domainkey.h

来自「MiniSip Client with DomainKeys Authentic」· C头文件 代码 · 共 307 行

#ifndef DOMAINKEY_H_
#define DOMAINKEY_H_

#include <libmcrypto/config.h>
#include <openssl/pem.h>
#include <openssl/evp.h>
#include <libmutil/Exception.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <libmcrypto/OpenSSLUtil.h>
#include <iostream>
#include <fstream>
#include <string>
#include <list>

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <dirent.h>


/**
 * This class represents a DomainKey (RSA Public Key).
 * According to the standard (RFC XXXX) the public keys are stored as a txt-record on a dns server. Once the key is fetched, it will be cached locally.
 * The implementation of this class referes to the openssl library. For querying the dns server, libresolv is used, too.
 */
class LIBMCRYPTO_API DomainKey{
	public:
		/**
		 * The constructor creates a new domain key.
		 * In this case, the local cache is checked for the corresponding key. If the key does not exist, the dns server is queried for the key.
		 * @param sipuri A String representing the SIP-URI of the desired domain key. i.e. [e-mail]
		 */
		DomainKey(std::string sipuri);	
		
		/**
		 * Destructor for the domain key.
		 */
		~DomainKey();
		
		/**
		 * This method verifies the signature of a data block.
		 * The verification process is implemented with the openssl functions.
		 * @param data byte_t array with the data
		 * @param dataLength The length of the data
		 * @param signature byte_t array with the signature
		 * @param signatureLength The length of the signatur
		 * @return boolean value which indicates if the verification is ok or not
		 */
		bool verify(byte_t* data, unsigned int dataLength, byte_t* signature, unsigned int signatureLength);

		/**
		 * Static method to delete a specific cache entry in the cache folder
		 * @param sipuri A String representing the SIP-URI of the domainkey to be deleted.
		 */
		static void deleteCacheEntry(std::string sipuri);
		
		/**
		 * This static method deletes all cached domainkeys in the cache directory.
		 */
		static void deleteCacheEntries();

		/**
		 * All cache entries will be listed by their SIP-URI 
		 * @return List of strings representing the SIP-URIs of the cached domainkeys.
		 */
		static std::list<std::string> listCacheEntries();

		/**
		 * Path to the cache directory
		 */
		static const std::string CACHE_DIR;
		
	private:
		/**
		 * openssl public key.
		 */
		EVP_PKEY* publicKey;

		/**
		 * This method checks if the desired domainkey is already chached.
		 * The filename is derived from the SIP-URI: [e-mail] --> foo._domainkey.bar.com --> foo._domainkey.bar.com.pem
		 * @param filename Filename (whole path)
		 * @return boolean value if the cache entry exists
		 */
		bool checkPublicKeyFile(std::string filename);

		/**
		 * Loads the cached domainkey (public key) from a local file.
		 * The filename is derived from the SIP-URI: [e-mail] --> foo._domainkey.bar.com --> foo._domainkey.bar.com.pem
 		 * @param filename Filename (whole path)
		 * @return boolean value if loading was successful
		 */
		bool loadPublicKeyFromFile(std::string filename);

		/**
		 * Saves the public key into the local cache.
		 * The filename is derived from the SIP-URI: [e-mail] --> foo._domainkey.bar.com --> foo._domainkey.bar.com.pem
		 * @param filename Filename (whole path)
		 */
		void savePublicKeyFile(std::string filename);

		/**
		 * This method queries the corresponding dns-server to get the public key.
		 * For querying the dns-server res_query() from libresolv is used.
		 * The answer of the dns-server has the following format according to RFC 1035:
		 * 
		 *     +---------------------+
		 *     |        Header       |
		 *     +---------------------+
		 *     |       Question      | the question for the name server
		 *     +---------------------+
		 *     |        Answer       | RRs answering the question
		 *     +---------------------+
		 *     |      Authority      | RRs pointing toward an authority
		 *     +---------------------+
		 *     |      Additional     | RRs holding additional information
		 *     +---------------------+
		 * 
		 * The header contains the following fields:
		 * 
		 *                                     1  1  1  1  1  1
		 *       0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                      ID                       |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                    QDCOUNT                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                    ANCOUNT                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                    NSCOUNT                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                    ARCOUNT                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 * 
		 * 
		 * Question section format:
		 * 
		 *                                     1  1  1  1  1  1
		 *       0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                                               |
		 *     /                     QNAME                     /
		 *     /                                               /
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                     QTYPE                     |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                     QCLASS                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 * 
		 * where:
		 * 
		 * QNAME           a domain name represented as a sequence of labels, where
		 *                 each label consists of a length octet followed by that
		 *                 number of octets.  The domain name terminates with the
		 *                 zero length octet for the null label of the root.  Note
		 *                 that this field may be an odd number of octets; no
		 *                 padding is used.
		 * 
		 * QTYPE           a two octet code which specifies the type of the query.
		 *                 The values for this field include all codes valid for a
		 *                 TYPE field, together with some more general codes which
		 *                 can match more than one type of RR.
		 * 
		 * QCLASS          a two octet code that specifies the class of the query.
		 *                 For example, the QCLASS field is IN for the Internet.
		 * 
		 * 
		 * Resource record format:
		 * 
		 *                                     1  1  1  1  1  1
		 *       0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                                               |
		 *     /                                               /
		 *     /                      NAME                     /
		 *     |                                               |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                      TYPE                     |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                     CLASS                     |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                      TTL                      |
		 *     |                                               |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 *     |                   RDLENGTH                    |
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
		 *     /                     RDATA                     /
		 *     /                                               /
		 *     +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
		 * 
		 * where:
		 * 
		 * NAME            a domain name to which this resource record pertains.
		 * 
		 * TYPE            two octets containing one of the RR type codes.  This
		 *                 field specifies the meaning of the data in the RDATA
		 *                 field.
		 * 
		 * CLASS           two octets which specify the class of the data in the
		 *                 RDATA field.
		 * 
		 * TTL             a 32 bit unsigned integer that specifies the time
		 *                 interval (in seconds) that the resource record may be
		 *                 cached before it should be discarded.  Zero values are
		 *                 interpreted to mean that the RR can only be used for the
		 *                 transaction in progress, and should not be cached.
		 * 
		 * RDLENGTH        an unsigned 16 bit integer that specifies the length in
		 *                 octets of the RDATA field.
		 * 
		 * RDATA           a variable length string of octets that describes the
		 *                 resource.  The format of this information varies
		 *                 according to the TYPE and CLASS of the resource record.
		 *                 For example, the if the TYPE is A and the CLASS is IN,
		 *                 the RDATA field is a 4 octet ARPA Internet address.
		 * 
		 * 
		 * @param sipuri A String representing the SIP-URI 
		 */
		void fetchPublicKey(std::string sipuri);

		/**
		 * Converts the SIP-URI to the DNS-URL.
		 * The DNS-URL is derived from the SIP-URI: [e-mail] --> foo._domainkey.bar.com 
		 * @param sipuri A String representing the SIP-URI 
		 * @return String representing the DNS-URL
		 */
		static std::string getDNSURL(std::string sipuri);
		
		/**
		 * Converts the DNS-URL back to the SIP-URI
		 * The SIP-URI is derived from the DNS-URL: foo._domainkey.bar.com --> [e-mail]
		 * @param dnsurl A String representing the DNS-URL
		 * @return String representing the SIP-URI
		 */ 
		static std::string getSipURI(std::string dnsurl);
		
		/**
		 * This method extracts the qname of the question section of the dns answer.
		 * 
		 *                                   1  1  1  1  1  1
	     *     0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
	     *   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	     *   |                                               |
	     *   /                     QNAME                     /
	     *   /                                               /
	     *   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	     *   |                     QTYPE                     |
	     *   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	     *   |                     QCLASS                    |
	     *   +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	     *   
	     *   where:
	     *   
	     *   QNAME           a domain name represented as a sequence of labels, where
	     *                   each label consists of a length octet followed by that
	     *                   number of octets.  The domain name terminates with the
	     *                   zero length octet for the null label of the root.  Note
	     *                   that this field may be an odd number of octets; no
	     *                   padding is used.
	     * 
		 * @param answer char array representing the dns answer
		 * @param index index of the beginning of qname
		 * @param qname_string Is a string in which the qname is stored
		 * @return The length of the qname (bytes used in the answer)
		 */
		int extractLabel(unsigned char * answer, int index, std::string& qname_string);
		
		/**
		 * Extracts the public key from the answer txt record.
		 * The public key is being extracted from the txt record. This extracted string is going the be formated as follows:
		 * - "-----BEGIN PUBLIC KEY-----\n" is inserted before the key
		 * - "\n-----END PUBLIC KEY-----" is inserted after the key
		 * - after every 64 byte a new line is inserted
		 * 
		 * @param answer_txt String representing the txt record.
		 * @return public key in openssl format
		 */
		EVP_PKEY* extractPublicKey(std::string answer_txt);

		/**
		 * This method checks if the cache directory exists for storing the files.
		 * If the directory does not exist, it will be created
		 */
		void checkCacheDirectory();
};

class LIBMCRYPTO_API DomainKeyException : public Exception{
	public:
		/**
		 * DomainKey exception representing an exception withing the domain key.
		 * @param desc Description of the exception
		 */
		DomainKeyException( const char *desc):Exception(desc){};
};

#endif /*DOMAINKEY_H_*/