236 lines
7.0 KiB
C
236 lines
7.0 KiB
C
//
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// rsa.c
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// c-libp2p
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//
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// Created by John Jones on 11/3/16.
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// Copyright © 2016 JMJAtlanta. All rights reserved.
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//
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#include <stdio.h>
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#include <string.h>
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#include "libp2p/crypto/rsa.h"
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// mbedtls stuff
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#include "mbedtls/config.h"
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#include "mbedtls/platform.h"
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#include "mbedtls/entropy.h"
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#include "mbedtls/ctr_drbg.h"
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#include "mbedtls/bignum.h"
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#include "mbedtls/x509.h"
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#include "mbedtls/rsa.h"
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#include "mbedtls/asn1write.h"
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#include "mbedtls/oid.h"
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#include "mbedtls/pk.h"
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/**
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* Take an rsa context and turn it into a der formatted byte stream.
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* NOTE: the stream starts from the right. So there could be a lot of padding in front.
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* Pay attention to the returned size to cut the padding.
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* @param rsa the rsa key to encode
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* @param buf where to put the bytes
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* @param size the max size of the buffer. The actual size used is returned in this value
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* @returns true(1) on success, else 0
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*/
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int libp2p_crypto_rsa_write_private_key_der( mbedtls_rsa_context *rsa, unsigned char *buf, size_t* size )
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{
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int ret;
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unsigned char *c = buf + *size;
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size_t len = 0;
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->QP ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->DQ ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->DP ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->Q ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->P ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->D ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->E ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &rsa->N ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
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MBEDTLS_ASN1_SEQUENCE ) );
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*size = len;
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return 1;
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}
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/**
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* Take a context and turn it into a der formatted byte stream.
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* @param key the key
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* @param buf the buffer to be filled
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* @param size the max size of the buffer. The actual size used is returned in this value
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* @returns true(1) on success, else false(0)
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*/
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int libp2p_crypto_rsa_write_public_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t* size )
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{
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int ret;
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unsigned char *c;
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size_t len = 0, par_len = 0, oid_len;
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const char *oid;
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c = buf + *size;
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) );
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if( c - buf < 1 ) // buffer is too small
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return 0;
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/*
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* SubjectPublicKeyInfo ::= SEQUENCE {
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* algorithm AlgorithmIdentifier,
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* subjectPublicKey BIT STRING }
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*/
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*--c = 0;
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len += 1;
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
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if( ( ret = mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_get_type( key ),
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&oid, &oid_len ) ) != 0 )
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{
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return 0;
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}
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, buf, oid, oid_len,
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par_len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
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MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
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MBEDTLS_ASN1_SEQUENCE ) );
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*size = len;
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return 1;
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}
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/***
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* Generate an RSA keypair of a certain size, and place the results in the struct
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* @param private_key where to put the results
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* @param num_bits_for_keypair the number of bits for the key, 1024 is the minimum
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* @returns true(1) on success
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*/
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int libp2p_crypto_rsa_generate_keypair(struct RsaPrivateKey* private_key, unsigned long num_bits_for_keypair) {
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mbedtls_rsa_context rsa;
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mbedtls_entropy_context entropy;
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mbedtls_ctr_drbg_context ctr_drbg;
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int exponent = 65537;
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int retVal = 1;
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unsigned char* buffer;
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const char *pers = "rsa_genkey";
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// initialize mbedtls structs
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mbedtls_ctr_drbg_init( &ctr_drbg );
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mbedtls_entropy_init( &entropy );
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// seed the routines
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if( ( retVal = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
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(const unsigned char *) pers,
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strlen( pers ) ) ) != 0 )
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{
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retVal = 0;
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goto exit;
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}
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// initialize the rsa struct
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mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
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// finally, generate the key
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if( ( retVal = mbedtls_rsa_gen_key( &rsa, mbedtls_ctr_drbg_random, &ctr_drbg, (unsigned int)num_bits_for_keypair,
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exponent ) ) != 0 )
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{
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retVal = 0;
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goto exit;
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}
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retVal = 1;
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// fill in values of structures
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private_key->D = *(rsa.D.p);
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private_key->DP = *(rsa.DP.p);
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private_key->DQ = *(rsa.DQ.p);
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private_key->E = *(rsa.E.p);
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private_key->N = *(rsa.N.p);
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private_key->P = *(rsa.P.p);
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private_key->Q = *(rsa.Q.p);
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private_key->QP = *(rsa.QP.p);
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size_t buffer_size = 1600;
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buffer = malloc(sizeof(char) * buffer_size);
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retVal = libp2p_crypto_rsa_write_private_key_der(&rsa, buffer, &buffer_size);
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if (retVal == 0)
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return 0;
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// allocate memory for the private key der
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private_key->der_length = buffer_size;
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private_key->der = malloc(sizeof(char) * buffer_size);
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// add in the der to the buffer
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memcpy(private_key->der, &buffer[1600-buffer_size], buffer_size);
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exit:
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if (buffer != NULL)
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free(buffer);
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mbedtls_rsa_free( &rsa );
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mbedtls_ctr_drbg_free( &ctr_drbg );
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mbedtls_entropy_free( &entropy );
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if (retVal != 0) {
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// now do the public key.
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retVal = libp2p_crypto_rsa_private_key_fill_public_key(private_key);
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}
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return retVal;
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}
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/**
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* Use the private key DER to fill in the public key DER
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* @param private_key the private key to use
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* @reutrns true(1) on success
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*/
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int libp2p_crypto_rsa_private_key_fill_public_key(struct RsaPrivateKey* private_key) {
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// first build the rsa context
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mbedtls_pk_context ctx;
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mbedtls_pk_init(&ctx);
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mbedtls_pk_parse_key(&ctx, private_key->der, private_key->der_length, NULL, 0);
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// buffer
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size_t buffer_size = 1600;
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unsigned char buffer[buffer_size];
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memset(buffer, 0, buffer_size);
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// generate public key der
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int retVal = libp2p_crypto_rsa_write_public_key_der(&ctx, buffer, &buffer_size);
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if (retVal == 0) {
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mbedtls_pk_free(&ctx);
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return 0;
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}
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// allocate memory for the public key der
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private_key->public_key_length = buffer_size;
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private_key->public_key_der = malloc(sizeof(char) * buffer_size);
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//copy it into the struct
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memcpy(private_key->public_key_der, &buffer[1600-buffer_size], buffer_size);
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mbedtls_pk_free(&ctx);
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return 1;
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}
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/***
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* Free resources used by RsaPrivateKey
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* @param private_key the resources
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* @returns true(1)
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*/
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int libp2p_crypto_rsa_rsa_private_key_free(struct RsaPrivateKey* private_key) {
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if (private_key->der != NULL)
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free(private_key->der);
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if (private_key->public_key_der != NULL)
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free(private_key->public_key_der);
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return 1;
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}
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