1 # Copyright (c) 1999-2001 Jason Gunthorpe <jgg@debian.org>
2 # Copyright (c) 2005 Joey Schulze <joey@infodrom.org>
4 # This program is free software; you can redistribute it and/or modify
5 # it under the terms of the GNU General Public License as published by
6 # the Free Software Foundation; either version 2 of the License, or
7 # (at your option) any later version.
9 # This program is distributed in the hope that it will be useful,
10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 # GNU General Public License for more details.
14 # You should have received a copy of the GNU General Public License
15 # along with this program; if not, write to the Free Software
16 # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 # - gpgm with a status FD being fed keymaterial and other interesting
20 # things does nothing.. If it could ID the keys and stuff over the
21 # status-fd I could decide what to do with them. I would also like it
22 # to report which key it selected for encryption (also if there
23 # were multi-matches..) Being able to detect a key-revoke cert would be
25 # - I would like to be able to fetch the comment and version fields from the
26 # packets so I can tell if a signature is made by pgp2 to enable the
27 # pgp2 encrypting mode.
29 import sys, StringIO, os, tempfile, re;
30 import time, fcntl, anydbm
31 import email, email.message
33 from userdir_exceptions import *
37 # "--load-extension","rsa",
41 "--no-default-keyring",
42 "--secret-keyring", "/dev/null",
45 GPGSigOptions = ["--output","-"];
46 GPGSearchOptions = ["--dry-run","--with-colons","--fingerprint",\
47 "--fingerprint", "--fixed-list-mode"];
48 GPGEncryptOptions = ["--output","-","--quiet","--always-trust",\
49 "--armor","--encrypt"];
50 GPGEncryptPGP2Options = ["--set-filename","","--rfc1991",\
51 "--load-extension","idea",\
52 "--cipher-algo","idea"] + GPGEncryptOptions;
54 # Replay cutoff times in seconds
55 CleanCutOff = 7*24*60*60;
56 AgeCutOff = 4*24*60*60;
57 FutureCutOff = 3*24*60*60;
62 # Set the keyrings, the input is a list of keyrings
63 def SetKeyrings(Rings):
65 GPGKeyRings.append("--keyring");
66 GPGKeyRings.append(x);
68 # GetClearSig takes an un-seekable email message stream (mimetools.Message)
69 # and returns a standard PGP '---BEGIN PGP SIGNED MESSAGE---' bounded
71 # If this is fed to gpg/pgp it will verify the signature and spit out the
72 # signed text component. Email headers and PGP mime (RFC 2015) is understood
73 # but no effort is made to cull any information outside the PGP boundaries
74 # Please note that in the event of a mime decode the mime headers will be
75 # present in the signature text! The return result is a tuple, the first
76 # element is the text itself the second is a mime flag indicating if the
77 # result should be mime processed after sig checking.
79 # Paranoid will check the message text to make sure that all the plaintext is
80 # in fact signed (bounded by a PGP packet)
82 # lax_multipart: treat multipart bodies other than multipart/signed
83 # as one big plain text body
84 def GetClearSig(Msg, Paranoid = 0, lax_multipart = False):
85 if not Msg.__class__ == email.message.Message:
86 raise RuntimeError, "GetClearSign() not called with a email.message.Message"
88 if Paranoid and lax_multipart:
89 raise RuntimeError, "Paranoid and lax_multipart don't mix well"
91 # See if this is a MIME encoded multipart signed message
92 if Msg.is_multipart():
93 if not Msg.get_content_type() == "multipart/signed":
95 payloads = Msg.get_payload()
96 msg = "\n".join(map( lambda p: p.get_payload(decode=True), payloads))
98 raise UDFormatError, "Cannot handle multipart messages not of type multipart/signed";
101 if Msg.preamble is not None and Msg.preamble.strip() != "":
102 raise UDFormatError,"Unsigned text in message (at start)";
103 if Msg.epilogue is not None and Msg.epilogue.strip() != "":
104 raise UDFormatError,"Unsigned text in message (at end)";
106 payloads = Msg.get_payload()
107 if len(payloads) != 2:
108 raise UDFormatError, "multipart/signed message with number of payloads != 2";
110 (Signed, Signature) = payloads
112 if Signed.get_content_type() != "text/plain" and not lax_multipart:
113 raise UDFormatError, "Invalid pgp/mime encoding for first part[wrong plaintext type]";
114 if Signature.get_content_type() != "application/pgp-signature":
115 raise UDFormatError, "Invalid pgp/mime encoding for second part [wrong signature type]";
117 # Append the PGP boundary header and the signature text to re-form the
118 # original signed block [needs to convert to \r\n]
119 Output = "-----BEGIN PGP SIGNED MESSAGE-----\r\n";
120 # Semi-evil hack to get the proper hash type inserted in the message
121 if Msg.get_param('micalg') != None:
122 Output = Output + "Hash: MD5,SHA1,%s\r\n"%(Msg.get_param('micalg')[4:].upper())
123 Output = Output + "\r\n";
124 Output = Output + Signed.as_string().replace("\n-","\n- -") + "\n" + Signature.get_payload(decode=True)
128 # Just return the message body
129 return (Msg.get_payload(decode=True), 0);
133 for x in Msg.get_payload(decode=True).split('\n'):
139 # Leading up to the signature
141 if x == "-----BEGIN PGP SIGNED MESSAGE-----":
144 raise UDFormatError,"Unsigned text in message (at start)";
147 # In the signature plain text
149 if x == "-----BEGIN PGP SIGNATURE-----":
155 if x == "-----END PGP SIGNATURE-----":
161 raise UDFormatError,"Unsigned text in message (at end)";
163 return ("\n".join(Body), 0);
165 # This opens GPG in 'write filter' mode. It takes Message and sends it
166 # to GPGs standard input, pipes the standard output to a temp file along
167 # with the status FD. The two tempfiles are passed to GPG by fd and are
168 # accessible from the filesystem for only a short period. Message may be
169 # None in which case GPGs stdin is closed directly after forking. This
170 # is best used for sig checking and encryption.
171 # The return result is a tuple (Exit,StatusFD,OutputFD), both fds are
172 # fully rewound and readable.
173 def GPGWriteFilter(Program,Options,Message):
174 # Make sure the tmp files we open are unreadable, there is a short race
175 # between when the temp file is opened and unlinked that some one else
176 # could open it or hard link it. This is not important however as no
177 # Secure data is fed through the temp files.
178 OldMask = os.umask(0777);
180 Output = tempfile.TemporaryFile("w+b");
181 GPGText = tempfile.TemporaryFile("w+b");
183 InPipe = [InPipe[0],InPipe[1]];
188 # Fork off GPG in a horrible way, we redirect most of its FDs
189 # Input comes from a pipe and its two outputs are spooled to unlinked
190 # temp files (ie private)
194 os.dup2(InPipe[0],0);
196 os.dup2(Output.fileno(),1);
197 os.dup2(os.open("/dev/null",os.O_WRONLY),2);
198 os.dup2(GPGText.fileno(),3);
200 Args = [Program,"--status-fd","3"] + GPGBasicOptions + GPGKeyRings + Options
201 os.execvp(Program,Args);
205 # Get rid of the other end of the pipe
212 os.write(InPipe[1],Message);
218 # Wait for GPG to finish
219 Exit = os.waitpid(Child,0);
221 # Create the result including the new readable file descriptors
222 Result = (Exit,os.fdopen(os.dup(GPGText.fileno()),"r"), \
223 os.fdopen(os.dup(Output.fileno()),"r"));
238 # This takes a text passage, a destination and a flag indicating the
239 # compatibility to use and returns an encrypted message to the recipient.
240 # It is best if the recipient is specified using the hex key fingerprint
241 # of the target, ie 0x64BE1319CCF6D393BF87FF9358A6D4EE
242 def GPGEncrypt(Message,To,PGP2):
243 Error = "KeyringError"
244 # Encrypt using the PGP5 block encoding and with the PGP5 option set.
245 # This will handle either RSA or DSA/DH asymetric keys.
246 # In PGP2 compatible mode IDEA and rfc1991 encoding are used so that
247 # PGP2 can read the result. RSA keys do not need PGP2 to be set, as GPG
248 # can read a message encrypted with blowfish and RSA.
249 searchkey = GPGKeySearch(To);
250 if len(searchkey) == 0:
251 raise Error, "No key found matching %s"%(To);
252 elif len(searchkey) > 1:
253 raise Error, "Multiple keys found matching %s"%(To);
254 if searchkey[0][4].find("E") < 0:
255 raise Error, "Key %s has no encryption capability - are all encryption subkeys expired or revoked? Are there any encryption subkeys?"%(To);
260 Res = GPGWriteFilter(GPGPath,["-r",To]+GPGEncryptOptions,Message);
263 Text = Res[2].read();
270 # We have to call gpg with a filename or it will create a packet that
271 # PGP2 cannot understand.
272 TmpName = tempfile.mktemp();
275 MsgFile = open(TmpName,"wc");
276 MsgFile.write(Message);
278 Res = GPGWriteFilter(GPGPath,["-r",To]+GPGEncryptPGP2Options+[TmpName],None);
281 Text = Res[2].read();
292 # Checks the signature of a standard PGP message, like that returned by
293 # GetClearSig. It returns a large tuple of the form:
294 # (Why,(SigId,Date,KeyFinger),(KeyID,KeyFinger,Owner,Length,PGP2),Text);
296 # Why = None if checking was OK otherwise an error string.
297 # SigID+Date represent something suitable for use in a replay cache. The
298 # date is returned as the number of seconds since the UTC epoch.
299 # The keyID is also in this tuple for easy use of the replay
301 # KeyID, KeyFinger and Owner represent the Key used to sign this message
302 # PGP2 indicates if the message was created using PGP 2.x
303 # Text is the full byte-for-byte signed text in a string
304 def GPGCheckSig(Message):
307 Res = GPGWriteFilter(GPGPath,GPGSigOptions,Message);
310 # Parse the GPG answer
321 # Grab and split up line
322 Line = Strm.readline();
325 Split = re.split("[ \n]",Line);
326 if Split[0] != "[GNUPG:]":
329 # We only process the first occurance of any tag.
330 if TagMap.has_key(Split[1]):
332 TagMap[Split[1]] = None;
334 # Good signature response
335 if Split[1] == "GOODSIG":
336 # Just in case GPG returned a bad signal before this (bug?)
340 Owner = ' '.join(Split[3:])
341 # If this message is signed with a subkey which has not yet
342 # expired, GnuPG will say GOODSIG here, even if the primary
343 # key already has expired. This came up in discussion of
344 # bug #489225. GPGKeySearch only returns non-expired keys.
345 Verify = GPGKeySearch(KeyID);
348 Why = "Key has expired (no unexpired key found in keyring matching %s)"%(KeyId);
350 # Bad signature response
351 if Split[1] == "BADSIG":
354 Why = "Verification of signature failed";
356 # Bad signature response
357 if Split[1] == "ERRSIG":
361 Why = "GPG error, ERRSIG status tag is invalid";
362 elif Split[7] == '9':
363 Why = "Unable to verify signature, signing key missing.";
364 elif Split[7] == '4':
365 Why = "Unable to verify signature, unknown packet format/key type";
367 Why = "Unable to verify signature, unknown reason";
369 if Split[1] == "NO_PUBKEY":
371 Why = "Unable to verify signature, signing key missing.";
374 if Split[1] == "EXPSIG":
376 Why = "Signature has expired";
379 if Split[1] == "EXPKEYSIG":
381 Why = "Signing key (%s, %s) has expired"%(Split[2], Split[3]);
384 if Split[1] == "KEYREVOKED" or Split[1] == "REVKEYSIG":
386 Why = "Signing key has been revoked";
389 if Split[1] == "NODATA" or Split[1] == "BADARMOR":
391 Why = "The packet was corrupted or contained no data";
394 if Split[1] == "SIG_ID":
396 Date = long(Split[4]);
398 # ValidSig has the key finger print
399 if Split[1] == "VALIDSIG":
400 # Use the fingerprint of the primary key when available
402 KeyFinger = Split[11];
404 KeyFinger = Split[2];
406 # Reopen the stream as a readable stream
407 Text = Res[2].read();
409 # A gpg failure is an automatic bad signature
410 if Exit[1] != 0 and Why == None:
412 Why = "GPG execution returned non-zero exit status: " + str(Exit[1]);
414 if GoodSig == 0 and (Why == None or len(Why) == 0):
415 Why = "Checking Failed";
417 # Try to decide if this message was sent using PGP2
419 if (re.search("-----[\n\r][\n\r]?Version: 2\\.",Message) != None):
422 return (Why,(SigId,Date,KeyFinger),(KeyID,KeyFinger,Owner,0,PGP2Message),Text);
429 def __init__(self, msg):
430 res = GPGCheckSig(msg)
432 self.sig_info = res[1]
433 self.key_info = res[2]
436 self.ok = self.why is None
438 self.sig_id = self.sig_info[0]
439 self.sig_date = self.sig_info[1]
440 self.sig_fpr = self.sig_info[2]
442 self.key_id = self.key_info[0]
443 self.key_fpr = self.key_info[1]
444 self.key_owner = self.key_info[2]
446 self.is_pgp2 = self.key_info[4]
448 # Search for keys given a search pattern. The pattern is passed directly
449 # to GPG for processing. The result is a list of tuples of the form:
450 # (KeyID,KeyFinger,Owner,Length)
451 # Which is similar to the key identification tuple output by GPGChecksig
453 # Do not return keys where the primary key has expired
454 def GPGKeySearch(SearchCriteria):
455 Args = [GPGPath] + GPGBasicOptions + GPGKeyRings + GPGSearchOptions + \
456 [SearchCriteria," 2> /dev/null"]
467 dir = os.path.expanduser("~/.gnupg")
468 if not os.path.isdir(dir):
472 # The GPG output will contain zero or more stanza, one stanza per match found.
473 # Each stanza consists of the following records, in order:
474 # tru : trust database information
475 # pub : primary key from which we extract
479 # field 11 - Capabilities
480 # fpr : fingerprint of primary key from which we extract
481 # field 9 - Fingerprint
482 # uid : first User ID attached to primary key from which we extract
484 # uid : (optional) additional multiple User IDs attached to primary key
485 # sub : (optional) secondary key
486 # fpr : (opitonal) fingerprint of secondary key if sub is present
487 Strm = os.popen(" ".join(Args),"r")
490 Line = Strm.readline()
493 Split = Line.split(":")
500 Length = int(Split[2])
502 Capabilities = Split[11]
507 Fingerprint = Split[9]
508 if Hits.has_key(Fingerprint):
509 Want = 'pub' # already seen, skip to next stanza
511 Hits[Fingerprint] = None
517 if Validity != 'e': # if not expired
518 Result.append( (KeyID,Fingerprint,Owner,Length,Capabilities) )
519 Want = 'pub' # finished, skip to next stanza
527 # Print the available key information in a format similar to GPG's output
528 # We do not know the values of all the feilds so they are just replaced
530 def GPGPrintKeyInfo(Ident):
531 print "pub %u?/%s ??-??-?? %s" % (Ident[3],Ident[0][-8:],Ident[2]);
532 print " key fingerprint = 0x%s" % (Ident[1]);
534 # Perform a substition of template
535 def TemplateSubst(Map,Template):
537 Template = Template.replace(x, Map[x])
540 # The replay class uses a python DB (BSD db if avail) to implement
541 # protection against replay. Replay is an attacker capturing the
542 # plain text signed message and sending it back to the victim at some
543 # later date. Each signature has a unique signature ID (and signing
544 # Key Fingerprint) as well as a timestamp. The first stage of replay
545 # protection is to ensure that the timestamp is reasonable, in particular
546 # not to far ahead or too far behind the current system time. The next
547 # step is to look up the signature + key fingerprint in the replay database
548 # and determine if it has been recived. The database is cleaned out
549 # periodically and old signatures are discarded. By using a timestamp the
550 # database size is bounded to being within the range of the allowed times
551 # plus a little fuzz. The cache is serialized with a flocked lock file
553 def __init__(self,Database):
554 self.Lock = open(Database + ".lock","w",0600);
555 fcntl.flock(self.Lock.fileno(),fcntl.LOCK_EX);
556 self.DB = anydbm.open(Database,"c",0600);
557 self.CleanCutOff = CleanCutOff;
558 self.AgeCutOff = AgeCutOff;
559 self.FutureCutOff = FutureCutOff;
562 # Close the cache and lock
569 # Clean out any old signatures
571 CutOff = time.time() - self.CleanCutOff;
572 for x in self.DB.keys():
573 if int(self.DB[x]) <= CutOff:
576 # Check a signature. 'sig' is a 3 tuple that has the sigId, date and
579 if Sig[0] == None or Sig[1] == None or Sig[2] == None:
580 return "Invalid signature";
581 if int(Sig[1]) > time.time() + self.FutureCutOff:
582 return "Signature has a time too far in the future";
583 if self.DB.has_key(Sig[0] + '-' + Sig[2]):
584 return "Signature has already been received";
585 if int(Sig[1]) < time.time() - self.AgeCutOff:
586 return "Signature has passed the age cut off ";
587 # + str(int(Sig[1])) + ',' + str(time.time()) + "," + str(Sig);
590 # Add a signature, the sig is the same as is given to Check
592 if Sig[0] == None or Sig[1] == None:
593 raise RuntimeError,"Invalid signature";
594 if Sig[1] < time.time() - self.CleanCutOff:
596 Key = Sig[0] + '-' + Sig[2]
597 if self.DB.has_key(Key):
598 if int(self.DB[Key]) < Sig[1]:
599 self.DB[Key] = str(int(Sig[1]));
601 self.DB[Key] = str(int(Sig[1]));
603 def process(self, sig_info):
604 r = self.Check(sig_info);
606 raise RuntimeError, "The replay cache rejected your message: %s."%(r);
612 # vim:set shiftwidth=3: