| /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved. |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| /* C port of DumpPublicKey.java from the Android Open source project with |
| * support for additional RSA key sizes. (platform/system/core,git/libmincrypt |
| * /tools/DumpPublicKey.java). Uses the OpenSSL X509 and BIGNUM library. |
| */ |
| |
| #include <inttypes.h> |
| #include <openssl/bn.h> |
| #include <openssl/evp.h> |
| #include <openssl/pem.h> |
| #include <openssl/x509.h> |
| #include <string.h> |
| #include <unistd.h> |
| |
| /* Command line tool to extract RSA public keys from X.509 certificates |
| * and output a pre-processed version of keys for use by RSA verification |
| * routines. |
| */ |
| |
| int check(RSA* key) { |
| int public_exponent = BN_get_word(key->e); |
| int modulus = BN_num_bits(key->n); |
| |
| if (public_exponent != 65537) { |
| fprintf(stderr, "WARNING: Public exponent should be 65537 (but is %d).\n", |
| public_exponent); |
| } |
| |
| if (modulus != 1024 && modulus != 2048 && modulus != 4096 |
| && modulus != 8192) { |
| fprintf(stderr, "ERROR: Unknown modulus length = %d.\n", modulus); |
| return 0; |
| } |
| return 1; |
| } |
| |
| /* Pre-processes and outputs RSA public key to standard out. |
| */ |
| void output(RSA* key) { |
| int i, nwords; |
| BIGNUM *N = key->n; |
| BIGNUM *Big1 = NULL, *Big2 = NULL, *Big32 = NULL, *BigMinus1 = NULL; |
| BIGNUM *B = NULL; |
| BIGNUM *N0inv= NULL, *R = NULL, *RR = NULL, *RRTemp = NULL, *NnumBits = NULL; |
| BIGNUM *n = NULL, *rr = NULL; |
| BN_CTX *bn_ctx = BN_CTX_new(); |
| uint32_t n0invout; |
| |
| N = key->n; |
| /* Output size of RSA key in 32-bit words */ |
| nwords = BN_num_bits(N) / 32; |
| if (-1 == write(1, &nwords, sizeof(nwords))) |
| goto failure; |
| |
| |
| /* Initialize BIGNUMs */ |
| Big1 = BN_new(); |
| Big2 = BN_new(); |
| Big32 = BN_new(); |
| BigMinus1 = BN_new(); |
| N0inv= BN_new(); |
| R = BN_new(); |
| RR = BN_new(); |
| RRTemp = BN_new(); |
| NnumBits = BN_new(); |
| n = BN_new(); |
| rr = BN_new(); |
| |
| |
| BN_set_word(Big1, 1L); |
| BN_set_word(Big2, 2L); |
| BN_set_word(Big32, 32L); |
| BN_sub(BigMinus1, Big1, Big2); |
| |
| B = BN_new(); |
| BN_exp(B, Big2, Big32, bn_ctx); /* B = 2^32 */ |
| |
| /* Calculate and output N0inv = -1 / N[0] mod 2^32 */ |
| BN_mod_inverse(N0inv, N, B, bn_ctx); |
| BN_sub(N0inv, B, N0inv); |
| n0invout = BN_get_word(N0inv); |
| if (-1 == write(1, &n0invout, sizeof(n0invout))) |
| goto failure; |
| |
| /* Calculate R = 2^(# of key bits) */ |
| BN_set_word(NnumBits, BN_num_bits(N)); |
| BN_exp(R, Big2, NnumBits, bn_ctx); |
| |
| /* Calculate RR = R^2 mod N */ |
| BN_copy(RR, R); |
| BN_mul(RRTemp, RR, R, bn_ctx); |
| BN_mod(RR, RRTemp, N, bn_ctx); |
| |
| |
| /* Write out modulus as little endian array of integers. */ |
| for (i = 0; i < nwords; ++i) { |
| uint32_t nout; |
| |
| BN_mod(n, N, B, bn_ctx); /* n = N mod B */ |
| nout = BN_get_word(n); |
| if (-1 == write(1, &nout, sizeof(nout))) |
| goto failure; |
| |
| BN_rshift(N, N, 32); /* N = N/B */ |
| } |
| |
| /* Write R^2 as little endian array of integers. */ |
| for (i = 0; i < nwords; ++i) { |
| uint32_t rrout; |
| |
| BN_mod(rr, RR, B, bn_ctx); /* rr = RR mod B */ |
| rrout = BN_get_word(rr); |
| if (-1 == write(1, &rrout, sizeof(rrout))) |
| goto failure; |
| |
| BN_rshift(RR, RR, 32); /* RR = RR/B */ |
| } |
| |
| failure: |
| /* Free BIGNUMs. */ |
| BN_free(Big1); |
| BN_free(Big2); |
| BN_free(Big32); |
| BN_free(BigMinus1); |
| BN_free(N0inv); |
| BN_free(R); |
| BN_free(RRTemp); |
| BN_free(NnumBits); |
| BN_free(n); |
| BN_free(rr); |
| |
| } |
| |
| int main(int argc, char* argv[]) { |
| FILE* fp; |
| X509* cert = NULL; |
| RSA* pubkey = NULL; |
| EVP_PKEY* key; |
| |
| if (argc != 2) { |
| fprintf(stderr, "Usage: %s <certfile>\n", argv[0]); |
| return -1; |
| } |
| |
| fp = fopen(argv[1], "r"); |
| |
| if (!fp) { |
| fprintf(stderr, "Couldn't open certificate file!\n"); |
| return -1; |
| } |
| |
| /* Read the certificate */ |
| if (!PEM_read_X509(fp, &cert, NULL, NULL)) { |
| fprintf(stderr, "Couldn't read certificate.\n"); |
| goto fail; |
| } |
| |
| /* Get the public key from the certificate. */ |
| key = X509_get_pubkey(cert); |
| |
| /* Convert to a RSA_style key. */ |
| if (!(pubkey = EVP_PKEY_get1_RSA(key))) { |
| fprintf(stderr, "Couldn't convert to a RSA style key.\n"); |
| goto fail; |
| } |
| |
| if (check(pubkey)) { |
| output (pubkey); |
| } |
| |
| fail: |
| X509_free(cert); |
| RSA_free(pubkey); |
| fclose(fp); |
| |
| return 0; |
| } |