+// Convert OpenSSL RSA private key to android pre-computed RSAPublicKey format.
+// Lifted from secure adb's mincrypt key generation.
+static int convert_to_mincrypt_format(RSA *rsa, RSAPublicKey *pkey)
+{
+ int ret = -1;
+ unsigned int i;
+
+ if (RSA_size(rsa) != RSANUMBYTES)
+ goto out;
+
+ BN_CTX* ctx = BN_CTX_new();
+ BIGNUM* r32 = BN_new();
+ BIGNUM* rr = BN_new();
+ BIGNUM* r = BN_new();
+ BIGNUM* rem = BN_new();
+ BIGNUM* n = BN_new();
+ BIGNUM* n0inv = BN_new();
+
+ BN_set_bit(r32, 32);
+ BN_copy(n, rsa->n);
+ BN_set_bit(r, RSANUMWORDS * 32);
+ BN_mod_sqr(rr, r, n, ctx);
+ BN_div(NULL, rem, n, r32, ctx);
+ BN_mod_inverse(n0inv, rem, r32, ctx);
+
+ pkey->len = RSANUMWORDS;
+ pkey->n0inv = 0 - BN_get_word(n0inv);
+ for (i = 0; i < RSANUMWORDS; i++) {
+ BN_div(rr, rem, rr, r32, ctx);
+ pkey->rr[i] = BN_get_word(rem);
+ BN_div(n, rem, n, r32, ctx);
+ pkey->n[i] = BN_get_word(rem);
+ }
+ pkey->exponent = BN_get_word(rsa->e);
+
+ ret = 0;
+
+ BN_free(n0inv);
+ BN_free(n);
+ BN_free(rem);
+ BN_free(r);
+ BN_free(rr);
+ BN_free(r32);
+ BN_CTX_free(ctx);
+
+out:
+ return ret;
+}
+