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openssl: add engine method for loading the key

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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.Bottomley@HansenPartnership.com>

Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20200528225920.6983-2-James.Bottomley@HansenPartnership.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19937.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
This commit is contained in:
James Bottomley 2020-05-28 15:59:18 -07:00 committed by Gert Doering
parent 7d65aad897
commit 8155f8aa0a
3 changed files with 73 additions and 0 deletions
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56
src/openvpn/crypto_openssl.c
View File

@ -63,6 +63,7 @@
#endif
#if HAVE_OPENSSL_ENGINE
#include <openssl/ui.h>
#include <openssl/engine.h>
static bool engine_initialized = false; /* GLOBAL */
@ -1070,4 +1071,59 @@ memcmp_constant_time(const void *a, const void *b, size_t size)
{
return CRYPTO_memcmp(a, b, size);
}
#if HAVE_OPENSSL_ENGINE
static int
ui_reader(UI *ui, UI_STRING *uis)
{
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);
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;
/* this will print out the error from BIO_read */
crypto_msg(M_INFO, "PEM_read_bio failed, now trying engine method to load private key");
ui = UI_create_method("openvpn");
if (!ui) {
crypto_msg(M_FATAL, "Engine UI creation failed");
return NULL;
}
UI_method_set_reader(ui, ui_reader);
ENGINE_init(engine_persist);
pkey = ENGINE_load_private_key(engine_persist, file, ui, ctx);
ENGINE_finish(engine_persist);
if (!pkey)
crypto_msg(M_FATAL, "Engine could not load key file");
UI_destroy_method(ui);
return pkey;
#else
return NULL;
#endif
}
#endif /* ENABLE_CRYPTO_OPENSSL */

12
src/openvpn/crypto_openssl.h
View File

@ -107,4 +107,16 @@ cipher_kt_var_key_size(const cipher_kt_t *cipher)
return EVP_CIPHER_flags(cipher) & EVP_CIPH_VARIABLE_LENGTH;
}
/**
* Load a key file from an engine
*
* @param file The engine file to load
* @param ui The UI method for the password prompt
* @param data The data to pass to the UI method
*
* @return The private key if successful or NULL if not
*/
EVP_PKEY *
engine_load_key(const char *file, SSL_CTX *ctx);
#endif /* CRYPTO_OPENSSL_H_ */

5
src/openvpn/ssl_openssl.c
View File

@ -1020,6 +1020,11 @@ tls_ctx_load_priv_file(struct tls_root_ctx *ctx, const char *priv_key_file,
pkey = PEM_read_bio_PrivateKey(in, NULL,
SSL_CTX_get_default_passwd_cb(ctx->ctx),
SSL_CTX_get_default_passwd_cb_userdata(ctx->ctx));
if (!pkey)
{
pkey = engine_load_key(priv_key_file, ctx->ctx);
}
if (!pkey || !SSL_CTX_use_PrivateKey(ssl_ctx, pkey))
{
#ifdef ENABLE_MANAGEMENT