#---------------------------------------------------------------------- # Copyright (c) 2008 Board of Trustees, Princeton University # # Permission is hereby granted, free of charge, to any person obtaining # a copy of this software and/or hardware specification (the "Work") to # deal in the Work without restriction, including without limitation the # rights to use, copy, modify, merge, publish, distribute, sublicense, # and/or sell copies of the Work, and to permit persons to whom the Work # is furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be # included in all copies or substantial portions of the Work. # # THE WORK IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS # OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT # HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, # WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, # OUT OF OR IN CONNECTION WITH THE WORK OR THE USE OR OTHER DEALINGS # IN THE WORK. #---------------------------------------------------------------------- ## # SFA 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. ## # import functools import os import tempfile import base64 from tempfile import mkstemp from OpenSSL import crypto import M2Crypto from M2Crypto import X509 from sfa.util.faults import CertExpired, CertMissingParent, CertNotSignedByParent from sfa.util.sfalogging import logger # this tends to generate quite some logs for little or no value debug_verify_chain = False glo_passphrase_callback = None ## # A global callback may be implemented for requesting passphrases from the # user. The function will be called with three arguments: # # keypair_obj: the keypair object that is calling the passphrase # string: the string containing the private key that's being loaded # x: unknown, appears to be 0, comes from pyOpenSSL and/or m2crypto # # The callback should return a string containing the passphrase. def set_passphrase_callback(callback_func): global glo_passphrase_callback glo_passphrase_callback = callback_func ## # Sets a fixed passphrase. def set_passphrase(passphrase): set_passphrase_callback( lambda k,s,x: passphrase ) ## # Check to see if a passphrase works for a particular private key string. # Intended to be used by passphrase callbacks for input validation. def test_passphrase(string, passphrase): try: crypto.load_privatekey(crypto.FILETYPE_PEM, string, (lambda x: passphrase)) return True except: return False def convert_public_key(key): keyconvert_path = "/usr/bin/keyconvert.py" 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: raise Exception, "keyconvert: dss keys are not supported" (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): raise Exception, "keyconvert: generated certificate not found. keyconvert may have failed." k = Keypair() try: k.load_pubkey_from_file(ssl_fn) return k except: logger.log_exc("convert_public_key caught exception") raise finally: # remove the temporary files if os.path.exists(ssh_fn): os.remove(ssh_fn) if os.path.exists(ssl_fn): os.remove(ssl_fn) ## # 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()) self.filename=filename ## # Load the private key from a file. Implicity the private key includes the public key. def load_from_file(self, filename): self.filename=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): if glo_passphrase_callback: self.key = crypto.load_privatekey(crypto.FILETYPE_PEM, string, functools.partial(glo_passphrase_callback, self, string) ) self.m2key = M2Crypto.EVP.load_key_string(string, functools.partial(glo_passphrase_callback, self, string) ) else: 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) # x509v3 so it can have extensions # prob not necc since this cert itself is junk but still... m2x509.set_version(2) 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() self.filename=filename ## # 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) ## # Return an M2Crypto key object def get_m2_pkey(self): if not self.m2key: self.m2key = M2Crypto.EVP.load_key_string(self.as_pem()) return self.m2key ## # Returns a string containing the public key represented by this object. def get_pubkey_string(self): m2pkey = self.get_m2_pkey() return base64.b64encode(m2pkey.as_der()) ## # 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) def compute_hash(self, value): return self.sign_string(str(value)) # only informative def get_filename(self): return getattr(self,'filename',None) def dump (self, *args, **kwargs): print self.dump_string(*args, **kwargs) def dump_string (self): result="" result += "KEYPAIR: pubkey=%40s..."%self.get_pubkey_string() filename=self.get_filename() if filename: result += "Filename %s\n"%filename return result ## # 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" # x509 = None # issuerKey = None # issuerSubject = None # parent = None isCA = None # will be a boolean once set separator="-----parent-----" ## # Create a certificate object. # # @param lifeDays life of cert in days - default is 1825==5 years # @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. # @param isCA If !=None, set whether this cert is for a CA def __init__(self, lifeDays=1825, create=False, subject=None, string=None, filename=None, isCA=None): # these used to be defined in the class ! self.x509 = None self.issuerKey = None self.issuerSubject = None self.parent = None self.data = {} if create or subject: self.create(lifeDays) if subject: self.set_subject(subject) if string: self.load_from_string(string) if filename: self.load_from_file(filename) # Set the CA bit if a value was supplied if isCA != None: self.set_is_ca(isCA) # Create a blank X509 certificate and store it in this object. def create(self, lifeDays=1825): self.x509 = crypto.X509() # FIXME: Use different serial #s self.x509.set_serial_number(3) self.x509.gmtime_adj_notBefore(0) # 0 means now self.x509.gmtime_adj_notAfter(lifeDays*60*60*24) # five years is default self.x509.set_version(2) # x509v3 so it can have extensions ## # Given a pyOpenSSL X509 object, store that object inside of this # certificate object. def load_from_pyopenssl_x509(self, x509): self.x509 = 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 (support for the ---parent--- tag as well as normal chained certs) string = string.strip() # If it's not in proper PEM format, wrap it if string.count('-----BEGIN CERTIFICATE') == 0: string = '-----BEGIN CERTIFICATE-----\n%s\n-----END CERTIFICATE-----' % string # If there is a PEM cert in there, but there is some other text first # such as the text of the certificate, skip the text beg = string.find('-----BEGIN CERTIFICATE') if beg > 0: # skipping over non cert beginning string = string[beg:] parts = [] if string.count('-----BEGIN CERTIFICATE-----') > 1 and \ string.count(Certificate.separator) == 0: parts = string.split('-----END CERTIFICATE-----',1) parts[0] += '-----END CERTIFICATE-----' else: parts = string.split(Certificate.separator, 1) self.x509 = 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 and 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) self.filename=filename ## # 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=True): string = crypto.dump_certificate(crypto.FILETYPE_PEM, self.x509) if save_parents and self.parent: string = string + 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=True, filep=None): string = self.save_to_string(save_parents=save_parents) if filep: f = filep else: f = open(filename, 'w') f.write(string) f.close() self.filename=filename ## # Save the certificate to a random file in /tmp/ # @param save_parents If save_parents==True, then also save the parent certificates. def save_to_random_tmp_file(self, save_parents=True): fp, filename = mkstemp(suffix='cert', text=True) fp = os.fdopen(fp, "w") self.save_to_file(filename, save_parents=True, filep=fp) return filename ## # 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, subject[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.x509.get_subject() assert(subject) self.issuerSubject = subject ## # Get the issuer name def get_issuer(self, which="CN"): x = self.x509.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.x509.set_subject(subj) ## # Get the subject name of the certificate def get_subject(self, which="CN"): x = self.x509.get_subject() return getattr(x, which) ## # Get a pretty-print subject name of the certificate # let's try to make this a little more usable as is makes logs hairy pretty_fields = ['email'] def filter_chunk(self, chunk): for field in self.pretty_fields: if field in chunk: return " "+chunk def pretty_cert(self): message = "[Cert." x = self.x509.get_subject() ou = getattr(x, "OU") if ou: message += " OU: {}".format(ou) cn = getattr(x, "CN") if cn: message += " CN: {}".format(cn) data = self.get_data(field='subjectAltName') if data: message += " SubjectAltName:" counter = 0 filtered = [self.filter_chunk(chunk) for chunk in data.split()] message += " ".join( [f for f in filtered if f]) omitted = len ([f for f in filtered if not f]) if omitted: message += "..+{} omitted".format(omitted) message += "]" return message ## # 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.x509.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.x509.get_pubkey() pkey.m2key = m2x509.get_pubkey() return pkey def set_intermediate_ca(self, val): return self.set_is_ca(val) # Set whether this cert is for a CA. All signers and only signers should be CAs. # The local member starts unset, letting us check that you only set it once # @param val Boolean indicating whether this cert is for a CA def set_is_ca(self, val): if val is None: return if self.isCA != None: # Can't double set properties raise Exception, "Cannot set basicConstraints CA:?? more than once. Was %s, trying to set as %s" % (self.isCA, val) self.isCA = val if val: self.add_extension('basicConstraints', 1, 'CA:TRUE') else: self.add_extension('basicConstraints', 1, 'CA:FALSE') ## # 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): oldExtVal = None try: oldExtVal = self.get_extension(name) except: # M2Crypto LookupError when the extension isn't there (yet) pass # This code limits you from adding the extension with the same value # The method comment says you shouldn't do this with the same name # But actually it (m2crypto) appears to allow you to do this. if oldExtVal and oldExtVal == value: # don't add this extension again # just do nothing as here return # FIXME: What if they are trying to set with a different value? # Is this ever OK? Or should we raise an exception? # elif oldExtVal: # raise "Cannot add extension %s which had val %s with new val %s" % (name, oldExtVal, value) ext = crypto.X509Extension (name, critical, value) self.x509.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, field='subjectAltName'): # 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.has_key(field): raise "Cannot set ", field, " more than once" self.data[field] = str self.add_extension(field, 0, str) ## # Return the data string that was previously set with set_data def get_data(self, field='subjectAltName'): if self.data.has_key(field): return self.data[field] try: uri = self.get_extension(field) self.data[field] = uri except LookupError: return None return self.data[field] ## # Sign the certificate using the issuer private key and issuer subject previous set with set_issuer(). def sign(self): logger.debug('certificate.sign') assert self.x509 != None assert self.issuerSubject != None assert self.issuerKey != None self.x509.set_issuer(self.issuerSubject) self.x509.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.x509.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. # Also require that parents are CAs. # # @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. # verify expiration time if self.x509.has_expired(): if debug_verify_chain: logger.debug("verify_chain: NO, Certificate %s has expired" % self.pretty_cert()) raise CertExpired(self.pretty_cert(), "client cert") # if this cert is signed by a trusted_cert, then we are set for trusted_cert in trusted_certs: if self.is_signed_by_cert(trusted_cert): # verify expiration of trusted_cert ? if not trusted_cert.x509.has_expired(): if debug_verify_chain: logger.debug("verify_chain: YES. Cert %s signed by trusted cert %s"%( self.pretty_cert(), trusted_cert.pretty_cert())) return trusted_cert else: if debug_verify_chain: logger.debug("verify_chain: NO. Cert %s is signed by trusted_cert %s, but that signer is expired..."%( self.pretty_cert(),trusted_cert.pretty_cert())) raise CertExpired(self.pretty_cert()," signer trusted_cert %s"%trusted_cert.pretty_cert()) # if there is no parent, then no way to verify the chain if not self.parent: if debug_verify_chain: logger.debug("verify_chain: NO. %s has no parent and issuer %s is not in %d trusted roots"%\ (self.pretty_cert(), self.get_issuer(), len(trusted_certs))) raise CertMissingParent(self.pretty_cert() + \ ": Issuer %s is not one of the %d trusted roots, and cert has no parent." %\ (self.get_issuer(), len(trusted_certs))) # if it wasn't signed by the parent... if not self.is_signed_by_cert(self.parent): if debug_verify_chain: logger.debug("verify_chain: NO. %s is not signed by parent %s, but by %s"%\ (self.pretty_cert(), self.parent.pretty_cert(), self.get_issuer())) raise CertNotSignedByParent("%s: Parent %s, issuer %s"\ % (self.pretty_cert(), self.parent.pretty_cert(), self.get_issuer())) # Confirm that the parent is a CA. Only CAs can be trusted as # signers. # Note that trusted roots are not parents, so don't need to be # CAs. # Ugly - cert objects aren't parsed so we need to read the # extension and hope there are no other basicConstraints if not self.parent.isCA and not (self.parent.get_extension('basicConstraints') == 'CA:TRUE'): logger.warn("verify_chain: cert %s's parent %s is not a CA" % \ (self.pretty_cert(), self.parent.pretty_cert())) raise CertNotSignedByParent("%s: Parent %s not a CA" % (self.pretty_cert(), self.parent.pretty_cert())) # if the parent isn't verified... if debug_verify_chain: logger.debug("verify_chain: .. %s, -> verifying parent %s"%\ (self.pretty_cert(),self.parent.pretty_cert())) self.parent.verify_chain(trusted_certs) return ### more introspection def get_extensions(self): # pyOpenSSL does not have a way to get extensions triples = [] m2x509 = X509.load_cert_string(self.save_to_string()) nb_extensions = m2x509.get_ext_count() logger.debug("X509 had %d extensions"%nb_extensions) for i in range(nb_extensions): ext=m2x509.get_ext_at(i) triples.append( (ext.get_name(), ext.get_value(), ext.get_critical(),) ) return triples def get_data_names(self): return self.data.keys() def get_all_datas (self): triples = self.get_extensions() for name in self.get_data_names(): triples.append( (name,self.get_data(name),'data',) ) return triples # only informative def get_filename(self): return getattr(self,'filename',None) def dump (self, *args, **kwargs): print self.dump_string(*args, **kwargs) def dump_string (self,show_extensions=False): result = "" result += "CERTIFICATE for %s\n"%self.pretty_cert() result += "Issued by %s\n"%self.get_issuer() filename=self.get_filename() if filename: result += "Filename %s\n"%filename if show_extensions: all_datas = self.get_all_datas() result += " has %d extensions/data attached"%len(all_datas) for (n, v, c) in all_datas: if c=='data': result += " data: %s=%s\n"%(n,v) else: result += " ext: %s (crit=%s)=<<<%s>>>\n"%(n,c,v) return result