Mbed TLS中关于密钥的处理

使用过程中，我们可能会需要直接从二进制格式得到所需要的密钥。

int binary_pk_get_public_key( mbedtls_pk_context *ctx, const unsigned char *pModulus, const unsigned char *pPublicExponent)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t n;
    mbedtls_rsa_context *pRSAKey;

    PK_VALIDATE_RET( ctx != NULL );

    mbedtls_pk_type_t pk_alg = MBEDTLS_PK_RSA;
    const mbedtls_pk_info_t *pk_info;

    if( ( pk_info = mbedtls_pk_info_from_type( pk_alg ) ) == NULL )
        return( MBEDTLS_ERR_PK_UNKNOWN_PK_ALG );

    if( ( ret = mbedtls_pk_setup( ctx, pk_info ) ) != 0 ) /* this will alloc the memory */
        return( ret );

    pRSAKey = ctx->pk_ctx; /* manipulate the underlying key as RSA key */
    pRSAKey->ver = 0; /* hard-coded */
    pRSAKey->len = 256; /* hard-coded */

    ret = mbedtls_mpi_read_binary( &pRSAKey->N, pModulus, 257); /* please refer to public key format. */
    ret = mbedtls_mpi_read_binary( &pRSAKey->E, pPublicExponent, 3); /* please refer to public key format. */

    memcpy(&g_TestRSAKey, ctx->pk_ctx, sizeof(g_TestRSAKey)); //xxx debug-purpose only.

    return( ret );
}

参考资料：《OpenSSL与网络信息安全》 王海志 编著 清华大学出版社 北京交通大学出版社

https://tls.mbed.org/