xref: /freebsd/contrib/sendmail/KNOWNBUGS (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
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2
3	     K N O W N   B U G S   I N   S E N D M A I L
4
5
6The following are bugs or deficiencies in sendmail that we are aware of
7but which have not been fixed in the current release.  You probably
8want to get the most up to date version of this from ftp.sendmail.org
9in /pub/sendmail/KNOWNBUGS.  For descriptions of bugs that have been
10fixed, see the file RELEASE_NOTES (in the root directory of the sendmail
11distribution).
12
13This list is not guaranteed to be complete.
14
15* Header values which are too long may be truncated.
16
17  If a value of a structured header is longer than 256 (MAXNAME)
18  characters then it may be truncated during output. For example,
19  if a single address in the To: header is longer than 256 characters
20  then it will be truncated which may result in a syntactically
21  invalid address.
22
23* Delivery to programs that generate too much output may cause problems
24
25  If e-mail is delivered to a program which generates too much
26  output, then sendmail may issue an error:
27
28  timeout waiting for input from local during Draining Input
29
30  Make sure that the program does not generate output beyond a
31  status message (corresponding to the exit status).  This may
32  require a wrapper around the actual program to redirect output
33  to /dev/null.
34
35  Such a problem has been reported for bulk_mailer.
36
37* Null bytes are not handled properly in headers.
38
39  Sendmail should handle full binary data.  As it stands, it handles
40  all values in the body, but not 0x00 in the header.  Changing
41  this would require a major restructuring of the code -- for
42  example, almost no C library support could be used to handle
43  strings.
44
45* Header checks are not called if header value is too long or empty.
46
47  If the value of a header is longer than 1250 (MAXNAME + MAXATOM - 6)
48  characters or it contains a single word longer than 256 (MAXNAME)
49  characters then no header check is done even if one is configured for
50  the header.
51
52* Header lines which are too long will be split incorrectly.
53
54  Header lines which are longer than 2045 characters will be split
55  but some characters might be lost.  Fix: obey RFC (2)822 and do not
56  send lines that are longer than 1000 characters.
57
58* milter communication fails if a single header is larger than 64K.
59
60  If a single header is larger than 64KB (which is not possible in the
61  default configuration) then it cannot be transferred in one block to
62  libmilter and hence the communication fails.  This can be avoided by
63  increasing the constant MILTER_CHUNK_SIZE in
64  include/libmilter/mfdef.h and recompiling sendmail, libmilter, and
65  all (statically linked) milters (or by using an undocumented compile
66  time option:  _FFR_MAXDATASIZE; you have to read the source code in
67  order to use this properly).
68
69* Sender addresses whose domain part cause a temporary A record lookup
70  failure but have a valid MX record will be temporarily rejected in
71  the default configuration.  Solution: fix the DNS at the sender side.
72  If that's not easy to achieve, possible workarounds are:
73  - add an entry to the access map:
74	dom.ain	OK
75  - (only for advanced users) replace
76
77# Resolve map (to check if a host exists in check_mail)
78Kresolve host -a<OKR> -T<TEMP>
79
80   with
81
82# Resolve map (to check if a host exists in check_mail)
83Kcanon host -a<OKR> -T<TEMP>
84Kdnsmx dns -R MX -a<OKR> -T<TEMP>
85Kresolve sequence dnsmx canon
86
87
88* Duplicate error messages.
89
90  Sometimes identical, duplicate error messages can be generated.  As
91  near as I can tell, this is rare and relatively innocuous.
92
93* Misleading error messages.
94
95  If an illegal address is specified on the command line together
96  with at least one valid address and PostmasterCopy is set, the
97  DSN does not contain the illegal address, but only the valid
98  address(es).
99
100* \231 considered harmful.
101
102  Header addresses that have the \231 character (and possibly others
103  in the range \201 - \237) behave in odd and usually unexpected ways.
104
105* accept() problem on SVR4.
106
107  Apparently, the sendmail daemon loop (doing accept()s on the network)
108  can get into a weird state on SVR4; it starts logging ``SYSERR:
109  getrequests: accept: Protocol Error''.  The workaround is to kill
110  and restart the sendmail daemon.  We don't have an SVR4 system at
111  Berkeley that carries more than token mail load, so I can't validate
112  this.  It is likely to be a glitch in the sockets emulation, since
113  "Protocol Error" is not possible error code with Berkeley TCP/IP.
114
115  I've also had someone report the message ``sendmail: accept:
116  SIOCGPGRP failed errno 22'' on an SVR4 system.  This message is
117  not in the sendmail source code, so I assume it is also a bug
118  in the sockets emulation.  (Errno 22 is EINVAL "Invalid Argument"
119  on all the systems I have available, including Solaris 2.x.)
120  Apparently, this problem is due to linking -lc before -lsocket;
121  if you are having this problem, check your Makefile.
122
123* accept() problem on Linux.
124
125  The accept() in sendmail daemon loop can return ETIMEDOUT.  An
126  error is reported to syslog:
127
128  Jun  9 17:14:12 hostname sendmail[207]: NOQUEUE: SYSERR(root):
129			getrequests: accept: Connection timed out
130
131  "Connection timed out" is not documented as a valid return from
132  accept(2) and this was believed to be a bug in the Linux kernel.
133  Later information from the Linux kernel group states that Linux
134  2.0 kernels follow RFC1122 while sendmail follows the original BSD
135  (now POSIX 1003.1g draft) specification.  The 2.1.X and later kernels
136  will follow the POSIX draft.
137
138* Excessive mailing list nesting can run out of file descriptors.
139
140  If you have a mailing list that includes lots of other mailing
141  lists, each of which has a separate owner, you can run out of
142  file descriptors.  Each mailing list with a separate owner uses
143  one open file descriptor (prior to 8.6.6 it was three open
144  file descriptors per list).  This is particularly egregious if
145  you have your connection cache set to be large.
146
147* Connection caching breaks if you pass the port number as an argument.
148
149  If you have a definition such as:
150
151	  Mport,          P=[IPC], F=kmDFMuX, S=11/31, R=21,
152			  M=2100000, T=DNS/RFC822/SMTP,
153			  A=IPC [127.0.0.1] $h
154
155  (i.e., where $h is the port number instead of the host name) the
156  connection caching code will break because it won't notice that
157  two messages addressed to different ports should use different
158  connections.
159
160* ESMTP SIZE underestimates the size of a message
161
162  Sendmail makes no allowance for headers that it adds, nor does it
163  account for the SMTP on-the-wire \r\n expansion.  It probably doesn't
164  allow for 8->7 bit MIME conversions either.
165
166* Client ignores SIZE parameter.
167
168  When sendmail acts as client and the server specifies a limit
169  for the mail size, sendmail will ignore this and try to send the
170  mail anyway.  The server will usually reject the MAIL command
171  which specifies the size of the message and hence this problem
172  is not significant.
173
174* Paths to programs being executed and the mode of program files are
175  not checked.  Essentially, the RunProgramInUnsafeDirPath and
176  RunWritableProgram bits in the DontBlameSendmail option are always
177  set.  This is not a problem if your system is well managed (that is,
178  if binaries and system directories are mode 755 instead of something
179  foolish like 777).
180
181* 8-bit data in GECOS field
182
183  If the GECOS (personal name) information in the passwd file contains
184  8-bit characters, those characters can be included in the message
185  header, which can cause problems when sending SMTP to hosts that
186  only accept 7-bit characters.
187
188* 8->7 bit MIME conversion
189
190  When sendmail is doing 8->7 bit MIME conversions, and the message
191  contains certain MIME body types that cannot be converted to 7-bit,
192  sendmail will pass the message as 8-bit.
193
194* 7->8 bit MIME conversion
195
196  If a message that is encoded as 7-bit MIME is converted to 8-bit and
197  that message when decoded is illegal (e.g., because of long lines or
198  illegal characters), sendmail can produce an illegal message.
199
200* MIME encoded full name phrases in the From: header
201
202  If a full name phrase includes characters from MustQuoteChars, sendmail
203  will quote the entire full name phrase.  If MustQuoteChars includes
204  characters which are not special characters according to STD 11 (RFC
205  822), this quotation can interfere with MIME encoded full name phrases.
206  By default, sendmail includes the single quote character (') in
207  MustQuoteChars even though it is not listed as a special character in
208  STD 11.
209
210* bestmx map with -z flag truncates the list of MX hosts
211
212  A bestmx map configured with the -z flag will truncate the list
213  of MX hosts.  This prevents creation of strings which are too
214  long for ruleset parsing.  This can have an adverse effect on the
215  relay_based_on_MX feature.
216
217* Saving to ~sender/dead.letter fails if su'ed to root
218
219  If ErrorMode is set to print and an error in sending mail occurs,
220  the normal action is to print a message to the screen and append
221  the message to a dead.letter file in the sender's home directory.
222  In the case where the sender is using su to act as root, the file
223  safety checks prevent sendmail from saving the dead.letter file
224  because the sender's uid and the current real uid do not match.
225
226* Berkeley DB 2.X race condition with fcntl() locking
227
228  There is a race condition for Berkeley DB 2.X databases on
229  operating systems which use fcntl() style locking, such as
230  Solaris.  Sendmail locks the map before calling db_open() to
231  prevent others from modifying the map while it is being opened.
232  Unfortunately, Berkeley DB opens the map, closes it, and then
233  reopens it.  fcntl() locking drops the lock when any file
234  descriptor pointing to the file is closed, even if it is a
235  different file descriptor than the one used to initially lock
236  the file.  As a result there is a possibility that entries in a
237  map might not be found during a map rebuild.  As a workaround,
238  you can use makemap to build a map with a new name and then
239  "mv" the new db file to replace the old one.
240
241  Sleepycat Software has added code to avoid this race condition to
242  Berkeley DB versions after 2.7.5.
243
244* File open timeouts not available on hard mounted NFS file systems
245
246  Since SIGALRM does not interrupt an RPC call for hard mounted
247  NFS file systems, it is impossible to implement a timeout on a file
248  open operation.  Therefore, while the NFS server is not responding,
249  attempts to open a file on that server will hang.  Systems with
250  local mail delivery and NFS hard mounted home directories should be
251  avoided, as attempts to open the forward files could hang.
252
253* Race condition for delivery to set-user-ID files
254
255  Sendmail will deliver to a fail if the file is owned by the DefaultUser
256  or has the set-user-ID bit set.  Unfortunately, some systems clear that bit
257  when a file is modified.  Sendmail compensates by resetting the file mode
258  back to it's original settings.  Unfortunately, there's still a
259  permission failure race as sendmail checks the permissions before locking
260  the file.  This is unavoidable as sendmail must verify the file is safe
261  to open before opening it.  A file can not be locked until it is open.
262
263* MAIL_HUB always takes precedence over LOCAL_RELAY
264
265  Despite the information in the documentation, MAIL_HUB ($H) will always
266  be used if set instead of LOCAL_RELAY ($R).  This will be fixed in a
267  future version.
268
269$Revision: 8.61 $, Last updated $Date: 2011/04/07 17:48:23 $
270