Am 26.01.18 um 21:30 schrieb James Bottomley:
> As well as doing crypto acceleration, engines can also be used to load
> key files.  If the engine is set, and the private key loading fails
> for bio methods, this patch makes openvpn try to get the engine to
> load the key.  If that succeeds, we end up using an engine based key.
> This can be used with the openssl tpm engines to make openvpn use a
> TPM wrapped key file.
> 
> Signed-off-by: James Bottomley <james.bottom...@hansenpartnership.com>
> 
> ---
> 
> v2: add better configuration guarding
> ---
>  src/openvpn/crypto_openssl.c | 55 
> ++++++++++++++++++++++++++++++++++++++++++++
>  src/openvpn/crypto_openssl.h | 12 ++++++++++
>  src/openvpn/ssl_openssl.c    |  6 ++++-
>  3 files changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
> index 20a519ec..d3f35030 100644
> --- a/src/openvpn/crypto_openssl.c
> +++ b/src/openvpn/crypto_openssl.c
> @@ -969,4 +969,59 @@ hmac_ctx_final(HMAC_CTX *ctx, uint8_t *dst)
>      HMAC_Final(ctx, dst, &in_hmac_len);
>  }
>  
> +#if HAVE_OPENSSL_ENGINE
> +static int
> +ui_read(UI *ui, UI_STRING *uis)

I would rather a bit more verbose method name here. ui_read seems a bit
too generic.

> +{
> +    SSL_CTX *ctx = UI_get0_user_data(ui);
> +
> +    if (UI_get_string_type(uis) == UIT_PROMPT) {
> +        pem_password_cb *cb = SSL_CTX_get_default_passwd_cb(ctx);
> +        void *d = SSL_CTX_get_default_passwd_cb_userdata(ctx);

This pointer is never used and the function also seem to have no side
effects. So seem like this can be removed.

> +        char password[64];
> +
> +        cb(password, sizeof(password), 0, d);
> +        UI_set_result(ui, uis, password);
> +
> +        return 1;
> +    }
> +    return 0;
> +}
> +#endif
> +
> +EVP_PKEY *
> +engine_load_key(const char *file, SSL_CTX *ctx)
> +{
> +#if HAVE_OPENSSL_ENGINE
> +    UI_METHOD *ui;
> +    EVP_PKEY *pkey;
> +
> +    if (!engine_persist)
> +        return NULL;
> +
> +    ui = UI_create_method("openvpn");
> +
> +    if (!ui)
> +        return NULL;
> +
> +    UI_method_set_reader(ui, ui_read);
> +
> +    ERR_clear_error();               /* BIO read failure */
> +    if (!ENGINE_init(engine_persist)) {
> +     ERR_print_errors_fp(stderr);

This should use our standard openssl error reporting. Not directly
writing to stderr.

> +     pkey = NULL;
> +     goto out;
> +    }
> +    pkey = ENGINE_load_private_key(engine_persist, file, ui, ctx);
> +    ENGINE_finish(engine_persist);
> +    if (!pkey)
> +     ERR_print_errors_fp(stderr);

Same as above.

> + out:
> +    UI_destroy_method(ui);
> +    return pkey;
> +#else
> +    return NULL;
> +#endif
> +}

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