1 OpenSSL - Frequently Asked Questions
2 --------------------------------------
4 [MISC] Miscellaneous questions
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 * How does the versioning scheme work?
15 [LEGAL] Legal questions
17 * Do I need patent licenses to use OpenSSL?
18 * Can I use OpenSSL with GPL software?
20 [USER] Questions on using the OpenSSL applications
22 * Why do I get a "PRNG not seeded" error message?
23 * Why do I get an "unable to write 'random state'" error message?
24 * How do I create certificates or certificate requests?
25 * Why can't I create certificate requests?
26 * Why does <SSL program> fail with a certificate verify error?
27 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
28 * How can I create DSA certificates?
29 * Why can't I make an SSL connection using a DSA certificate?
30 * How can I remove the passphrase on a private key?
31 * Why can't I use OpenSSL certificates with SSL client authentication?
32 * Why does my browser give a warning about a mismatched hostname?
33 * How do I install a CA certificate into a browser?
34 * Why is OpenSSL x509 DN output not conformant to RFC2253?
35 * What is a "128 bit certificate"? Can I create one with OpenSSL?
36 * Why does OpenSSL set the authority key identifier extension incorrectly?
37 * How can I set up a bundle of commercial root CA certificates?
38 * Some secure servers 'hang' with OpenSSL 1.0.1, is this a bug?
40 [BUILD] Questions about building and testing OpenSSL
42 * Why does the linker complain about undefined symbols?
43 * Why does the OpenSSL test fail with "bc: command not found"?
44 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
45 * Why does the OpenSSL test fail with "bc: stack empty"?
46 * Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
47 * Why does the OpenSSL compilation fail with "ar: command not found"?
48 * Why does the OpenSSL compilation fail on Win32 with VC++?
49 * What is special about OpenSSL on Redhat?
50 * Why does the OpenSSL compilation fail on MacOS X?
51 * Why does the OpenSSL test suite fail on MacOS X?
52 * Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
53 * Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
54 * Why does the OpenSSL test suite fail in sha512t on x86 CPU?
55 * Why does compiler fail to compile sha512.c?
56 * Test suite still fails, what to do?
57 * I think I've found a bug, what should I do?
58 * I'm SURE I've found a bug, how do I report it?
59 * I've found a security issue, how do I report it?
61 [PROG] Questions about programming with OpenSSL
63 * Is OpenSSL thread-safe?
64 * I've compiled a program under Windows and it crashes: why?
65 * How do I read or write a DER encoded buffer using the ASN1 functions?
66 * OpenSSL uses DER but I need BER format: does OpenSSL support BER?
67 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
68 * I've called <some function> and it fails, why?
69 * I just get a load of numbers for the error output, what do they mean?
70 * Why do I get errors about unknown algorithms?
71 * Why can't the OpenSSH configure script detect OpenSSL?
72 * Can I use OpenSSL's SSL library with non-blocking I/O?
73 * Why doesn't my server application receive a client certificate?
74 * Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
75 * I think I've detected a memory leak, is this a bug?
76 * Why does Valgrind complain about the use of uninitialized data?
77 * Why doesn't a memory BIO work when a file does?
78 * Where are the declarations and implementations of d2i_X509() etc?
79 * When debugging I observe SIGILL during OpenSSL initialization: why?
81 ===============================================================================
83 [MISC] ========================================================================
85 * Which is the current version of OpenSSL?
87 The current version is available from <URL: http://www.openssl.org>.
89 In addition to the current stable release, you can also access daily
90 snapshots of the OpenSSL development version at <URL:
91 ftp://ftp.openssl.org/snapshot/>, or get it by anonymous Git access.
94 * Where is the documentation?
96 OpenSSL is a library that provides cryptographic functionality to
97 applications such as secure web servers. Be sure to read the
98 documentation of the application you want to use. The INSTALL file
99 explains how to install this library.
101 OpenSSL includes a command line utility that can be used to perform a
102 variety of cryptographic functions. It is described in the openssl(1)
103 manpage. Documentation for developers is currently being written. Many
104 manual pages are available; overviews over libcrypto and
105 libssl are given in the crypto(3) and ssl(3) manpages.
107 The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
108 different directory if you specified one as described in INSTALL).
109 In addition, you can read the most current versions at
110 <URL: http://www.openssl.org/docs/>. Note that the online documents refer
111 to the very latest development versions of OpenSSL and may include features
112 not present in released versions. If in doubt refer to the documentation
113 that came with the version of OpenSSL you are using. The pod format
114 documentation is included in each OpenSSL distribution under the docs
117 For information on parts of libcrypto that are not yet documented, you
118 might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
119 predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much
120 of this still applies to OpenSSL.
122 There is some documentation about certificate extensions and PKCS#12
125 The original SSLeay documentation is included in OpenSSL as
126 doc/ssleay.txt. It may be useful when none of the other resources
127 help, but please note that it reflects the obsolete version SSLeay
131 * How can I contact the OpenSSL developers?
133 The README file describes how to submit bug reports and patches to
134 OpenSSL. Information on the OpenSSL mailing lists is available from
135 <URL: http://www.openssl.org>.
138 * Where can I get a compiled version of OpenSSL?
140 You can finder pointers to binary distributions in
141 <URL: http://www.openssl.org/related/binaries.html> .
143 Some applications that use OpenSSL are distributed in binary form.
144 When using such an application, you don't need to install OpenSSL
145 yourself; the application will include the required parts (e.g. DLLs).
147 If you want to build OpenSSL on a Windows system and you don't have
148 a C compiler, read the "Mingw32" section of INSTALL.W32 for information
149 on how to obtain and install the free GNU C compiler.
151 A number of Linux and *BSD distributions include OpenSSL.
154 * Why aren't tools like 'autoconf' and 'libtool' used?
156 autoconf will probably be used in future OpenSSL versions. If it was
157 less Unix-centric, it might have been used much earlier.
159 * What is an 'engine' version?
161 With version 0.9.6 OpenSSL was extended to interface to external crypto
162 hardware. This was realized in a special release '0.9.6-engine'. With
163 version 0.9.7 the changes were merged into the main development line,
164 so that the special release is no longer necessary.
166 * How do I check the authenticity of the OpenSSL distribution?
168 We provide MD5 digests and ASC signatures of each tarball.
169 Use MD5 to check that a tarball from a mirror site is identical:
171 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
173 You can check authenticity using pgp or gpg. You need the OpenSSL team
174 member public key used to sign it (download it from a key server, see a
175 list of keys at <URL: http://www.openssl.org/about/>). Then
180 * How does the versioning scheme work?
182 After the release of OpenSSL 1.0.0 the versioning scheme changed. Letter
183 releases (e.g. 1.0.1a) can only contain bug and security fixes and no
184 new features. Minor releases change the last number (e.g. 1.0.2) and
185 can contain new features that retain binary compatibility. Changes to
186 the middle number are considered major releases and neither source nor
187 binary compatibility is guaranteed.
189 Therefore the answer to the common question "when will feature X be
190 backported to OpenSSL 1.0.0/0.9.8?" is "never" but it could appear
191 in the next minor release.
193 * What happens when the letter release reaches z?
195 It was decided after the release of OpenSSL 0.9.8y the next version should
196 be 0.9.8za then 0.9.8zb and so on.
199 [LEGAL] =======================================================================
201 * Do I need patent licenses to use OpenSSL?
203 For information on intellectual property rights, please consult a lawyer.
204 The OpenSSL team does not offer legal advice.
206 You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using
207 ./config no-idea no-mdc2 no-rc5
210 * Can I use OpenSSL with GPL software?
212 On many systems including the major Linux and BSD distributions, yes (the
213 GPL does not place restrictions on using libraries that are part of the
214 normal operating system distribution).
216 On other systems, the situation is less clear. Some GPL software copyright
217 holders claim that you infringe on their rights if you use OpenSSL with
218 their software on operating systems that don't normally include OpenSSL.
220 If you develop open source software that uses OpenSSL, you may find it
221 useful to choose an other license than the GPL, or state explicitly that
222 "This program is released under the GPL with the additional exemption that
223 compiling, linking, and/or using OpenSSL is allowed." If you are using
224 GPL software developed by others, you may want to ask the copyright holder
225 for permission to use their software with OpenSSL.
228 [USER] ========================================================================
230 * Why do I get a "PRNG not seeded" error message?
232 Cryptographic software needs a source of unpredictable data to work
233 correctly. Many open source operating systems provide a "randomness
234 device" (/dev/urandom or /dev/random) that serves this purpose.
235 All OpenSSL versions try to use /dev/urandom by default; starting with
236 version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not
239 On other systems, applications have to call the RAND_add() or
240 RAND_seed() function with appropriate data before generating keys or
241 performing public key encryption. (These functions initialize the
242 pseudo-random number generator, PRNG.) Some broken applications do
243 not do this. As of version 0.9.5, the OpenSSL functions that need
244 randomness report an error if the random number generator has not been
245 seeded with at least 128 bits of randomness. If this error occurs and
246 is not discussed in the documentation of the application you are
247 using, please contact the author of that application; it is likely
248 that it never worked correctly. OpenSSL 0.9.5 and later make the
249 error visible by refusing to perform potentially insecure encryption.
251 If you are using Solaris 8, you can add /dev/urandom and /dev/random
252 devices by installing patch 112438 (Sparc) or 112439 (x86), which are
253 available via the Patchfinder at <URL: http://sunsolve.sun.com>
254 (Solaris 9 includes these devices by default). For /dev/random support
255 for earlier Solaris versions, see Sun's statement at
256 <URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski>
257 (the SUNWski package is available in patch 105710).
259 On systems without /dev/urandom and /dev/random, it is a good idea to
260 use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for
261 details. Starting with version 0.9.7, OpenSSL will automatically look
262 for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and
265 Most components of the openssl command line utility automatically try
266 to seed the random number generator from a file. The name of the
267 default seeding file is determined as follows: If environment variable
268 RANDFILE is set, then it names the seeding file. Otherwise if
269 environment variable HOME is set, then the seeding file is $HOME/.rnd.
270 If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will
271 use file .rnd in the current directory while OpenSSL 0.9.6a uses no
272 default seeding file at all. OpenSSL 0.9.6b and later will behave
273 similarly to 0.9.6a, but will use a default of "C:\" for HOME on
274 Windows systems if the environment variable has not been set.
276 If the default seeding file does not exist or is too short, the "PRNG
277 not seeded" error message may occur.
279 The openssl command line utility will write back a new state to the
280 default seeding file (and create this file if necessary) unless
281 there was no sufficient seeding.
283 Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work.
284 Use the "-rand" option of the OpenSSL command line tools instead.
285 The $RANDFILE environment variable and $HOME/.rnd are only used by the
286 OpenSSL command line tools. Applications using the OpenSSL library
287 provide their own configuration options to specify the entropy source,
288 please check out the documentation coming the with application.
291 * Why do I get an "unable to write 'random state'" error message?
294 Sometimes the openssl command line utility does not abort with
295 a "PRNG not seeded" error message, but complains that it is
296 "unable to write 'random state'". This message refers to the
297 default seeding file (see previous answer). A possible reason
298 is that no default filename is known because neither RANDFILE
299 nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the
300 current directory in this case, but this has changed with 0.9.6a.)
303 * How do I create certificates or certificate requests?
305 Check out the CA.pl(1) manual page. This provides a simple wrapper round
306 the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
307 out the manual pages for the individual utilities and the certificate
308 extensions documentation (in ca(1), req(1), x509v3_config(5) )
311 * Why can't I create certificate requests?
313 You typically get the error:
315 unable to find 'distinguished_name' in config
316 problems making Certificate Request
318 This is because it can't find the configuration file. Check out the
319 DIAGNOSTICS section of req(1) for more information.
322 * Why does <SSL program> fail with a certificate verify error?
324 This problem is usually indicated by log messages saying something like
325 "unable to get local issuer certificate" or "self signed certificate".
326 When a certificate is verified its root CA must be "trusted" by OpenSSL
327 this typically means that the CA certificate must be placed in a directory
328 or file and the relevant program configured to read it. The OpenSSL program
329 'verify' behaves in a similar way and issues similar error messages: check
330 the verify(1) program manual page for more information.
333 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
335 This is almost certainly because you are using an old "export grade" browser
336 which only supports weak encryption. Upgrade your browser to support 128 bit
340 * How can I create DSA certificates?
342 Check the CA.pl(1) manual page for a DSA certificate example.
345 * Why can't I make an SSL connection to a server using a DSA certificate?
347 Typically you'll see a message saying there are no shared ciphers when
348 the same setup works fine with an RSA certificate. There are two possible
349 causes. The client may not support connections to DSA servers most web
350 browsers (including Netscape and MSIE) only support connections to servers
351 supporting RSA cipher suites. The other cause is that a set of DH parameters
352 has not been supplied to the server. DH parameters can be created with the
353 dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
354 check the source to s_server in apps/s_server.c for an example.
357 * How can I remove the passphrase on a private key?
359 Firstly you should be really *really* sure you want to do this. Leaving
360 a private key unencrypted is a major security risk. If you decide that
361 you do have to do this check the EXAMPLES sections of the rsa(1) and
365 * Why can't I use OpenSSL certificates with SSL client authentication?
367 What will typically happen is that when a server requests authentication
368 it will either not include your certificate or tell you that you have
369 no client certificates (Netscape) or present you with an empty list box
370 (MSIE). The reason for this is that when a server requests a client
371 certificate it includes a list of CAs names which it will accept. Browsers
372 will only let you select certificates from the list on the grounds that
373 there is little point presenting a certificate which the server will
376 The solution is to add the relevant CA certificate to your servers "trusted
377 CA list". How you do this depends on the server software in uses. You can
378 print out the servers list of acceptable CAs using the OpenSSL s_client tool:
380 openssl s_client -connect www.some.host:443 -prexit
382 If your server only requests certificates on certain URLs then you may need
383 to manually issue an HTTP GET command to get the list when s_client connects:
385 GET /some/page/needing/a/certificate.html
387 If your CA does not appear in the list then this confirms the problem.
390 * Why does my browser give a warning about a mismatched hostname?
392 Browsers expect the server's hostname to match the value in the commonName
393 (CN) field of the certificate. If it does not then you get a warning.
396 * How do I install a CA certificate into a browser?
398 The usual way is to send the DER encoded certificate to the browser as
399 MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
400 link. On MSIE certain extensions such as .der or .cacert may also work, or you
401 can import the certificate using the certificate import wizard.
403 You can convert a certificate to DER form using the command:
405 openssl x509 -in ca.pem -outform DER -out ca.der
407 Occasionally someone suggests using a command such as:
409 openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
411 DO NOT DO THIS! This command will give away your CAs private key and
412 reduces its security to zero: allowing anyone to forge certificates in
413 whatever name they choose.
415 * Why is OpenSSL x509 DN output not conformant to RFC2253?
417 The ways to print out the oneline format of the DN (Distinguished Name) have
418 been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex()
419 interface, the "-nameopt" option could be introduded. See the manual
420 page of the "openssl x509" commandline tool for details. The old behaviour
421 has however been left as default for the sake of compatibility.
423 * What is a "128 bit certificate"? Can I create one with OpenSSL?
425 The term "128 bit certificate" is a highly misleading marketing term. It does
426 *not* refer to the size of the public key in the certificate! A certificate
427 containing a 128 bit RSA key would have negligible security.
429 There were various other names such as "magic certificates", "SGC
430 certificates", "step up certificates" etc.
432 You can't generally create such a certificate using OpenSSL but there is no
433 need to any more. Nowadays web browsers using unrestricted strong encryption
434 are generally available.
436 When there were tight restrictions on the export of strong encryption
437 software from the US only weak encryption algorithms could be freely exported
438 (initially 40 bit and then 56 bit). It was widely recognised that this was
439 inadequate. A relaxation of the rules allowed the use of strong encryption but
440 only to an authorised server.
442 Two slighly different techniques were developed to support this, one used by
443 Netscape was called "step up", the other used by MSIE was called "Server Gated
444 Cryptography" (SGC). When a browser initially connected to a server it would
445 check to see if the certificate contained certain extensions and was issued by
446 an authorised authority. If these test succeeded it would reconnect using
449 Only certain (initially one) certificate authorities could issue the
450 certificates and they generally cost more than ordinary certificates.
452 Although OpenSSL can create certificates containing the appropriate extensions
453 the certificate would not come from a permitted authority and so would not
456 The export laws were later changed to allow almost unrestricted use of strong
457 encryption so these certificates are now obsolete.
460 * Why does OpenSSL set the authority key identifier (AKID) extension incorrectly?
462 It doesn't: this extension is often the cause of confusion.
464 Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose
465 certificate C contains AKID.
467 The purpose of this extension is to identify the authority certificate B. This
468 can be done either by including the subject key identifier of B or its issuer
469 name and serial number.
471 In this latter case because it is identifying certifcate B it must contain the
472 issuer name and serial number of B.
474 It is often wrongly assumed that it should contain the subject name of B. If it
475 did this would be redundant information because it would duplicate the issuer
479 * How can I set up a bundle of commercial root CA certificates?
481 The OpenSSL software is shipped without any root CA certificate as the
482 OpenSSL project does not have any policy on including or excluding
483 any specific CA and does not intend to set up such a policy. Deciding
484 about which CAs to support is up to application developers or
487 Other projects do have other policies so you can for example extract the CA
488 bundle used by Mozilla and/or modssl as described in this article:
490 <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html>
493 * Some secure servers 'hang' with OpenSSL 1.0.1, is this a bug?
495 OpenSSL 1.0.1 is the first release to support TLS 1.2, among other things,
496 this increases the size of the default ClientHello message to more than
497 255 bytes in length. Some software cannot handle this and hangs. For more
498 details and workarounds see:
500 <URL: http://rt.openssl.org/Ticket/Display.html?user=guest&pass=guest&id=2771>
503 [BUILD] =======================================================================
505 * Why does the linker complain about undefined symbols?
507 Maybe the compilation was interrupted, and make doesn't notice that
508 something is missing. Run "make clean; make".
510 If you used ./Configure instead of ./config, make sure that you
511 selected the right target. File formats may differ slightly between
512 OS versions (for example sparcv8/sparcv9, or a.out/elf).
514 In case you get errors about the following symbols, use the config
515 option "no-asm", as described in INSTALL:
517 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
518 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
519 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
520 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
521 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
522 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
523 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
525 If none of these helps, you may want to try using the current snapshot.
526 If the problem persists, please submit a bug report.
529 * Why does the OpenSSL test fail with "bc: command not found"?
531 You didn't install "bc", the Unix calculator. If you want to run the
532 tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
535 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
537 On some SCO installations or versions, bc has a bug that gets triggered
538 when you run the test suite (using "make test"). The message returned is
539 "bc: 1 not implemented".
541 The best way to deal with this is to find another implementation of bc
542 and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
543 for download instructions) can be safely used, for example.
546 * Why does the OpenSSL test fail with "bc: stack empty"?
548 On some DG/ux versions, bc seems to have a too small stack for calculations
549 that the OpenSSL bntest throws at it. This gets triggered when you run the
550 test suite (using "make test"). The message returned is "bc: stack empty".
552 The best way to deal with this is to find another implementation of bc
553 and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
554 for download instructions) can be safely used, for example.
557 * Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
559 On some Alpha installations running Tru64 Unix and Compaq C, the compilation
560 of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual
561 memory to continue compilation.' As far as the tests have shown, this may be
562 a compiler bug. What happens is that it eats up a lot of resident memory
563 to build something, probably a table. The problem is clearly in the
564 optimization code, because if one eliminates optimization completely (-O0),
565 the compilation goes through (and the compiler consumes about 2MB of resident
566 memory instead of 240MB or whatever one's limit is currently).
568 There are three options to solve this problem:
570 1. set your current data segment size soft limit higher. Experience shows
571 that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do
572 this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
573 kbytes to set the limit to.
575 2. If you have a hard limit that is lower than what you need and you can't
576 get it changed, you can compile all of OpenSSL with -O0 as optimization
577 level. This is however not a very nice thing to do for those who expect to
578 get the best result from OpenSSL. A bit more complicated solution is the
581 ----- snip:start -----
582 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \
583 sed -e 's/ -O[0-9] / -O0 /'`"
584 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'`
588 This will only compile sha_dgst.c with -O0, the rest with the optimization
589 level chosen by the configuration process. When the above is done, do the
590 test and installation and you're set.
592 3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It
593 should not be used and is not used in SSL/TLS nor any other recognized
594 protocol in either case.
597 * Why does the OpenSSL compilation fail with "ar: command not found"?
599 Getting this message is quite usual on Solaris 2, because Sun has hidden
600 away 'ar' and other development commands in directories that aren't in
601 $PATH by default. One of those directories is '/usr/ccs/bin'. The
602 quickest way to fix this is to do the following (it assumes you use sh
603 or any sh-compatible shell):
605 ----- snip:start -----
606 PATH=${PATH}:/usr/ccs/bin; export PATH
609 and then redo the compilation. What you should really do is make sure
610 '/usr/ccs/bin' is permanently in your $PATH, for example through your
611 '.profile' (again, assuming you use a sh-compatible shell).
614 * Why does the OpenSSL compilation fail on Win32 with VC++?
616 Sometimes, you may get reports from VC++ command line (cl) that it
617 can't find standard include files like stdio.h and other weirdnesses.
618 One possible cause is that the environment isn't correctly set up.
619 To solve that problem for VC++ versions up to 6, one should run
620 VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++
621 installation directory (somewhere under 'Program Files'). For VC++
622 version 7 (and up?), which is also called VS.NET, the file is called
623 VSVARS32.BAT instead.
624 This needs to be done prior to running NMAKE, and the changes are only
625 valid for the current DOS session.
628 * What is special about OpenSSL on Redhat?
630 Red Hat Linux (release 7.0 and later) include a preinstalled limited
631 version of OpenSSL. Red Hat has chosen to disable support for IDEA, RC5 and
632 MDC2 in this version. The same may apply to other Linux distributions.
633 Users may therefore wish to install more or all of the features left out.
635 To do this you MUST ensure that you do not overwrite the openssl that is in
636 /usr/bin on your Red Hat machine. Several packages depend on this file,
637 including sendmail and ssh. /usr/local/bin is a good alternative choice. The
638 libraries that come with Red Hat 7.0 onwards have different names and so are
639 not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and
640 /lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and
641 /lib/libcrypto.so.2 respectively).
643 Please note that we have been advised by Red Hat attempting to recompile the
644 openssl rpm with all the cryptography enabled will not work. All other
645 packages depend on the original Red Hat supplied openssl package. It is also
646 worth noting that due to the way Red Hat supplies its packages, updates to
647 openssl on each distribution never change the package version, only the
648 build number. For example, on Red Hat 7.1, the latest openssl package has
649 version number 0.9.6 and build number 9 even though it contains all the
650 relevant updates in packages up to and including 0.9.6b.
652 A possible way around this is to persuade Red Hat to produce a non-US
653 version of Red Hat Linux.
656 * Why does the OpenSSL compilation fail on MacOS X?
658 If the failure happens when trying to build the "openssl" binary, with
659 a large number of undefined symbols, it's very probable that you have
660 OpenSSL 0.9.6b delivered with the operating system (you can find out by
661 running '/usr/bin/openssl version') and that you were trying to build
662 OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in
663 MacOS X has a misfeature that's quite difficult to go around.
664 Look in the file PROBLEMS for a more detailed explanation and for possible
668 * Why does the OpenSSL test suite fail on MacOS X?
670 If the failure happens when running 'make test' and the RC4 test fails,
671 it's very probable that you have OpenSSL 0.9.6b delivered with the
672 operating system (you can find out by running '/usr/bin/openssl version')
673 and that you were trying to build OpenSSL 0.9.6d. The problem is that
674 the loader ('ld') in MacOS X has a misfeature that's quite difficult to
675 go around and has linked the programs "openssl" and the test programs
676 with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the
677 libraries you just built.
678 Look in the file PROBLEMS for a more detailed explanation and for possible
681 * Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
683 Failure in BN_sqr test is most likely caused by a failure to configure the
684 toolkit for current platform or lack of support for the platform in question.
685 Run './config -t' and './apps/openssl version -p'. Do these platform
686 identifiers match? If they don't, then you most likely failed to run
687 ./config and you're hereby advised to do so before filing a bug report.
688 If ./config itself fails to run, then it's most likely problem with your
689 local environment and you should turn to your system administrator (or
690 similar). If identifiers match (and/or no alternative identifier is
691 suggested by ./config script), then the platform is unsupported. There might
692 or might not be a workaround. Most notably on SPARC64 platforms with GNU
693 C compiler you should be able to produce a working build by running
694 './config -m32'. I understand that -m32 might not be what you want/need,
695 but the build should be operational. For further details turn to
696 <openssl-dev@openssl.org>.
698 * Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
700 As of 0.9.7 assembler routines were overhauled for position independence
701 of the machine code, which is essential for shared library support. For
702 some reason OpenBSD is equipped with an out-of-date GNU assembler which
703 finds the new code offensive. To work around the problem, configure with
704 no-asm (and sacrifice a great deal of performance) or patch your assembler
705 according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>.
706 For your convenience a pre-compiled replacement binary is provided at
707 <URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>.
708 Reportedly elder *BSD a.out platforms also suffer from this problem and
709 remedy should be same. Provided binary is statically linked and should be
710 working across wider range of *BSD branches, not just OpenBSD.
712 * Why does the OpenSSL test suite fail in sha512t on x86 CPU?
714 If the test program in question fails withs SIGILL, Illegal Instruction
715 exception, then you more than likely to run SSE2-capable CPU, such as
716 Intel P4, under control of kernel which does not support SSE2
717 instruction extensions. See accompanying INSTALL file and
718 OPENSSL_ia32cap(3) documentation page for further information.
720 * Why does compiler fail to compile sha512.c?
722 OpenSSL SHA-512 implementation depends on compiler support for 64-bit
723 integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a
724 couple] lack support for this and therefore are incapable of compiling
725 the module in question. The recommendation is to disable SHA-512 by
726 adding no-sha512 to ./config [or ./Configure] command line. Another
727 possible alternative might be to switch to GCC.
729 * Test suite still fails, what to do?
731 Another common reason for failure to complete some particular test is
732 simply bad code generated by a buggy component in toolchain or deficiency
733 in run-time environment. There are few cases documented in PROBLEMS file,
734 consult it for possible workaround before you beat the drum. Even if you
735 don't find solution or even mention there, do reserve for possibility of
736 a compiler bug. Compiler bugs might appear in rather bizarre ways, they
737 never make sense, and tend to emerge when you least expect them. In order
738 to identify one, drop optimization level, e.g. by editing CFLAG line in
739 top-level Makefile, recompile and re-run the test.
742 * I think I've found a bug, what should I do?
744 If you are a new user then it is quite likely you haven't found a bug and
745 something is happening you aren't familiar with. Check this FAQ, the associated
746 documentation and the mailing lists for similar queries. If you are still
747 unsure whether it is a bug or not submit a query to the openssl-users mailing
750 If you think you have found a bug based on the output of static analysis tools
751 then please manually check the issue is genuine. Such tools can produce a
752 LOT of false positives.
755 * I'm SURE I've found a bug, how do I report it?
757 To avoid duplicated reports check the mailing lists and release notes for the
758 relevant version of OpenSSL to see if the problem has been reported already.
760 Bug reports with no security implications should be sent to the request
761 tracker. This can be done by mailing the report to <rt@openssl.org> (or its
762 alias <openssl-bugs@openssl.org>), please note that messages sent to the
763 request tracker also appear in the public openssl-dev mailing list.
765 The report should be in plain text. Any patches should be sent as
766 plain text attachments because some mailers corrupt patches sent inline.
767 If your issue affects multiple versions of OpenSSL check any patches apply
768 cleanly and, if possible include patches to each affected version.
770 The report should be given a meaningful subject line briefly summarising the
771 issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful.
773 By sending reports to the request tracker the bug can then be given a priority
774 and assigned to the appropriate maintainer. The history of discussions can be
775 accessed and if the issue has been addressed or a reason why not. If patches
776 are only sent to openssl-dev they can be mislaid if a team member has to
777 wade through months of old messages to review the discussion.
779 See also <URL: http://www.openssl.org/support/rt.html>
782 * I've found a security issue, how do I report it?
784 If you think your bug has security implications then please send it to
785 openssl-security@openssl.org if you don't get a prompt reply at least
786 acknowledging receipt then resend or mail it directly to one of the
787 more active team members (e.g. Steve). If you wish to use PGP to send
788 in a report please use one or more of the keys of the team members listed
789 at <URL: http://www.openssl.org/about/>
791 Note that bugs only present in the openssl utility are not in general
792 considered to be security issues.
794 [PROG] ========================================================================
796 * Is OpenSSL thread-safe?
798 Yes (with limitations: an SSL connection may not concurrently be used
799 by multiple threads). On Windows and many Unix systems, OpenSSL
800 automatically uses the multi-threaded versions of the standard
801 libraries. If your platform is not one of these, consult the INSTALL
804 Multi-threaded applications must provide two callback functions to
805 OpenSSL by calling CRYPTO_set_locking_callback() and
806 CRYPTO_set_id_callback(), for all versions of OpenSSL up to and
807 including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback()
808 and associated APIs are deprecated by CRYPTO_THREADID_set_callback()
809 and friends. This is described in the threads(3) manpage.
811 * I've compiled a program under Windows and it crashes: why?
813 This is usually because you've missed the comment in INSTALL.W32.
814 Your application must link against the same version of the Win32
815 C-Runtime against which your openssl libraries were linked. The
816 default version for OpenSSL is /MD - "Multithreaded DLL".
818 If you are using Microsoft Visual C++'s IDE (Visual Studio), in
819 many cases, your new project most likely defaulted to "Debug
820 Singlethreaded" - /ML. This is NOT interchangeable with /MD and your
821 program will crash, typically on the first BIO related read or write
824 For each of the six possible link stage configurations within Win32,
825 your application must link against the same by which OpenSSL was
826 built. If you are using MS Visual C++ (Studio) this can be changed
829 1. Select Settings... from the Project Menu.
830 2. Select the C/C++ Tab.
831 3. Select "Code Generation from the "Category" drop down list box
832 4. Select the Appropriate library (see table below) from the "Use
833 run-time library" drop down list box. Perform this step for both
834 your debug and release versions of your application (look at the
835 top left of the settings panel to change between the two)
837 Single Threaded /ML - MS VC++ often defaults to
839 version of a new project.
840 Debug Single Threaded /MLd - MS VC++ often defaults to
841 this for the debug version
844 Debug Multithreaded /MTd
845 Multithreaded DLL /MD - OpenSSL defaults to this.
846 Debug Multithreaded DLL /MDd
848 Note that debug and release libraries are NOT interchangeable. If you
849 built OpenSSL with /MD your application must use /MD and cannot use /MDd.
851 As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL
852 .DLLs compiled with some specific run-time option [we insist on the
853 default /MD] can be deployed with application compiled with different
854 option or even different compiler. But there is a catch! Instead of
855 re-compiling OpenSSL toolkit, as you would have to with prior versions,
856 you have to compile small C snippet with compiler and/or options of
857 your choice. The snippet gets installed as
858 <install-root>/include/openssl/applink.c and should be either added to
859 your application project or simply #include-d in one [and only one]
860 of your application source files. Failure to link this shim module
861 into your application manifests itself as fatal "no OPENSSL_Applink"
862 run-time error. An explicit reminder is due that in this situation
863 [mixing compiler options] it is as important to add CRYPTO_malloc_init
864 prior first call to OpenSSL.
866 * How do I read or write a DER encoded buffer using the ASN1 functions?
868 You have two options. You can either use a memory BIO in conjunction
869 with the i2d_*_bio() or d2i_*_bio() functions or you can use the
870 i2d_*(), d2i_*() functions directly. Since these are often the
871 cause of grief here are some code fragments using PKCS7 as an example:
873 unsigned char *buf, *p;
876 len = i2d_PKCS7(p7, NULL);
877 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */
881 At this point buf contains the len bytes of the DER encoding of
884 The opposite assumes we already have len bytes in buf:
888 p7 = d2i_PKCS7(NULL, &p, len);
890 At this point p7 contains a valid PKCS7 structure or NULL if an error
891 occurred. If an error occurred ERR_print_errors(bio) should give more
894 The reason for the temporary variable 'p' is that the ASN1 functions
895 increment the passed pointer so it is ready to read or write the next
896 structure. This is often a cause of problems: without the temporary
897 variable the buffer pointer is changed to point just after the data
898 that has been read or written. This may well be uninitialized data
899 and attempts to free the buffer will have unpredictable results
900 because it no longer points to the same address.
902 Memory allocation and encoding can also be combined in a single
903 operation by the ASN1 routines:
905 unsigned char *buf = NULL; /* mandatory */
907 len = i2d_PKCS7(p7, &buf);
910 /* Do some things with 'buf' */
911 /* Finished with buf: free it */
914 In this special case the "buf" parameter is *not* incremented, it points
915 to the start of the encoding.
918 * OpenSSL uses DER but I need BER format: does OpenSSL support BER?
920 The short answer is yes, because DER is a special case of BER and OpenSSL
921 ASN1 decoders can process BER.
923 The longer answer is that ASN1 structures can be encoded in a number of
924 different ways. One set of ways is the Basic Encoding Rules (BER) with various
925 permissible encodings. A restriction of BER is the Distinguished Encoding
926 Rules (DER): these uniquely specify how a given structure is encoded.
928 Therefore, because DER is a special case of BER, DER is an acceptable encoding
932 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
934 This usually happens when you try compiling something using the PKCS#12
935 macros with a C++ compiler. There is hardly ever any need to use the
936 PKCS#12 macros in a program, it is much easier to parse and create
937 PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions
938 documented in doc/openssl.txt and with examples in demos/pkcs12. The
939 'pkcs12' application has to use the macros because it prints out
940 debugging information.
943 * I've called <some function> and it fails, why?
945 Before submitting a report or asking in one of the mailing lists, you
946 should try to determine the cause. In particular, you should call
947 ERR_print_errors() or ERR_print_errors_fp() after the failed call
948 and see if the message helps. Note that the problem may occur earlier
949 than you think -- you should check for errors after every call where
950 it is possible, otherwise the actual problem may be hidden because
951 some OpenSSL functions clear the error state.
954 * I just get a load of numbers for the error output, what do they mean?
956 The actual format is described in the ERR_print_errors() manual page.
957 You should call the function ERR_load_crypto_strings() before hand and
958 the message will be output in text form. If you can't do this (for example
959 it is a pre-compiled binary) you can use the errstr utility on the error
960 code itself (the hex digits after the second colon).
963 * Why do I get errors about unknown algorithms?
965 The cause is forgetting to load OpenSSL's table of algorithms with
966 OpenSSL_add_all_algorithms(). See the manual page for more information. This
967 can cause several problems such as being unable to read in an encrypted
968 PEM file, unable to decrypt a PKCS#12 file or signature failure when
969 verifying certificates.
971 * Why can't the OpenSSH configure script detect OpenSSL?
973 Several reasons for problems with the automatic detection exist.
974 OpenSSH requires at least version 0.9.5a of the OpenSSL libraries.
975 Sometimes the distribution has installed an older version in the system
976 locations that is detected instead of a new one installed. The OpenSSL
977 library might have been compiled for another CPU or another mode (32/64 bits).
978 Permissions might be wrong.
980 The general answer is to check the config.log file generated when running
981 the OpenSSH configure script. It should contain the detailed information
982 on why the OpenSSL library was not detected or considered incompatible.
985 * Can I use OpenSSL's SSL library with non-blocking I/O?
987 Yes; make sure to read the SSL_get_error(3) manual page!
989 A pitfall to avoid: Don't assume that SSL_read() will just read from
990 the underlying transport or that SSL_write() will just write to it --
991 it is also possible that SSL_write() cannot do any useful work until
992 there is data to read, or that SSL_read() cannot do anything until it
993 is possible to send data. One reason for this is that the peer may
994 request a new TLS/SSL handshake at any time during the protocol,
995 requiring a bi-directional message exchange; both SSL_read() and
996 SSL_write() will try to continue any pending handshake.
999 * Why doesn't my server application receive a client certificate?
1001 Due to the TLS protocol definition, a client will only send a certificate,
1002 if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the
1003 SSL_CTX_set_verify() function to enable the use of client certificates.
1006 * Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
1008 For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier
1009 versions, uniqueIdentifier was incorrectly used for X.509 certificates.
1010 The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier.
1011 Change your code to use the new name when compiling against OpenSSL 0.9.7.
1014 * I think I've detected a memory leak, is this a bug?
1016 In most cases the cause of an apparent memory leak is an OpenSSL internal table
1017 that is allocated when an application starts up. Since such tables do not grow
1018 in size over time they are harmless.
1020 These internal tables can be freed up when an application closes using various
1021 functions. Currently these include following:
1023 Thread-local cleanup functions:
1027 Application-global cleanup functions that are aware of usage (and therefore
1030 ENGINE_cleanup() and CONF_modules_unload()
1032 "Brutal" (thread-unsafe) Application-global cleanup functions:
1034 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data().
1037 * Why does Valgrind complain about the use of uninitialized data?
1039 When OpenSSL's PRNG routines are called to generate random numbers the supplied
1040 buffer contents are mixed into the entropy pool: so it technically does not
1041 matter whether the buffer is initialized at this point or not. Valgrind (and
1042 other test tools) will complain about this. When using Valgrind, make sure the
1043 OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY)
1044 to get rid of these warnings.
1047 * Why doesn't a memory BIO work when a file does?
1049 This can occur in several cases for example reading an S/MIME email message.
1050 The reason is that a memory BIO can do one of two things when all the data
1051 has been read from it.
1053 The default behaviour is to indicate that no more data is available and that
1054 the call should be retried, this is to allow the application to fill up the BIO
1057 Alternatively it can indicate that no more data is available and that EOF has
1060 If a memory BIO is to behave in the same way as a file this second behaviour
1061 is needed. This must be done by calling:
1063 BIO_set_mem_eof_return(bio, 0);
1065 See the manual pages for more details.
1068 * Where are the declarations and implementations of d2i_X509() etc?
1070 These are defined and implemented by macros of the form:
1073 DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509)
1075 The implementation passes an ASN1 "template" defining the structure into an
1076 ASN1 interpreter using generalised functions such as ASN1_item_d2i().
1078 * When debugging I observe SIGILL during OpenSSL initialization: why?
1080 OpenSSL adapts to processor it executes on and for this reason has to
1081 query its capabilities. Unfortunately on some processors the only way
1082 to achieve this for non-privileged code is to attempt instructions
1083 that can cause Illegal Instruction exceptions. The initialization
1084 procedure is coded to handle these exceptions to manipulate corresponding
1085 bits in capabilities vector. This normally appears transparent, except
1086 when you execute it under debugger, which stops prior delivering signal
1087 to handler. Simply resuming execution does the trick, but when debugging
1088 a lot it might feel counterproductive. Two options. Either set explicit
1089 capability environment variable in order to bypass the capability query
1090 (see corresponding crypto/*cap.c for details). Or configure debugger not
1091 to stop upon SIGILL exception, e.g. in gdb case add 'handle SIGILL nostop'
1094 ===============================================================================