Import OpenSSL-1.0.1a.
[dragonfly.git] / crypto / openssl / FAQ
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1OpenSSL - Frequently Asked Questions
2--------------------------------------
3
4[MISC] Miscellaneous questions
5
6* Which is the current version of OpenSSL?
7* Where is the documentation?
8* How can I contact the OpenSSL developers?
9* Where can I get a compiled version of OpenSSL?
10* Why aren't tools like 'autoconf' and 'libtool' used?
11* What is an 'engine' version?
12* How do I check the authenticity of the OpenSSL distribution?
13
14[LEGAL] Legal questions
15
16* Do I need patent licenses to use OpenSSL?
17* Can I use OpenSSL with GPL software?
18
19[USER] Questions on using the OpenSSL applications
20
21* Why do I get a "PRNG not seeded" error message?
22* Why do I get an "unable to write 'random state'" error message?
23* How do I create certificates or certificate requests?
24* Why can't I create certificate requests?
25* Why does <SSL program> fail with a certificate verify error?
26* Why can I only use weak ciphers when I connect to a server using OpenSSL?
27* How can I create DSA certificates?
28* Why can't I make an SSL connection using a DSA certificate?
29* How can I remove the passphrase on a private key?
30* Why can't I use OpenSSL certificates with SSL client authentication?
31* Why does my browser give a warning about a mismatched hostname?
32* How do I install a CA certificate into a browser?
33* Why is OpenSSL x509 DN output not conformant to RFC2253?
74093195 34* What is a "128 bit certificate"? Can I create one with OpenSSL?
683caddb 35* Why does OpenSSL set the authority key identifier extension incorrectly?
2e6ca3d0 36* How can I set up a bundle of commercial root CA certificates?
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37
38[BUILD] Questions about building and testing OpenSSL
39
40* Why does the linker complain about undefined symbols?
41* Why does the OpenSSL test fail with "bc: command not found"?
42* Why does the OpenSSL test fail with "bc: 1 no implemented"?
43* Why does the OpenSSL test fail with "bc: stack empty"?
44* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
45* Why does the OpenSSL compilation fail with "ar: command not found"?
46* Why does the OpenSSL compilation fail on Win32 with VC++?
47* What is special about OpenSSL on Redhat?
48* Why does the OpenSSL compilation fail on MacOS X?
49* Why does the OpenSSL test suite fail on MacOS X?
50* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
51* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
52* Why does the OpenSSL test suite fail in sha512t on x86 CPU?
53* Why does compiler fail to compile sha512.c?
74093195 54* Test suite still fails, what to do?
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55* I think I've found a bug, what should I do?
56* I'm SURE I've found a bug, how do I report it?
57* I've found a security issue, how do I report it?
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58
59[PROG] Questions about programming with OpenSSL
60
61* Is OpenSSL thread-safe?
62* I've compiled a program under Windows and it crashes: why?
63* How do I read or write a DER encoded buffer using the ASN1 functions?
64* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
65* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
66* I've called <some function> and it fails, why?
67* I just get a load of numbers for the error output, what do they mean?
68* Why do I get errors about unknown algorithms?
69* Why can't the OpenSSH configure script detect OpenSSL?
70* Can I use OpenSSL's SSL library with non-blocking I/O?
71* Why doesn't my server application receive a client certificate?
72* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
73* I think I've detected a memory leak, is this a bug?
e6bc27f5 74* Why does Valgrind complain about the use of uninitialized data?
683caddb 75* Why doesn't a memory BIO work when a file does?
919b01cc 76* Where are the declarations and implementations of d2i_X509() etc?
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77
78===============================================================================
79
80[MISC] ========================================================================
81
82* Which is the current version of OpenSSL?
83
84The current version is available from <URL: http://www.openssl.org>.
503f6d4b 85OpenSSL 1.0.1a was released on Apr 19th, 2012.
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86
87In addition to the current stable release, you can also access daily
88snapshots of the OpenSSL development version at <URL:
89ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access.
90
91
92* Where is the documentation?
93
94OpenSSL is a library that provides cryptographic functionality to
95applications such as secure web servers. Be sure to read the
96documentation of the application you want to use. The INSTALL file
97explains how to install this library.
98
99OpenSSL includes a command line utility that can be used to perform a
100variety of cryptographic functions. It is described in the openssl(1)
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101manpage. Documentation for developers is currently being written. Many
102manual pages are available; overviews over libcrypto and
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103libssl are given in the crypto(3) and ssl(3) manpages.
104
105The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
106different directory if you specified one as described in INSTALL).
107In addition, you can read the most current versions at
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108<URL: http://www.openssl.org/docs/>. Note that the online documents refer
109to the very latest development versions of OpenSSL and may include features
110not present in released versions. If in doubt refer to the documentation
111that came with the version of OpenSSL you are using.
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112
113For information on parts of libcrypto that are not yet documented, you
114might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
115predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much
116of this still applies to OpenSSL.
117
118There is some documentation about certificate extensions and PKCS#12
119in doc/openssl.txt
120
121The original SSLeay documentation is included in OpenSSL as
122doc/ssleay.txt. It may be useful when none of the other resources
123help, but please note that it reflects the obsolete version SSLeay
1240.6.6.
125
126
127* How can I contact the OpenSSL developers?
128
129The README file describes how to submit bug reports and patches to
130OpenSSL. Information on the OpenSSL mailing lists is available from
131<URL: http://www.openssl.org>.
132
133
134* Where can I get a compiled version of OpenSSL?
135
136You can finder pointers to binary distributions in
ea552218 137<URL: http://www.openssl.org/related/binaries.html> .
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138
139Some applications that use OpenSSL are distributed in binary form.
140When using such an application, you don't need to install OpenSSL
141yourself; the application will include the required parts (e.g. DLLs).
142
143If you want to build OpenSSL on a Windows system and you don't have
144a C compiler, read the "Mingw32" section of INSTALL.W32 for information
145on how to obtain and install the free GNU C compiler.
146
147A number of Linux and *BSD distributions include OpenSSL.
148
149
150* Why aren't tools like 'autoconf' and 'libtool' used?
151
152autoconf will probably be used in future OpenSSL versions. If it was
153less Unix-centric, it might have been used much earlier.
154
155* What is an 'engine' version?
156
157With version 0.9.6 OpenSSL was extended to interface to external crypto
158hardware. This was realized in a special release '0.9.6-engine'. With
159version 0.9.7 the changes were merged into the main development line,
160so that the special release is no longer necessary.
161
162* How do I check the authenticity of the OpenSSL distribution?
163
164We provide MD5 digests and ASC signatures of each tarball.
165Use MD5 to check that a tarball from a mirror site is identical:
166
167 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
168
169You can check authenticity using pgp or gpg. You need the OpenSSL team
170member public key used to sign it (download it from a key server, see a
171list of keys at <URL: http://www.openssl.org/about/>). Then
172just do:
173
174 pgp TARBALL.asc
175
176[LEGAL] =======================================================================
177
178* Do I need patent licenses to use OpenSSL?
179
180The patents section of the README file lists patents that may apply to
181you if you want to use OpenSSL. For information on intellectual
182property rights, please consult a lawyer. The OpenSSL team does not
183offer legal advice.
184
185You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using
186 ./config no-idea no-mdc2 no-rc5
187
188
189* Can I use OpenSSL with GPL software?
190
191On many systems including the major Linux and BSD distributions, yes (the
192GPL does not place restrictions on using libraries that are part of the
193normal operating system distribution).
194
195On other systems, the situation is less clear. Some GPL software copyright
196holders claim that you infringe on their rights if you use OpenSSL with
197their software on operating systems that don't normally include OpenSSL.
198
199If you develop open source software that uses OpenSSL, you may find it
200useful to choose an other license than the GPL, or state explicitly that
201"This program is released under the GPL with the additional exemption that
202compiling, linking, and/or using OpenSSL is allowed." If you are using
203GPL software developed by others, you may want to ask the copyright holder
204for permission to use their software with OpenSSL.
205
206
207[USER] ========================================================================
208
209* Why do I get a "PRNG not seeded" error message?
210
211Cryptographic software needs a source of unpredictable data to work
212correctly. Many open source operating systems provide a "randomness
213device" (/dev/urandom or /dev/random) that serves this purpose.
214All OpenSSL versions try to use /dev/urandom by default; starting with
215version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not
216available.
217
218On other systems, applications have to call the RAND_add() or
219RAND_seed() function with appropriate data before generating keys or
220performing public key encryption. (These functions initialize the
221pseudo-random number generator, PRNG.) Some broken applications do
222not do this. As of version 0.9.5, the OpenSSL functions that need
223randomness report an error if the random number generator has not been
224seeded with at least 128 bits of randomness. If this error occurs and
225is not discussed in the documentation of the application you are
226using, please contact the author of that application; it is likely
227that it never worked correctly. OpenSSL 0.9.5 and later make the
228error visible by refusing to perform potentially insecure encryption.
229
230If you are using Solaris 8, you can add /dev/urandom and /dev/random
231devices by installing patch 112438 (Sparc) or 112439 (x86), which are
232available via the Patchfinder at <URL: http://sunsolve.sun.com>
233(Solaris 9 includes these devices by default). For /dev/random support
234for earlier Solaris versions, see Sun's statement at
235<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski>
236(the SUNWski package is available in patch 105710).
237
238On systems without /dev/urandom and /dev/random, it is a good idea to
239use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for
240details. Starting with version 0.9.7, OpenSSL will automatically look
241for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and
242/etc/entropy.
243
244Most components of the openssl command line utility automatically try
245to seed the random number generator from a file. The name of the
246default seeding file is determined as follows: If environment variable
247RANDFILE is set, then it names the seeding file. Otherwise if
248environment variable HOME is set, then the seeding file is $HOME/.rnd.
249If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will
250use file .rnd in the current directory while OpenSSL 0.9.6a uses no
251default seeding file at all. OpenSSL 0.9.6b and later will behave
252similarly to 0.9.6a, but will use a default of "C:\" for HOME on
253Windows systems if the environment variable has not been set.
254
255If the default seeding file does not exist or is too short, the "PRNG
256not seeded" error message may occur.
257
258The openssl command line utility will write back a new state to the
259default seeding file (and create this file if necessary) unless
260there was no sufficient seeding.
261
262Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work.
263Use the "-rand" option of the OpenSSL command line tools instead.
264The $RANDFILE environment variable and $HOME/.rnd are only used by the
265OpenSSL command line tools. Applications using the OpenSSL library
266provide their own configuration options to specify the entropy source,
267please check out the documentation coming the with application.
268
269
270* Why do I get an "unable to write 'random state'" error message?
271
272
273Sometimes the openssl command line utility does not abort with
274a "PRNG not seeded" error message, but complains that it is
275"unable to write 'random state'". This message refers to the
276default seeding file (see previous answer). A possible reason
277is that no default filename is known because neither RANDFILE
278nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the
279current directory in this case, but this has changed with 0.9.6a.)
280
281
282* How do I create certificates or certificate requests?
283
284Check out the CA.pl(1) manual page. This provides a simple wrapper round
285the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
286out the manual pages for the individual utilities and the certificate
287extensions documentation (currently in doc/openssl.txt).
288
289
290* Why can't I create certificate requests?
291
292You typically get the error:
293
294 unable to find 'distinguished_name' in config
295 problems making Certificate Request
296
297This is because it can't find the configuration file. Check out the
298DIAGNOSTICS section of req(1) for more information.
299
300
301* Why does <SSL program> fail with a certificate verify error?
302
303This problem is usually indicated by log messages saying something like
304"unable to get local issuer certificate" or "self signed certificate".
305When a certificate is verified its root CA must be "trusted" by OpenSSL
306this typically means that the CA certificate must be placed in a directory
307or file and the relevant program configured to read it. The OpenSSL program
308'verify' behaves in a similar way and issues similar error messages: check
309the verify(1) program manual page for more information.
310
311
312* Why can I only use weak ciphers when I connect to a server using OpenSSL?
313
314This is almost certainly because you are using an old "export grade" browser
315which only supports weak encryption. Upgrade your browser to support 128 bit
316ciphers.
317
318
319* How can I create DSA certificates?
320
321Check the CA.pl(1) manual page for a DSA certificate example.
322
323
324* Why can't I make an SSL connection to a server using a DSA certificate?
325
326Typically you'll see a message saying there are no shared ciphers when
327the same setup works fine with an RSA certificate. There are two possible
328causes. The client may not support connections to DSA servers most web
329browsers (including Netscape and MSIE) only support connections to servers
330supporting RSA cipher suites. The other cause is that a set of DH parameters
331has not been supplied to the server. DH parameters can be created with the
332dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
333check the source to s_server in apps/s_server.c for an example.
334
335
336* How can I remove the passphrase on a private key?
337
338Firstly you should be really *really* sure you want to do this. Leaving
339a private key unencrypted is a major security risk. If you decide that
340you do have to do this check the EXAMPLES sections of the rsa(1) and
341dsa(1) manual pages.
342
343
344* Why can't I use OpenSSL certificates with SSL client authentication?
345
346What will typically happen is that when a server requests authentication
347it will either not include your certificate or tell you that you have
348no client certificates (Netscape) or present you with an empty list box
349(MSIE). The reason for this is that when a server requests a client
350certificate it includes a list of CAs names which it will accept. Browsers
351will only let you select certificates from the list on the grounds that
352there is little point presenting a certificate which the server will
353reject.
354
355The solution is to add the relevant CA certificate to your servers "trusted
356CA list". How you do this depends on the server software in uses. You can
357print out the servers list of acceptable CAs using the OpenSSL s_client tool:
358
359openssl s_client -connect www.some.host:443 -prexit
360
361If your server only requests certificates on certain URLs then you may need
362to manually issue an HTTP GET command to get the list when s_client connects:
363
364GET /some/page/needing/a/certificate.html
365
366If your CA does not appear in the list then this confirms the problem.
367
368
369* Why does my browser give a warning about a mismatched hostname?
370
371Browsers expect the server's hostname to match the value in the commonName
372(CN) field of the certificate. If it does not then you get a warning.
373
374
375* How do I install a CA certificate into a browser?
376
377The usual way is to send the DER encoded certificate to the browser as
378MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
379link. On MSIE certain extensions such as .der or .cacert may also work, or you
380can import the certificate using the certificate import wizard.
381
382You can convert a certificate to DER form using the command:
383
384openssl x509 -in ca.pem -outform DER -out ca.der
385
386Occasionally someone suggests using a command such as:
387
388openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
389
390DO NOT DO THIS! This command will give away your CAs private key and
391reduces its security to zero: allowing anyone to forge certificates in
392whatever name they choose.
393
394* Why is OpenSSL x509 DN output not conformant to RFC2253?
395
396The ways to print out the oneline format of the DN (Distinguished Name) have
397been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex()
398interface, the "-nameopt" option could be introduded. See the manual
399page of the "openssl x509" commandline tool for details. The old behaviour
400has however been left as default for the sake of compatibility.
401
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402* What is a "128 bit certificate"? Can I create one with OpenSSL?
403
404The term "128 bit certificate" is a highly misleading marketing term. It does
405*not* refer to the size of the public key in the certificate! A certificate
406containing a 128 bit RSA key would have negligible security.
407
408There were various other names such as "magic certificates", "SGC
409certificates", "step up certificates" etc.
410
411You can't generally create such a certificate using OpenSSL but there is no
412need to any more. Nowadays web browsers using unrestricted strong encryption
413are generally available.
414
683caddb 415When there were tight restrictions on the export of strong encryption
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416software from the US only weak encryption algorithms could be freely exported
417(initially 40 bit and then 56 bit). It was widely recognised that this was
683caddb 418inadequate. A relaxation of the rules allowed the use of strong encryption but
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419only to an authorised server.
420
421Two slighly different techniques were developed to support this, one used by
422Netscape was called "step up", the other used by MSIE was called "Server Gated
423Cryptography" (SGC). When a browser initially connected to a server it would
424check to see if the certificate contained certain extensions and was issued by
425an authorised authority. If these test succeeded it would reconnect using
426strong encryption.
427
428Only certain (initially one) certificate authorities could issue the
429certificates and they generally cost more than ordinary certificates.
430
431Although OpenSSL can create certificates containing the appropriate extensions
432the certificate would not come from a permitted authority and so would not
433be recognized.
434
435The export laws were later changed to allow almost unrestricted use of strong
436encryption so these certificates are now obsolete.
437
438
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439* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly?
440
441It doesn't: this extension is often the cause of confusion.
442
443Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose
444certificate C contains AKID.
445
446The purpose of this extension is to identify the authority certificate B. This
447can be done either by including the subject key identifier of B or its issuer
448name and serial number.
449
450In this latter case because it is identifying certifcate B it must contain the
451issuer name and serial number of B.
452
453It is often wrongly assumed that it should contain the subject name of B. If it
454did this would be redundant information because it would duplicate the issuer
455name of C.
456
457
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458* How can I set up a bundle of commercial root CA certificates?
459
460The OpenSSL software is shipped without any root CA certificate as the
461OpenSSL project does not have any policy on including or excluding
462any specific CA and does not intend to set up such a policy. Deciding
463about which CAs to support is up to application developers or
464administrators.
465
466Other projects do have other policies so you can for example extract the CA
467bundle used by Mozilla and/or modssl as described in this article:
468
ea552218 469 <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html>
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470
471
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472[BUILD] =======================================================================
473
474* Why does the linker complain about undefined symbols?
475
476Maybe the compilation was interrupted, and make doesn't notice that
477something is missing. Run "make clean; make".
478
479If you used ./Configure instead of ./config, make sure that you
480selected the right target. File formats may differ slightly between
481OS versions (for example sparcv8/sparcv9, or a.out/elf).
482
483In case you get errors about the following symbols, use the config
484option "no-asm", as described in INSTALL:
485
486 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
487 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
488 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
489 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
490 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
491 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
492 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
493
494If none of these helps, you may want to try using the current snapshot.
495If the problem persists, please submit a bug report.
496
497
498* Why does the OpenSSL test fail with "bc: command not found"?
499
500You didn't install "bc", the Unix calculator. If you want to run the
501tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
502
503
504* Why does the OpenSSL test fail with "bc: 1 no implemented"?
505
506On some SCO installations or versions, bc has a bug that gets triggered
507when you run the test suite (using "make test"). The message returned is
508"bc: 1 not implemented".
509
510The best way to deal with this is to find another implementation of bc
ea552218 511and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
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512for download instructions) can be safely used, for example.
513
514
515* Why does the OpenSSL test fail with "bc: stack empty"?
516
517On some DG/ux versions, bc seems to have a too small stack for calculations
518that the OpenSSL bntest throws at it. This gets triggered when you run the
519test suite (using "make test"). The message returned is "bc: stack empty".
520
521The best way to deal with this is to find another implementation of bc
ea552218 522and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
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523for download instructions) can be safely used, for example.
524
525
526* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
527
528On some Alpha installations running Tru64 Unix and Compaq C, the compilation
529of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual
530memory to continue compilation.' As far as the tests have shown, this may be
531a compiler bug. What happens is that it eats up a lot of resident memory
532to build something, probably a table. The problem is clearly in the
533optimization code, because if one eliminates optimization completely (-O0),
534the compilation goes through (and the compiler consumes about 2MB of resident
535memory instead of 240MB or whatever one's limit is currently).
536
537There are three options to solve this problem:
538
5391. set your current data segment size soft limit higher. Experience shows
540that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do
541this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
542kbytes to set the limit to.
543
5442. If you have a hard limit that is lower than what you need and you can't
545get it changed, you can compile all of OpenSSL with -O0 as optimization
546level. This is however not a very nice thing to do for those who expect to
547get the best result from OpenSSL. A bit more complicated solution is the
548following:
549
550----- snip:start -----
551 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \
552 sed -e 's/ -O[0-9] / -O0 /'`"
553 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'`
554 make
555----- snip:end -----
556
557This will only compile sha_dgst.c with -O0, the rest with the optimization
558level chosen by the configuration process. When the above is done, do the
559test and installation and you're set.
560
5613. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It
562should not be used and is not used in SSL/TLS nor any other recognized
563protocol in either case.
564
565
566* Why does the OpenSSL compilation fail with "ar: command not found"?
567
568Getting this message is quite usual on Solaris 2, because Sun has hidden
569away 'ar' and other development commands in directories that aren't in
570$PATH by default. One of those directories is '/usr/ccs/bin'. The
571quickest way to fix this is to do the following (it assumes you use sh
572or any sh-compatible shell):
573
574----- snip:start -----
575 PATH=${PATH}:/usr/ccs/bin; export PATH
576----- snip:end -----
577
578and then redo the compilation. What you should really do is make sure
579'/usr/ccs/bin' is permanently in your $PATH, for example through your
580'.profile' (again, assuming you use a sh-compatible shell).
581
582
583* Why does the OpenSSL compilation fail on Win32 with VC++?
584
585Sometimes, you may get reports from VC++ command line (cl) that it
586can't find standard include files like stdio.h and other weirdnesses.
587One possible cause is that the environment isn't correctly set up.
588To solve that problem for VC++ versions up to 6, one should run
589VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++
590installation directory (somewhere under 'Program Files'). For VC++
591version 7 (and up?), which is also called VS.NET, the file is called
592VSVARS32.BAT instead.
593This needs to be done prior to running NMAKE, and the changes are only
594valid for the current DOS session.
595
596
597* What is special about OpenSSL on Redhat?
598
599Red Hat Linux (release 7.0 and later) include a preinstalled limited
600version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2
601is disabled in this version. The same may apply to other Linux distributions.
602Users may therefore wish to install more or all of the features left out.
603
604To do this you MUST ensure that you do not overwrite the openssl that is in
605/usr/bin on your Red Hat machine. Several packages depend on this file,
606including sendmail and ssh. /usr/local/bin is a good alternative choice. The
607libraries that come with Red Hat 7.0 onwards have different names and so are
608not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and
609/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and
610/lib/libcrypto.so.2 respectively).
611
612Please note that we have been advised by Red Hat attempting to recompile the
613openssl rpm with all the cryptography enabled will not work. All other
614packages depend on the original Red Hat supplied openssl package. It is also
615worth noting that due to the way Red Hat supplies its packages, updates to
616openssl on each distribution never change the package version, only the
617build number. For example, on Red Hat 7.1, the latest openssl package has
618version number 0.9.6 and build number 9 even though it contains all the
619relevant updates in packages up to and including 0.9.6b.
620
621A possible way around this is to persuade Red Hat to produce a non-US
622version of Red Hat Linux.
623
624FYI: Patent numbers and expiry dates of US patents:
625MDC-2: 4,908,861 13/03/2007
626IDEA: 5,214,703 25/05/2010
627RC5: 5,724,428 03/03/2015
628
629
630* Why does the OpenSSL compilation fail on MacOS X?
631
632If the failure happens when trying to build the "openssl" binary, with
633a large number of undefined symbols, it's very probable that you have
634OpenSSL 0.9.6b delivered with the operating system (you can find out by
635running '/usr/bin/openssl version') and that you were trying to build
636OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in
637MacOS X has a misfeature that's quite difficult to go around.
638Look in the file PROBLEMS for a more detailed explanation and for possible
639solutions.
640
641
642* Why does the OpenSSL test suite fail on MacOS X?
643
644If the failure happens when running 'make test' and the RC4 test fails,
645it's very probable that you have OpenSSL 0.9.6b delivered with the
646operating system (you can find out by running '/usr/bin/openssl version')
647and that you were trying to build OpenSSL 0.9.6d. The problem is that
648the loader ('ld') in MacOS X has a misfeature that's quite difficult to
649go around and has linked the programs "openssl" and the test programs
650with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the
651libraries you just built.
652Look in the file PROBLEMS for a more detailed explanation and for possible
653solutions.
654
655* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
656
657Failure in BN_sqr test is most likely caused by a failure to configure the
658toolkit for current platform or lack of support for the platform in question.
659Run './config -t' and './apps/openssl version -p'. Do these platform
660identifiers match? If they don't, then you most likely failed to run
661./config and you're hereby advised to do so before filing a bug report.
662If ./config itself fails to run, then it's most likely problem with your
663local environment and you should turn to your system administrator (or
664similar). If identifiers match (and/or no alternative identifier is
665suggested by ./config script), then the platform is unsupported. There might
666or might not be a workaround. Most notably on SPARC64 platforms with GNU
667C compiler you should be able to produce a working build by running
668'./config -m32'. I understand that -m32 might not be what you want/need,
669but the build should be operational. For further details turn to
670<openssl-dev@openssl.org>.
671
672* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
673
674As of 0.9.7 assembler routines were overhauled for position independence
675of the machine code, which is essential for shared library support. For
676some reason OpenBSD is equipped with an out-of-date GNU assembler which
677finds the new code offensive. To work around the problem, configure with
678no-asm (and sacrifice a great deal of performance) or patch your assembler
679according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>.
680For your convenience a pre-compiled replacement binary is provided at
681<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>.
682Reportedly elder *BSD a.out platforms also suffer from this problem and
683remedy should be same. Provided binary is statically linked and should be
684working across wider range of *BSD branches, not just OpenBSD.
685
686* Why does the OpenSSL test suite fail in sha512t on x86 CPU?
687
688If the test program in question fails withs SIGILL, Illegal Instruction
689exception, then you more than likely to run SSE2-capable CPU, such as
690Intel P4, under control of kernel which does not support SSE2
691instruction extentions. See accompanying INSTALL file and
692OPENSSL_ia32cap(3) documentation page for further information.
693
694* Why does compiler fail to compile sha512.c?
695
696OpenSSL SHA-512 implementation depends on compiler support for 64-bit
697integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a
698couple] lack support for this and therefore are incapable of compiling
699the module in question. The recommendation is to disable SHA-512 by
700adding no-sha512 to ./config [or ./Configure] command line. Another
701possible alternative might be to switch to GCC.
702
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703* Test suite still fails, what to do?
704
705Another common reason for failure to complete some particular test is
706simply bad code generated by a buggy component in toolchain or deficiency
707in run-time environment. There are few cases documented in PROBLEMS file,
708consult it for possible workaround before you beat the drum. Even if you
709don't find solution or even mention there, do reserve for possibility of
710a compiler bug. Compiler bugs might appear in rather bizarre ways, they
711never make sense, and tend to emerge when you least expect them. In order
712to identify one, drop optimization level, e.g. by editing CFLAG line in
713top-level Makefile, recompile and re-run the test.
714
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715* I think I've found a bug, what should I do?
716
717If you are a new user then it is quite likely you haven't found a bug and
718something is happening you aren't familiar with. Check this FAQ, the associated
719documentation and the mailing lists for similar queries. If you are still
720unsure whether it is a bug or not submit a query to the openssl-users mailing
721list.
722
723
724* I'm SURE I've found a bug, how do I report it?
725
726Bug reports with no security implications should be sent to the request
727tracker. This can be done by mailing the report to <rt@openssl.org> (or its
728alias <openssl-bugs@openssl.org>), please note that messages sent to the
729request tracker also appear in the public openssl-dev mailing list.
730
731The report should be in plain text. Any patches should be sent as
732plain text attachments because some mailers corrupt patches sent inline.
733If your issue affects multiple versions of OpenSSL check any patches apply
734cleanly and, if possible include patches to each affected version.
735
736The report should be given a meaningful subject line briefly summarising the
737issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful.
738
739By sending reports to the request tracker the bug can then be given a priority
740and assigned to the appropriate maintainer. The history of discussions can be
741accessed and if the issue has been addressed or a reason why not. If patches
742are only sent to openssl-dev they can be mislaid if a team member has to
743wade through months of old messages to review the discussion.
744
745See also <URL: http://www.openssl.org/support/rt.html>
746
747
748* I've found a security issue, how do I report it?
749
750If you think your bug has security implications then please send it to
751openssl-security@openssl.org if you don't get a prompt reply at least
752acknowledging receipt then resend or mail it directly to one of the
753more active team members (e.g. Steve).
754
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755[PROG] ========================================================================
756
757* Is OpenSSL thread-safe?
758
759Yes (with limitations: an SSL connection may not concurrently be used
760by multiple threads). On Windows and many Unix systems, OpenSSL
761automatically uses the multi-threaded versions of the standard
762libraries. If your platform is not one of these, consult the INSTALL
763file.
764
765Multi-threaded applications must provide two callback functions to
74093195 766OpenSSL by calling CRYPTO_set_locking_callback() and
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767CRYPTO_set_id_callback(), for all versions of OpenSSL up to and
768including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback()
769and associated APIs are deprecated by CRYPTO_THREADID_set_callback()
770and friends. This is described in the threads(3) manpage.
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771
772* I've compiled a program under Windows and it crashes: why?
773
774This is usually because you've missed the comment in INSTALL.W32.
775Your application must link against the same version of the Win32
776C-Runtime against which your openssl libraries were linked. The
777default version for OpenSSL is /MD - "Multithreaded DLL".
778
779If you are using Microsoft Visual C++'s IDE (Visual Studio), in
780many cases, your new project most likely defaulted to "Debug
781Singlethreaded" - /ML. This is NOT interchangeable with /MD and your
782program will crash, typically on the first BIO related read or write
783operation.
784
785For each of the six possible link stage configurations within Win32,
786your application must link against the same by which OpenSSL was
787built. If you are using MS Visual C++ (Studio) this can be changed
788by:
789
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790 1. Select Settings... from the Project Menu.
791 2. Select the C/C++ Tab.
792 3. Select "Code Generation from the "Category" drop down list box
793 4. Select the Appropriate library (see table below) from the "Use
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794 run-time library" drop down list box. Perform this step for both
795 your debug and release versions of your application (look at the
796 top left of the settings panel to change between the two)
797
798 Single Threaded /ML - MS VC++ often defaults to
799 this for the release
800 version of a new project.
801 Debug Single Threaded /MLd - MS VC++ often defaults to
802 this for the debug version
803 of a new project.
804 Multithreaded /MT
805 Debug Multithreaded /MTd
806 Multithreaded DLL /MD - OpenSSL defaults to this.
807 Debug Multithreaded DLL /MDd
808
809Note that debug and release libraries are NOT interchangeable. If you
810built OpenSSL with /MD your application must use /MD and cannot use /MDd.
811
812As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL
74093195 813.DLLs compiled with some specific run-time option [we insist on the
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814default /MD] can be deployed with application compiled with different
815option or even different compiler. But there is a catch! Instead of
816re-compiling OpenSSL toolkit, as you would have to with prior versions,
817you have to compile small C snippet with compiler and/or options of
818your choice. The snippet gets installed as
819<install-root>/include/openssl/applink.c and should be either added to
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820your application project or simply #include-d in one [and only one]
821of your application source files. Failure to link this shim module
822into your application manifests itself as fatal "no OPENSSL_Applink"
823run-time error. An explicit reminder is due that in this situation
824[mixing compiler options] it is as important to add CRYPTO_malloc_init
825prior first call to OpenSSL.
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826
827* How do I read or write a DER encoded buffer using the ASN1 functions?
828
829You have two options. You can either use a memory BIO in conjunction
830with the i2d_*_bio() or d2i_*_bio() functions or you can use the
831i2d_*(), d2i_*() functions directly. Since these are often the
832cause of grief here are some code fragments using PKCS7 as an example:
833
834 unsigned char *buf, *p;
835 int len;
836
837 len = i2d_PKCS7(p7, NULL);
838 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */
839 p = buf;
840 i2d_PKCS7(p7, &p);
841
842At this point buf contains the len bytes of the DER encoding of
843p7.
844
845The opposite assumes we already have len bytes in buf:
846
847 unsigned char *p;
848 p = buf;
849 p7 = d2i_PKCS7(NULL, &p, len);
850
851At this point p7 contains a valid PKCS7 structure of NULL if an error
852occurred. If an error occurred ERR_print_errors(bio) should give more
853information.
854
855The reason for the temporary variable 'p' is that the ASN1 functions
856increment the passed pointer so it is ready to read or write the next
857structure. This is often a cause of problems: without the temporary
858variable the buffer pointer is changed to point just after the data
859that has been read or written. This may well be uninitialized data
860and attempts to free the buffer will have unpredictable results
861because it no longer points to the same address.
862
863
864* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
865
866The short answer is yes, because DER is a special case of BER and OpenSSL
867ASN1 decoders can process BER.
868
869The longer answer is that ASN1 structures can be encoded in a number of
870different ways. One set of ways is the Basic Encoding Rules (BER) with various
871permissible encodings. A restriction of BER is the Distinguished Encoding
872Rules (DER): these uniquely specify how a given structure is encoded.
873
874Therefore, because DER is a special case of BER, DER is an acceptable encoding
875for BER.
876
877
878* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
879
880This usually happens when you try compiling something using the PKCS#12
881macros with a C++ compiler. There is hardly ever any need to use the
882PKCS#12 macros in a program, it is much easier to parse and create
883PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions
884documented in doc/openssl.txt and with examples in demos/pkcs12. The
885'pkcs12' application has to use the macros because it prints out
886debugging information.
887
888
889* I've called <some function> and it fails, why?
890
891Before submitting a report or asking in one of the mailing lists, you
892should try to determine the cause. In particular, you should call
893ERR_print_errors() or ERR_print_errors_fp() after the failed call
894and see if the message helps. Note that the problem may occur earlier
895than you think -- you should check for errors after every call where
896it is possible, otherwise the actual problem may be hidden because
897some OpenSSL functions clear the error state.
898
899
900* I just get a load of numbers for the error output, what do they mean?
901
902The actual format is described in the ERR_print_errors() manual page.
903You should call the function ERR_load_crypto_strings() before hand and
904the message will be output in text form. If you can't do this (for example
905it is a pre-compiled binary) you can use the errstr utility on the error
906code itself (the hex digits after the second colon).
907
908
909* Why do I get errors about unknown algorithms?
910
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911The cause is forgetting to load OpenSSL's table of algorithms with
912OpenSSL_add_all_algorithms(). See the manual page for more information. This
913can cause several problems such as being unable to read in an encrypted
914PEM file, unable to decrypt a PKCS#12 file or signature failure when
915verifying certificates.
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916
917* Why can't the OpenSSH configure script detect OpenSSL?
918
919Several reasons for problems with the automatic detection exist.
920OpenSSH requires at least version 0.9.5a of the OpenSSL libraries.
921Sometimes the distribution has installed an older version in the system
922locations that is detected instead of a new one installed. The OpenSSL
923library might have been compiled for another CPU or another mode (32/64 bits).
924Permissions might be wrong.
925
926The general answer is to check the config.log file generated when running
927the OpenSSH configure script. It should contain the detailed information
928on why the OpenSSL library was not detected or considered incompatible.
929
930
931* Can I use OpenSSL's SSL library with non-blocking I/O?
932
933Yes; make sure to read the SSL_get_error(3) manual page!
934
935A pitfall to avoid: Don't assume that SSL_read() will just read from
936the underlying transport or that SSL_write() will just write to it --
937it is also possible that SSL_write() cannot do any useful work until
938there is data to read, or that SSL_read() cannot do anything until it
939is possible to send data. One reason for this is that the peer may
940request a new TLS/SSL handshake at any time during the protocol,
941requiring a bi-directional message exchange; both SSL_read() and
942SSL_write() will try to continue any pending handshake.
943
944
945* Why doesn't my server application receive a client certificate?
946
947Due to the TLS protocol definition, a client will only send a certificate,
948if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the
949SSL_CTX_set_verify() function to enable the use of client certificates.
950
951
952* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
953
954For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier
955versions, uniqueIdentifier was incorrectly used for X.509 certificates.
956The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier.
957Change your code to use the new name when compiling against OpenSSL 0.9.7.
958
959
960* I think I've detected a memory leak, is this a bug?
961
962In most cases the cause of an apparent memory leak is an OpenSSL internal table
963that is allocated when an application starts up. Since such tables do not grow
964in size over time they are harmless.
965
966These internal tables can be freed up when an application closes using various
967functions. Currently these include following:
968
969Thread-local cleanup functions:
970
971 ERR_remove_state()
972
973Application-global cleanup functions that are aware of usage (and therefore
974thread-safe):
975
976 ENGINE_cleanup() and CONF_modules_unload()
977
978"Brutal" (thread-unsafe) Application-global cleanup functions:
979
980 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data().
981
982
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983* Why does Valgrind complain about the use of uninitialized data?
984
985When OpenSSL's PRNG routines are called to generate random numbers the supplied
986buffer contents are mixed into the entropy pool: so it technically does not
987matter whether the buffer is initialized at this point or not. Valgrind (and
988other test tools) will complain about this. When using Valgrind, make sure the
989OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY)
990to get rid of these warnings.
991
992
683caddb 993* Why doesn't a memory BIO work when a file does?
56276539 994
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995This can occur in several cases for example reading an S/MIME email message.
996The reason is that a memory BIO can do one of two things when all the data
997has been read from it.
998
999The default behaviour is to indicate that no more data is available and that
1000the call should be retried, this is to allow the application to fill up the BIO
1001again if necessary.
1002
1003Alternatively it can indicate that no more data is available and that EOF has
1004been reached.
1005
1006If a memory BIO is to behave in the same way as a file this second behaviour
1007is needed. This must be done by calling:
1008
1009 BIO_set_mem_eof_return(bio, 0);
1010
1011See the manual pages for more details.
1012
1013
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1014* Where are the declarations and implementations of d2i_X509() etc?
1015
1016These are defined and implemented by macros of the form:
1017
1018
1019 DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509)
1020
1021The implementation passes an ASN1 "template" defining the structure into an
1022ASN1 interpreter using generalised functions such as ASN1_item_d2i().
1023
1024
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