## # Geniwrapper uses two crypto libraries: pyOpenSSL and M2Crypto to implement # the necessary crypto functionality. Ideally just one of these libraries # would be used, but unfortunately each of these libraries is independently # lacking. The pyOpenSSL library is missing many necessary functions, and # the M2Crypto library has crashed inside of some of the functions. The # design decision is to use pyOpenSSL whenever possible as it seems more # stable, and only use M2Crypto for those functions that are not possible # in pyOpenSSL. # # This module exports two classes: Keypair and Certificate. ## # ### $Id$ ### $URL$ # import os import tempfile import base64 from OpenSSL import crypto import M2Crypto from M2Crypto import X509 from M2Crypto import EVP from sfa.util.faults import * def convert_public_key(key): keyconvert_path = "/usr/share/keyconvert/keyconvert" if not os.path.isfile(keyconvert_path): raise IOError, "Could not find keyconvert in %s" % keyconvert_path # we can only convert rsa keys if "ssh-dss" in key: print "XXX: DSA key encountered, ignoring" return None (ssh_f, ssh_fn) = tempfile.mkstemp() ssl_fn = tempfile.mktemp() os.write(ssh_f, key) os.close(ssh_f) cmd = keyconvert_path + " " + ssh_fn + " " + ssl_fn os.system(cmd) # this check leaves the temporary file containing the public key so # that it can be expected to see why it failed. # TODO: for production, cleanup the temporary files if not os.path.exists(ssl_fn): report.trace(" failed to convert key from " + ssh_fn + " to " + ssl_fn) return None k = Keypair() try: k.load_pubkey_from_file(ssl_fn) except: print "XXX: Error while converting key: ", key_str k = None # remove the temporary files os.remove(ssh_fn) os.remove(ssl_fn) return k ## # Public-private key pairs are implemented by the Keypair class. # A Keypair object may represent both a public and private key pair, or it # may represent only a public key (this usage is consistent with OpenSSL). class Keypair: key = None # public/private keypair m2key = None # public key (m2crypto format) ## # Creates a Keypair object # @param create If create==True, creates a new public/private key and # stores it in the object # @param string If string!=None, load the keypair from the string (PEM) # @param filename If filename!=None, load the keypair from the file def __init__(self, create=False, string=None, filename=None): if create: self.create() if string: self.load_from_string(string) if filename: self.load_from_file(filename) ## # Create a RSA public/private key pair and store it inside the keypair object def create(self): self.key = crypto.PKey() self.key.generate_key(crypto.TYPE_RSA, 1024) ## # Save the private key to a file # @param filename name of file to store the keypair in def save_to_file(self, filename): open(filename, 'w').write(self.as_pem()) ## # Load the private key from a file. Implicity the private key includes the public key. def load_from_file(self, filename): buffer = open(filename, 'r').read() self.load_from_string(buffer) ## # Load the private key from a string. Implicitly the private key includes the public key. def load_from_string(self, string): self.key = crypto.load_privatekey(crypto.FILETYPE_PEM, string) self.m2key = M2Crypto.EVP.load_key_string(string) ## # Load the public key from a string. No private key is loaded. def load_pubkey_from_file(self, filename): # load the m2 public key m2rsakey = M2Crypto.RSA.load_pub_key(filename) self.m2key = M2Crypto.EVP.PKey() self.m2key.assign_rsa(m2rsakey) # create an m2 x509 cert m2name = M2Crypto.X509.X509_Name() m2name.add_entry_by_txt(field="CN", type=0x1001, entry="junk", len=-1, loc=-1, set=0) m2x509 = M2Crypto.X509.X509() m2x509.set_pubkey(self.m2key) m2x509.set_serial_number(0) m2x509.set_issuer_name(m2name) m2x509.set_subject_name(m2name) ASN1 = M2Crypto.ASN1.ASN1_UTCTIME() ASN1.set_time(500) m2x509.set_not_before(ASN1) m2x509.set_not_after(ASN1) junk_key = Keypair(create=True) m2x509.sign(pkey=junk_key.get_m2_pkey(), md="sha1") # convert the m2 x509 cert to a pyopenssl x509 m2pem = m2x509.as_pem() pyx509 = crypto.load_certificate(crypto.FILETYPE_PEM, m2pem) # get the pyopenssl pkey from the pyopenssl x509 self.key = pyx509.get_pubkey() ## # Load the public key from a string. No private key is loaded. def load_pubkey_from_string(self, string): (f, fn) = tempfile.mkstemp() os.write(f, string) os.close(f) self.load_pubkey_from_file(fn) os.remove(fn) ## # Return the private key in PEM format. def as_pem(self): return crypto.dump_privatekey(crypto.FILETYPE_PEM, self.key) def get_m2_pkey(self): if not self.m2key: self.m2key = M2Crypto.EVP.load_key_string(self.as_pem()) return self.m2key ## # Return an OpenSSL pkey object def get_openssl_pkey(self): return self.key ## # Given another Keypair object, return TRUE if the two keys are the same. def is_same(self, pkey): return self.as_pem() == pkey.as_pem() def sign_string(self, data): k = self.get_m2_pkey() k.sign_init() k.sign_update(data) return base64.b64encode(k.sign_final()) def verify_string(self, data, sig): k = self.get_m2_pkey() k.verify_init() k.verify_update(data) return M2Crypto.m2.verify_final(k.ctx, base64.b64decode(sig), k.pkey) ## # The certificate class implements a general purpose X509 certificate, making # use of the appropriate pyOpenSSL or M2Crypto abstractions. It also adds # several addition features, such as the ability to maintain a chain of # parent certificates, and storage of application-specific data. # # Certificates include the ability to maintain a chain of parents. Each # certificate includes a pointer to it's parent certificate. When loaded # from a file or a string, the parent chain will be automatically loaded. # When saving a certificate to a file or a string, the caller can choose # whether to save the parent certificates as well. class Certificate: digest = "md5" data = None cert = None issuerKey = None issuerSubject = None parent = None separator="-----parent-----" ## # Create a certificate object. # # @param create If create==True, then also create a blank X509 certificate. # @param subject If subject!=None, then create a blank certificate and set # it's subject name. # @param string If string!=None, load the certficate from the string. # @param filename If filename!=None, load the certficiate from the file. def __init__(self, create=False, subject=None, string=None, filename=None): if create or subject: self.create() if subject: self.set_subject(subject) if string: self.load_from_string(string) if filename: self.load_from_file(filename) ## # Create a blank X509 certificate and store it in this object. def create(self): self.cert = crypto.X509() self.cert.set_serial_number(1) self.cert.gmtime_adj_notBefore(0) self.cert.gmtime_adj_notAfter(60*60*24*365*5) # five years ## # Given a pyOpenSSL X509 object, store that object inside of this # certificate object. def load_from_pyopenssl_x509(self, x509): self.cert = x509 ## # Load the certificate from a string def load_from_string(self, string): # if it is a chain of multiple certs, then split off the first one and # load it parts = string.split(Certificate.separator, 1) self.cert = crypto.load_certificate(crypto.FILETYPE_PEM, parts[0]) # if there are more certs, then create a parent and let the parent load # itself from the remainder of the string if len(parts) > 1: self.parent = self.__class__() self.parent.load_from_string(parts[1]) ## # Load the certificate from a file def load_from_file(self, filename): file = open(filename) string = file.read() self.load_from_string(string) ## # Save the certificate to a string. # # @param save_parents If save_parents==True, then also save the parent certificates. def save_to_string(self, save_parents=False): string = crypto.dump_certificate(crypto.FILETYPE_PEM, self.cert) if save_parents and self.parent: string = string + Certificate.separator + self.parent.save_to_string(save_parents) return string ## # Save the certificate to a file. # @param save_parents If save_parents==True, then also save the parent certificates. def save_to_file(self, filename, save_parents=False): string = self.save_to_string(save_parents=save_parents) open(filename, 'w').write(string) ## # Sets the issuer private key and name # @param key Keypair object containing the private key of the issuer # @param subject String containing the name of the issuer # @param cert (optional) Certificate object containing the name of the issuer def set_issuer(self, key, subject=None, cert=None): self.issuerKey = key if subject: # it's a mistake to use subject and cert params at the same time assert(not cert) if isinstance(subject, dict) or isinstance(subject, str): req = crypto.X509Req() reqSubject = req.get_subject() if (isinstance(subject, dict)): for key in reqSubject.keys(): setattr(reqSubject, key, name[key]) else: setattr(reqSubject, "CN", subject) subject = reqSubject # subject is not valid once req is out of scope, so save req self.issuerReq = req if cert: # if a cert was supplied, then get the subject from the cert subject = cert.cert.get_issuer() assert(subject) self.issuerSubject = subject ## # Get the issuer name def get_issuer(self, which="CN"): x = self.cert.get_issuer() return getattr(x, which) ## # Set the subject name of the certificate def set_subject(self, name): req = crypto.X509Req() subj = req.get_subject() if (isinstance(name, dict)): for key in name.keys(): setattr(subj, key, name[key]) else: setattr(subj, "CN", name) self.cert.set_subject(subj) ## # Get the subject name of the certificate def get_subject(self, which="CN"): x = self.cert.get_subject() return getattr(x, which) ## # Get the public key of the certificate. # # @param key Keypair object containing the public key def set_pubkey(self, key): assert(isinstance(key, Keypair)) self.cert.set_pubkey(key.get_openssl_pkey()) ## # Get the public key of the certificate. # It is returned in the form of a Keypair object. def get_pubkey(self): m2x509 = X509.load_cert_string(self.save_to_string()) pkey = Keypair() pkey.key = self.cert.get_pubkey() pkey.m2key = m2x509.get_pubkey() return pkey ## # Add an X509 extension to the certificate. Add_extension can only be called # once for a particular extension name, due to limitations in the underlying # library. # # @param name string containing name of extension # @param value string containing value of the extension def add_extension(self, name, critical, value): ext = crypto.X509Extension (name, critical, value) self.cert.add_extensions([ext]) ## # Get an X509 extension from the certificate def get_extension(self, name): # pyOpenSSL does not have a way to get extensions m2x509 = X509.load_cert_string(self.save_to_string()) value = m2x509.get_ext(name).get_value() return value ## # Set_data is a wrapper around add_extension. It stores the parameter str in # the X509 subject_alt_name extension. Set_data can only be called once, due # to limitations in the underlying library. def set_data(self, str): # pyOpenSSL only allows us to add extensions, so if we try to set the # same extension more than once, it will not work if self.data != None: raise "cannot set subjectAltName more than once" self.data = str self.add_extension("subjectAltName", 0, "URI:http://" + str) ## # Return the data string that was previously set with set_data def get_data(self): if self.data: return self.data try: uri = self.get_extension("subjectAltName") except LookupError: self.data = None return self.data if not uri.startswith("URI:http://"): raise "bad encoding in subjectAltName" self.data = uri[11:] return self.data ## # Sign the certificate using the issuer private key and issuer subject previous set with set_issuer(). def sign(self): assert self.cert != None assert self.issuerSubject != None assert self.issuerKey != None self.cert.set_issuer(self.issuerSubject) self.cert.sign(self.issuerKey.get_openssl_pkey(), self.digest) ## # Verify the authenticity of a certificate. # @param pkey is a Keypair object representing a public key. If Pkey # did not sign the certificate, then an exception will be thrown. def verify(self, pkey): # pyOpenSSL does not have a way to verify signatures m2x509 = X509.load_cert_string(self.save_to_string()) m2pkey = pkey.get_m2_pkey() # verify it return m2x509.verify(m2pkey) # XXX alternatively, if openssl has been patched, do the much simpler: # try: # self.cert.verify(pkey.get_openssl_key()) # return 1 # except: # return 0 ## # Return True if pkey is identical to the public key that is contained in the certificate. # @param pkey Keypair object def is_pubkey(self, pkey): return self.get_pubkey().is_same(pkey) ## # Given a certificate cert, verify that this certificate was signed by the # public key contained in cert. Throw an exception otherwise. # # @param cert certificate object def is_signed_by_cert(self, cert): k = cert.get_pubkey() result = self.verify(k) return result ## # Set the parent certficiate. # # @param p certificate object. def set_parent(self, p): self.parent = p ## # Return the certificate object of the parent of this certificate. def get_parent(self): return self.parent ## # Verification examines a chain of certificates to ensure that each parent # signs the child, and that some certificate in the chain is signed by a # trusted certificate. # # Verification is a basic recursion:
   #     if this_certificate was signed by trusted_certs:
   #         return
   #     else
   #         return verify_chain(parent, trusted_certs)
   # 
# # At each recursion, the parent is tested to ensure that it did sign the # child. If a parent did not sign a child, then an exception is thrown. If # the bottom of the recursion is reached and the certificate does not match # a trusted root, then an exception is thrown. # # @param Trusted_certs is a list of certificates that are trusted. # def verify_chain(self, trusted_certs = None): # Verify a chain of certificates. Each certificate must be signed by # the public key contained in it's parent. The chain is recursed # until a certificate is found that is signed by a trusted root. # TODO: verify expiration time # if this cert is signed by a trusted_cert, then we are set for trusted_cert in trusted_certs: # TODO: verify expiration of trusted_cert ? if self.is_signed_by_cert(trusted_cert): #print self.get_subject(), "is signed by a root" return # if there is no parent, then no way to verify the chain if not self.parent: #print self.get_subject(), "has no parent" raise CertMissingParent(self.get_subject()) # if it wasn't signed by the parent... if not self.is_signed_by_cert(self.parent): #print self.get_subject(), "is not signed by parent" return CertNotSignedByParent(self.get_subject()) # if the parent isn't verified... self.parent.verify_chain(trusted_certs) return