FAQ revision 237657
1OpenSSL - Frequently Asked Questions 2-------------------------------------- 3 4[MISC] Miscellaneous questions 5 6* Which is the current version of OpenSSL? 7* Where is the documentation? 8* How can I contact the OpenSSL developers? 9* Where can I get a compiled version of OpenSSL? 10* Why aren't tools like 'autoconf' and 'libtool' used? 11* What is an 'engine' version? 12* How do I check the authenticity of the OpenSSL distribution? 13* How does the versioning scheme work? 14 15[LEGAL] Legal questions 16 17* Do I need patent licenses to use OpenSSL? 18* Can I use OpenSSL with GPL software? 19 20[USER] Questions on using the OpenSSL applications 21 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 39[BUILD] Questions about building and testing OpenSSL 40 41* Why does the linker complain about undefined symbols? 42* Why does the OpenSSL test fail with "bc: command not found"? 43* Why does the OpenSSL test fail with "bc: 1 no implemented"? 44* Why does the OpenSSL test fail with "bc: stack empty"? 45* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 46* Why does the OpenSSL compilation fail with "ar: command not found"? 47* Why does the OpenSSL compilation fail on Win32 with VC++? 48* What is special about OpenSSL on Redhat? 49* Why does the OpenSSL compilation fail on MacOS X? 50* Why does the OpenSSL test suite fail on MacOS X? 51* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 52* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 53* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 54* Why does compiler fail to compile sha512.c? 55* Test suite still fails, what to do? 56* I think I've found a bug, what should I do? 57* I'm SURE I've found a bug, how do I report it? 58* I've found a security issue, how do I report it? 59 60[PROG] Questions about programming with OpenSSL 61 62* Is OpenSSL thread-safe? 63* I've compiled a program under Windows and it crashes: why? 64* How do I read or write a DER encoded buffer using the ASN1 functions? 65* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 66* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 67* I've called <some function> and it fails, why? 68* I just get a load of numbers for the error output, what do they mean? 69* Why do I get errors about unknown algorithms? 70* Why can't the OpenSSH configure script detect OpenSSL? 71* Can I use OpenSSL's SSL library with non-blocking I/O? 72* Why doesn't my server application receive a client certificate? 73* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 74* I think I've detected a memory leak, is this a bug? 75* Why does Valgrind complain about the use of uninitialized data? 76* Why doesn't a memory BIO work when a file does? 77* Where are the declarations and implementations of d2i_X509() etc? 78 79=============================================================================== 80 81[MISC] ======================================================================== 82 83* Which is the current version of OpenSSL? 84 85The current version is available from <URL: http://www.openssl.org>. 86OpenSSL 1.0.1c was released on May 10th, 2012. 87 88In addition to the current stable release, you can also access daily 89snapshots of the OpenSSL development version at <URL: 90ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 91 92 93* Where is the documentation? 94 95OpenSSL is a library that provides cryptographic functionality to 96applications such as secure web servers. Be sure to read the 97documentation of the application you want to use. The INSTALL file 98explains how to install this library. 99 100OpenSSL includes a command line utility that can be used to perform a 101variety of cryptographic functions. It is described in the openssl(1) 102manpage. Documentation for developers is currently being written. Many 103manual pages are available; overviews over libcrypto and 104libssl are given in the crypto(3) and ssl(3) manpages. 105 106The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 107different directory if you specified one as described in INSTALL). 108In addition, you can read the most current versions at 109<URL: http://www.openssl.org/docs/>. Note that the online documents refer 110to the very latest development versions of OpenSSL and may include features 111not present in released versions. If in doubt refer to the documentation 112that came with the version of OpenSSL you are using. The pod format 113documentation is included in each OpenSSL distribution under the docs 114directory. 115 116For information on parts of libcrypto that are not yet documented, you 117might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 118predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 119of this still applies to OpenSSL. 120 121There is some documentation about certificate extensions and PKCS#12 122in doc/openssl.txt 123 124The original SSLeay documentation is included in OpenSSL as 125doc/ssleay.txt. It may be useful when none of the other resources 126help, but please note that it reflects the obsolete version SSLeay 1270.6.6. 128 129 130* How can I contact the OpenSSL developers? 131 132The README file describes how to submit bug reports and patches to 133OpenSSL. Information on the OpenSSL mailing lists is available from 134<URL: http://www.openssl.org>. 135 136 137* Where can I get a compiled version of OpenSSL? 138 139You can finder pointers to binary distributions in 140<URL: http://www.openssl.org/related/binaries.html> . 141 142Some applications that use OpenSSL are distributed in binary form. 143When using such an application, you don't need to install OpenSSL 144yourself; the application will include the required parts (e.g. DLLs). 145 146If you want to build OpenSSL on a Windows system and you don't have 147a C compiler, read the "Mingw32" section of INSTALL.W32 for information 148on how to obtain and install the free GNU C compiler. 149 150A number of Linux and *BSD distributions include OpenSSL. 151 152 153* Why aren't tools like 'autoconf' and 'libtool' used? 154 155autoconf will probably be used in future OpenSSL versions. If it was 156less Unix-centric, it might have been used much earlier. 157 158* What is an 'engine' version? 159 160With version 0.9.6 OpenSSL was extended to interface to external crypto 161hardware. This was realized in a special release '0.9.6-engine'. With 162version 0.9.7 the changes were merged into the main development line, 163so that the special release is no longer necessary. 164 165* How do I check the authenticity of the OpenSSL distribution? 166 167We provide MD5 digests and ASC signatures of each tarball. 168Use MD5 to check that a tarball from a mirror site is identical: 169 170 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 171 172You can check authenticity using pgp or gpg. You need the OpenSSL team 173member public key used to sign it (download it from a key server, see a 174list of keys at <URL: http://www.openssl.org/about/>). Then 175just do: 176 177 pgp TARBALL.asc 178 179* How does the versioning scheme work? 180 181After the release of OpenSSL 1.0.0 the versioning scheme changed. Letter 182releases (e.g. 1.0.1a) can only contain bug and security fixes and no 183new features. Minor releases change the last number (e.g. 1.0.2) and 184can contain new features that retain binary compatibility. Changes to 185the middle number are considered major releases and neither source nor 186binary compatibility is guaranteed. 187 188Therefore the answer to the common question "when will feature X be 189backported to OpenSSL 1.0.0/0.9.8?" is "never" but it could appear 190in the next minor release. 191 192[LEGAL] ======================================================================= 193 194* Do I need patent licenses to use OpenSSL? 195 196The patents section of the README file lists patents that may apply to 197you if you want to use OpenSSL. For information on intellectual 198property rights, please consult a lawyer. The OpenSSL team does not 199offer legal advice. 200 201You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using 202 ./config no-idea no-mdc2 no-rc5 203 204 205* Can I use OpenSSL with GPL software? 206 207On many systems including the major Linux and BSD distributions, yes (the 208GPL does not place restrictions on using libraries that are part of the 209normal operating system distribution). 210 211On other systems, the situation is less clear. Some GPL software copyright 212holders claim that you infringe on their rights if you use OpenSSL with 213their software on operating systems that don't normally include OpenSSL. 214 215If you develop open source software that uses OpenSSL, you may find it 216useful to choose an other license than the GPL, or state explicitly that 217"This program is released under the GPL with the additional exemption that 218compiling, linking, and/or using OpenSSL is allowed." If you are using 219GPL software developed by others, you may want to ask the copyright holder 220for permission to use their software with OpenSSL. 221 222 223[USER] ======================================================================== 224 225* Why do I get a "PRNG not seeded" error message? 226 227Cryptographic software needs a source of unpredictable data to work 228correctly. Many open source operating systems provide a "randomness 229device" (/dev/urandom or /dev/random) that serves this purpose. 230All OpenSSL versions try to use /dev/urandom by default; starting with 231version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 232available. 233 234On other systems, applications have to call the RAND_add() or 235RAND_seed() function with appropriate data before generating keys or 236performing public key encryption. (These functions initialize the 237pseudo-random number generator, PRNG.) Some broken applications do 238not do this. As of version 0.9.5, the OpenSSL functions that need 239randomness report an error if the random number generator has not been 240seeded with at least 128 bits of randomness. If this error occurs and 241is not discussed in the documentation of the application you are 242using, please contact the author of that application; it is likely 243that it never worked correctly. OpenSSL 0.9.5 and later make the 244error visible by refusing to perform potentially insecure encryption. 245 246If you are using Solaris 8, you can add /dev/urandom and /dev/random 247devices by installing patch 112438 (Sparc) or 112439 (x86), which are 248available via the Patchfinder at <URL: http://sunsolve.sun.com> 249(Solaris 9 includes these devices by default). For /dev/random support 250for earlier Solaris versions, see Sun's statement at 251<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 252(the SUNWski package is available in patch 105710). 253 254On systems without /dev/urandom and /dev/random, it is a good idea to 255use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 256details. Starting with version 0.9.7, OpenSSL will automatically look 257for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 258/etc/entropy. 259 260Most components of the openssl command line utility automatically try 261to seed the random number generator from a file. The name of the 262default seeding file is determined as follows: If environment variable 263RANDFILE is set, then it names the seeding file. Otherwise if 264environment variable HOME is set, then the seeding file is $HOME/.rnd. 265If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 266use file .rnd in the current directory while OpenSSL 0.9.6a uses no 267default seeding file at all. OpenSSL 0.9.6b and later will behave 268similarly to 0.9.6a, but will use a default of "C:\" for HOME on 269Windows systems if the environment variable has not been set. 270 271If the default seeding file does not exist or is too short, the "PRNG 272not seeded" error message may occur. 273 274The openssl command line utility will write back a new state to the 275default seeding file (and create this file if necessary) unless 276there was no sufficient seeding. 277 278Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 279Use the "-rand" option of the OpenSSL command line tools instead. 280The $RANDFILE environment variable and $HOME/.rnd are only used by the 281OpenSSL command line tools. Applications using the OpenSSL library 282provide their own configuration options to specify the entropy source, 283please check out the documentation coming the with application. 284 285 286* Why do I get an "unable to write 'random state'" error message? 287 288 289Sometimes the openssl command line utility does not abort with 290a "PRNG not seeded" error message, but complains that it is 291"unable to write 'random state'". This message refers to the 292default seeding file (see previous answer). A possible reason 293is that no default filename is known because neither RANDFILE 294nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 295current directory in this case, but this has changed with 0.9.6a.) 296 297 298* How do I create certificates or certificate requests? 299 300Check out the CA.pl(1) manual page. This provides a simple wrapper round 301the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 302out the manual pages for the individual utilities and the certificate 303extensions documentation (in ca(1), req(1), x509v3_config(5) ) 304 305 306* Why can't I create certificate requests? 307 308You typically get the error: 309 310 unable to find 'distinguished_name' in config 311 problems making Certificate Request 312 313This is because it can't find the configuration file. Check out the 314DIAGNOSTICS section of req(1) for more information. 315 316 317* Why does <SSL program> fail with a certificate verify error? 318 319This problem is usually indicated by log messages saying something like 320"unable to get local issuer certificate" or "self signed certificate". 321When a certificate is verified its root CA must be "trusted" by OpenSSL 322this typically means that the CA certificate must be placed in a directory 323or file and the relevant program configured to read it. The OpenSSL program 324'verify' behaves in a similar way and issues similar error messages: check 325the verify(1) program manual page for more information. 326 327 328* Why can I only use weak ciphers when I connect to a server using OpenSSL? 329 330This is almost certainly because you are using an old "export grade" browser 331which only supports weak encryption. Upgrade your browser to support 128 bit 332ciphers. 333 334 335* How can I create DSA certificates? 336 337Check the CA.pl(1) manual page for a DSA certificate example. 338 339 340* Why can't I make an SSL connection to a server using a DSA certificate? 341 342Typically you'll see a message saying there are no shared ciphers when 343the same setup works fine with an RSA certificate. There are two possible 344causes. The client may not support connections to DSA servers most web 345browsers (including Netscape and MSIE) only support connections to servers 346supporting RSA cipher suites. The other cause is that a set of DH parameters 347has not been supplied to the server. DH parameters can be created with the 348dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 349check the source to s_server in apps/s_server.c for an example. 350 351 352* How can I remove the passphrase on a private key? 353 354Firstly you should be really *really* sure you want to do this. Leaving 355a private key unencrypted is a major security risk. If you decide that 356you do have to do this check the EXAMPLES sections of the rsa(1) and 357dsa(1) manual pages. 358 359 360* Why can't I use OpenSSL certificates with SSL client authentication? 361 362What will typically happen is that when a server requests authentication 363it will either not include your certificate or tell you that you have 364no client certificates (Netscape) or present you with an empty list box 365(MSIE). The reason for this is that when a server requests a client 366certificate it includes a list of CAs names which it will accept. Browsers 367will only let you select certificates from the list on the grounds that 368there is little point presenting a certificate which the server will 369reject. 370 371The solution is to add the relevant CA certificate to your servers "trusted 372CA list". How you do this depends on the server software in uses. You can 373print out the servers list of acceptable CAs using the OpenSSL s_client tool: 374 375openssl s_client -connect www.some.host:443 -prexit 376 377If your server only requests certificates on certain URLs then you may need 378to manually issue an HTTP GET command to get the list when s_client connects: 379 380GET /some/page/needing/a/certificate.html 381 382If your CA does not appear in the list then this confirms the problem. 383 384 385* Why does my browser give a warning about a mismatched hostname? 386 387Browsers expect the server's hostname to match the value in the commonName 388(CN) field of the certificate. If it does not then you get a warning. 389 390 391* How do I install a CA certificate into a browser? 392 393The usual way is to send the DER encoded certificate to the browser as 394MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 395link. On MSIE certain extensions such as .der or .cacert may also work, or you 396can import the certificate using the certificate import wizard. 397 398You can convert a certificate to DER form using the command: 399 400openssl x509 -in ca.pem -outform DER -out ca.der 401 402Occasionally someone suggests using a command such as: 403 404openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 405 406DO NOT DO THIS! This command will give away your CAs private key and 407reduces its security to zero: allowing anyone to forge certificates in 408whatever name they choose. 409 410* Why is OpenSSL x509 DN output not conformant to RFC2253? 411 412The ways to print out the oneline format of the DN (Distinguished Name) have 413been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 414interface, the "-nameopt" option could be introduded. See the manual 415page of the "openssl x509" commandline tool for details. The old behaviour 416has however been left as default for the sake of compatibility. 417 418* What is a "128 bit certificate"? Can I create one with OpenSSL? 419 420The term "128 bit certificate" is a highly misleading marketing term. It does 421*not* refer to the size of the public key in the certificate! A certificate 422containing a 128 bit RSA key would have negligible security. 423 424There were various other names such as "magic certificates", "SGC 425certificates", "step up certificates" etc. 426 427You can't generally create such a certificate using OpenSSL but there is no 428need to any more. Nowadays web browsers using unrestricted strong encryption 429are generally available. 430 431When there were tight restrictions on the export of strong encryption 432software from the US only weak encryption algorithms could be freely exported 433(initially 40 bit and then 56 bit). It was widely recognised that this was 434inadequate. A relaxation of the rules allowed the use of strong encryption but 435only to an authorised server. 436 437Two slighly different techniques were developed to support this, one used by 438Netscape was called "step up", the other used by MSIE was called "Server Gated 439Cryptography" (SGC). When a browser initially connected to a server it would 440check to see if the certificate contained certain extensions and was issued by 441an authorised authority. If these test succeeded it would reconnect using 442strong encryption. 443 444Only certain (initially one) certificate authorities could issue the 445certificates and they generally cost more than ordinary certificates. 446 447Although OpenSSL can create certificates containing the appropriate extensions 448the certificate would not come from a permitted authority and so would not 449be recognized. 450 451The export laws were later changed to allow almost unrestricted use of strong 452encryption so these certificates are now obsolete. 453 454 455* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? 456 457It doesn't: this extension is often the cause of confusion. 458 459Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose 460certificate C contains AKID. 461 462The purpose of this extension is to identify the authority certificate B. This 463can be done either by including the subject key identifier of B or its issuer 464name and serial number. 465 466In this latter case because it is identifying certifcate B it must contain the 467issuer name and serial number of B. 468 469It is often wrongly assumed that it should contain the subject name of B. If it 470did this would be redundant information because it would duplicate the issuer 471name of C. 472 473 474* How can I set up a bundle of commercial root CA certificates? 475 476The OpenSSL software is shipped without any root CA certificate as the 477OpenSSL project does not have any policy on including or excluding 478any specific CA and does not intend to set up such a policy. Deciding 479about which CAs to support is up to application developers or 480administrators. 481 482Other projects do have other policies so you can for example extract the CA 483bundle used by Mozilla and/or modssl as described in this article: 484 485 <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html> 486 487 488[BUILD] ======================================================================= 489 490* Why does the linker complain about undefined symbols? 491 492Maybe the compilation was interrupted, and make doesn't notice that 493something is missing. Run "make clean; make". 494 495If you used ./Configure instead of ./config, make sure that you 496selected the right target. File formats may differ slightly between 497OS versions (for example sparcv8/sparcv9, or a.out/elf). 498 499In case you get errors about the following symbols, use the config 500option "no-asm", as described in INSTALL: 501 502 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 503 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 504 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 505 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 506 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 507 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 508 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 509 510If none of these helps, you may want to try using the current snapshot. 511If the problem persists, please submit a bug report. 512 513 514* Why does the OpenSSL test fail with "bc: command not found"? 515 516You didn't install "bc", the Unix calculator. If you want to run the 517tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 518 519 520* Why does the OpenSSL test fail with "bc: 1 no implemented"? 521 522On some SCO installations or versions, bc has a bug that gets triggered 523when you run the test suite (using "make test"). The message returned is 524"bc: 1 not implemented". 525 526The best way to deal with this is to find another implementation of bc 527and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> 528for download instructions) can be safely used, for example. 529 530 531* Why does the OpenSSL test fail with "bc: stack empty"? 532 533On some DG/ux versions, bc seems to have a too small stack for calculations 534that the OpenSSL bntest throws at it. This gets triggered when you run the 535test suite (using "make test"). The message returned is "bc: stack empty". 536 537The best way to deal with this is to find another implementation of bc 538and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> 539for download instructions) can be safely used, for example. 540 541 542* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 543 544On some Alpha installations running Tru64 Unix and Compaq C, the compilation 545of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 546memory to continue compilation.' As far as the tests have shown, this may be 547a compiler bug. What happens is that it eats up a lot of resident memory 548to build something, probably a table. The problem is clearly in the 549optimization code, because if one eliminates optimization completely (-O0), 550the compilation goes through (and the compiler consumes about 2MB of resident 551memory instead of 240MB or whatever one's limit is currently). 552 553There are three options to solve this problem: 554 5551. set your current data segment size soft limit higher. Experience shows 556that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 557this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 558kbytes to set the limit to. 559 5602. If you have a hard limit that is lower than what you need and you can't 561get it changed, you can compile all of OpenSSL with -O0 as optimization 562level. This is however not a very nice thing to do for those who expect to 563get the best result from OpenSSL. A bit more complicated solution is the 564following: 565 566----- snip:start ----- 567 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 568 sed -e 's/ -O[0-9] / -O0 /'`" 569 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 570 make 571----- snip:end ----- 572 573This will only compile sha_dgst.c with -O0, the rest with the optimization 574level chosen by the configuration process. When the above is done, do the 575test and installation and you're set. 576 5773. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 578should not be used and is not used in SSL/TLS nor any other recognized 579protocol in either case. 580 581 582* Why does the OpenSSL compilation fail with "ar: command not found"? 583 584Getting this message is quite usual on Solaris 2, because Sun has hidden 585away 'ar' and other development commands in directories that aren't in 586$PATH by default. One of those directories is '/usr/ccs/bin'. The 587quickest way to fix this is to do the following (it assumes you use sh 588or any sh-compatible shell): 589 590----- snip:start ----- 591 PATH=${PATH}:/usr/ccs/bin; export PATH 592----- snip:end ----- 593 594and then redo the compilation. What you should really do is make sure 595'/usr/ccs/bin' is permanently in your $PATH, for example through your 596'.profile' (again, assuming you use a sh-compatible shell). 597 598 599* Why does the OpenSSL compilation fail on Win32 with VC++? 600 601Sometimes, you may get reports from VC++ command line (cl) that it 602can't find standard include files like stdio.h and other weirdnesses. 603One possible cause is that the environment isn't correctly set up. 604To solve that problem for VC++ versions up to 6, one should run 605VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 606installation directory (somewhere under 'Program Files'). For VC++ 607version 7 (and up?), which is also called VS.NET, the file is called 608VSVARS32.BAT instead. 609This needs to be done prior to running NMAKE, and the changes are only 610valid for the current DOS session. 611 612 613* What is special about OpenSSL on Redhat? 614 615Red Hat Linux (release 7.0 and later) include a preinstalled limited 616version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 617is disabled in this version. The same may apply to other Linux distributions. 618Users may therefore wish to install more or all of the features left out. 619 620To do this you MUST ensure that you do not overwrite the openssl that is in 621/usr/bin on your Red Hat machine. Several packages depend on this file, 622including sendmail and ssh. /usr/local/bin is a good alternative choice. The 623libraries that come with Red Hat 7.0 onwards have different names and so are 624not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 625/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 626/lib/libcrypto.so.2 respectively). 627 628Please note that we have been advised by Red Hat attempting to recompile the 629openssl rpm with all the cryptography enabled will not work. All other 630packages depend on the original Red Hat supplied openssl package. It is also 631worth noting that due to the way Red Hat supplies its packages, updates to 632openssl on each distribution never change the package version, only the 633build number. For example, on Red Hat 7.1, the latest openssl package has 634version number 0.9.6 and build number 9 even though it contains all the 635relevant updates in packages up to and including 0.9.6b. 636 637A possible way around this is to persuade Red Hat to produce a non-US 638version of Red Hat Linux. 639 640FYI: Patent numbers and expiry dates of US patents: 641MDC-2: 4,908,861 13/03/2007 642IDEA: 5,214,703 25/05/2010 643RC5: 5,724,428 03/03/2015 644 645 646* Why does the OpenSSL compilation fail on MacOS X? 647 648If the failure happens when trying to build the "openssl" binary, with 649a large number of undefined symbols, it's very probable that you have 650OpenSSL 0.9.6b delivered with the operating system (you can find out by 651running '/usr/bin/openssl version') and that you were trying to build 652OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 653MacOS X has a misfeature that's quite difficult to go around. 654Look in the file PROBLEMS for a more detailed explanation and for possible 655solutions. 656 657 658* Why does the OpenSSL test suite fail on MacOS X? 659 660If the failure happens when running 'make test' and the RC4 test fails, 661it's very probable that you have OpenSSL 0.9.6b delivered with the 662operating system (you can find out by running '/usr/bin/openssl version') 663and that you were trying to build OpenSSL 0.9.6d. The problem is that 664the loader ('ld') in MacOS X has a misfeature that's quite difficult to 665go around and has linked the programs "openssl" and the test programs 666with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 667libraries you just built. 668Look in the file PROBLEMS for a more detailed explanation and for possible 669solutions. 670 671* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 672 673Failure in BN_sqr test is most likely caused by a failure to configure the 674toolkit for current platform or lack of support for the platform in question. 675Run './config -t' and './apps/openssl version -p'. Do these platform 676identifiers match? If they don't, then you most likely failed to run 677./config and you're hereby advised to do so before filing a bug report. 678If ./config itself fails to run, then it's most likely problem with your 679local environment and you should turn to your system administrator (or 680similar). If identifiers match (and/or no alternative identifier is 681suggested by ./config script), then the platform is unsupported. There might 682or might not be a workaround. Most notably on SPARC64 platforms with GNU 683C compiler you should be able to produce a working build by running 684'./config -m32'. I understand that -m32 might not be what you want/need, 685but the build should be operational. For further details turn to 686<openssl-dev@openssl.org>. 687 688* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 689 690As of 0.9.7 assembler routines were overhauled for position independence 691of the machine code, which is essential for shared library support. For 692some reason OpenBSD is equipped with an out-of-date GNU assembler which 693finds the new code offensive. To work around the problem, configure with 694no-asm (and sacrifice a great deal of performance) or patch your assembler 695according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 696For your convenience a pre-compiled replacement binary is provided at 697<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 698Reportedly elder *BSD a.out platforms also suffer from this problem and 699remedy should be same. Provided binary is statically linked and should be 700working across wider range of *BSD branches, not just OpenBSD. 701 702* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 703 704If the test program in question fails withs SIGILL, Illegal Instruction 705exception, then you more than likely to run SSE2-capable CPU, such as 706Intel P4, under control of kernel which does not support SSE2 707instruction extentions. See accompanying INSTALL file and 708OPENSSL_ia32cap(3) documentation page for further information. 709 710* Why does compiler fail to compile sha512.c? 711 712OpenSSL SHA-512 implementation depends on compiler support for 64-bit 713integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a 714couple] lack support for this and therefore are incapable of compiling 715the module in question. The recommendation is to disable SHA-512 by 716adding no-sha512 to ./config [or ./Configure] command line. Another 717possible alternative might be to switch to GCC. 718 719* Test suite still fails, what to do? 720 721Another common reason for failure to complete some particular test is 722simply bad code generated by a buggy component in toolchain or deficiency 723in run-time environment. There are few cases documented in PROBLEMS file, 724consult it for possible workaround before you beat the drum. Even if you 725don't find solution or even mention there, do reserve for possibility of 726a compiler bug. Compiler bugs might appear in rather bizarre ways, they 727never make sense, and tend to emerge when you least expect them. In order 728to identify one, drop optimization level, e.g. by editing CFLAG line in 729top-level Makefile, recompile and re-run the test. 730 731* I think I've found a bug, what should I do? 732 733If you are a new user then it is quite likely you haven't found a bug and 734something is happening you aren't familiar with. Check this FAQ, the associated 735documentation and the mailing lists for similar queries. If you are still 736unsure whether it is a bug or not submit a query to the openssl-users mailing 737list. 738 739 740* I'm SURE I've found a bug, how do I report it? 741 742Bug reports with no security implications should be sent to the request 743tracker. This can be done by mailing the report to <rt@openssl.org> (or its 744alias <openssl-bugs@openssl.org>), please note that messages sent to the 745request tracker also appear in the public openssl-dev mailing list. 746 747The report should be in plain text. Any patches should be sent as 748plain text attachments because some mailers corrupt patches sent inline. 749If your issue affects multiple versions of OpenSSL check any patches apply 750cleanly and, if possible include patches to each affected version. 751 752The report should be given a meaningful subject line briefly summarising the 753issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful. 754 755By sending reports to the request tracker the bug can then be given a priority 756and assigned to the appropriate maintainer. The history of discussions can be 757accessed and if the issue has been addressed or a reason why not. If patches 758are only sent to openssl-dev they can be mislaid if a team member has to 759wade through months of old messages to review the discussion. 760 761See also <URL: http://www.openssl.org/support/rt.html> 762 763 764* I've found a security issue, how do I report it? 765 766If you think your bug has security implications then please send it to 767openssl-security@openssl.org if you don't get a prompt reply at least 768acknowledging receipt then resend or mail it directly to one of the 769more active team members (e.g. Steve). 770 771[PROG] ======================================================================== 772 773* Is OpenSSL thread-safe? 774 775Yes (with limitations: an SSL connection may not concurrently be used 776by multiple threads). On Windows and many Unix systems, OpenSSL 777automatically uses the multi-threaded versions of the standard 778libraries. If your platform is not one of these, consult the INSTALL 779file. 780 781Multi-threaded applications must provide two callback functions to 782OpenSSL by calling CRYPTO_set_locking_callback() and 783CRYPTO_set_id_callback(), for all versions of OpenSSL up to and 784including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback() 785and associated APIs are deprecated by CRYPTO_THREADID_set_callback() 786and friends. This is described in the threads(3) manpage. 787 788* I've compiled a program under Windows and it crashes: why? 789 790This is usually because you've missed the comment in INSTALL.W32. 791Your application must link against the same version of the Win32 792C-Runtime against which your openssl libraries were linked. The 793default version for OpenSSL is /MD - "Multithreaded DLL". 794 795If you are using Microsoft Visual C++'s IDE (Visual Studio), in 796many cases, your new project most likely defaulted to "Debug 797Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 798program will crash, typically on the first BIO related read or write 799operation. 800 801For each of the six possible link stage configurations within Win32, 802your application must link against the same by which OpenSSL was 803built. If you are using MS Visual C++ (Studio) this can be changed 804by: 805 806 1. Select Settings... from the Project Menu. 807 2. Select the C/C++ Tab. 808 3. Select "Code Generation from the "Category" drop down list box 809 4. Select the Appropriate library (see table below) from the "Use 810 run-time library" drop down list box. Perform this step for both 811 your debug and release versions of your application (look at the 812 top left of the settings panel to change between the two) 813 814 Single Threaded /ML - MS VC++ often defaults to 815 this for the release 816 version of a new project. 817 Debug Single Threaded /MLd - MS VC++ often defaults to 818 this for the debug version 819 of a new project. 820 Multithreaded /MT 821 Debug Multithreaded /MTd 822 Multithreaded DLL /MD - OpenSSL defaults to this. 823 Debug Multithreaded DLL /MDd 824 825Note that debug and release libraries are NOT interchangeable. If you 826built OpenSSL with /MD your application must use /MD and cannot use /MDd. 827 828As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL 829.DLLs compiled with some specific run-time option [we insist on the 830default /MD] can be deployed with application compiled with different 831option or even different compiler. But there is a catch! Instead of 832re-compiling OpenSSL toolkit, as you would have to with prior versions, 833you have to compile small C snippet with compiler and/or options of 834your choice. The snippet gets installed as 835<install-root>/include/openssl/applink.c and should be either added to 836your application project or simply #include-d in one [and only one] 837of your application source files. Failure to link this shim module 838into your application manifests itself as fatal "no OPENSSL_Applink" 839run-time error. An explicit reminder is due that in this situation 840[mixing compiler options] it is as important to add CRYPTO_malloc_init 841prior first call to OpenSSL. 842 843* How do I read or write a DER encoded buffer using the ASN1 functions? 844 845You have two options. You can either use a memory BIO in conjunction 846with the i2d_*_bio() or d2i_*_bio() functions or you can use the 847i2d_*(), d2i_*() functions directly. Since these are often the 848cause of grief here are some code fragments using PKCS7 as an example: 849 850 unsigned char *buf, *p; 851 int len; 852 853 len = i2d_PKCS7(p7, NULL); 854 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 855 p = buf; 856 i2d_PKCS7(p7, &p); 857 858At this point buf contains the len bytes of the DER encoding of 859p7. 860 861The opposite assumes we already have len bytes in buf: 862 863 unsigned char *p; 864 p = buf; 865 p7 = d2i_PKCS7(NULL, &p, len); 866 867At this point p7 contains a valid PKCS7 structure of NULL if an error 868occurred. If an error occurred ERR_print_errors(bio) should give more 869information. 870 871The reason for the temporary variable 'p' is that the ASN1 functions 872increment the passed pointer so it is ready to read or write the next 873structure. This is often a cause of problems: without the temporary 874variable the buffer pointer is changed to point just after the data 875that has been read or written. This may well be uninitialized data 876and attempts to free the buffer will have unpredictable results 877because it no longer points to the same address. 878 879 880* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 881 882The short answer is yes, because DER is a special case of BER and OpenSSL 883ASN1 decoders can process BER. 884 885The longer answer is that ASN1 structures can be encoded in a number of 886different ways. One set of ways is the Basic Encoding Rules (BER) with various 887permissible encodings. A restriction of BER is the Distinguished Encoding 888Rules (DER): these uniquely specify how a given structure is encoded. 889 890Therefore, because DER is a special case of BER, DER is an acceptable encoding 891for BER. 892 893 894* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 895 896This usually happens when you try compiling something using the PKCS#12 897macros with a C++ compiler. There is hardly ever any need to use the 898PKCS#12 macros in a program, it is much easier to parse and create 899PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 900documented in doc/openssl.txt and with examples in demos/pkcs12. The 901'pkcs12' application has to use the macros because it prints out 902debugging information. 903 904 905* I've called <some function> and it fails, why? 906 907Before submitting a report or asking in one of the mailing lists, you 908should try to determine the cause. In particular, you should call 909ERR_print_errors() or ERR_print_errors_fp() after the failed call 910and see if the message helps. Note that the problem may occur earlier 911than you think -- you should check for errors after every call where 912it is possible, otherwise the actual problem may be hidden because 913some OpenSSL functions clear the error state. 914 915 916* I just get a load of numbers for the error output, what do they mean? 917 918The actual format is described in the ERR_print_errors() manual page. 919You should call the function ERR_load_crypto_strings() before hand and 920the message will be output in text form. If you can't do this (for example 921it is a pre-compiled binary) you can use the errstr utility on the error 922code itself (the hex digits after the second colon). 923 924 925* Why do I get errors about unknown algorithms? 926 927The cause is forgetting to load OpenSSL's table of algorithms with 928OpenSSL_add_all_algorithms(). See the manual page for more information. This 929can cause several problems such as being unable to read in an encrypted 930PEM file, unable to decrypt a PKCS#12 file or signature failure when 931verifying certificates. 932 933* Why can't the OpenSSH configure script detect OpenSSL? 934 935Several reasons for problems with the automatic detection exist. 936OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 937Sometimes the distribution has installed an older version in the system 938locations that is detected instead of a new one installed. The OpenSSL 939library might have been compiled for another CPU or another mode (32/64 bits). 940Permissions might be wrong. 941 942The general answer is to check the config.log file generated when running 943the OpenSSH configure script. It should contain the detailed information 944on why the OpenSSL library was not detected or considered incompatible. 945 946 947* Can I use OpenSSL's SSL library with non-blocking I/O? 948 949Yes; make sure to read the SSL_get_error(3) manual page! 950 951A pitfall to avoid: Don't assume that SSL_read() will just read from 952the underlying transport or that SSL_write() will just write to it -- 953it is also possible that SSL_write() cannot do any useful work until 954there is data to read, or that SSL_read() cannot do anything until it 955is possible to send data. One reason for this is that the peer may 956request a new TLS/SSL handshake at any time during the protocol, 957requiring a bi-directional message exchange; both SSL_read() and 958SSL_write() will try to continue any pending handshake. 959 960 961* Why doesn't my server application receive a client certificate? 962 963Due to the TLS protocol definition, a client will only send a certificate, 964if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 965SSL_CTX_set_verify() function to enable the use of client certificates. 966 967 968* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 969 970For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 971versions, uniqueIdentifier was incorrectly used for X.509 certificates. 972The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 973Change your code to use the new name when compiling against OpenSSL 0.9.7. 974 975 976* I think I've detected a memory leak, is this a bug? 977 978In most cases the cause of an apparent memory leak is an OpenSSL internal table 979that is allocated when an application starts up. Since such tables do not grow 980in size over time they are harmless. 981 982These internal tables can be freed up when an application closes using various 983functions. Currently these include following: 984 985Thread-local cleanup functions: 986 987 ERR_remove_state() 988 989Application-global cleanup functions that are aware of usage (and therefore 990thread-safe): 991 992 ENGINE_cleanup() and CONF_modules_unload() 993 994"Brutal" (thread-unsafe) Application-global cleanup functions: 995 996 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). 997 998 999* Why does Valgrind complain about the use of uninitialized data? 1000 1001When OpenSSL's PRNG routines are called to generate random numbers the supplied 1002buffer contents are mixed into the entropy pool: so it technically does not 1003matter whether the buffer is initialized at this point or not. Valgrind (and 1004other test tools) will complain about this. When using Valgrind, make sure the 1005OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) 1006to get rid of these warnings. 1007 1008 1009* Why doesn't a memory BIO work when a file does? 1010 1011This can occur in several cases for example reading an S/MIME email message. 1012The reason is that a memory BIO can do one of two things when all the data 1013has been read from it. 1014 1015The default behaviour is to indicate that no more data is available and that 1016the call should be retried, this is to allow the application to fill up the BIO 1017again if necessary. 1018 1019Alternatively it can indicate that no more data is available and that EOF has 1020been reached. 1021 1022If a memory BIO is to behave in the same way as a file this second behaviour 1023is needed. This must be done by calling: 1024 1025 BIO_set_mem_eof_return(bio, 0); 1026 1027See the manual pages for more details. 1028 1029 1030* Where are the declarations and implementations of d2i_X509() etc? 1031 1032These are defined and implemented by macros of the form: 1033 1034 1035 DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509) 1036 1037The implementation passes an ASN1 "template" defining the structure into an 1038ASN1 interpreter using generalised functions such as ASN1_item_d2i(). 1039 1040 1041=============================================================================== 1042