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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
/* HACK: we need the RSAPublicKey struct
* but RSA_verify conflits with openssl */
#define RSA_verify RSA_verify_mincrypt
#include "mincrypt/rsa.h"
#undef RSA_verify
#include <openssl/evp.h>
#include <openssl/objects.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>
#include <openssl/sha.h>
// 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;
}
static int write_public_keyfile(RSA *private_key, const char *private_key_path)
{
RSAPublicKey pkey;
BIO *bfile = NULL;
char *path = NULL;
int ret = -1;
if (asprintf(&path, "%s.pub", private_key_path) < 0)
goto out;
if (convert_to_mincrypt_format(private_key, &pkey) < 0)
goto out;
bfile = BIO_new_file(path, "w");
if (!bfile)
goto out;
BIO_write(bfile, &pkey, sizeof(pkey));
BIO_flush(bfile);
ret = 0;
out:
BIO_free_all(bfile);
free(path);
return ret;
}
static int generate_key(const char *file)
{
int ret = -1;
FILE *f = NULL;
RSA* rsa = RSA_new();
BIGNUM* exponent = BN_new();
EVP_PKEY* pkey = EVP_PKEY_new();
if (!pkey || !exponent || !rsa) {
printf("Failed to allocate key\n");
goto out;
}
BN_set_word(exponent, RSA_F4);
RSA_generate_key_ex(rsa, 2048, exponent, NULL);
EVP_PKEY_set1_RSA(pkey, rsa);
f = fopen(file, "w");
if (!f) {
printf("Failed to open '%s'\n", file);
goto out;
}
if (!PEM_write_PrivateKey(f, pkey, NULL, NULL, 0, NULL, NULL)) {
printf("Failed to write key\n");
goto out;
}
if (write_public_keyfile(rsa, file) < 0) {
printf("Failed to write public key\n");
goto out;
}
ret = 0;
out:
if (f)
fclose(f);
EVP_PKEY_free(pkey);
RSA_free(rsa);
BN_free(exponent);
return ret;
}
static void usage(){
printf("Usage: generate_verity_key <path-to-key>");
}
int main(int argc, char *argv[]) {
if (argc != 2) {
usage();
exit(-1);
}
return generate_key(argv[1]);
}
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