FAQ revision 194206
1OpenSSL - Frequently Asked Questions 2-------------------------------------- 3 4[MISC] Miscellaneous questions 5 6* Which is the current version of OpenSSL? 7* Where is the documentation? 8* How can I contact the OpenSSL developers? 9* Where can I get a compiled version of OpenSSL? 10* Why aren't tools like 'autoconf' and 'libtool' used? 11* What is an 'engine' version? 12* How do I check the authenticity of the OpenSSL distribution? 13 14[LEGAL] Legal questions 15 16* Do I need patent licenses to use OpenSSL? 17* Can I use OpenSSL with GPL software? 18 19[USER] Questions on using the OpenSSL applications 20 21* Why do I get a "PRNG not seeded" error message? 22* Why do I get an "unable to write 'random state'" error message? 23* How do I create certificates or certificate requests? 24* Why can't I create certificate requests? 25* Why does <SSL program> fail with a certificate verify error? 26* Why can I only use weak ciphers when I connect to a server using OpenSSL? 27* How can I create DSA certificates? 28* Why can't I make an SSL connection using a DSA certificate? 29* How can I remove the passphrase on a private key? 30* Why can't I use OpenSSL certificates with SSL client authentication? 31* Why does my browser give a warning about a mismatched hostname? 32* How do I install a CA certificate into a browser? 33* Why is OpenSSL x509 DN output not conformant to RFC2253? 34* What is a "128 bit certificate"? Can I create one with OpenSSL? 35* Why does OpenSSL set the authority key identifier extension incorrectly? 36* How can I set up a bundle of commercial root CA certificates? 37 38[BUILD] Questions about building and testing OpenSSL 39 40* Why does the linker complain about undefined symbols? 41* Why does the OpenSSL test fail with "bc: command not found"? 42* Why does the OpenSSL test fail with "bc: 1 no implemented"? 43* Why does the OpenSSL test fail with "bc: stack empty"? 44* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 45* Why does the OpenSSL compilation fail with "ar: command not found"? 46* Why does the OpenSSL compilation fail on Win32 with VC++? 47* What is special about OpenSSL on Redhat? 48* Why does the OpenSSL compilation fail on MacOS X? 49* Why does the OpenSSL test suite fail on MacOS X? 50* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 51* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 52* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 53* Why does compiler fail to compile sha512.c? 54* Test suite still fails, what to do? 55 56[PROG] Questions about programming with OpenSSL 57 58* Is OpenSSL thread-safe? 59* I've compiled a program under Windows and it crashes: why? 60* How do I read or write a DER encoded buffer using the ASN1 functions? 61* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 62* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 63* I've called <some function> and it fails, why? 64* I just get a load of numbers for the error output, what do they mean? 65* Why do I get errors about unknown algorithms? 66* Why can't the OpenSSH configure script detect OpenSSL? 67* Can I use OpenSSL's SSL library with non-blocking I/O? 68* Why doesn't my server application receive a client certificate? 69* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 70* I think I've detected a memory leak, is this a bug? 71* Why does Valgrind complain about the use of uninitialized data? 72* Why doesn't a memory BIO work when a file does? 73 74=============================================================================== 75 76[MISC] ======================================================================== 77 78* Which is the current version of OpenSSL? 79 80The current version is available from <URL: http://www.openssl.org>. 81OpenSSL 0.9.8k was released on Mar 25th, 2009. 82 83In addition to the current stable release, you can also access daily 84snapshots of the OpenSSL development version at <URL: 85ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 86 87 88* Where is the documentation? 89 90OpenSSL is a library that provides cryptographic functionality to 91applications such as secure web servers. Be sure to read the 92documentation of the application you want to use. The INSTALL file 93explains how to install this library. 94 95OpenSSL includes a command line utility that can be used to perform a 96variety of cryptographic functions. It is described in the openssl(1) 97manpage. Documentation for developers is currently being written. A 98few manual pages already are available; overviews over libcrypto and 99libssl are given in the crypto(3) and ssl(3) manpages. 100 101The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 102different directory if you specified one as described in INSTALL). 103In addition, you can read the most current versions at 104<URL: http://www.openssl.org/docs/>. 105 106For information on parts of libcrypto that are not yet documented, you 107might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 108predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 109of this still applies to OpenSSL. 110 111There is some documentation about certificate extensions and PKCS#12 112in doc/openssl.txt 113 114The original SSLeay documentation is included in OpenSSL as 115doc/ssleay.txt. It may be useful when none of the other resources 116help, but please note that it reflects the obsolete version SSLeay 1170.6.6. 118 119 120* How can I contact the OpenSSL developers? 121 122The README file describes how to submit bug reports and patches to 123OpenSSL. Information on the OpenSSL mailing lists is available from 124<URL: http://www.openssl.org>. 125 126 127* Where can I get a compiled version of OpenSSL? 128 129You can finder pointers to binary distributions in 130http://www.openssl.org/related/binaries.html . 131 132Some applications that use OpenSSL are distributed in binary form. 133When using such an application, you don't need to install OpenSSL 134yourself; the application will include the required parts (e.g. DLLs). 135 136If you want to build OpenSSL on a Windows system and you don't have 137a C compiler, read the "Mingw32" section of INSTALL.W32 for information 138on how to obtain and install the free GNU C compiler. 139 140A number of Linux and *BSD distributions include OpenSSL. 141 142 143* Why aren't tools like 'autoconf' and 'libtool' used? 144 145autoconf will probably be used in future OpenSSL versions. If it was 146less Unix-centric, it might have been used much earlier. 147 148* What is an 'engine' version? 149 150With version 0.9.6 OpenSSL was extended to interface to external crypto 151hardware. This was realized in a special release '0.9.6-engine'. With 152version 0.9.7 the changes were merged into the main development line, 153so that the special release is no longer necessary. 154 155* How do I check the authenticity of the OpenSSL distribution? 156 157We provide MD5 digests and ASC signatures of each tarball. 158Use MD5 to check that a tarball from a mirror site is identical: 159 160 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 161 162You can check authenticity using pgp or gpg. You need the OpenSSL team 163member public key used to sign it (download it from a key server, see a 164list of keys at <URL: http://www.openssl.org/about/>). Then 165just do: 166 167 pgp TARBALL.asc 168 169[LEGAL] ======================================================================= 170 171* Do I need patent licenses to use OpenSSL? 172 173The patents section of the README file lists patents that may apply to 174you if you want to use OpenSSL. For information on intellectual 175property rights, please consult a lawyer. The OpenSSL team does not 176offer legal advice. 177 178You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using 179 ./config no-idea no-mdc2 no-rc5 180 181 182* Can I use OpenSSL with GPL software? 183 184On many systems including the major Linux and BSD distributions, yes (the 185GPL does not place restrictions on using libraries that are part of the 186normal operating system distribution). 187 188On other systems, the situation is less clear. Some GPL software copyright 189holders claim that you infringe on their rights if you use OpenSSL with 190their software on operating systems that don't normally include OpenSSL. 191 192If you develop open source software that uses OpenSSL, you may find it 193useful to choose an other license than the GPL, or state explicitly that 194"This program is released under the GPL with the additional exemption that 195compiling, linking, and/or using OpenSSL is allowed." If you are using 196GPL software developed by others, you may want to ask the copyright holder 197for permission to use their software with OpenSSL. 198 199 200[USER] ======================================================================== 201 202* Why do I get a "PRNG not seeded" error message? 203 204Cryptographic software needs a source of unpredictable data to work 205correctly. Many open source operating systems provide a "randomness 206device" (/dev/urandom or /dev/random) that serves this purpose. 207All OpenSSL versions try to use /dev/urandom by default; starting with 208version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 209available. 210 211On other systems, applications have to call the RAND_add() or 212RAND_seed() function with appropriate data before generating keys or 213performing public key encryption. (These functions initialize the 214pseudo-random number generator, PRNG.) Some broken applications do 215not do this. As of version 0.9.5, the OpenSSL functions that need 216randomness report an error if the random number generator has not been 217seeded with at least 128 bits of randomness. If this error occurs and 218is not discussed in the documentation of the application you are 219using, please contact the author of that application; it is likely 220that it never worked correctly. OpenSSL 0.9.5 and later make the 221error visible by refusing to perform potentially insecure encryption. 222 223If you are using Solaris 8, you can add /dev/urandom and /dev/random 224devices by installing patch 112438 (Sparc) or 112439 (x86), which are 225available via the Patchfinder at <URL: http://sunsolve.sun.com> 226(Solaris 9 includes these devices by default). For /dev/random support 227for earlier Solaris versions, see Sun's statement at 228<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 229(the SUNWski package is available in patch 105710). 230 231On systems without /dev/urandom and /dev/random, it is a good idea to 232use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 233details. Starting with version 0.9.7, OpenSSL will automatically look 234for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 235/etc/entropy. 236 237Most components of the openssl command line utility automatically try 238to seed the random number generator from a file. The name of the 239default seeding file is determined as follows: If environment variable 240RANDFILE is set, then it names the seeding file. Otherwise if 241environment variable HOME is set, then the seeding file is $HOME/.rnd. 242If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 243use file .rnd in the current directory while OpenSSL 0.9.6a uses no 244default seeding file at all. OpenSSL 0.9.6b and later will behave 245similarly to 0.9.6a, but will use a default of "C:\" for HOME on 246Windows systems if the environment variable has not been set. 247 248If the default seeding file does not exist or is too short, the "PRNG 249not seeded" error message may occur. 250 251The openssl command line utility will write back a new state to the 252default seeding file (and create this file if necessary) unless 253there was no sufficient seeding. 254 255Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 256Use the "-rand" option of the OpenSSL command line tools instead. 257The $RANDFILE environment variable and $HOME/.rnd are only used by the 258OpenSSL command line tools. Applications using the OpenSSL library 259provide their own configuration options to specify the entropy source, 260please check out the documentation coming the with application. 261 262 263* Why do I get an "unable to write 'random state'" error message? 264 265 266Sometimes the openssl command line utility does not abort with 267a "PRNG not seeded" error message, but complains that it is 268"unable to write 'random state'". This message refers to the 269default seeding file (see previous answer). A possible reason 270is that no default filename is known because neither RANDFILE 271nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 272current directory in this case, but this has changed with 0.9.6a.) 273 274 275* How do I create certificates or certificate requests? 276 277Check out the CA.pl(1) manual page. This provides a simple wrapper round 278the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 279out the manual pages for the individual utilities and the certificate 280extensions documentation (currently in doc/openssl.txt). 281 282 283* Why can't I create certificate requests? 284 285You typically get the error: 286 287 unable to find 'distinguished_name' in config 288 problems making Certificate Request 289 290This is because it can't find the configuration file. Check out the 291DIAGNOSTICS section of req(1) for more information. 292 293 294* Why does <SSL program> fail with a certificate verify error? 295 296This problem is usually indicated by log messages saying something like 297"unable to get local issuer certificate" or "self signed certificate". 298When a certificate is verified its root CA must be "trusted" by OpenSSL 299this typically means that the CA certificate must be placed in a directory 300or file and the relevant program configured to read it. The OpenSSL program 301'verify' behaves in a similar way and issues similar error messages: check 302the verify(1) program manual page for more information. 303 304 305* Why can I only use weak ciphers when I connect to a server using OpenSSL? 306 307This is almost certainly because you are using an old "export grade" browser 308which only supports weak encryption. Upgrade your browser to support 128 bit 309ciphers. 310 311 312* How can I create DSA certificates? 313 314Check the CA.pl(1) manual page for a DSA certificate example. 315 316 317* Why can't I make an SSL connection to a server using a DSA certificate? 318 319Typically you'll see a message saying there are no shared ciphers when 320the same setup works fine with an RSA certificate. There are two possible 321causes. The client may not support connections to DSA servers most web 322browsers (including Netscape and MSIE) only support connections to servers 323supporting RSA cipher suites. The other cause is that a set of DH parameters 324has not been supplied to the server. DH parameters can be created with the 325dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 326check the source to s_server in apps/s_server.c for an example. 327 328 329* How can I remove the passphrase on a private key? 330 331Firstly you should be really *really* sure you want to do this. Leaving 332a private key unencrypted is a major security risk. If you decide that 333you do have to do this check the EXAMPLES sections of the rsa(1) and 334dsa(1) manual pages. 335 336 337* Why can't I use OpenSSL certificates with SSL client authentication? 338 339What will typically happen is that when a server requests authentication 340it will either not include your certificate or tell you that you have 341no client certificates (Netscape) or present you with an empty list box 342(MSIE). The reason for this is that when a server requests a client 343certificate it includes a list of CAs names which it will accept. Browsers 344will only let you select certificates from the list on the grounds that 345there is little point presenting a certificate which the server will 346reject. 347 348The solution is to add the relevant CA certificate to your servers "trusted 349CA list". How you do this depends on the server software in uses. You can 350print out the servers list of acceptable CAs using the OpenSSL s_client tool: 351 352openssl s_client -connect www.some.host:443 -prexit 353 354If your server only requests certificates on certain URLs then you may need 355to manually issue an HTTP GET command to get the list when s_client connects: 356 357GET /some/page/needing/a/certificate.html 358 359If your CA does not appear in the list then this confirms the problem. 360 361 362* Why does my browser give a warning about a mismatched hostname? 363 364Browsers expect the server's hostname to match the value in the commonName 365(CN) field of the certificate. If it does not then you get a warning. 366 367 368* How do I install a CA certificate into a browser? 369 370The usual way is to send the DER encoded certificate to the browser as 371MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 372link. On MSIE certain extensions such as .der or .cacert may also work, or you 373can import the certificate using the certificate import wizard. 374 375You can convert a certificate to DER form using the command: 376 377openssl x509 -in ca.pem -outform DER -out ca.der 378 379Occasionally someone suggests using a command such as: 380 381openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 382 383DO NOT DO THIS! This command will give away your CAs private key and 384reduces its security to zero: allowing anyone to forge certificates in 385whatever name they choose. 386 387* Why is OpenSSL x509 DN output not conformant to RFC2253? 388 389The ways to print out the oneline format of the DN (Distinguished Name) have 390been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 391interface, the "-nameopt" option could be introduded. See the manual 392page of the "openssl x509" commandline tool for details. The old behaviour 393has however been left as default for the sake of compatibility. 394 395* What is a "128 bit certificate"? Can I create one with OpenSSL? 396 397The term "128 bit certificate" is a highly misleading marketing term. It does 398*not* refer to the size of the public key in the certificate! A certificate 399containing a 128 bit RSA key would have negligible security. 400 401There were various other names such as "magic certificates", "SGC 402certificates", "step up certificates" etc. 403 404You can't generally create such a certificate using OpenSSL but there is no 405need to any more. Nowadays web browsers using unrestricted strong encryption 406are generally available. 407 408When there were tight restrictions on the export of strong encryption 409software from the US only weak encryption algorithms could be freely exported 410(initially 40 bit and then 56 bit). It was widely recognised that this was 411inadequate. A relaxation of the rules allowed the use of strong encryption but 412only to an authorised server. 413 414Two slighly different techniques were developed to support this, one used by 415Netscape was called "step up", the other used by MSIE was called "Server Gated 416Cryptography" (SGC). When a browser initially connected to a server it would 417check to see if the certificate contained certain extensions and was issued by 418an authorised authority. If these test succeeded it would reconnect using 419strong encryption. 420 421Only certain (initially one) certificate authorities could issue the 422certificates and they generally cost more than ordinary certificates. 423 424Although OpenSSL can create certificates containing the appropriate extensions 425the certificate would not come from a permitted authority and so would not 426be recognized. 427 428The export laws were later changed to allow almost unrestricted use of strong 429encryption so these certificates are now obsolete. 430 431 432* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? 433 434It doesn't: this extension is often the cause of confusion. 435 436Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose 437certificate C contains AKID. 438 439The purpose of this extension is to identify the authority certificate B. This 440can be done either by including the subject key identifier of B or its issuer 441name and serial number. 442 443In this latter case because it is identifying certifcate B it must contain the 444issuer name and serial number of B. 445 446It is often wrongly assumed that it should contain the subject name of B. If it 447did this would be redundant information because it would duplicate the issuer 448name of C. 449 450 451* How can I set up a bundle of commercial root CA certificates? 452 453The OpenSSL software is shipped without any root CA certificate as the 454OpenSSL project does not have any policy on including or excluding 455any specific CA and does not intend to set up such a policy. Deciding 456about which CAs to support is up to application developers or 457administrators. 458 459Other projects do have other policies so you can for example extract the CA 460bundle used by Mozilla and/or modssl as described in this article: 461 462 http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html 463 464 465[BUILD] ======================================================================= 466 467* Why does the linker complain about undefined symbols? 468 469Maybe the compilation was interrupted, and make doesn't notice that 470something is missing. Run "make clean; make". 471 472If you used ./Configure instead of ./config, make sure that you 473selected the right target. File formats may differ slightly between 474OS versions (for example sparcv8/sparcv9, or a.out/elf). 475 476In case you get errors about the following symbols, use the config 477option "no-asm", as described in INSTALL: 478 479 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 480 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 481 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 482 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 483 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 484 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 485 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 486 487If none of these helps, you may want to try using the current snapshot. 488If the problem persists, please submit a bug report. 489 490 491* Why does the OpenSSL test fail with "bc: command not found"? 492 493You didn't install "bc", the Unix calculator. If you want to run the 494tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 495 496 497* Why does the OpenSSL test fail with "bc: 1 no implemented"? 498 499On some SCO installations or versions, bc has a bug that gets triggered 500when you run the test suite (using "make test"). The message returned is 501"bc: 1 not implemented". 502 503The best way to deal with this is to find another implementation of bc 504and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 505for download instructions) can be safely used, for example. 506 507 508* Why does the OpenSSL test fail with "bc: stack empty"? 509 510On some DG/ux versions, bc seems to have a too small stack for calculations 511that the OpenSSL bntest throws at it. This gets triggered when you run the 512test suite (using "make test"). The message returned is "bc: stack empty". 513 514The best way to deal with this is to find another implementation of bc 515and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 516for download instructions) can be safely used, for example. 517 518 519* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 520 521On some Alpha installations running Tru64 Unix and Compaq C, the compilation 522of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 523memory to continue compilation.' As far as the tests have shown, this may be 524a compiler bug. What happens is that it eats up a lot of resident memory 525to build something, probably a table. The problem is clearly in the 526optimization code, because if one eliminates optimization completely (-O0), 527the compilation goes through (and the compiler consumes about 2MB of resident 528memory instead of 240MB or whatever one's limit is currently). 529 530There are three options to solve this problem: 531 5321. set your current data segment size soft limit higher. Experience shows 533that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 534this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 535kbytes to set the limit to. 536 5372. If you have a hard limit that is lower than what you need and you can't 538get it changed, you can compile all of OpenSSL with -O0 as optimization 539level. This is however not a very nice thing to do for those who expect to 540get the best result from OpenSSL. A bit more complicated solution is the 541following: 542 543----- snip:start ----- 544 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 545 sed -e 's/ -O[0-9] / -O0 /'`" 546 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 547 make 548----- snip:end ----- 549 550This will only compile sha_dgst.c with -O0, the rest with the optimization 551level chosen by the configuration process. When the above is done, do the 552test and installation and you're set. 553 5543. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 555should not be used and is not used in SSL/TLS nor any other recognized 556protocol in either case. 557 558 559* Why does the OpenSSL compilation fail with "ar: command not found"? 560 561Getting this message is quite usual on Solaris 2, because Sun has hidden 562away 'ar' and other development commands in directories that aren't in 563$PATH by default. One of those directories is '/usr/ccs/bin'. The 564quickest way to fix this is to do the following (it assumes you use sh 565or any sh-compatible shell): 566 567----- snip:start ----- 568 PATH=${PATH}:/usr/ccs/bin; export PATH 569----- snip:end ----- 570 571and then redo the compilation. What you should really do is make sure 572'/usr/ccs/bin' is permanently in your $PATH, for example through your 573'.profile' (again, assuming you use a sh-compatible shell). 574 575 576* Why does the OpenSSL compilation fail on Win32 with VC++? 577 578Sometimes, you may get reports from VC++ command line (cl) that it 579can't find standard include files like stdio.h and other weirdnesses. 580One possible cause is that the environment isn't correctly set up. 581To solve that problem for VC++ versions up to 6, one should run 582VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 583installation directory (somewhere under 'Program Files'). For VC++ 584version 7 (and up?), which is also called VS.NET, the file is called 585VSVARS32.BAT instead. 586This needs to be done prior to running NMAKE, and the changes are only 587valid for the current DOS session. 588 589 590* What is special about OpenSSL on Redhat? 591 592Red Hat Linux (release 7.0 and later) include a preinstalled limited 593version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 594is disabled in this version. The same may apply to other Linux distributions. 595Users may therefore wish to install more or all of the features left out. 596 597To do this you MUST ensure that you do not overwrite the openssl that is in 598/usr/bin on your Red Hat machine. Several packages depend on this file, 599including sendmail and ssh. /usr/local/bin is a good alternative choice. The 600libraries that come with Red Hat 7.0 onwards have different names and so are 601not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 602/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 603/lib/libcrypto.so.2 respectively). 604 605Please note that we have been advised by Red Hat attempting to recompile the 606openssl rpm with all the cryptography enabled will not work. All other 607packages depend on the original Red Hat supplied openssl package. It is also 608worth noting that due to the way Red Hat supplies its packages, updates to 609openssl on each distribution never change the package version, only the 610build number. For example, on Red Hat 7.1, the latest openssl package has 611version number 0.9.6 and build number 9 even though it contains all the 612relevant updates in packages up to and including 0.9.6b. 613 614A possible way around this is to persuade Red Hat to produce a non-US 615version of Red Hat Linux. 616 617FYI: Patent numbers and expiry dates of US patents: 618MDC-2: 4,908,861 13/03/2007 619IDEA: 5,214,703 25/05/2010 620RC5: 5,724,428 03/03/2015 621 622 623* Why does the OpenSSL compilation fail on MacOS X? 624 625If the failure happens when trying to build the "openssl" binary, with 626a large number of undefined symbols, it's very probable that you have 627OpenSSL 0.9.6b delivered with the operating system (you can find out by 628running '/usr/bin/openssl version') and that you were trying to build 629OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 630MacOS X has a misfeature that's quite difficult to go around. 631Look in the file PROBLEMS for a more detailed explanation and for possible 632solutions. 633 634 635* Why does the OpenSSL test suite fail on MacOS X? 636 637If the failure happens when running 'make test' and the RC4 test fails, 638it's very probable that you have OpenSSL 0.9.6b delivered with the 639operating system (you can find out by running '/usr/bin/openssl version') 640and that you were trying to build OpenSSL 0.9.6d. The problem is that 641the loader ('ld') in MacOS X has a misfeature that's quite difficult to 642go around and has linked the programs "openssl" and the test programs 643with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 644libraries you just built. 645Look in the file PROBLEMS for a more detailed explanation and for possible 646solutions. 647 648* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 649 650Failure in BN_sqr test is most likely caused by a failure to configure the 651toolkit for current platform or lack of support for the platform in question. 652Run './config -t' and './apps/openssl version -p'. Do these platform 653identifiers match? If they don't, then you most likely failed to run 654./config and you're hereby advised to do so before filing a bug report. 655If ./config itself fails to run, then it's most likely problem with your 656local environment and you should turn to your system administrator (or 657similar). If identifiers match (and/or no alternative identifier is 658suggested by ./config script), then the platform is unsupported. There might 659or might not be a workaround. Most notably on SPARC64 platforms with GNU 660C compiler you should be able to produce a working build by running 661'./config -m32'. I understand that -m32 might not be what you want/need, 662but the build should be operational. For further details turn to 663<openssl-dev@openssl.org>. 664 665* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 666 667As of 0.9.7 assembler routines were overhauled for position independence 668of the machine code, which is essential for shared library support. For 669some reason OpenBSD is equipped with an out-of-date GNU assembler which 670finds the new code offensive. To work around the problem, configure with 671no-asm (and sacrifice a great deal of performance) or patch your assembler 672according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 673For your convenience a pre-compiled replacement binary is provided at 674<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 675Reportedly elder *BSD a.out platforms also suffer from this problem and 676remedy should be same. Provided binary is statically linked and should be 677working across wider range of *BSD branches, not just OpenBSD. 678 679* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 680 681If the test program in question fails withs SIGILL, Illegal Instruction 682exception, then you more than likely to run SSE2-capable CPU, such as 683Intel P4, under control of kernel which does not support SSE2 684instruction extentions. See accompanying INSTALL file and 685OPENSSL_ia32cap(3) documentation page for further information. 686 687* Why does compiler fail to compile sha512.c? 688 689OpenSSL SHA-512 implementation depends on compiler support for 64-bit 690integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a 691couple] lack support for this and therefore are incapable of compiling 692the module in question. The recommendation is to disable SHA-512 by 693adding no-sha512 to ./config [or ./Configure] command line. Another 694possible alternative might be to switch to GCC. 695 696* Test suite still fails, what to do? 697 698Another common reason for failure to complete some particular test is 699simply bad code generated by a buggy component in toolchain or deficiency 700in run-time environment. There are few cases documented in PROBLEMS file, 701consult it for possible workaround before you beat the drum. Even if you 702don't find solution or even mention there, do reserve for possibility of 703a compiler bug. Compiler bugs might appear in rather bizarre ways, they 704never make sense, and tend to emerge when you least expect them. In order 705to identify one, drop optimization level, e.g. by editing CFLAG line in 706top-level Makefile, recompile and re-run the test. 707 708[PROG] ======================================================================== 709 710* Is OpenSSL thread-safe? 711 712Yes (with limitations: an SSL connection may not concurrently be used 713by multiple threads). On Windows and many Unix systems, OpenSSL 714automatically uses the multi-threaded versions of the standard 715libraries. If your platform is not one of these, consult the INSTALL 716file. 717 718Multi-threaded applications must provide two callback functions to 719OpenSSL by calling CRYPTO_set_locking_callback() and 720CRYPTO_set_id_callback(). This is described in the threads(3) 721manpage. 722 723* I've compiled a program under Windows and it crashes: why? 724 725This is usually because you've missed the comment in INSTALL.W32. 726Your application must link against the same version of the Win32 727C-Runtime against which your openssl libraries were linked. The 728default version for OpenSSL is /MD - "Multithreaded DLL". 729 730If you are using Microsoft Visual C++'s IDE (Visual Studio), in 731many cases, your new project most likely defaulted to "Debug 732Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 733program will crash, typically on the first BIO related read or write 734operation. 735 736For each of the six possible link stage configurations within Win32, 737your application must link against the same by which OpenSSL was 738built. If you are using MS Visual C++ (Studio) this can be changed 739by: 740 741 1. Select Settings... from the Project Menu. 742 2. Select the C/C++ Tab. 743 3. Select "Code Generation from the "Category" drop down list box 744 4. Select the Appropriate library (see table below) from the "Use 745 run-time library" drop down list box. Perform this step for both 746 your debug and release versions of your application (look at the 747 top left of the settings panel to change between the two) 748 749 Single Threaded /ML - MS VC++ often defaults to 750 this for the release 751 version of a new project. 752 Debug Single Threaded /MLd - MS VC++ often defaults to 753 this for the debug version 754 of a new project. 755 Multithreaded /MT 756 Debug Multithreaded /MTd 757 Multithreaded DLL /MD - OpenSSL defaults to this. 758 Debug Multithreaded DLL /MDd 759 760Note that debug and release libraries are NOT interchangeable. If you 761built OpenSSL with /MD your application must use /MD and cannot use /MDd. 762 763As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL 764.DLLs compiled with some specific run-time option [we insist on the 765default /MD] can be deployed with application compiled with different 766option or even different compiler. But there is a catch! Instead of 767re-compiling OpenSSL toolkit, as you would have to with prior versions, 768you have to compile small C snippet with compiler and/or options of 769your choice. The snippet gets installed as 770<install-root>/include/openssl/applink.c and should be either added to 771your application project or simply #include-d in one [and only one] 772of your application source files. Failure to link this shim module 773into your application manifests itself as fatal "no OPENSSL_Applink" 774run-time error. An explicit reminder is due that in this situation 775[mixing compiler options] it is as important to add CRYPTO_malloc_init 776prior first call to OpenSSL. 777 778* How do I read or write a DER encoded buffer using the ASN1 functions? 779 780You have two options. You can either use a memory BIO in conjunction 781with the i2d_*_bio() or d2i_*_bio() functions or you can use the 782i2d_*(), d2i_*() functions directly. Since these are often the 783cause of grief here are some code fragments using PKCS7 as an example: 784 785 unsigned char *buf, *p; 786 int len; 787 788 len = i2d_PKCS7(p7, NULL); 789 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 790 p = buf; 791 i2d_PKCS7(p7, &p); 792 793At this point buf contains the len bytes of the DER encoding of 794p7. 795 796The opposite assumes we already have len bytes in buf: 797 798 unsigned char *p; 799 p = buf; 800 p7 = d2i_PKCS7(NULL, &p, len); 801 802At this point p7 contains a valid PKCS7 structure of NULL if an error 803occurred. If an error occurred ERR_print_errors(bio) should give more 804information. 805 806The reason for the temporary variable 'p' is that the ASN1 functions 807increment the passed pointer so it is ready to read or write the next 808structure. This is often a cause of problems: without the temporary 809variable the buffer pointer is changed to point just after the data 810that has been read or written. This may well be uninitialized data 811and attempts to free the buffer will have unpredictable results 812because it no longer points to the same address. 813 814 815* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 816 817The short answer is yes, because DER is a special case of BER and OpenSSL 818ASN1 decoders can process BER. 819 820The longer answer is that ASN1 structures can be encoded in a number of 821different ways. One set of ways is the Basic Encoding Rules (BER) with various 822permissible encodings. A restriction of BER is the Distinguished Encoding 823Rules (DER): these uniquely specify how a given structure is encoded. 824 825Therefore, because DER is a special case of BER, DER is an acceptable encoding 826for BER. 827 828 829* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 830 831This usually happens when you try compiling something using the PKCS#12 832macros with a C++ compiler. There is hardly ever any need to use the 833PKCS#12 macros in a program, it is much easier to parse and create 834PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 835documented in doc/openssl.txt and with examples in demos/pkcs12. The 836'pkcs12' application has to use the macros because it prints out 837debugging information. 838 839 840* I've called <some function> and it fails, why? 841 842Before submitting a report or asking in one of the mailing lists, you 843should try to determine the cause. In particular, you should call 844ERR_print_errors() or ERR_print_errors_fp() after the failed call 845and see if the message helps. Note that the problem may occur earlier 846than you think -- you should check for errors after every call where 847it is possible, otherwise the actual problem may be hidden because 848some OpenSSL functions clear the error state. 849 850 851* I just get a load of numbers for the error output, what do they mean? 852 853The actual format is described in the ERR_print_errors() manual page. 854You should call the function ERR_load_crypto_strings() before hand and 855the message will be output in text form. If you can't do this (for example 856it is a pre-compiled binary) you can use the errstr utility on the error 857code itself (the hex digits after the second colon). 858 859 860* Why do I get errors about unknown algorithms? 861 862The cause is forgetting to load OpenSSL's table of algorithms with 863OpenSSL_add_all_algorithms(). See the manual page for more information. This 864can cause several problems such as being unable to read in an encrypted 865PEM file, unable to decrypt a PKCS#12 file or signature failure when 866verifying certificates. 867 868* Why can't the OpenSSH configure script detect OpenSSL? 869 870Several reasons for problems with the automatic detection exist. 871OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 872Sometimes the distribution has installed an older version in the system 873locations that is detected instead of a new one installed. The OpenSSL 874library might have been compiled for another CPU or another mode (32/64 bits). 875Permissions might be wrong. 876 877The general answer is to check the config.log file generated when running 878the OpenSSH configure script. It should contain the detailed information 879on why the OpenSSL library was not detected or considered incompatible. 880 881 882* Can I use OpenSSL's SSL library with non-blocking I/O? 883 884Yes; make sure to read the SSL_get_error(3) manual page! 885 886A pitfall to avoid: Don't assume that SSL_read() will just read from 887the underlying transport or that SSL_write() will just write to it -- 888it is also possible that SSL_write() cannot do any useful work until 889there is data to read, or that SSL_read() cannot do anything until it 890is possible to send data. One reason for this is that the peer may 891request a new TLS/SSL handshake at any time during the protocol, 892requiring a bi-directional message exchange; both SSL_read() and 893SSL_write() will try to continue any pending handshake. 894 895 896* Why doesn't my server application receive a client certificate? 897 898Due to the TLS protocol definition, a client will only send a certificate, 899if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 900SSL_CTX_set_verify() function to enable the use of client certificates. 901 902 903* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 904 905For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 906versions, uniqueIdentifier was incorrectly used for X.509 certificates. 907The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 908Change your code to use the new name when compiling against OpenSSL 0.9.7. 909 910 911* I think I've detected a memory leak, is this a bug? 912 913In most cases the cause of an apparent memory leak is an OpenSSL internal table 914that is allocated when an application starts up. Since such tables do not grow 915in size over time they are harmless. 916 917These internal tables can be freed up when an application closes using various 918functions. Currently these include following: 919 920Thread-local cleanup functions: 921 922 ERR_remove_state() 923 924Application-global cleanup functions that are aware of usage (and therefore 925thread-safe): 926 927 ENGINE_cleanup() and CONF_modules_unload() 928 929"Brutal" (thread-unsafe) Application-global cleanup functions: 930 931 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). 932 933 934* Why does Valgrind complain about the use of uninitialized data? 935 936When OpenSSL's PRNG routines are called to generate random numbers the supplied 937buffer contents are mixed into the entropy pool: so it technically does not 938matter whether the buffer is initialized at this point or not. Valgrind (and 939other test tools) will complain about this. When using Valgrind, make sure the 940OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) 941to get rid of these warnings. 942 943 944* Why doesn't a memory BIO work when a file does? 945 946This can occur in several cases for example reading an S/MIME email message. 947The reason is that a memory BIO can do one of two things when all the data 948has been read from it. 949 950The default behaviour is to indicate that no more data is available and that 951the call should be retried, this is to allow the application to fill up the BIO 952again if necessary. 953 954Alternatively it can indicate that no more data is available and that EOF has 955been reached. 956 957If a memory BIO is to behave in the same way as a file this second behaviour 958is needed. This must be done by calling: 959 960 BIO_set_mem_eof_return(bio, 0); 961 962See the manual pages for more details. 963 964 965=============================================================================== 966