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 GPGEncryptOptions = ["--output","-","--quiet","--always-trust",\
48 "--armor","--encrypt"];
49 GPGEncryptPGP2Options = ["--set-filename","","--rfc1991",\
50 "--load-extension","idea",\
51 "--cipher-algo","idea"] + GPGEncryptOptions;
53 # Replay cutoff times in seconds
54 CleanCutOff = 7*24*60*60;
55 AgeCutOff = 4*24*60*60;
56 FutureCutOff = 3*24*60*60;
61 # Set the keyrings, the input is a list of keyrings
62 def SetKeyrings(Rings):
64 GPGKeyRings.append("--keyring");
65 GPGKeyRings.append(x);
67 # GetClearSig takes an un-seekable email message stream (mimetools.Message)
68 # and returns a standard PGP '---BEGIN PGP SIGNED MESSAGE---' bounded
70 # If this is fed to gpg/pgp it will verify the signature and spit out the
71 # signed text component. Email headers and PGP mime (RFC 2015) is understood
72 # but no effort is made to cull any information outside the PGP boundaries
73 # Please note that in the event of a mime decode the mime headers will be
74 # present in the signature text! The return result is a tuple, the first
75 # element is the text itself the second is a mime flag indicating if the
76 # result should be mime processed after sig checking.
78 # Paranoid will check the message text to make sure that all the plaintext is
79 # in fact signed (bounded by a PGP packet)
80 def GetClearSig(Msg,Paranoid = 0):
81 if not Msg.__class__ == email.message.Message:
82 raise RuntimeError, "GetClearSign() not called with a email.message.Message"
84 # See if this is a MIME encoded multipart signed message
85 if Msg.is_multipart():
86 if not Msg.get_content_type() == "multipart/signed":
87 raise UDFormatError, "Cannot handle multipart messages not of type multipart/signed";
90 if Msg.preamble is not None and Msg.preamble.strip() != "":
91 raise UDFormatError,"Unsigned text in message (at start)";
92 if Msg.epilogue is not None and Msg.epilogue.strip() != "":
93 raise UDFormatError,"Unsigned text in message (at end)";
95 payloads = Msg.get_payload()
96 if len(payloads) != 2:
97 raise UDFormatError, "multipart/signed message with number of payloads != 2";
99 (Signed, Signature) = payloads
101 if Signed.get_content_type() != "text/plain":
102 raise UDFormatError, "Invalid pgp/mime encoding [wrong plaintext type]";
103 if Signature.get_content_type() != "application/pgp-signature":
104 raise UDFormatError, "Invalid pgp/mime encoding [wrong signature type]";
106 # Append the PGP boundary header and the signature text to re-form the
107 # original signed block [needs to convert to \r\n]
108 Output = "-----BEGIN PGP SIGNED MESSAGE-----\r\n";
109 # Semi-evil hack to get the proper hash type inserted in the message
110 if Msg.get_param('micalg') != None:
111 Output = Output + "Hash: MD5,SHA1,%s\r\n"%(Msg.get_param('micalg')[4:].upper())
112 Output = Output + "\r\n";
113 Output = Output + Signed.as_string().replace("\n-","\n- -") + "\n" + Signature.get_payload(decode=True)
117 # Just return the message body
118 return (Msg.get_payload(decode=True), 0);
122 for x in Msg.get_payload(decode=True).split('\n'):
128 # Leading up to the signature
130 if x == "-----BEGIN PGP SIGNED MESSAGE-----":
133 raise UDFormatError,"Unsigned text in message (at start)";
136 # In the signature plain text
138 if x == "-----BEGIN PGP SIGNATURE-----":
144 if x == "-----END PGP SIGNATURE-----":
150 raise UDFormatError,"Unsigned text in message (at end)";
152 return ("\n".join(Body), 0);
154 # This opens GPG in 'write filter' mode. It takes Message and sends it
155 # to GPGs standard input, pipes the standard output to a temp file along
156 # with the status FD. The two tempfiles are passed to GPG by fd and are
157 # accessible from the filesystem for only a short period. Message may be
158 # None in which case GPGs stdin is closed directly after forking. This
159 # is best used for sig checking and encryption.
160 # The return result is a tuple (Exit,StatusFD,OutputFD), both fds are
161 # fully rewound and readable.
162 def GPGWriteFilter(Program,Options,Message):
163 # Make sure the tmp files we open are unreadable, there is a short race
164 # between when the temp file is opened and unlinked that some one else
165 # could open it or hard link it. This is not important however as no
166 # Secure data is fed through the temp files.
167 OldMask = os.umask(0777);
169 Output = tempfile.TemporaryFile("w+b");
170 GPGText = tempfile.TemporaryFile("w+b");
172 InPipe = [InPipe[0],InPipe[1]];
177 # Fork off GPG in a horrible way, we redirect most of its FDs
178 # Input comes from a pipe and its two outputs are spooled to unlinked
179 # temp files (ie private)
183 os.dup2(InPipe[0],0);
185 os.dup2(Output.fileno(),1);
186 os.dup2(os.open("/dev/null",os.O_WRONLY),2);
187 os.dup2(GPGText.fileno(),3);
189 Args = [Program,"--status-fd","3"] + GPGBasicOptions + GPGKeyRings + Options
190 os.execvp(Program,Args);
194 # Get rid of the other end of the pipe
201 os.write(InPipe[1],Message);
207 # Wait for GPG to finish
208 Exit = os.waitpid(Child,0);
210 # Create the result including the new readable file descriptors
211 Result = (Exit,os.fdopen(os.dup(GPGText.fileno()),"r"), \
212 os.fdopen(os.dup(Output.fileno()),"r"));
227 # This takes a text passage, a destination and a flag indicating the
228 # compatibility to use and returns an encrypted message to the recipient.
229 # It is best if the recipient is specified using the hex key fingerprint
230 # of the target, ie 0x64BE1319CCF6D393BF87FF9358A6D4EE
231 def GPGEncrypt(Message,To,PGP2):
232 Error = "KeyringError"
233 # Encrypt using the PGP5 block encoding and with the PGP5 option set.
234 # This will handle either RSA or DSA/DH asymetric keys.
235 # In PGP2 compatible mode IDEA and rfc1991 encoding are used so that
236 # PGP2 can read the result. RSA keys do not need PGP2 to be set, as GPG
237 # can read a message encrypted with blowfish and RSA.
238 searchkey = GPGKeySearch(To);
239 if len(searchkey) == 0:
240 raise Error, "No key found matching %s"%(To);
241 elif len(searchkey) > 1:
242 raise Error, "Multiple keys found matching %s"%(To);
243 if searchkey[0][4].find("E") < 0:
244 raise Error, "Key %s has no encryption capability - are all encryption subkeys expired or revoked? Are there any encryption subkeys?"%(To);
249 Res = GPGWriteFilter(GPGPath,["-r",To]+GPGEncryptOptions,Message);
252 Text = Res[2].read();
259 # We have to call gpg with a filename or it will create a packet that
260 # PGP2 cannot understand.
261 TmpName = tempfile.mktemp();
264 MsgFile = open(TmpName,"wc");
265 MsgFile.write(Message);
267 Res = GPGWriteFilter(GPGPath,["-r",To]+GPGEncryptPGP2Options+[TmpName],None);
270 Text = Res[2].read();
281 # Checks the signature of a standard PGP message, like that returned by
282 # GetClearSig. It returns a large tuple of the form:
283 # (Why,(SigId,Date,KeyFinger),(KeyID,KeyFinger,Owner,Length,PGP2),Text);
285 # Why = None if checking was OK otherwise an error string.
286 # SigID+Date represent something suitable for use in a replay cache. The
287 # date is returned as the number of seconds since the UTC epoch.
288 # The keyID is also in this tuple for easy use of the replay
290 # KeyID, KeyFinger and Owner represent the Key used to sign this message
291 # PGP2 indicates if the message was created using PGP 2.x
292 # Text is the full byte-for-byte signed text in a string
293 def GPGCheckSig(Message):
296 Res = GPGWriteFilter(GPGPath,GPGSigOptions,Message);
299 # Parse the GPG answer
310 # Grab and split up line
311 Line = Strm.readline();
314 Split = re.split("[ \n]",Line);
315 if Split[0] != "[GNUPG:]":
318 # We only process the first occurance of any tag.
319 if TagMap.has_key(Split[1]):
321 TagMap[Split[1]] = None;
323 # Good signature response
324 if Split[1] == "GOODSIG":
325 # Just in case GPG returned a bad signal before this (bug?)
329 Owner = ' '.join(Split[3:])
330 # If this message is signed with a subkey which has not yet
331 # expired, GnuPG will say GOODSIG here, even if the primary
332 # key already has expired. This came up in discussion of
333 # bug #489225. GPGKeySearch only returns non-expired keys.
334 Verify = GPGKeySearch(KeyID);
337 Why = "Key has expired (no unexpired key found in keyring matching %s)"%(KeyId);
339 # Bad signature response
340 if Split[1] == "BADSIG":
343 Why = "Verification of signature failed";
345 # Bad signature response
346 if Split[1] == "ERRSIG":
350 Why = "GPG error, ERRSIG status tag is invalid";
351 elif Split[7] == '9':
352 Why = "Unable to verify signature, signing key missing.";
353 elif Split[7] == '4':
354 Why = "Unable to verify signature, unknown packet format/key type";
356 Why = "Unable to verify signature, unknown reason";
358 if Split[1] == "NO_PUBKEY":
360 Why = "Unable to verify signature, signing key missing.";
363 if Split[1] == "EXPSIG":
365 Why = "Signature has expired";
368 if Split[1] == "EXPKEYSIG":
370 Why = "Signing key (%s, %s) has expired"%(Split[2], Split[3]);
373 if Split[1] == "KEYREVOKED" or Split[1] == "REVKEYSIG":
375 Why = "Signing key has been revoked";
378 if Split[1] == "NODATA" or Split[1] == "BADARMOR":
380 Why = "The packet was corrupted or contained no data";
383 if Split[1] == "SIG_ID":
385 Date = long(Split[4]);
387 # ValidSig has the key finger print
388 if Split[1] == "VALIDSIG":
389 # Use the fingerprint of the primary key when available
391 KeyFinger = Split[11];
393 KeyFinger = Split[2];
395 # Reopen the stream as a readable stream
396 Text = Res[2].read();
398 # A gpg failure is an automatic bad signature
399 if Exit[1] != 0 and Why == None:
401 Why = "GPG execution returned non-zero exit status: " + str(Exit[1]);
403 if GoodSig == 0 and (Why == None or len(Why) == 0):
404 Why = "Checking Failed";
406 # Try to decide if this message was sent using PGP2
408 if (re.search("-----[\n\r][\n\r]?Version: 2\\.",Message) != None):
411 return (Why,(SigId,Date,KeyFinger),(KeyID,KeyFinger,Owner,0,PGP2Message),Text);
418 def __init__(self, msg):
419 res = GPGCheckSig(msg)
421 self.sig_info = res[1]
422 self.key_info = res[2]
425 self.ok = self.why is None
427 self.sig_id = self.sig_info[0]
428 self.sig_date = self.sig_info[1]
429 self.sig_fpr = self.sig_info[2]
431 self.key_id = self.key_info[0]
432 self.key_fpr = self.key_info[1]
433 self.key_owner = self.key_info[2]
435 self.is_pgp2 = self.key_info[4]
437 # Search for keys given a search pattern. The pattern is passed directly
438 # to GPG for processing. The result is a list of tuples of the form:
439 # (KeyID,KeyFinger,Owner,Length)
440 # Which is similar to the key identification tuple output by GPGChecksig
442 # Do not return keys where the primary key has expired
443 def GPGKeySearch(SearchCriteria):
444 Args = [GPGPath] + GPGBasicOptions + GPGKeyRings + GPGSearchOptions + \
445 [SearchCriteria," 2> /dev/null"]
454 dir = os.path.expanduser("~/.gnupg")
455 if not os.path.isdir(dir):
459 Strm = os.popen(" ".join(Args),"r")
462 # Grab and split up line
463 Line = Strm.readline();
466 Split = Line.split(":")
468 # Store some of the key fields
469 if Split[0] == 'pub':
472 Length = int(Split[2])
473 Capabilities = Split[11]
474 Expired = Split[1] == 'e'
477 if Split[0] == 'fpr':
478 if Hits.has_key(Split[9]):
480 Hits[Split[9]] = None;
482 Result.append( (KeyID,Split[9],Owner,Length,Capabilities) );
488 # Print the available key information in a format similar to GPG's output
489 # We do not know the values of all the feilds so they are just replaced
491 def GPGPrintKeyInfo(Ident):
492 print "pub %u?/%s ??-??-?? %s" % (Ident[3],Ident[0][-8:],Ident[2]);
493 print " key fingerprint = 0x%s" % (Ident[1]);
495 # Perform a substition of template
496 def TemplateSubst(Map,Template):
498 Template = Template.replace(x, Map[x])
501 # The replay class uses a python DB (BSD db if avail) to implement
502 # protection against replay. Replay is an attacker capturing the
503 # plain text signed message and sending it back to the victim at some
504 # later date. Each signature has a unique signature ID (and signing
505 # Key Fingerprint) as well as a timestamp. The first stage of replay
506 # protection is to ensure that the timestamp is reasonable, in particular
507 # not to far ahead or too far behind the current system time. The next
508 # step is to look up the signature + key fingerprint in the replay database
509 # and determine if it has been recived. The database is cleaned out
510 # periodically and old signatures are discarded. By using a timestamp the
511 # database size is bounded to being within the range of the allowed times
512 # plus a little fuzz. The cache is serialized with a flocked lock file
514 def __init__(self,Database):
515 self.Lock = open(Database + ".lock","w",0600);
516 fcntl.flock(self.Lock.fileno(),fcntl.LOCK_EX);
517 self.DB = anydbm.open(Database,"c",0600);
518 self.CleanCutOff = CleanCutOff;
519 self.AgeCutOff = AgeCutOff;
520 self.FutureCutOff = FutureCutOff;
523 # Close the cache and lock
530 # Clean out any old signatures
532 CutOff = time.time() - self.CleanCutOff;
533 for x in self.DB.keys():
534 if int(self.DB[x]) <= CutOff:
537 # Check a signature. 'sig' is a 3 tuple that has the sigId, date and
540 if Sig[0] == None or Sig[1] == None or Sig[2] == None:
541 return "Invalid signature";
542 if int(Sig[1]) > time.time() + self.FutureCutOff:
543 return "Signature has a time too far in the future";
544 if self.DB.has_key(Sig[0] + '-' + Sig[2]):
545 return "Signature has already been received";
546 if int(Sig[1]) < time.time() - self.AgeCutOff:
547 return "Signature has passed the age cut off ";
548 # + str(int(Sig[1])) + ',' + str(time.time()) + "," + str(Sig);
551 # Add a signature, the sig is the same as is given to Check
553 if Sig[0] == None or Sig[1] == None:
554 raise RuntimeError,"Invalid signature";
555 if Sig[1] < time.time() - self.CleanCutOff:
557 Key = Sig[0] + '-' + Sig[2]
558 if self.DB.has_key(Key):
559 if int(self.DB[Key]) < Sig[1]:
560 self.DB[Key] = str(int(Sig[1]));
562 self.DB[Key] = str(int(Sig[1]));
564 def process(self, sig_info):
565 r = self.Check(sig_info);
567 raise RuntimeError, "The replay cache rejected your message: %s."%(r);
573 # vim:set shiftwidth=3: