (unsigned char*)msg, (unsigned char*)encrypt,
keypair, RSA_PKCS1_OAEP_PADDING)) == -1) {
ERR_load_crypto_strings();
ERR_error_string(ERR_get_error(), err);
fprintf(stderr, "Error encrypting message: %s\n", err);
goto free_stuff;
}
#ifdef WRITE_TO_FILE
// Write the encrypted message to a file
FILE *out = fopen("out.bin", "w");
fwrite(encrypt, sizeof(*encrypt), RSA_size(keypair), out);
fclose(out);
printf("Encrypted message written to file.\n");
free(encrypt);
encrypt = NULL;
// Read it back
printf("Reading back encrypted message and attempting decryption...\n");
encrypt = malloc(RSA_size(keypair));
out = fopen("out.bin", "r");
fread(encrypt, sizeof(*encrypt), RSA_size(keypair), out);
fclose(out);
#endif
// Decrypt it
decrypt = malloc(encrypt_len);
if(RSA_private_decrypt(encrypt_len, (unsigned char*)encrypt, (unsigned char*)decrypt,
keypair, RSA_PKCS1_OAEP_PADDING) == -1) {
ERR_load_crypto_strings();
ERR_error_string(ERR_get_error(), err);
fprintf(stderr, "Error decrypting message: %s\n", err);
goto free_stuff;
}
printf("Decrypted message: %s\n", decrypt);
end = clock();
time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
printf("time spent %f\n", time_spent);
free_stuff:
RSA_free(keypair);
BIO_free_all(pub);
BIO_free_all(pri);
free(pri_key);
free(pub_key);
free(encrypt);
free(decrypt);
free(err);
RSA_free(r);
BN_free(bne);
return 0;
}