dnssec: prevent duplicate PKCS11 module loading

src/dnssec/Makefile.am

@@ -129,6 +129,8 @@ libdnssec_la_SOURCES = \
 	lib/nsec/bitmap.c \
 	lib/nsec/hash.c \
 	lib/nsec/nsec.c \
+	lib/p11/p11.c \
+	lib/p11/p11.h \
 	lib/random.c \
 	lib/sign/der.c \
 	lib/sign/der.h \

src/dnssec/lib/crypto.c

@@ -18,6 +18,7 @@
 #include <gnutls/pkcs11.h>
 
 #include "crypto.h"
+#include "p11/p11.h"
 #include "shared.h"
 
 _public_
@@ -35,6 +36,7 @@ void dnssec_crypto_cleanup(void)
 	gnutls_global_deinit();
 #ifdef ENABLE_PKCS11
 	gnutls_pkcs11_deinit();
+	p11_cleanup();
 #endif
 }
 

src/dnssec/lib/dnssec/error.h

@@ -91,7 +91,11 @@ enum dnssec_error {
 
 	DNSSEC_KEYSTORE_INVALID_BACKEND,
 	DNSSEC_KEYSTORE_INVALID_CONFIG,
-	DNSSEC_KEYSTORE_FAILED_TO_LOAD_P11_MODULE,
+
+	DNSSEC_P11_INVALID_CONFIG,
+	DNSSEC_P11_FAILED_TO_LOAD_MODULE,
+	DNSSEC_P11_TOO_MANY_MODULES,
+	DNSSEC_P11_TOKEN_NOT_AVAILABLE,
 
 	DNSSEC_ERROR_MAX = -1001
 };

src/dnssec/lib/error.c

@@ -68,7 +68,11 @@ static const error_message_t ERROR_MESSAGES[] = {
 
 	{ DNSSEC_KEYSTORE_INVALID_BACKEND, "invalid KASP keystore backend" },
 	{ DNSSEC_KEYSTORE_INVALID_CONFIG,  "invalid KASP keystore configuration" },
-	{ DNSSEC_KEYSTORE_FAILED_TO_LOAD_P11_MODULE, "failed to load PKCS #11 module" },
+
+	{ DNSSEC_P11_INVALID_CONFIG,        "invalid PKCS #11 configuration" },
+	{ DNSSEC_P11_FAILED_TO_LOAD_MODULE, "failed to load PKCS #11 module" },
+	{ DNSSEC_P11_TOO_MANY_MODULES,      "too many PKCS #11 modules loaded" },
+	{ DNSSEC_P11_TOKEN_NOT_AVAILABLE,   "PKCS #11 token not available" },
 
 	{ 0 }
 };

src/dnssec/lib/keystore/pkcs11.c

@@ -23,6 +23,7 @@
 #include "keyid_gnutls.h"
 #include "keystore.h"
 #include "keystore/internal.h"
+#include "p11/p11.h"
 #include "pem.h"
 #include "shared.h"
 
@@ -119,18 +120,18 @@ static int safe_open(const char *config, char **url_ptr)
 		return r;
 	}
 
-	r = gnutls_pkcs11_add_provider(module, NULL);
+	r = p11_load_module(module);
 	free(module);
 	if (r != GNUTLS_E_SUCCESS) {
 		free(url);
-		return DNSSEC_KEYSTORE_FAILED_TO_LOAD_P11_MODULE;
+		return DNSSEC_P11_FAILED_TO_LOAD_MODULE;
 	}
 
 	unsigned int flags = 0;
 	r = gnutls_pkcs11_token_get_flags(url, &flags);
 	if (r != GNUTLS_E_SUCCESS) {
 		free(url);
-		return DNSSEC_KEYSTORE_FAILED_TO_LOAD_P11_MODULE;
+		return DNSSEC_P11_TOKEN_NOT_AVAILABLE;
 	}
 
 	*url_ptr = url;
@@ -241,7 +242,7 @@ static int pkcs11_list_keys(void *_ctx, dnssec_list_t **list)
 	int r = gnutls_pkcs11_obj_list_import_url4(&objects, &count, ctx->url, flags);
 	if (r != GNUTLS_E_SUCCESS) {
 		dnssec_list_free(ids);
-		return DNSSEC_ERROR; // TODO
+		return DNSSEC_P11_TOKEN_NOT_AVAILABLE;
 	}
 
 	for (unsigned i = 0; i < count; i++) {

src/dnssec/lib/p11/p11.c

+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "p11/p11.h"
+#include "error.h"
+
+#include <assert.h>
+#include <gnutls/pkcs11.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define PKCS11_MODULES_MAX 16
+
+static char *pkcs11_modules[PKCS11_MODULES_MAX] = { 0 };
+static int pkcs11_modules_count = 0;
+
+int p11_load_module(const char *module)
+{
+	for (int i = 0; i < pkcs11_modules_count; i++) {
+		if (strcmp(pkcs11_modules[i], module) == 0) {
+			return DNSSEC_EOK;
+		}
+	}
+
+	assert(pkcs11_modules_count <= PKCS11_MODULES_MAX);
+	if (pkcs11_modules_count == PKCS11_MODULES_MAX) {
+		return DNSSEC_P11_TOO_MANY_MODULES;
+	}
+
+	char *copy = strdup(module);
+	if (!copy) {
+		return DNSSEC_ENOMEM;
+	}
+
+	int r = gnutls_pkcs11_add_provider(module, NULL);
+	if (r != GNUTLS_E_SUCCESS) {
+		free(copy);
+		return DNSSEC_P11_FAILED_TO_LOAD_MODULE;
+	}
+
+	pkcs11_modules[pkcs11_modules_count] = copy;
+	pkcs11_modules_count += 1;
+
+	return DNSSEC_EOK;
+}
+
+void p11_cleanup(void)
+{
+	for (int i = 0; i < pkcs11_modules_count; i++) {
+		free(pkcs11_modules[i]);
+		pkcs11_modules[i] = NULL;
+	}
+
+	pkcs11_modules_count = 0;
+}

src/dnssec/lib/p11/p11.h

+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+/*!
+ * Load PKCS11 module unless the module was already loaded.
+ *
+ * Duplicates are detected based on the module path.
+ */
+int p11_load_module(const char *name);
+
+/*!
+ * Clenaup list of loaded modules.
+ *
+ * Should be called when the library is deinitialized to prevent memory leaks.
+ */
+void p11_cleanup(void);