FAQ revision 215697
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* Where are the declarations and implementations of d2i_X509() etc? 74 75=============================================================================== 76 77[MISC] ======================================================================== 78 79* Which is the current version of OpenSSL? 80 81The current version is available from <URL: http://www.openssl.org>. 82OpenSSL 1.0.0b was released on Nov 16th, 2010. 83 84In addition to the current stable release, you can also access daily 85snapshots of the OpenSSL development version at <URL: 86ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 87 88 89* Where is the documentation? 90 91OpenSSL is a library that provides cryptographic functionality to 92applications such as secure web servers. Be sure to read the 93documentation of the application you want to use. The INSTALL file 94explains how to install this library. 95 96OpenSSL includes a command line utility that can be used to perform a 97variety of cryptographic functions. It is described in the openssl(1) 98manpage. Documentation for developers is currently being written. Many 99manual pages are available; overviews over libcrypto and 100libssl are given in the crypto(3) and ssl(3) manpages. 101 102The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 103different directory if you specified one as described in INSTALL). 104In addition, you can read the most current versions at 105<URL: http://www.openssl.org/docs/>. Note that the online documents refer 106to the very latest development versions of OpenSSL and may include features 107not present in released versions. If in doubt refer to the documentation 108that came with the version of OpenSSL you are using. 109 110For information on parts of libcrypto that are not yet documented, you 111might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 112predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 113of this still applies to OpenSSL. 114 115There is some documentation about certificate extensions and PKCS#12 116in doc/openssl.txt 117 118The original SSLeay documentation is included in OpenSSL as 119doc/ssleay.txt. It may be useful when none of the other resources 120help, but please note that it reflects the obsolete version SSLeay 1210.6.6. 122 123 124* How can I contact the OpenSSL developers? 125 126The README file describes how to submit bug reports and patches to 127OpenSSL. Information on the OpenSSL mailing lists is available from 128<URL: http://www.openssl.org>. 129 130 131* Where can I get a compiled version of OpenSSL? 132 133You can finder pointers to binary distributions in 134http://www.openssl.org/related/binaries.html . 135 136Some applications that use OpenSSL are distributed in binary form. 137When using such an application, you don't need to install OpenSSL 138yourself; the application will include the required parts (e.g. DLLs). 139 140If you want to build OpenSSL on a Windows system and you don't have 141a C compiler, read the "Mingw32" section of INSTALL.W32 for information 142on how to obtain and install the free GNU C compiler. 143 144A number of Linux and *BSD distributions include OpenSSL. 145 146 147* Why aren't tools like 'autoconf' and 'libtool' used? 148 149autoconf will probably be used in future OpenSSL versions. If it was 150less Unix-centric, it might have been used much earlier. 151 152* What is an 'engine' version? 153 154With version 0.9.6 OpenSSL was extended to interface to external crypto 155hardware. This was realized in a special release '0.9.6-engine'. With 156version 0.9.7 the changes were merged into the main development line, 157so that the special release is no longer necessary. 158 159* How do I check the authenticity of the OpenSSL distribution? 160 161We provide MD5 digests and ASC signatures of each tarball. 162Use MD5 to check that a tarball from a mirror site is identical: 163 164 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 165 166You can check authenticity using pgp or gpg. You need the OpenSSL team 167member public key used to sign it (download it from a key server, see a 168list of keys at <URL: http://www.openssl.org/about/>). Then 169just do: 170 171 pgp TARBALL.asc 172 173[LEGAL] ======================================================================= 174 175* Do I need patent licenses to use OpenSSL? 176 177The patents section of the README file lists patents that may apply to 178you if you want to use OpenSSL. For information on intellectual 179property rights, please consult a lawyer. The OpenSSL team does not 180offer legal advice. 181 182You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using 183 ./config no-idea no-mdc2 no-rc5 184 185 186* Can I use OpenSSL with GPL software? 187 188On many systems including the major Linux and BSD distributions, yes (the 189GPL does not place restrictions on using libraries that are part of the 190normal operating system distribution). 191 192On other systems, the situation is less clear. Some GPL software copyright 193holders claim that you infringe on their rights if you use OpenSSL with 194their software on operating systems that don't normally include OpenSSL. 195 196If you develop open source software that uses OpenSSL, you may find it 197useful to choose an other license than the GPL, or state explicitly that 198"This program is released under the GPL with the additional exemption that 199compiling, linking, and/or using OpenSSL is allowed." If you are using 200GPL software developed by others, you may want to ask the copyright holder 201for permission to use their software with OpenSSL. 202 203 204[USER] ======================================================================== 205 206* Why do I get a "PRNG not seeded" error message? 207 208Cryptographic software needs a source of unpredictable data to work 209correctly. Many open source operating systems provide a "randomness 210device" (/dev/urandom or /dev/random) that serves this purpose. 211All OpenSSL versions try to use /dev/urandom by default; starting with 212version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 213available. 214 215On other systems, applications have to call the RAND_add() or 216RAND_seed() function with appropriate data before generating keys or 217performing public key encryption. (These functions initialize the 218pseudo-random number generator, PRNG.) Some broken applications do 219not do this. As of version 0.9.5, the OpenSSL functions that need 220randomness report an error if the random number generator has not been 221seeded with at least 128 bits of randomness. If this error occurs and 222is not discussed in the documentation of the application you are 223using, please contact the author of that application; it is likely 224that it never worked correctly. OpenSSL 0.9.5 and later make the 225error visible by refusing to perform potentially insecure encryption. 226 227If you are using Solaris 8, you can add /dev/urandom and /dev/random 228devices by installing patch 112438 (Sparc) or 112439 (x86), which are 229available via the Patchfinder at <URL: http://sunsolve.sun.com> 230(Solaris 9 includes these devices by default). For /dev/random support 231for earlier Solaris versions, see Sun's statement at 232<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 233(the SUNWski package is available in patch 105710). 234 235On systems without /dev/urandom and /dev/random, it is a good idea to 236use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 237details. Starting with version 0.9.7, OpenSSL will automatically look 238for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 239/etc/entropy. 240 241Most components of the openssl command line utility automatically try 242to seed the random number generator from a file. The name of the 243default seeding file is determined as follows: If environment variable 244RANDFILE is set, then it names the seeding file. Otherwise if 245environment variable HOME is set, then the seeding file is $HOME/.rnd. 246If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 247use file .rnd in the current directory while OpenSSL 0.9.6a uses no 248default seeding file at all. OpenSSL 0.9.6b and later will behave 249similarly to 0.9.6a, but will use a default of "C:\" for HOME on 250Windows systems if the environment variable has not been set. 251 252If the default seeding file does not exist or is too short, the "PRNG 253not seeded" error message may occur. 254 255The openssl command line utility will write back a new state to the 256default seeding file (and create this file if necessary) unless 257there was no sufficient seeding. 258 259Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 260Use the "-rand" option of the OpenSSL command line tools instead. 261The $RANDFILE environment variable and $HOME/.rnd are only used by the 262OpenSSL command line tools. Applications using the OpenSSL library 263provide their own configuration options to specify the entropy source, 264please check out the documentation coming the with application. 265 266 267* Why do I get an "unable to write 'random state'" error message? 268 269 270Sometimes the openssl command line utility does not abort with 271a "PRNG not seeded" error message, but complains that it is 272"unable to write 'random state'". This message refers to the 273default seeding file (see previous answer). A possible reason 274is that no default filename is known because neither RANDFILE 275nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 276current directory in this case, but this has changed with 0.9.6a.) 277 278 279* How do I create certificates or certificate requests? 280 281Check out the CA.pl(1) manual page. This provides a simple wrapper round 282the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 283out the manual pages for the individual utilities and the certificate 284extensions documentation (currently in doc/openssl.txt). 285 286 287* Why can't I create certificate requests? 288 289You typically get the error: 290 291 unable to find 'distinguished_name' in config 292 problems making Certificate Request 293 294This is because it can't find the configuration file. Check out the 295DIAGNOSTICS section of req(1) for more information. 296 297 298* Why does <SSL program> fail with a certificate verify error? 299 300This problem is usually indicated by log messages saying something like 301"unable to get local issuer certificate" or "self signed certificate". 302When a certificate is verified its root CA must be "trusted" by OpenSSL 303this typically means that the CA certificate must be placed in a directory 304or file and the relevant program configured to read it. The OpenSSL program 305'verify' behaves in a similar way and issues similar error messages: check 306the verify(1) program manual page for more information. 307 308 309* Why can I only use weak ciphers when I connect to a server using OpenSSL? 310 311This is almost certainly because you are using an old "export grade" browser 312which only supports weak encryption. Upgrade your browser to support 128 bit 313ciphers. 314 315 316* How can I create DSA certificates? 317 318Check the CA.pl(1) manual page for a DSA certificate example. 319 320 321* Why can't I make an SSL connection to a server using a DSA certificate? 322 323Typically you'll see a message saying there are no shared ciphers when 324the same setup works fine with an RSA certificate. There are two possible 325causes. The client may not support connections to DSA servers most web 326browsers (including Netscape and MSIE) only support connections to servers 327supporting RSA cipher suites. The other cause is that a set of DH parameters 328has not been supplied to the server. DH parameters can be created with the 329dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 330check the source to s_server in apps/s_server.c for an example. 331 332 333* How can I remove the passphrase on a private key? 334 335Firstly you should be really *really* sure you want to do this. Leaving 336a private key unencrypted is a major security risk. If you decide that 337you do have to do this check the EXAMPLES sections of the rsa(1) and 338dsa(1) manual pages. 339 340 341* Why can't I use OpenSSL certificates with SSL client authentication? 342 343What will typically happen is that when a server requests authentication 344it will either not include your certificate or tell you that you have 345no client certificates (Netscape) or present you with an empty list box 346(MSIE). The reason for this is that when a server requests a client 347certificate it includes a list of CAs names which it will accept. Browsers 348will only let you select certificates from the list on the grounds that 349there is little point presenting a certificate which the server will 350reject. 351 352The solution is to add the relevant CA certificate to your servers "trusted 353CA list". How you do this depends on the server software in uses. You can 354print out the servers list of acceptable CAs using the OpenSSL s_client tool: 355 356openssl s_client -connect www.some.host:443 -prexit 357 358If your server only requests certificates on certain URLs then you may need 359to manually issue an HTTP GET command to get the list when s_client connects: 360 361GET /some/page/needing/a/certificate.html 362 363If your CA does not appear in the list then this confirms the problem. 364 365 366* Why does my browser give a warning about a mismatched hostname? 367 368Browsers expect the server's hostname to match the value in the commonName 369(CN) field of the certificate. If it does not then you get a warning. 370 371 372* How do I install a CA certificate into a browser? 373 374The usual way is to send the DER encoded certificate to the browser as 375MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 376link. On MSIE certain extensions such as .der or .cacert may also work, or you 377can import the certificate using the certificate import wizard. 378 379You can convert a certificate to DER form using the command: 380 381openssl x509 -in ca.pem -outform DER -out ca.der 382 383Occasionally someone suggests using a command such as: 384 385openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 386 387DO NOT DO THIS! This command will give away your CAs private key and 388reduces its security to zero: allowing anyone to forge certificates in 389whatever name they choose. 390 391* Why is OpenSSL x509 DN output not conformant to RFC2253? 392 393The ways to print out the oneline format of the DN (Distinguished Name) have 394been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 395interface, the "-nameopt" option could be introduded. See the manual 396page of the "openssl x509" commandline tool for details. The old behaviour 397has however been left as default for the sake of compatibility. 398 399* What is a "128 bit certificate"? Can I create one with OpenSSL? 400 401The term "128 bit certificate" is a highly misleading marketing term. It does 402*not* refer to the size of the public key in the certificate! A certificate 403containing a 128 bit RSA key would have negligible security. 404 405There were various other names such as "magic certificates", "SGC 406certificates", "step up certificates" etc. 407 408You can't generally create such a certificate using OpenSSL but there is no 409need to any more. Nowadays web browsers using unrestricted strong encryption 410are generally available. 411 412When there were tight restrictions on the export of strong encryption 413software from the US only weak encryption algorithms could be freely exported 414(initially 40 bit and then 56 bit). It was widely recognised that this was 415inadequate. A relaxation of the rules allowed the use of strong encryption but 416only to an authorised server. 417 418Two slighly different techniques were developed to support this, one used by 419Netscape was called "step up", the other used by MSIE was called "Server Gated 420Cryptography" (SGC). When a browser initially connected to a server it would 421check to see if the certificate contained certain extensions and was issued by 422an authorised authority. If these test succeeded it would reconnect using 423strong encryption. 424 425Only certain (initially one) certificate authorities could issue the 426certificates and they generally cost more than ordinary certificates. 427 428Although OpenSSL can create certificates containing the appropriate extensions 429the certificate would not come from a permitted authority and so would not 430be recognized. 431 432The export laws were later changed to allow almost unrestricted use of strong 433encryption so these certificates are now obsolete. 434 435 436* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? 437 438It doesn't: this extension is often the cause of confusion. 439 440Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose 441certificate C contains AKID. 442 443The purpose of this extension is to identify the authority certificate B. This 444can be done either by including the subject key identifier of B or its issuer 445name and serial number. 446 447In this latter case because it is identifying certifcate B it must contain the 448issuer name and serial number of B. 449 450It is often wrongly assumed that it should contain the subject name of B. If it 451did this would be redundant information because it would duplicate the issuer 452name of C. 453 454 455* How can I set up a bundle of commercial root CA certificates? 456 457The OpenSSL software is shipped without any root CA certificate as the 458OpenSSL project does not have any policy on including or excluding 459any specific CA and does not intend to set up such a policy. Deciding 460about which CAs to support is up to application developers or 461administrators. 462 463Other projects do have other policies so you can for example extract the CA 464bundle used by Mozilla and/or modssl as described in this article: 465 466 http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html 467 468 469[BUILD] ======================================================================= 470 471* Why does the linker complain about undefined symbols? 472 473Maybe the compilation was interrupted, and make doesn't notice that 474something is missing. Run "make clean; make". 475 476If you used ./Configure instead of ./config, make sure that you 477selected the right target. File formats may differ slightly between 478OS versions (for example sparcv8/sparcv9, or a.out/elf). 479 480In case you get errors about the following symbols, use the config 481option "no-asm", as described in INSTALL: 482 483 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 484 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 485 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 486 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 487 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 488 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 489 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 490 491If none of these helps, you may want to try using the current snapshot. 492If the problem persists, please submit a bug report. 493 494 495* Why does the OpenSSL test fail with "bc: command not found"? 496 497You didn't install "bc", the Unix calculator. If you want to run the 498tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 499 500 501* Why does the OpenSSL test fail with "bc: 1 no implemented"? 502 503On some SCO installations or versions, bc has a bug that gets triggered 504when you run the test suite (using "make test"). The message returned is 505"bc: 1 not implemented". 506 507The best way to deal with this is to find another implementation of bc 508and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 509for download instructions) can be safely used, for example. 510 511 512* Why does the OpenSSL test fail with "bc: stack empty"? 513 514On some DG/ux versions, bc seems to have a too small stack for calculations 515that the OpenSSL bntest throws at it. This gets triggered when you run the 516test suite (using "make test"). The message returned is "bc: stack empty". 517 518The best way to deal with this is to find another implementation of bc 519and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 520for download instructions) can be safely used, for example. 521 522 523* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 524 525On some Alpha installations running Tru64 Unix and Compaq C, the compilation 526of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 527memory to continue compilation.' As far as the tests have shown, this may be 528a compiler bug. What happens is that it eats up a lot of resident memory 529to build something, probably a table. The problem is clearly in the 530optimization code, because if one eliminates optimization completely (-O0), 531the compilation goes through (and the compiler consumes about 2MB of resident 532memory instead of 240MB or whatever one's limit is currently). 533 534There are three options to solve this problem: 535 5361. set your current data segment size soft limit higher. Experience shows 537that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 538this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 539kbytes to set the limit to. 540 5412. If you have a hard limit that is lower than what you need and you can't 542get it changed, you can compile all of OpenSSL with -O0 as optimization 543level. This is however not a very nice thing to do for those who expect to 544get the best result from OpenSSL. A bit more complicated solution is the 545following: 546 547----- snip:start ----- 548 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 549 sed -e 's/ -O[0-9] / -O0 /'`" 550 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 551 make 552----- snip:end ----- 553 554This will only compile sha_dgst.c with -O0, the rest with the optimization 555level chosen by the configuration process. When the above is done, do the 556test and installation and you're set. 557 5583. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 559should not be used and is not used in SSL/TLS nor any other recognized 560protocol in either case. 561 562 563* Why does the OpenSSL compilation fail with "ar: command not found"? 564 565Getting this message is quite usual on Solaris 2, because Sun has hidden 566away 'ar' and other development commands in directories that aren't in 567$PATH by default. One of those directories is '/usr/ccs/bin'. The 568quickest way to fix this is to do the following (it assumes you use sh 569or any sh-compatible shell): 570 571----- snip:start ----- 572 PATH=${PATH}:/usr/ccs/bin; export PATH 573----- snip:end ----- 574 575and then redo the compilation. What you should really do is make sure 576'/usr/ccs/bin' is permanently in your $PATH, for example through your 577'.profile' (again, assuming you use a sh-compatible shell). 578 579 580* Why does the OpenSSL compilation fail on Win32 with VC++? 581 582Sometimes, you may get reports from VC++ command line (cl) that it 583can't find standard include files like stdio.h and other weirdnesses. 584One possible cause is that the environment isn't correctly set up. 585To solve that problem for VC++ versions up to 6, one should run 586VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 587installation directory (somewhere under 'Program Files'). For VC++ 588version 7 (and up?), which is also called VS.NET, the file is called 589VSVARS32.BAT instead. 590This needs to be done prior to running NMAKE, and the changes are only 591valid for the current DOS session. 592 593 594* What is special about OpenSSL on Redhat? 595 596Red Hat Linux (release 7.0 and later) include a preinstalled limited 597version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 598is disabled in this version. The same may apply to other Linux distributions. 599Users may therefore wish to install more or all of the features left out. 600 601To do this you MUST ensure that you do not overwrite the openssl that is in 602/usr/bin on your Red Hat machine. Several packages depend on this file, 603including sendmail and ssh. /usr/local/bin is a good alternative choice. The 604libraries that come with Red Hat 7.0 onwards have different names and so are 605not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 606/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 607/lib/libcrypto.so.2 respectively). 608 609Please note that we have been advised by Red Hat attempting to recompile the 610openssl rpm with all the cryptography enabled will not work. All other 611packages depend on the original Red Hat supplied openssl package. It is also 612worth noting that due to the way Red Hat supplies its packages, updates to 613openssl on each distribution never change the package version, only the 614build number. For example, on Red Hat 7.1, the latest openssl package has 615version number 0.9.6 and build number 9 even though it contains all the 616relevant updates in packages up to and including 0.9.6b. 617 618A possible way around this is to persuade Red Hat to produce a non-US 619version of Red Hat Linux. 620 621FYI: Patent numbers and expiry dates of US patents: 622MDC-2: 4,908,861 13/03/2007 623IDEA: 5,214,703 25/05/2010 624RC5: 5,724,428 03/03/2015 625 626 627* Why does the OpenSSL compilation fail on MacOS X? 628 629If the failure happens when trying to build the "openssl" binary, with 630a large number of undefined symbols, it's very probable that you have 631OpenSSL 0.9.6b delivered with the operating system (you can find out by 632running '/usr/bin/openssl version') and that you were trying to build 633OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 634MacOS X has a misfeature that's quite difficult to go around. 635Look in the file PROBLEMS for a more detailed explanation and for possible 636solutions. 637 638 639* Why does the OpenSSL test suite fail on MacOS X? 640 641If the failure happens when running 'make test' and the RC4 test fails, 642it's very probable that you have OpenSSL 0.9.6b delivered with the 643operating system (you can find out by running '/usr/bin/openssl version') 644and that you were trying to build OpenSSL 0.9.6d. The problem is that 645the loader ('ld') in MacOS X has a misfeature that's quite difficult to 646go around and has linked the programs "openssl" and the test programs 647with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 648libraries you just built. 649Look in the file PROBLEMS for a more detailed explanation and for possible 650solutions. 651 652* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 653 654Failure in BN_sqr test is most likely caused by a failure to configure the 655toolkit for current platform or lack of support for the platform in question. 656Run './config -t' and './apps/openssl version -p'. Do these platform 657identifiers match? If they don't, then you most likely failed to run 658./config and you're hereby advised to do so before filing a bug report. 659If ./config itself fails to run, then it's most likely problem with your 660local environment and you should turn to your system administrator (or 661similar). If identifiers match (and/or no alternative identifier is 662suggested by ./config script), then the platform is unsupported. There might 663or might not be a workaround. Most notably on SPARC64 platforms with GNU 664C compiler you should be able to produce a working build by running 665'./config -m32'. I understand that -m32 might not be what you want/need, 666but the build should be operational. For further details turn to 667<openssl-dev@openssl.org>. 668 669* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 670 671As of 0.9.7 assembler routines were overhauled for position independence 672of the machine code, which is essential for shared library support. For 673some reason OpenBSD is equipped with an out-of-date GNU assembler which 674finds the new code offensive. To work around the problem, configure with 675no-asm (and sacrifice a great deal of performance) or patch your assembler 676according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 677For your convenience a pre-compiled replacement binary is provided at 678<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 679Reportedly elder *BSD a.out platforms also suffer from this problem and 680remedy should be same. Provided binary is statically linked and should be 681working across wider range of *BSD branches, not just OpenBSD. 682 683* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 684 685If the test program in question fails withs SIGILL, Illegal Instruction 686exception, then you more than likely to run SSE2-capable CPU, such as 687Intel P4, under control of kernel which does not support SSE2 688instruction extentions. See accompanying INSTALL file and 689OPENSSL_ia32cap(3) documentation page for further information. 690 691* Why does compiler fail to compile sha512.c? 692 693OpenSSL SHA-512 implementation depends on compiler support for 64-bit 694integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a 695couple] lack support for this and therefore are incapable of compiling 696the module in question. The recommendation is to disable SHA-512 by 697adding no-sha512 to ./config [or ./Configure] command line. Another 698possible alternative might be to switch to GCC. 699 700* Test suite still fails, what to do? 701 702Another common reason for failure to complete some particular test is 703simply bad code generated by a buggy component in toolchain or deficiency 704in run-time environment. There are few cases documented in PROBLEMS file, 705consult it for possible workaround before you beat the drum. Even if you 706don't find solution or even mention there, do reserve for possibility of 707a compiler bug. Compiler bugs might appear in rather bizarre ways, they 708never make sense, and tend to emerge when you least expect them. In order 709to identify one, drop optimization level, e.g. by editing CFLAG line in 710top-level Makefile, recompile and re-run the test. 711 712[PROG] ======================================================================== 713 714* Is OpenSSL thread-safe? 715 716Yes (with limitations: an SSL connection may not concurrently be used 717by multiple threads). On Windows and many Unix systems, OpenSSL 718automatically uses the multi-threaded versions of the standard 719libraries. If your platform is not one of these, consult the INSTALL 720file. 721 722Multi-threaded applications must provide two callback functions to 723OpenSSL by calling CRYPTO_set_locking_callback() and 724CRYPTO_set_id_callback(), for all versions of OpenSSL up to and 725including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback() 726and associated APIs are deprecated by CRYPTO_THREADID_set_callback() 727and friends. This is described in the threads(3) manpage. 728 729* I've compiled a program under Windows and it crashes: why? 730 731This is usually because you've missed the comment in INSTALL.W32. 732Your application must link against the same version of the Win32 733C-Runtime against which your openssl libraries were linked. The 734default version for OpenSSL is /MD - "Multithreaded DLL". 735 736If you are using Microsoft Visual C++'s IDE (Visual Studio), in 737many cases, your new project most likely defaulted to "Debug 738Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 739program will crash, typically on the first BIO related read or write 740operation. 741 742For each of the six possible link stage configurations within Win32, 743your application must link against the same by which OpenSSL was 744built. If you are using MS Visual C++ (Studio) this can be changed 745by: 746 747 1. Select Settings... from the Project Menu. 748 2. Select the C/C++ Tab. 749 3. Select "Code Generation from the "Category" drop down list box 750 4. Select the Appropriate library (see table below) from the "Use 751 run-time library" drop down list box. Perform this step for both 752 your debug and release versions of your application (look at the 753 top left of the settings panel to change between the two) 754 755 Single Threaded /ML - MS VC++ often defaults to 756 this for the release 757 version of a new project. 758 Debug Single Threaded /MLd - MS VC++ often defaults to 759 this for the debug version 760 of a new project. 761 Multithreaded /MT 762 Debug Multithreaded /MTd 763 Multithreaded DLL /MD - OpenSSL defaults to this. 764 Debug Multithreaded DLL /MDd 765 766Note that debug and release libraries are NOT interchangeable. If you 767built OpenSSL with /MD your application must use /MD and cannot use /MDd. 768 769As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL 770.DLLs compiled with some specific run-time option [we insist on the 771default /MD] can be deployed with application compiled with different 772option or even different compiler. But there is a catch! Instead of 773re-compiling OpenSSL toolkit, as you would have to with prior versions, 774you have to compile small C snippet with compiler and/or options of 775your choice. The snippet gets installed as 776<install-root>/include/openssl/applink.c and should be either added to 777your application project or simply #include-d in one [and only one] 778of your application source files. Failure to link this shim module 779into your application manifests itself as fatal "no OPENSSL_Applink" 780run-time error. An explicit reminder is due that in this situation 781[mixing compiler options] it is as important to add CRYPTO_malloc_init 782prior first call to OpenSSL. 783 784* How do I read or write a DER encoded buffer using the ASN1 functions? 785 786You have two options. You can either use a memory BIO in conjunction 787with the i2d_*_bio() or d2i_*_bio() functions or you can use the 788i2d_*(), d2i_*() functions directly. Since these are often the 789cause of grief here are some code fragments using PKCS7 as an example: 790 791 unsigned char *buf, *p; 792 int len; 793 794 len = i2d_PKCS7(p7, NULL); 795 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 796 p = buf; 797 i2d_PKCS7(p7, &p); 798 799At this point buf contains the len bytes of the DER encoding of 800p7. 801 802The opposite assumes we already have len bytes in buf: 803 804 unsigned char *p; 805 p = buf; 806 p7 = d2i_PKCS7(NULL, &p, len); 807 808At this point p7 contains a valid PKCS7 structure of NULL if an error 809occurred. If an error occurred ERR_print_errors(bio) should give more 810information. 811 812The reason for the temporary variable 'p' is that the ASN1 functions 813increment the passed pointer so it is ready to read or write the next 814structure. This is often a cause of problems: without the temporary 815variable the buffer pointer is changed to point just after the data 816that has been read or written. This may well be uninitialized data 817and attempts to free the buffer will have unpredictable results 818because it no longer points to the same address. 819 820 821* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 822 823The short answer is yes, because DER is a special case of BER and OpenSSL 824ASN1 decoders can process BER. 825 826The longer answer is that ASN1 structures can be encoded in a number of 827different ways. One set of ways is the Basic Encoding Rules (BER) with various 828permissible encodings. A restriction of BER is the Distinguished Encoding 829Rules (DER): these uniquely specify how a given structure is encoded. 830 831Therefore, because DER is a special case of BER, DER is an acceptable encoding 832for BER. 833 834 835* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 836 837This usually happens when you try compiling something using the PKCS#12 838macros with a C++ compiler. There is hardly ever any need to use the 839PKCS#12 macros in a program, it is much easier to parse and create 840PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 841documented in doc/openssl.txt and with examples in demos/pkcs12. The 842'pkcs12' application has to use the macros because it prints out 843debugging information. 844 845 846* I've called <some function> and it fails, why? 847 848Before submitting a report or asking in one of the mailing lists, you 849should try to determine the cause. In particular, you should call 850ERR_print_errors() or ERR_print_errors_fp() after the failed call 851and see if the message helps. Note that the problem may occur earlier 852than you think -- you should check for errors after every call where 853it is possible, otherwise the actual problem may be hidden because 854some OpenSSL functions clear the error state. 855 856 857* I just get a load of numbers for the error output, what do they mean? 858 859The actual format is described in the ERR_print_errors() manual page. 860You should call the function ERR_load_crypto_strings() before hand and 861the message will be output in text form. If you can't do this (for example 862it is a pre-compiled binary) you can use the errstr utility on the error 863code itself (the hex digits after the second colon). 864 865 866* Why do I get errors about unknown algorithms? 867 868The cause is forgetting to load OpenSSL's table of algorithms with 869OpenSSL_add_all_algorithms(). See the manual page for more information. This 870can cause several problems such as being unable to read in an encrypted 871PEM file, unable to decrypt a PKCS#12 file or signature failure when 872verifying certificates. 873 874* Why can't the OpenSSH configure script detect OpenSSL? 875 876Several reasons for problems with the automatic detection exist. 877OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 878Sometimes the distribution has installed an older version in the system 879locations that is detected instead of a new one installed. The OpenSSL 880library might have been compiled for another CPU or another mode (32/64 bits). 881Permissions might be wrong. 882 883The general answer is to check the config.log file generated when running 884the OpenSSH configure script. It should contain the detailed information 885on why the OpenSSL library was not detected or considered incompatible. 886 887 888* Can I use OpenSSL's SSL library with non-blocking I/O? 889 890Yes; make sure to read the SSL_get_error(3) manual page! 891 892A pitfall to avoid: Don't assume that SSL_read() will just read from 893the underlying transport or that SSL_write() will just write to it -- 894it is also possible that SSL_write() cannot do any useful work until 895there is data to read, or that SSL_read() cannot do anything until it 896is possible to send data. One reason for this is that the peer may 897request a new TLS/SSL handshake at any time during the protocol, 898requiring a bi-directional message exchange; both SSL_read() and 899SSL_write() will try to continue any pending handshake. 900 901 902* Why doesn't my server application receive a client certificate? 903 904Due to the TLS protocol definition, a client will only send a certificate, 905if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 906SSL_CTX_set_verify() function to enable the use of client certificates. 907 908 909* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 910 911For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 912versions, uniqueIdentifier was incorrectly used for X.509 certificates. 913The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 914Change your code to use the new name when compiling against OpenSSL 0.9.7. 915 916 917* I think I've detected a memory leak, is this a bug? 918 919In most cases the cause of an apparent memory leak is an OpenSSL internal table 920that is allocated when an application starts up. Since such tables do not grow 921in size over time they are harmless. 922 923These internal tables can be freed up when an application closes using various 924functions. Currently these include following: 925 926Thread-local cleanup functions: 927 928 ERR_remove_state() 929 930Application-global cleanup functions that are aware of usage (and therefore 931thread-safe): 932 933 ENGINE_cleanup() and CONF_modules_unload() 934 935"Brutal" (thread-unsafe) Application-global cleanup functions: 936 937 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). 938 939 940* Why does Valgrind complain about the use of uninitialized data? 941 942When OpenSSL's PRNG routines are called to generate random numbers the supplied 943buffer contents are mixed into the entropy pool: so it technically does not 944matter whether the buffer is initialized at this point or not. Valgrind (and 945other test tools) will complain about this. When using Valgrind, make sure the 946OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) 947to get rid of these warnings. 948 949 950* Why doesn't a memory BIO work when a file does? 951 952This can occur in several cases for example reading an S/MIME email message. 953The reason is that a memory BIO can do one of two things when all the data 954has been read from it. 955 956The default behaviour is to indicate that no more data is available and that 957the call should be retried, this is to allow the application to fill up the BIO 958again if necessary. 959 960Alternatively it can indicate that no more data is available and that EOF has 961been reached. 962 963If a memory BIO is to behave in the same way as a file this second behaviour 964is needed. This must be done by calling: 965 966 BIO_set_mem_eof_return(bio, 0); 967 968See the manual pages for more details. 969 970 971* Where are the declarations and implementations of d2i_X509() etc? 972 973These are defined and implemented by macros of the form: 974 975 976 DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509) 977 978The implementation passes an ASN1 "template" defining the structure into an 979ASN1 interpreter using generalised functions such as ASN1_item_d2i(). 980 981 982=============================================================================== 983