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#include <openssl/bn.h>
#include <openssl/rsa.h>
#if OPENSSL_VERSION_NUMBER >= 0x10100000L
/* re-calculate the decryption key `d` for the given key
* the product of e and d must be congruent to 1, and since we are messing
* with e to generate our keys, we must re-calculate d */
int
key_update_d(RSA *rsa_key) {
const BIGNUM *p = NULL;
const BIGNUM *q = NULL;
const BIGNUM *d = NULL;
const BIGNUM *e = NULL;
BIGNUM *gcd = BN_secure_new();
BIGNUM *p1 = BN_secure_new();
BIGNUM *q1 = BN_secure_new();
BIGNUM *p1q1 = BN_secure_new();
BIGNUM *lambda_n = BN_secure_new();
BIGNUM *true_d = BN_secure_new();
BIGNUM *true_dmp1 = BN_secure_new();
BIGNUM *true_dmq1 = BN_secure_new();
BIGNUM *true_iqmp = BN_secure_new();
BN_CTX *bn_ctx = BN_CTX_secure_new();
if (!(bn_ctx && gcd && p1 && q1 && p1q1 && lambda_n && true_d &&
true_dmp1 && true_dmq1 && true_iqmp)) {
perror("bignum or bignum context allocation");
return 1;
}
RSA_get0_key(rsa_key, NULL, &e, &d);
RSA_get0_factors(rsa_key, &p, &q);
/* calculate p-1 and q-1 and their product */
BN_sub(p1, p, BN_value_one());
BN_sub(q1, q, BN_value_one());
BN_mul(p1q1, p1, q1, bn_ctx);
/* calculate LCM of p1,q1 with p1*q1/gcd(p1,q1) */
BN_gcd(gcd, p1, q1, bn_ctx);
BN_div(lambda_n, NULL, p1q1, gcd, bn_ctx);
BN_mod_inverse(true_d, e, lambda_n, bn_ctx);
BN_mod_inverse(true_iqmp, q, p, bn_ctx);
BN_mod(true_dmp1, true_d, p1, bn_ctx);
BN_mod(true_dmq1, true_d, q1, bn_ctx);
/* cleanup BN structs not managed by RSA internal functions */
BN_clear_free(gcd);
BN_clear_free(p1);
BN_clear_free(q1);
BN_clear_free(p1q1);
BN_clear_free(lambda_n);
BN_CTX_free(bn_ctx);
if (!RSA_set0_key(rsa_key, NULL, NULL, true_d)) {
fprintf(stderr, "setting d failed\n");
return 1;
}
if (!RSA_set0_crt_params(rsa_key, true_dmp1, true_dmq1, true_iqmp)) {
fprintf(stderr, "setting crt params failed\n");
return 1;
}
return 0;
}
#else
/* re-calculate the decryption key `d` for the given key
* the product of e and d must be congruent to 1, and since we are messing
* with e to generate our keys, we must re-calculate d */
int
key_update_d(RSA *rsa_key) {
BIGNUM *gcd = BN_new();
BIGNUM *p1 = BN_new();
BIGNUM *q1 = BN_new();
BIGNUM *p1q1 = BN_new();
BIGNUM *lambda_n = BN_new();
BIGNUM *true_d = BN_new();
BIGNUM *true_dmp1 = BN_new();
BIGNUM *true_dmq1 = BN_new();
BIGNUM *true_iqmp = BN_new();
BN_CTX *bn_ctx = BN_CTX_new();
if (!(bn_ctx && gcd && p1 && q1 && p1q1 && lambda_n && true_d &&
true_dmp1 && true_dmq1 && true_iqmp)) {
perror("bignum or bignum context allocation");
return 1;
}
/* calculate p-1 and q-1 and their product */
BN_sub(p1, rsa_key->p, BN_value_one());
BN_sub(q1, rsa_key->q, BN_value_one());
BN_mul(p1q1, p1, q1, bn_ctx);
/* calculate LCM of p1,q1 with p1*q1/gcd(p1,q1) */
BN_gcd(gcd, p1, q1, bn_ctx);
BN_div(lambda_n, NULL, p1q1, gcd, bn_ctx);
BN_mod_inverse(rsa_key->d, rsa_key->e, lambda_n, bn_ctx);
BN_mod_inverse(true_iqmp, rsa_key->q, rsa_key->p, bn_ctx);
BN_mod(rsa_key->dmp1, rsa_key->d, p1, bn_ctx);
BN_mod(rsa_key->dmq1, rsa_key->d, q1, bn_ctx);
/* cleanup BN structs not managed by RSA internal functions */
BN_clear_free(gcd);
BN_clear_free(p1);
BN_clear_free(q1);
BN_clear_free(p1q1);
BN_clear_free(lambda_n);
BN_CTX_free(bn_ctx);
return 0;
}
#endif
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