Implemented permanent certificate coupling plugin

src/libcharon/plugins/coupling/coupling_validator.c

@@ -0,0 +1,258 @@
+/*
+ * Copyright (C) 2011 Martin Willi
+ * Copyright (C) 2011 revosec AG
+ *
+ * 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 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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.
+ */
+
+#include "coupling_validator.h"
+
+#include <errno.h>
+#include <time.h>
+
+#include <daemon.h>
+#include <threading/mutex.h>
+
+/* buffer size for hex-encoded hash */
+#define MAX_HASH_SIZE (HASH_SIZE_SHA512 * 2 + 1)
+
+typedef struct private_coupling_validator_t private_coupling_validator_t;
+
+/**
+ * Private data of an coupling_validator_t object.
+ */
+struct private_coupling_validator_t {
+
+	/**
+	 * Public coupling_validator_t interface.
+	 */
+	coupling_validator_t public;
+
+	/**
+	 * Mutex
+	 */
+	mutex_t *mutex;
+
+	/**
+	 * File with device couplings
+	 */
+	FILE *f;
+
+	/**
+	 * Hasher to create hashes
+	 */
+	hasher_t *hasher;
+
+	/**
+	 * maximum number of couplings
+	 */
+	int max_couplings;
+};
+
+/**
+ * Get hash of a certificate
+ */
+static bool get_cert_hash(private_coupling_validator_t *this,
+						  certificate_t *cert, char *hex)
+{
+	char buf[MAX_HASH_SIZE];
+	chunk_t encoding;
+
+	if (!cert->get_encoding(cert, CERT_ASN1_DER, &encoding))
+	{
+		return FALSE;
+	}
+	this->hasher->get_hash(this->hasher, encoding, buf);
+	free(encoding.ptr);
+	chunk_to_hex(chunk_create(buf, this->hasher->get_hash_size(this->hasher)),
+				 hex, FALSE);
+	return TRUE;
+}
+
+/**
+ * Check if we have an entry for a given hash
+ */
+static bool has_entry(private_coupling_validator_t *this, char *hash)
+{
+	char line[256];
+	int hash_len;
+
+	hash_len = strlen(hash);
+	rewind(this->f);
+
+	while (fgets(line, sizeof(line), this->f))
+	{
+		if (strlen(line) >= hash_len &&
+			strncaseeq(line, hash, hash_len))
+		{
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+/**
+ * Get the number of coupling entries we currently have
+ */
+static int get_number_of_entries(private_coupling_validator_t *this)
+{
+	char line[256];
+	int count = 0;
+
+	rewind(this->f);
+
+	while (fgets(line, sizeof(line), this->f))
+	{
+		/* valid entries start with hex encoded hash */
+		if (strchr("1234567890abcdefABCDEF", line[0]))
+		{
+			count++;
+		}
+	}
+	return count;
+}
+
+/**
+ * Add a new entry to the file
+ */
+static bool add_entry(private_coupling_validator_t *this, char *hash,
+					  identification_t *id)
+{
+	return fseek(this->f, 0, SEEK_END) == 0 &&
+		   fprintf(this->f, "%s %u '%Y'\n", hash, time(NULL), id) > 0;
+}
+
+METHOD(cert_validator_t, validate, bool,
+	private_coupling_validator_t *this,
+	certificate_t *subject, certificate_t *issuer,
+	bool online, u_int pathlen, bool anchor, auth_cfg_t *auth)
+{
+	bool valid = FALSE;
+	char hash[MAX_HASH_SIZE];
+
+	if (pathlen != 0)
+	{
+		return TRUE;
+	}
+	if (get_cert_hash(this, subject, hash))
+	{
+		this->mutex->lock(this->mutex);
+		if (has_entry(this, hash))
+		{
+			DBG1(DBG_CFG, "coupled certificate '%Y' found, accepted",
+				 subject->get_subject(subject));
+			valid = TRUE;
+		}
+		else if (get_number_of_entries(this) < this->max_couplings)
+		{
+			if (add_entry(this, hash, subject->get_subject(subject)))
+			{
+				DBG1(DBG_CFG, "coupled new certificate '%Y'",
+					 subject->get_subject(subject));
+				valid = TRUE;
+			}
+			else
+			{
+				DBG1(DBG_CFG, "coupling new certificate '%Y' failed",
+					 subject->get_subject(subject));
+			}
+		}
+		else
+		{
+			DBG1(DBG_CFG, "coupling new certificate '%Y' failed, limit of %d "
+				 "couplings reached", subject->get_subject(subject),
+				 this->max_couplings);
+		}
+		this->mutex->unlock(this->mutex);
+	}
+	return valid;
+}
+
+METHOD(coupling_validator_t, destroy, void,
+	private_coupling_validator_t *this)
+{
+	if (this->f)
+	{
+		fclose(this->f);
+	}
+	DESTROY_IF(this->hasher);
+	this->mutex->destroy(this->mutex);
+	free(this);
+}
+
+/**
+ * See header
+ */
+coupling_validator_t *coupling_validator_create()
+{
+	private_coupling_validator_t *this;
+	char *path, *hash;
+	int i;
+	struct {
+		hash_algorithm_t alg;
+		char *name;
+	} hash_types[] = {
+		{ HASH_MD5,		"md5"},
+		{ HASH_SHA1,	"sha1"},
+		{ HASH_SHA256,	"sha256"},
+		{ HASH_SHA384,	"sha384"},
+		{ HASH_SHA512,	"sha512"},
+	};
+
+	INIT(this,
+		.public = {
+			.validator = {
+				.validate = _validate,
+			},
+			.destroy = _destroy,
+		},
+		.mutex = mutex_create(MUTEX_TYPE_DEFAULT),
+		.max_couplings = lib->settings->get_int(lib->settings,
+									  "charon.plugins.coupling.max", 1),
+	);
+
+	hash = lib->settings->get_str(lib->settings,
+								  "charon.plugins.coupling.hash", "sha1");
+	for (i = 0; i < countof(hash_types); i++)
+	{
+		if (strcaseeq(hash_types[i].name, hash))
+		{
+			this->hasher = lib->crypto->create_hasher(lib->crypto,
+													  hash_types[i].alg);
+			break;
+		}
+	}
+	if (!this->hasher)
+	{
+		DBG1(DBG_CFG, "unsupported coupling hash algorithm: %s", hash);
+		destroy(this);
+		return NULL;
+	}
+
+	path = lib->settings->get_str(lib->settings,
+								  "charon.plugins.coupling.file", NULL);
+	if (!path)
+	{
+		DBG1(DBG_CFG, "coupling file path unspecified");
+		destroy(this);
+		return NULL;
+	}
+	this->f = fopen(path, "a+");
+	if (!this->f)
+	{
+		DBG1(DBG_CFG, "opening coupling file '%s' failed: %s",
+			 path, strerror(errno));
+		destroy(this);
+		return NULL;
+	}
+	setlinebuf(this->f);
+	return &this->public;
+}