On Mon, 2018-01-29 at 08:43 +0100, Arne Schwabe wrote:
> 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 <[email protected]
> > om>
> >
> > ---
> >
> > 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.
I can call it anything you like, but the naming scheme in the file
seems to be <openssl structure>_<function>, like md_ctx_init() etc,
EVP_MD_CTX is the structure and init the function. Here UI is the
structure and read the function. Would you prefer UI_reader to match
the method set name?
> > +{
> > + 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.
It's used two lines below:
> >
> > + char password[64];
> > +
> > + cb(password, sizeof(password), 0, d);
Here -----------------------------^
If you mean it can be removed because the openssl password callback
data pointer is never used in the openvpn implementation then, yes,
that's true, but I think following the openssl standard practice is
better otherwise engine keys would break if someone ever found a future
openvpn use for the data pointer.
> > + 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.
Agreed, I'll make them crypto_msg() calls.
James
> >
> > + 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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