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0001 OpenSSL  -  Frequently Asked Questions
0002 --------------------------------------
0003 
0004 [MISC] Miscellaneous questions
0005 
0006 * Which is the current version of OpenSSL?
0007 * Where is the documentation?
0008 * How can I contact the OpenSSL developers?
0009 * Where can I get a compiled version of OpenSSL?
0010 * Why aren't tools like 'autoconf' and 'libtool' used?
0011 * What is an 'engine' version?
0012 * How do I check the authenticity of the OpenSSL distribution?
0013 * How does the versioning scheme work?
0014 
0015 [LEGAL] Legal questions
0016 
0017 * Do I need patent licenses to use OpenSSL?
0018 * Can I use OpenSSL with GPL software? 
0019 
0020 [USER] Questions on using the OpenSSL applications
0021 
0022 * Why do I get a "PRNG not seeded" error message?
0023 * Why do I get an "unable to write 'random state'" error message?
0024 * How do I create certificates or certificate requests?
0025 * Why can't I create certificate requests?
0026 * Why does <SSL program> fail with a certificate verify error?
0027 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
0028 * How can I create DSA certificates?
0029 * Why can't I make an SSL connection using a DSA certificate?
0030 * How can I remove the passphrase on a private key?
0031 * Why can't I use OpenSSL certificates with SSL client authentication?
0032 * Why does my browser give a warning about a mismatched hostname?
0033 * How do I install a CA certificate into a browser?
0034 * Why is OpenSSL x509 DN output not conformant to RFC2253?
0035 * What is a "128 bit certificate"? Can I create one with OpenSSL?
0036 * Why does OpenSSL set the authority key identifier extension incorrectly?
0037 * How can I set up a bundle of commercial root CA certificates?
0038 
0039 [BUILD] Questions about building and testing OpenSSL
0040 
0041 * Why does the linker complain about undefined symbols?
0042 * Why does the OpenSSL test fail with "bc: command not found"?
0043 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
0044 * Why does the OpenSSL test fail with "bc: stack empty"?
0045 * Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
0046 * Why does the OpenSSL compilation fail with "ar: command not found"?
0047 * Why does the OpenSSL compilation fail on Win32 with VC++?
0048 * What is special about OpenSSL on Redhat?
0049 * Why does the OpenSSL compilation fail on MacOS X?
0050 * Why does the OpenSSL test suite fail on MacOS X?
0051 * Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
0052 * Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
0053 * Why does the OpenSSL test suite fail in sha512t on x86 CPU?
0054 * Why does compiler fail to compile sha512.c?
0055 * Test suite still fails, what to do?
0056 * I think I've found a bug, what should I do?
0057 * I'm SURE I've found a bug, how do I report it?
0058 * I've found a security issue, how do I report it?
0059 
0060 [PROG] Questions about programming with OpenSSL
0061 
0062 * Is OpenSSL thread-safe?
0063 * I've compiled a program under Windows and it crashes: why?
0064 * How do I read or write a DER encoded buffer using the ASN1 functions?
0065 * OpenSSL uses DER but I need BER format: does OpenSSL support BER?
0066 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
0067 * I've called <some function> and it fails, why?
0068 * I just get a load of numbers for the error output, what do they mean?
0069 * Why do I get errors about unknown algorithms?
0070 * Why can't the OpenSSH configure script detect OpenSSL?
0071 * Can I use OpenSSL's SSL library with non-blocking I/O?
0072 * Why doesn't my server application receive a client certificate?
0073 * Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
0074 * I think I've detected a memory leak, is this a bug?
0075 * Why does Valgrind complain about the use of uninitialized data?
0076 * Why doesn't a memory BIO work when a file does?
0077 * Where are the declarations and implementations of d2i_X509() etc?
0078 
0079 ===============================================================================
0080 
0081 [MISC] ========================================================================
0082 
0083 * Which is the current version of OpenSSL?
0084 
0085 The current version is available from <URL: http://www.openssl.org>.
0086 OpenSSL 1.0.1e was released on Feb 11th, 2013.
0087 
0088 In addition to the current stable release, you can also access daily
0089 snapshots of the OpenSSL development version at <URL:
0090 ftp://ftp.openssl.org/snapshot/>, or get it by anonymous Git access.
0091 
0092 
0093 * Where is the documentation?
0094 
0095 OpenSSL is a library that provides cryptographic functionality to
0096 applications such as secure web servers.  Be sure to read the
0097 documentation of the application you want to use.  The INSTALL file
0098 explains how to install this library.
0099 
0100 OpenSSL includes a command line utility that can be used to perform a
0101 variety of cryptographic functions.  It is described in the openssl(1)
0102 manpage.  Documentation for developers is currently being written. Many
0103 manual pages are available; overviews over libcrypto and
0104 libssl are given in the crypto(3) and ssl(3) manpages.
0105 
0106 The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
0107 different directory if you specified one as described in INSTALL).
0108 In addition, you can read the most current versions at
0109 <URL: http://www.openssl.org/docs/>. Note that the online documents refer
0110 to the very latest development versions of OpenSSL and may include features
0111 not present in released versions. If in doubt refer to the documentation
0112 that came with the version of OpenSSL you are using. The pod format
0113 documentation is included in each OpenSSL distribution under the docs
0114 directory.
0115 
0116 For information on parts of libcrypto that are not yet documented, you
0117 might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
0118 predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>.  Much
0119 of this still applies to OpenSSL.
0120 
0121 There is some documentation about certificate extensions and PKCS#12
0122 in doc/openssl.txt
0123 
0124 The original SSLeay documentation is included in OpenSSL as
0125 doc/ssleay.txt.  It may be useful when none of the other resources
0126 help, but please note that it reflects the obsolete version SSLeay
0127 0.6.6.
0128 
0129 
0130 * How can I contact the OpenSSL developers?
0131 
0132 The README file describes how to submit bug reports and patches to
0133 OpenSSL.  Information on the OpenSSL mailing lists is available from
0134 <URL: http://www.openssl.org>.
0135 
0136 
0137 * Where can I get a compiled version of OpenSSL?
0138 
0139 You can finder pointers to binary distributions in
0140 <URL: http://www.openssl.org/related/binaries.html> .
0141 
0142 Some applications that use OpenSSL are distributed in binary form.
0143 When using such an application, you don't need to install OpenSSL
0144 yourself; the application will include the required parts (e.g. DLLs).
0145 
0146 If you want to build OpenSSL on a Windows system and you don't have
0147 a C compiler, read the "Mingw32" section of INSTALL.W32 for information
0148 on how to obtain and install the free GNU C compiler.
0149 
0150 A number of Linux and *BSD distributions include OpenSSL.
0151 
0152 
0153 * Why aren't tools like 'autoconf' and 'libtool' used?
0154 
0155 autoconf will probably be used in future OpenSSL versions. If it was
0156 less Unix-centric, it might have been used much earlier.
0157 
0158 * What is an 'engine' version?
0159 
0160 With version 0.9.6 OpenSSL was extended to interface to external crypto
0161 hardware. This was realized in a special release '0.9.6-engine'. With
0162 version 0.9.7 the changes were merged into the main development line,
0163 so that the special release is no longer necessary.
0164 
0165 * How do I check the authenticity of the OpenSSL distribution?
0166 
0167 We provide MD5 digests and ASC signatures of each tarball.
0168 Use MD5 to check that a tarball from a mirror site is identical:
0169 
0170    md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
0171 
0172 You can check authenticity using pgp or gpg. You need the OpenSSL team
0173 member public key used to sign it (download it from a key server, see a
0174 list of keys at <URL: http://www.openssl.org/about/>). Then
0175 just do:
0176 
0177    pgp TARBALL.asc
0178 
0179 * How does the versioning scheme work?
0180 
0181 After the release of OpenSSL 1.0.0 the versioning scheme changed. Letter 
0182 releases (e.g. 1.0.1a) can only contain bug and security fixes and no
0183 new features. Minor releases change the last number (e.g. 1.0.2) and 
0184 can contain new features that retain binary compatibility. Changes to
0185 the middle number are considered major releases and neither source nor
0186 binary compatibility is guaranteed.
0187 
0188 Therefore the answer to the common question "when will feature X be
0189 backported to OpenSSL 1.0.0/0.9.8?" is "never" but it could appear
0190 in the next minor release.
0191 
0192 [LEGAL] =======================================================================
0193 
0194 * Do I need patent licenses to use OpenSSL?
0195 
0196 The patents section of the README file lists patents that may apply to
0197 you if you want to use OpenSSL.  For information on intellectual
0198 property rights, please consult a lawyer.  The OpenSSL team does not
0199 offer legal advice.
0200 
0201 You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using
0202  ./config no-idea no-mdc2 no-rc5
0203 
0204 
0205 * Can I use OpenSSL with GPL software?
0206 
0207 On many systems including the major Linux and BSD distributions, yes (the
0208 GPL does not place restrictions on using libraries that are part of the
0209 normal operating system distribution).
0210 
0211 On other systems, the situation is less clear. Some GPL software copyright
0212 holders claim that you infringe on their rights if you use OpenSSL with
0213 their software on operating systems that don't normally include OpenSSL.
0214 
0215 If you develop open source software that uses OpenSSL, you may find it
0216 useful to choose an other license than the GPL, or state explicitly that
0217 "This program is released under the GPL with the additional exemption that
0218 compiling, linking, and/or using OpenSSL is allowed."  If you are using
0219 GPL software developed by others, you may want to ask the copyright holder
0220 for permission to use their software with OpenSSL.
0221 
0222 
0223 [USER] ========================================================================
0224 
0225 * Why do I get a "PRNG not seeded" error message?
0226 
0227 Cryptographic software needs a source of unpredictable data to work
0228 correctly.  Many open source operating systems provide a "randomness
0229 device" (/dev/urandom or /dev/random) that serves this purpose.
0230 All OpenSSL versions try to use /dev/urandom by default; starting with
0231 version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not
0232 available.
0233 
0234 On other systems, applications have to call the RAND_add() or
0235 RAND_seed() function with appropriate data before generating keys or
0236 performing public key encryption. (These functions initialize the
0237 pseudo-random number generator, PRNG.)  Some broken applications do
0238 not do this.  As of version 0.9.5, the OpenSSL functions that need
0239 randomness report an error if the random number generator has not been
0240 seeded with at least 128 bits of randomness.  If this error occurs and
0241 is not discussed in the documentation of the application you are
0242 using, please contact the author of that application; it is likely
0243 that it never worked correctly.  OpenSSL 0.9.5 and later make the
0244 error visible by refusing to perform potentially insecure encryption.
0245 
0246 If you are using Solaris 8, you can add /dev/urandom and /dev/random
0247 devices by installing patch 112438 (Sparc) or 112439 (x86), which are
0248 available via the Patchfinder at <URL: http://sunsolve.sun.com>
0249 (Solaris 9 includes these devices by default). For /dev/random support
0250 for earlier Solaris versions, see Sun's statement at
0251 <URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski>
0252 (the SUNWski package is available in patch 105710).
0253 
0254 On systems without /dev/urandom and /dev/random, it is a good idea to
0255 use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for
0256 details.  Starting with version 0.9.7, OpenSSL will automatically look
0257 for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and
0258 /etc/entropy.
0259 
0260 Most components of the openssl command line utility automatically try
0261 to seed the random number generator from a file.  The name of the
0262 default seeding file is determined as follows: If environment variable
0263 RANDFILE is set, then it names the seeding file.  Otherwise if
0264 environment variable HOME is set, then the seeding file is $HOME/.rnd.
0265 If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will
0266 use file .rnd in the current directory while OpenSSL 0.9.6a uses no
0267 default seeding file at all.  OpenSSL 0.9.6b and later will behave
0268 similarly to 0.9.6a, but will use a default of "C:\" for HOME on
0269 Windows systems if the environment variable has not been set.
0270 
0271 If the default seeding file does not exist or is too short, the "PRNG
0272 not seeded" error message may occur.
0273 
0274 The openssl command line utility will write back a new state to the
0275 default seeding file (and create this file if necessary) unless
0276 there was no sufficient seeding.
0277 
0278 Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work.
0279 Use the "-rand" option of the OpenSSL command line tools instead.
0280 The $RANDFILE environment variable and $HOME/.rnd are only used by the
0281 OpenSSL command line tools. Applications using the OpenSSL library
0282 provide their own configuration options to specify the entropy source,
0283 please check out the documentation coming the with application.
0284 
0285 
0286 * Why do I get an "unable to write 'random state'" error message?
0287 
0288 
0289 Sometimes the openssl command line utility does not abort with
0290 a "PRNG not seeded" error message, but complains that it is
0291 "unable to write 'random state'".  This message refers to the
0292 default seeding file (see previous answer).  A possible reason
0293 is that no default filename is known because neither RANDFILE
0294 nor HOME is set.  (Versions up to 0.9.6 used file ".rnd" in the
0295 current directory in this case, but this has changed with 0.9.6a.)
0296 
0297 
0298 * How do I create certificates or certificate requests?
0299 
0300 Check out the CA.pl(1) manual page. This provides a simple wrapper round
0301 the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
0302 out the manual pages for the individual utilities and the certificate
0303 extensions documentation (in ca(1), req(1), x509v3_config(5) )
0304 
0305 
0306 * Why can't I create certificate requests?
0307 
0308 You typically get the error:
0309 
0310         unable to find 'distinguished_name' in config
0311         problems making Certificate Request
0312 
0313 This is because it can't find the configuration file. Check out the
0314 DIAGNOSTICS section of req(1) for more information.
0315 
0316 
0317 * Why does <SSL program> fail with a certificate verify error?
0318 
0319 This problem is usually indicated by log messages saying something like
0320 "unable to get local issuer certificate" or "self signed certificate".
0321 When a certificate is verified its root CA must be "trusted" by OpenSSL
0322 this typically means that the CA certificate must be placed in a directory
0323 or file and the relevant program configured to read it. The OpenSSL program
0324 'verify' behaves in a similar way and issues similar error messages: check
0325 the verify(1) program manual page for more information.
0326 
0327 
0328 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
0329 
0330 This is almost certainly because you are using an old "export grade" browser
0331 which only supports weak encryption. Upgrade your browser to support 128 bit
0332 ciphers.
0333 
0334 
0335 * How can I create DSA certificates?
0336 
0337 Check the CA.pl(1) manual page for a DSA certificate example.
0338 
0339 
0340 * Why can't I make an SSL connection to a server using a DSA certificate?
0341 
0342 Typically you'll see a message saying there are no shared ciphers when
0343 the same setup works fine with an RSA certificate. There are two possible
0344 causes. The client may not support connections to DSA servers most web
0345 browsers (including Netscape and MSIE) only support connections to servers
0346 supporting RSA cipher suites. The other cause is that a set of DH parameters
0347 has not been supplied to the server. DH parameters can be created with the
0348 dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
0349 check the source to s_server in apps/s_server.c for an example.
0350 
0351 
0352 * How can I remove the passphrase on a private key?
0353 
0354 Firstly you should be really *really* sure you want to do this. Leaving
0355 a private key unencrypted is a major security risk. If you decide that
0356 you do have to do this check the EXAMPLES sections of the rsa(1) and
0357 dsa(1) manual pages.
0358 
0359 
0360 * Why can't I use OpenSSL certificates with SSL client authentication?
0361 
0362 What will typically happen is that when a server requests authentication
0363 it will either not include your certificate or tell you that you have
0364 no client certificates (Netscape) or present you with an empty list box
0365 (MSIE). The reason for this is that when a server requests a client
0366 certificate it includes a list of CAs names which it will accept. Browsers
0367 will only let you select certificates from the list on the grounds that
0368 there is little point presenting a certificate which the server will
0369 reject.
0370 
0371 The solution is to add the relevant CA certificate to your servers "trusted
0372 CA list". How you do this depends on the server software in uses. You can
0373 print out the servers list of acceptable CAs using the OpenSSL s_client tool:
0374 
0375 openssl s_client -connect www.some.host:443 -prexit
0376 
0377 If your server only requests certificates on certain URLs then you may need
0378 to manually issue an HTTP GET command to get the list when s_client connects:
0379 
0380 GET /some/page/needing/a/certificate.html
0381 
0382 If your CA does not appear in the list then this confirms the problem.
0383 
0384 
0385 * Why does my browser give a warning about a mismatched hostname?
0386 
0387 Browsers expect the server's hostname to match the value in the commonName
0388 (CN) field of the certificate. If it does not then you get a warning.
0389 
0390 
0391 * How do I install a CA certificate into a browser?
0392 
0393 The usual way is to send the DER encoded certificate to the browser as
0394 MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
0395 link. On MSIE certain extensions such as .der or .cacert may also work, or you
0396 can import the certificate using the certificate import wizard.
0397 
0398 You can convert a certificate to DER form using the command:
0399 
0400 openssl x509 -in ca.pem -outform DER -out ca.der
0401 
0402 Occasionally someone suggests using a command such as:
0403 
0404 openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
0405 
0406 DO NOT DO THIS! This command will give away your CAs private key and
0407 reduces its security to zero: allowing anyone to forge certificates in
0408 whatever name they choose.
0409 
0410 * Why is OpenSSL x509 DN output not conformant to RFC2253?
0411 
0412 The ways to print out the oneline format of the DN (Distinguished Name) have
0413 been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex()
0414 interface, the "-nameopt" option could be introduded. See the manual
0415 page of the "openssl x509" commandline tool for details. The old behaviour
0416 has however been left as default for the sake of compatibility.
0417 
0418 * What is a "128 bit certificate"? Can I create one with OpenSSL?
0419 
0420 The term "128 bit certificate" is a highly misleading marketing term. It does
0421 *not* refer to the size of the public key in the certificate! A certificate
0422 containing a 128 bit RSA key would have negligible security.
0423 
0424 There were various other names such as "magic certificates", "SGC
0425 certificates", "step up certificates" etc.
0426 
0427 You can't generally create such a certificate using OpenSSL but there is no
0428 need to any more. Nowadays web browsers using unrestricted strong encryption
0429 are generally available.
0430 
0431 When there were tight restrictions on the export of strong encryption
0432 software from the US only weak encryption algorithms could be freely exported
0433 (initially 40 bit and then 56 bit). It was widely recognised that this was
0434 inadequate. A relaxation of the rules allowed the use of strong encryption but
0435 only to an authorised server.
0436 
0437 Two slighly different techniques were developed to support this, one used by
0438 Netscape was called "step up", the other used by MSIE was called "Server Gated
0439 Cryptography" (SGC). When a browser initially connected to a server it would
0440 check to see if the certificate contained certain extensions and was issued by
0441 an authorised authority. If these test succeeded it would reconnect using
0442 strong encryption.
0443 
0444 Only certain (initially one) certificate authorities could issue the
0445 certificates and they generally cost more than ordinary certificates.
0446 
0447 Although OpenSSL can create certificates containing the appropriate extensions
0448 the certificate would not come from a permitted authority and so would not
0449 be recognized.
0450 
0451 The export laws were later changed to allow almost unrestricted use of strong
0452 encryption so these certificates are now obsolete.
0453 
0454 
0455 * Why does OpenSSL set the authority key identifier (AKID) extension incorrectly?
0456 
0457 It doesn't: this extension is often the cause of confusion.
0458 
0459 Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose
0460 certificate C contains AKID.
0461 
0462 The purpose of this extension is to identify the authority certificate B. This
0463 can be done either by including the subject key identifier of B or its issuer
0464 name and serial number.
0465 
0466 In this latter case because it is identifying certifcate B it must contain the
0467 issuer name and serial number of B.
0468 
0469 It is often wrongly assumed that it should contain the subject name of B. If it
0470 did this would be redundant information because it would duplicate the issuer
0471 name of C.
0472 
0473 
0474 * How can I set up a bundle of commercial root CA certificates?
0475 
0476 The OpenSSL software is shipped without any root CA certificate as the
0477 OpenSSL project does not have any policy on including or excluding
0478 any specific CA and does not intend to set up such a policy. Deciding
0479 about which CAs to support is up to application developers or
0480 administrators.
0481 
0482 Other projects do have other policies so you can for example extract the CA
0483 bundle used by Mozilla and/or modssl as described in this article:
0484 
0485   <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html>
0486 
0487 
0488 [BUILD] =======================================================================
0489 
0490 * Why does the linker complain about undefined symbols?
0491 
0492 Maybe the compilation was interrupted, and make doesn't notice that
0493 something is missing.  Run "make clean; make".
0494 
0495 If you used ./Configure instead of ./config, make sure that you
0496 selected the right target.  File formats may differ slightly between
0497 OS versions (for example sparcv8/sparcv9, or a.out/elf).
0498 
0499 In case you get errors about the following symbols, use the config
0500 option "no-asm", as described in INSTALL:
0501 
0502  BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
0503  CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
0504  RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
0505  bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
0506  bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
0507  des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
0508  des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
0509 
0510 If none of these helps, you may want to try using the current snapshot.
0511 If the problem persists, please submit a bug report.
0512 
0513 
0514 * Why does the OpenSSL test fail with "bc: command not found"?
0515 
0516 You didn't install "bc", the Unix calculator.  If you want to run the
0517 tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
0518 
0519 
0520 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
0521 
0522 On some SCO installations or versions, bc has a bug that gets triggered
0523 when you run the test suite (using "make test").  The message returned is
0524 "bc: 1 not implemented".
0525 
0526 The best way to deal with this is to find another implementation of bc
0527 and compile/install it.  GNU bc (see <URL: http://www.gnu.org/software/software.html>
0528 for download instructions) can be safely used, for example.
0529 
0530 
0531 * Why does the OpenSSL test fail with "bc: stack empty"?
0532 
0533 On some DG/ux versions, bc seems to have a too small stack for calculations
0534 that the OpenSSL bntest throws at it.  This gets triggered when you run the
0535 test suite (using "make test").  The message returned is "bc: stack empty".
0536 
0537 The best way to deal with this is to find another implementation of bc
0538 and compile/install it.  GNU bc (see <URL: http://www.gnu.org/software/software.html>
0539 for download instructions) can be safely used, for example.
0540 
0541 
0542 * Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
0543 
0544 On some Alpha installations running Tru64 Unix and Compaq C, the compilation
0545 of crypto/sha/sha_dgst.c fails with the message 'Fatal:  Insufficient virtual
0546 memory to continue compilation.'  As far as the tests have shown, this may be
0547 a compiler bug.  What happens is that it eats up a lot of resident memory
0548 to build something, probably a table.  The problem is clearly in the
0549 optimization code, because if one eliminates optimization completely (-O0),
0550 the compilation goes through (and the compiler consumes about 2MB of resident
0551 memory instead of 240MB or whatever one's limit is currently).
0552 
0553 There are three options to solve this problem:
0554 
0555 1. set your current data segment size soft limit higher.  Experience shows
0556 that about 241000 kbytes seems to be enough on an AlphaServer DS10.  You do
0557 this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
0558 kbytes to set the limit to.
0559 
0560 2. If you have a hard limit that is lower than what you need and you can't
0561 get it changed, you can compile all of OpenSSL with -O0 as optimization
0562 level.  This is however not a very nice thing to do for those who expect to
0563 get the best result from OpenSSL.  A bit more complicated solution is the
0564 following:
0565 
0566 ----- snip:start -----
0567   make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \
0568        sed -e 's/ -O[0-9] / -O0 /'`"
0569   rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'`
0570   make
0571 ----- snip:end -----
0572 
0573 This will only compile sha_dgst.c with -O0, the rest with the optimization
0574 level chosen by the configuration process.  When the above is done, do the
0575 test and installation and you're set.
0576 
0577 3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 
0578 should not be used and is not used in SSL/TLS nor any other recognized
0579 protocol in either case.
0580 
0581 
0582 * Why does the OpenSSL compilation fail with "ar: command not found"?
0583 
0584 Getting this message is quite usual on Solaris 2, because Sun has hidden
0585 away 'ar' and other development commands in directories that aren't in
0586 $PATH by default.  One of those directories is '/usr/ccs/bin'.  The
0587 quickest way to fix this is to do the following (it assumes you use sh
0588 or any sh-compatible shell):
0589 
0590 ----- snip:start -----
0591   PATH=${PATH}:/usr/ccs/bin; export PATH
0592 ----- snip:end -----
0593 
0594 and then redo the compilation.  What you should really do is make sure
0595 '/usr/ccs/bin' is permanently in your $PATH, for example through your
0596 '.profile' (again, assuming you use a sh-compatible shell).
0597 
0598 
0599 * Why does the OpenSSL compilation fail on Win32 with VC++?
0600 
0601 Sometimes, you may get reports from VC++ command line (cl) that it
0602 can't find standard include files like stdio.h and other weirdnesses.
0603 One possible cause is that the environment isn't correctly set up.
0604 To solve that problem for VC++ versions up to 6, one should run
0605 VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++
0606 installation directory (somewhere under 'Program Files').  For VC++
0607 version 7 (and up?), which is also called VS.NET, the file is called
0608 VSVARS32.BAT instead.
0609 This needs to be done prior to running NMAKE, and the changes are only
0610 valid for the current DOS session.
0611 
0612 
0613 * What is special about OpenSSL on Redhat?
0614 
0615 Red Hat Linux (release 7.0 and later) include a preinstalled limited
0616 version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2
0617 is disabled in this version. The same may apply to other Linux distributions.
0618 Users may therefore wish to install more or all of the features left out.
0619 
0620 To do this you MUST ensure that you do not overwrite the openssl that is in
0621 /usr/bin on your Red Hat machine. Several packages depend on this file,
0622 including sendmail and ssh. /usr/local/bin is a good alternative choice. The
0623 libraries that come with Red Hat 7.0 onwards have different names and so are
0624 not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and
0625 /lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and
0626 /lib/libcrypto.so.2 respectively).
0627 
0628 Please note that we have been advised by Red Hat attempting to recompile the
0629 openssl rpm with all the cryptography enabled will not work. All other
0630 packages depend on the original Red Hat supplied openssl package. It is also
0631 worth noting that due to the way Red Hat supplies its packages, updates to
0632 openssl on each distribution never change the package version, only the
0633 build number. For example, on Red Hat 7.1, the latest openssl package has
0634 version number 0.9.6 and build number 9 even though it contains all the
0635 relevant updates in packages up to and including 0.9.6b.
0636 
0637 A possible way around this is to persuade Red Hat to produce a non-US
0638 version of Red Hat Linux.
0639 
0640 FYI: Patent numbers and expiry dates of US patents:
0641 MDC-2: 4,908,861 13/03/2007
0642 IDEA:  5,214,703 25/05/2010
0643 RC5:   5,724,428 03/03/2015
0644 
0645 
0646 * Why does the OpenSSL compilation fail on MacOS X?
0647 
0648 If the failure happens when trying to build the "openssl" binary, with
0649 a large number of undefined symbols, it's very probable that you have
0650 OpenSSL 0.9.6b delivered with the operating system (you can find out by
0651 running '/usr/bin/openssl version') and that you were trying to build
0652 OpenSSL 0.9.7 or newer.  The problem is that the loader ('ld') in
0653 MacOS X has a misfeature that's quite difficult to go around.
0654 Look in the file PROBLEMS for a more detailed explanation and for possible
0655 solutions.
0656 
0657 
0658 * Why does the OpenSSL test suite fail on MacOS X?
0659 
0660 If the failure happens when running 'make test' and the RC4 test fails,
0661 it's very probable that you have OpenSSL 0.9.6b delivered with the
0662 operating system (you can find out by running '/usr/bin/openssl version')
0663 and that you were trying to build OpenSSL 0.9.6d.  The problem is that
0664 the loader ('ld') in MacOS X has a misfeature that's quite difficult to
0665 go around and has linked the programs "openssl" and the test programs
0666 with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the
0667 libraries you just built.
0668 Look in the file PROBLEMS for a more detailed explanation and for possible
0669 solutions.
0670 
0671 * Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
0672 
0673 Failure in BN_sqr test is most likely caused by a failure to configure the
0674 toolkit for current platform or lack of support for the platform in question.
0675 Run './config -t' and './apps/openssl version -p'. Do these platform
0676 identifiers match? If they don't, then you most likely failed to run
0677 ./config and you're hereby advised to do so before filing a bug report.
0678 If ./config itself fails to run, then it's most likely problem with your
0679 local environment and you should turn to your system administrator (or
0680 similar). If identifiers match (and/or no alternative identifier is
0681 suggested by ./config script), then the platform is unsupported. There might
0682 or might not be a workaround. Most notably on SPARC64 platforms with GNU
0683 C compiler you should be able to produce a working build by running
0684 './config -m32'. I understand that -m32 might not be what you want/need,
0685 but the build should be operational. For further details turn to
0686 <openssl-dev@openssl.org>.
0687 
0688 * Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
0689 
0690 As of 0.9.7 assembler routines were overhauled for position independence
0691 of the machine code, which is essential for shared library support. For
0692 some reason OpenBSD is equipped with an out-of-date GNU assembler which
0693 finds the new code offensive. To work around the problem, configure with
0694 no-asm (and sacrifice a great deal of performance) or patch your assembler
0695 according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>.
0696 For your convenience a pre-compiled replacement binary is provided at
0697 <URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>.
0698 Reportedly elder *BSD a.out platforms also suffer from this problem and
0699 remedy should be same. Provided binary is statically linked and should be
0700 working across wider range of *BSD branches, not just OpenBSD.
0701 
0702 * Why does the OpenSSL test suite fail in sha512t on x86 CPU?
0703 
0704 If the test program in question fails withs SIGILL, Illegal Instruction
0705 exception, then you more than likely to run SSE2-capable CPU, such as
0706 Intel P4, under control of kernel which does not support SSE2
0707 instruction extentions. See accompanying INSTALL file and
0708 OPENSSL_ia32cap(3) documentation page for further information.
0709 
0710 * Why does compiler fail to compile sha512.c?
0711 
0712 OpenSSL SHA-512 implementation depends on compiler support for 64-bit
0713 integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a
0714 couple] lack support for this and therefore are incapable of compiling
0715 the module in question. The recommendation is to disable SHA-512 by
0716 adding no-sha512 to ./config [or ./Configure] command line. Another
0717 possible alternative might be to switch to GCC.
0718 
0719 * Test suite still fails, what to do?
0720 
0721 Another common reason for failure to complete some particular test is
0722 simply bad code generated by a buggy component in toolchain or deficiency
0723 in run-time environment. There are few cases documented in PROBLEMS file,
0724 consult it for possible workaround before you beat the drum. Even if you
0725 don't find solution or even mention there, do reserve for possibility of
0726 a compiler bug. Compiler bugs might appear in rather bizarre ways, they
0727 never make sense, and tend to emerge when you least expect them. In order
0728 to identify one, drop optimization level, e.g. by editing CFLAG line in
0729 top-level Makefile, recompile and re-run the test.
0730 
0731 * I think I've found a bug, what should I do?
0732 
0733 If you are a new user then it is quite likely you haven't found a bug and
0734 something is happening you aren't familiar with. Check this FAQ, the associated
0735 documentation and the mailing lists for similar queries. If you are still
0736 unsure whether it is a bug or not submit a query to the openssl-users mailing
0737 list.
0738 
0739 
0740 * I'm SURE I've found a bug, how do I report it?
0741 
0742 Bug reports with no security implications should be sent to the request
0743 tracker. This can be done by mailing the report to <rt@openssl.org> (or its
0744 alias <openssl-bugs@openssl.org>), please note that messages sent to the
0745 request tracker also appear in the public openssl-dev mailing list.
0746 
0747 The report should be in plain text. Any patches should be sent as
0748 plain text attachments because some mailers corrupt patches sent inline.
0749 If your issue affects multiple versions of OpenSSL check any patches apply
0750 cleanly and, if possible include patches to each affected version.
0751 
0752 The report should be given a meaningful subject line briefly summarising the
0753 issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful.
0754 
0755 By sending reports to the request tracker the bug can then be given a priority
0756 and assigned to the appropriate maintainer. The history of discussions can be
0757 accessed and if the issue has been addressed or a reason why not. If patches
0758 are only sent to openssl-dev they can be mislaid if a team member has to
0759 wade through months of old messages to review the discussion.
0760 
0761 See also <URL: http://www.openssl.org/support/rt.html>
0762 
0763 
0764 * I've found a security issue, how do I report it?
0765 
0766 If you think your bug has security implications then please send it to
0767 openssl-security@openssl.org if you don't get a prompt reply at least 
0768 acknowledging receipt then resend or mail it directly to one of the
0769 more active team members (e.g. Steve).
0770 
0771 Note that bugs only present in the openssl utility are not in general
0772 considered to be security issues. 
0773 
0774 [PROG] ========================================================================
0775 
0776 * Is OpenSSL thread-safe?
0777 
0778 Yes (with limitations: an SSL connection may not concurrently be used
0779 by multiple threads).  On Windows and many Unix systems, OpenSSL
0780 automatically uses the multi-threaded versions of the standard
0781 libraries.  If your platform is not one of these, consult the INSTALL
0782 file.
0783 
0784 Multi-threaded applications must provide two callback functions to
0785 OpenSSL by calling CRYPTO_set_locking_callback() and
0786 CRYPTO_set_id_callback(), for all versions of OpenSSL up to and
0787 including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback()
0788 and associated APIs are deprecated by CRYPTO_THREADID_set_callback()
0789 and friends. This is described in the threads(3) manpage.
0790 
0791 * I've compiled a program under Windows and it crashes: why?
0792 
0793 This is usually because you've missed the comment in INSTALL.W32.
0794 Your application must link against the same version of the Win32
0795 C-Runtime against which your openssl libraries were linked.  The
0796 default version for OpenSSL is /MD - "Multithreaded DLL".
0797 
0798 If you are using Microsoft Visual C++'s IDE (Visual Studio), in
0799 many cases, your new project most likely defaulted to "Debug
0800 Singlethreaded" - /ML.  This is NOT interchangeable with /MD and your
0801 program will crash, typically on the first BIO related read or write
0802 operation.
0803 
0804 For each of the six possible link stage configurations within Win32,
0805 your application must link  against the same by which OpenSSL was
0806 built.  If you are using MS Visual C++ (Studio) this can be changed
0807 by:
0808 
0809  1. Select Settings... from the Project Menu.
0810  2. Select the C/C++ Tab.
0811  3. Select "Code Generation from the "Category" drop down list box
0812  4. Select the Appropriate library (see table below) from the "Use
0813     run-time library" drop down list box.  Perform this step for both
0814     your debug and release versions of your application (look at the
0815     top left of the settings panel to change between the two)
0816 
0817     Single Threaded           /ML        -  MS VC++ often defaults to
0818                                             this for the release
0819                                             version of a new project.
0820     Debug Single Threaded     /MLd       -  MS VC++ often defaults to
0821                                             this for the debug version
0822                                             of a new project.
0823     Multithreaded             /MT
0824     Debug Multithreaded       /MTd
0825     Multithreaded DLL         /MD        -  OpenSSL defaults to this.
0826     Debug Multithreaded DLL   /MDd
0827 
0828 Note that debug and release libraries are NOT interchangeable.  If you
0829 built OpenSSL with /MD your application must use /MD and cannot use /MDd.
0830 
0831 As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL
0832 .DLLs compiled with some specific run-time option [we insist on the
0833 default /MD] can be deployed with application compiled with different
0834 option or even different compiler. But there is a catch! Instead of
0835 re-compiling OpenSSL toolkit, as you would have to with prior versions,
0836 you have to compile small C snippet with compiler and/or options of
0837 your choice. The snippet gets installed as
0838 <install-root>/include/openssl/applink.c and should be either added to
0839 your application project or simply #include-d in one [and only one]
0840 of your application source files. Failure to link this shim module
0841 into your application manifests itself as fatal "no OPENSSL_Applink"
0842 run-time error. An explicit reminder is due that in this situation
0843 [mixing compiler options] it is as important to add CRYPTO_malloc_init
0844 prior first call to OpenSSL.
0845 
0846 * How do I read or write a DER encoded buffer using the ASN1 functions?
0847 
0848 You have two options. You can either use a memory BIO in conjunction
0849 with the i2d_*_bio() or d2i_*_bio() functions or you can use the
0850 i2d_*(), d2i_*() functions directly. Since these are often the
0851 cause of grief here are some code fragments using PKCS7 as an example:
0852 
0853  unsigned char *buf, *p;
0854  int len;
0855 
0856  len = i2d_PKCS7(p7, NULL);
0857  buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */
0858  p = buf;
0859  i2d_PKCS7(p7, &p);
0860 
0861 At this point buf contains the len bytes of the DER encoding of
0862 p7.
0863 
0864 The opposite assumes we already have len bytes in buf:
0865 
0866  unsigned char *p;
0867  p = buf;
0868  p7 = d2i_PKCS7(NULL, &p, len);
0869 
0870 At this point p7 contains a valid PKCS7 structure of NULL if an error
0871 occurred. If an error occurred ERR_print_errors(bio) should give more
0872 information.
0873 
0874 The reason for the temporary variable 'p' is that the ASN1 functions
0875 increment the passed pointer so it is ready to read or write the next
0876 structure. This is often a cause of problems: without the temporary
0877 variable the buffer pointer is changed to point just after the data
0878 that has been read or written. This may well be uninitialized data
0879 and attempts to free the buffer will have unpredictable results
0880 because it no longer points to the same address.
0881 
0882 
0883 * OpenSSL uses DER but I need BER format: does OpenSSL support BER?
0884 
0885 The short answer is yes, because DER is a special case of BER and OpenSSL
0886 ASN1 decoders can process BER.
0887 
0888 The longer answer is that ASN1 structures can be encoded in a number of
0889 different ways. One set of ways is the Basic Encoding Rules (BER) with various
0890 permissible encodings. A restriction of BER is the Distinguished Encoding
0891 Rules (DER): these uniquely specify how a given structure is encoded.
0892 
0893 Therefore, because DER is a special case of BER, DER is an acceptable encoding
0894 for BER.
0895 
0896 
0897 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
0898 
0899 This usually happens when you try compiling something using the PKCS#12
0900 macros with a C++ compiler. There is hardly ever any need to use the
0901 PKCS#12 macros in a program, it is much easier to parse and create
0902 PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions
0903 documented in doc/openssl.txt and with examples in demos/pkcs12. The
0904 'pkcs12' application has to use the macros because it prints out 
0905 debugging information.
0906 
0907 
0908 * I've called <some function> and it fails, why?
0909 
0910 Before submitting a report or asking in one of the mailing lists, you
0911 should try to determine the cause. In particular, you should call
0912 ERR_print_errors() or ERR_print_errors_fp() after the failed call
0913 and see if the message helps. Note that the problem may occur earlier
0914 than you think -- you should check for errors after every call where
0915 it is possible, otherwise the actual problem may be hidden because
0916 some OpenSSL functions clear the error state.
0917 
0918 
0919 * I just get a load of numbers for the error output, what do they mean?
0920 
0921 The actual format is described in the ERR_print_errors() manual page.
0922 You should call the function ERR_load_crypto_strings() before hand and
0923 the message will be output in text form. If you can't do this (for example
0924 it is a pre-compiled binary) you can use the errstr utility on the error
0925 code itself (the hex digits after the second colon).
0926 
0927 
0928 * Why do I get errors about unknown algorithms?
0929 
0930 The cause is forgetting to load OpenSSL's table of algorithms with
0931 OpenSSL_add_all_algorithms(). See the manual page for more information. This
0932 can cause several problems such as being unable to read in an encrypted
0933 PEM file, unable to decrypt a PKCS#12 file or signature failure when
0934 verifying certificates.
0935 
0936 * Why can't the OpenSSH configure script detect OpenSSL?
0937 
0938 Several reasons for problems with the automatic detection exist.
0939 OpenSSH requires at least version 0.9.5a of the OpenSSL libraries.
0940 Sometimes the distribution has installed an older version in the system
0941 locations that is detected instead of a new one installed. The OpenSSL
0942 library might have been compiled for another CPU or another mode (32/64 bits).
0943 Permissions might be wrong.
0944 
0945 The general answer is to check the config.log file generated when running
0946 the OpenSSH configure script. It should contain the detailed information
0947 on why the OpenSSL library was not detected or considered incompatible.
0948 
0949 
0950 * Can I use OpenSSL's SSL library with non-blocking I/O?
0951 
0952 Yes; make sure to read the SSL_get_error(3) manual page!
0953 
0954 A pitfall to avoid: Don't assume that SSL_read() will just read from
0955 the underlying transport or that SSL_write() will just write to it --
0956 it is also possible that SSL_write() cannot do any useful work until
0957 there is data to read, or that SSL_read() cannot do anything until it
0958 is possible to send data.  One reason for this is that the peer may
0959 request a new TLS/SSL handshake at any time during the protocol,
0960 requiring a bi-directional message exchange; both SSL_read() and
0961 SSL_write() will try to continue any pending handshake.
0962 
0963 
0964 * Why doesn't my server application receive a client certificate?
0965 
0966 Due to the TLS protocol definition, a client will only send a certificate,
0967 if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the
0968 SSL_CTX_set_verify() function to enable the use of client certificates.
0969 
0970 
0971 * Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
0972 
0973 For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier
0974 versions, uniqueIdentifier was incorrectly used for X.509 certificates.
0975 The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier.
0976 Change your code to use the new name when compiling against OpenSSL 0.9.7.
0977 
0978 
0979 * I think I've detected a memory leak, is this a bug?
0980 
0981 In most cases the cause of an apparent memory leak is an OpenSSL internal table
0982 that is allocated when an application starts up. Since such tables do not grow
0983 in size over time they are harmless.
0984 
0985 These internal tables can be freed up when an application closes using various
0986 functions.  Currently these include following:
0987 
0988 Thread-local cleanup functions:
0989 
0990   ERR_remove_state()
0991 
0992 Application-global cleanup functions that are aware of usage (and therefore
0993 thread-safe):
0994 
0995   ENGINE_cleanup() and CONF_modules_unload()
0996 
0997 "Brutal" (thread-unsafe) Application-global cleanup functions:
0998 
0999   ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data().
1000 
1001 
1002 * Why does Valgrind complain about the use of uninitialized data?
1003 
1004 When OpenSSL's PRNG routines are called to generate random numbers the supplied
1005 buffer contents are mixed into the entropy pool: so it technically does not
1006 matter whether the buffer is initialized at this point or not.  Valgrind (and
1007 other test tools) will complain about this. When using Valgrind, make sure the
1008 OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY)
1009 to get rid of these warnings.
1010 
1011 
1012 * Why doesn't a memory BIO work when a file does?
1013 
1014 This can occur in several cases for example reading an S/MIME email message.
1015 The reason is that a memory BIO can do one of two things when all the data
1016 has been read from it.
1017 
1018 The default behaviour is to indicate that no more data is available and that
1019 the call should be retried, this is to allow the application to fill up the BIO
1020 again if necessary.
1021 
1022 Alternatively it can indicate that no more data is available and that EOF has
1023 been reached.
1024 
1025 If a memory BIO is to behave in the same way as a file this second behaviour
1026 is needed. This must be done by calling:
1027 
1028    BIO_set_mem_eof_return(bio, 0);
1029 
1030 See the manual pages for more details.
1031 
1032 
1033 * Where are the declarations and implementations of d2i_X509() etc?
1034 
1035 These are defined and implemented by macros of the form:
1036 
1037 
1038  DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509)
1039 
1040 The implementation passes an ASN1 "template" defining the structure into an
1041 ASN1 interpreter using generalised functions such as ASN1_item_d2i().
1042 
1043 
1044 ===============================================================================