FAQ revision 279265
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 1.0.1d was released on Feb 5th, 2013. 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 Git 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 116There is some documentation about certificate extensions and PKCS#12 117in doc/openssl.txt 118 119The original SSLeay documentation is included in OpenSSL as 120doc/ssleay.txt. It may be useful when none of the other resources 121help, but please note that it reflects the obsolete version SSLeay 1220.6.6. 123 124 125* How can I contact the OpenSSL developers? 126 127The README file describes how to submit bug reports and patches to 128OpenSSL. Information on the OpenSSL mailing lists is available from 129<URL: http://www.openssl.org>. 130 131 132* Where can I get a compiled version of OpenSSL? 133 134You can finder pointers to binary distributions in 135<URL: http://www.openssl.org/related/binaries.html> . 136 137Some applications that use OpenSSL are distributed in binary form. 138When using such an application, you don't need to install OpenSSL 139yourself; the application will include the required parts (e.g. DLLs). 140 141If you want to build OpenSSL on a Windows system and you don't have 142a C compiler, read the "Mingw32" section of INSTALL.W32 for information 143on how to obtain and install the free GNU C compiler. 144 145A number of Linux and *BSD distributions include OpenSSL. 146 147 148* Why aren't tools like 'autoconf' and 'libtool' used? 149 150autoconf will probably be used in future OpenSSL versions. If it was 151less Unix-centric, it might have been used much earlier. 152 153* What is an 'engine' version? 154 155With version 0.9.6 OpenSSL was extended to interface to external crypto 156hardware. This was realized in a special release '0.9.6-engine'. With 157version 0.9.7 the changes were merged into the main development line, 158so that the special release is no longer necessary. 159 160* How do I check the authenticity of the OpenSSL distribution? 161 162We provide MD5 digests and ASC signatures of each tarball. 163Use MD5 to check that a tarball from a mirror site is identical: 164 165 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 166 167You can check authenticity using pgp or gpg. You need the OpenSSL team 168member public key used to sign it (download it from a key server, see a 169list of keys at <URL: http://www.openssl.org/about/>). Then 170just do: 171 172 pgp TARBALL.asc 173 174* How does the versioning scheme work? 175 176After the release of OpenSSL 1.0.0 the versioning scheme changed. Letter 177releases (e.g. 1.0.1a) can only contain bug and security fixes and no 178new features. Minor releases change the last number (e.g. 1.0.2) and 179can contain new features that retain binary compatibility. Changes to 180the middle number are considered major releases and neither source nor 181binary compatibility is guaranteed. 182 183Therefore the answer to the common question "when will feature X be 184backported to OpenSSL 1.0.0/0.9.8?" is "never" but it could appear 185in the next minor release. 186 187[LEGAL] ======================================================================= 188 189* Do I need patent licenses to use OpenSSL? 190 191The patents section of the README file lists patents that may apply to 192you if you want to use OpenSSL. For information on intellectual 193property rights, please consult a lawyer. The OpenSSL team does not 194offer legal advice. 195 196You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using 197 ./config no-idea no-mdc2 no-rc5 198 199 200* Can I use OpenSSL with GPL software? 201 202On many systems including the major Linux and BSD distributions, yes (the 203GPL does not place restrictions on using libraries that are part of the 204normal operating system distribution). 205 206On other systems, the situation is less clear. Some GPL software copyright 207holders claim that you infringe on their rights if you use OpenSSL with 208their software on operating systems that don't normally include OpenSSL. 209 210If you develop open source software that uses OpenSSL, you may find it 211useful to choose an other license than the GPL, or state explicitly that 212"This program is released under the GPL with the additional exemption that 213compiling, linking, and/or using OpenSSL is allowed." If you are using 214GPL software developed by others, you may want to ask the copyright holder 215for permission to use their software with OpenSSL. 216 217 218[USER] ======================================================================== 219 220* Why do I get a "PRNG not seeded" error message? 221 222Cryptographic software needs a source of unpredictable data to work 223correctly. Many open source operating systems provide a "randomness 224device" (/dev/urandom or /dev/random) that serves this purpose. 225All OpenSSL versions try to use /dev/urandom by default; starting with 226version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 227available. 228 229On other systems, applications have to call the RAND_add() or 230RAND_seed() function with appropriate data before generating keys or 231performing public key encryption. (These functions initialize the 232pseudo-random number generator, PRNG.) Some broken applications do 233not do this. As of version 0.9.5, the OpenSSL functions that need 234randomness report an error if the random number generator has not been 235seeded with at least 128 bits of randomness. If this error occurs and 236is not discussed in the documentation of the application you are 237using, please contact the author of that application; it is likely 238that it never worked correctly. OpenSSL 0.9.5 and later make the 239error visible by refusing to perform potentially insecure encryption. 240 241If you are using Solaris 8, you can add /dev/urandom and /dev/random 242devices by installing patch 112438 (Sparc) or 112439 (x86), which are 243available via the Patchfinder at <URL: http://sunsolve.sun.com> 244(Solaris 9 includes these devices by default). For /dev/random support 245for earlier Solaris versions, see Sun's statement at 246<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 247(the SUNWski package is available in patch 105710). 248 249On systems without /dev/urandom and /dev/random, it is a good idea to 250use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 251details. Starting with version 0.9.7, OpenSSL will automatically look 252for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 253/etc/entropy. 254 255Most components of the openssl command line utility automatically try 256to seed the random number generator from a file. The name of the 257default seeding file is determined as follows: If environment variable 258RANDFILE is set, then it names the seeding file. Otherwise if 259environment variable HOME is set, then the seeding file is $HOME/.rnd. 260If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 261use file .rnd in the current directory while OpenSSL 0.9.6a uses no 262default seeding file at all. OpenSSL 0.9.6b and later will behave 263similarly to 0.9.6a, but will use a default of "C:\" for HOME on 264Windows systems if the environment variable has not been set. 265 266If the default seeding file does not exist or is too short, the "PRNG 267not seeded" error message may occur. 268 269The openssl command line utility will write back a new state to the 270default seeding file (and create this file if necessary) unless 271there was no sufficient seeding. 272 273Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 274Use the "-rand" option of the OpenSSL command line tools instead. 275The $RANDFILE environment variable and $HOME/.rnd are only used by the 276OpenSSL command line tools. Applications using the OpenSSL library 277provide their own configuration options to specify the entropy source, 278please check out the documentation coming the with application. 279 280 281* Why do I get an "unable to write 'random state'" error message? 282 283 284Sometimes the openssl command line utility does not abort with 285a "PRNG not seeded" error message, but complains that it is 286"unable to write 'random state'". This message refers to the 287default seeding file (see previous answer). A possible reason 288is that no default filename is known because neither RANDFILE 289nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 290current directory in this case, but this has changed with 0.9.6a.) 291 292 293* How do I create certificates or certificate requests? 294 295Check out the CA.pl(1) manual page. This provides a simple wrapper round 296the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 297out the manual pages for the individual utilities and the certificate 298extensions documentation (in ca(1), req(1), x509v3_config(5) ) 299 300 301* Why can't I create certificate requests? 302 303You typically get the error: 304 305 unable to find 'distinguished_name' in config 306 problems making Certificate Request 307 308This is because it can't find the configuration file. Check out the 309DIAGNOSTICS section of req(1) for more information. 310 311 312* Why does <SSL program> fail with a certificate verify error? 313 314This problem is usually indicated by log messages saying something like 315"unable to get local issuer certificate" or "self signed certificate". 316When a certificate is verified its root CA must be "trusted" by OpenSSL 317this typically means that the CA certificate must be placed in a directory 318or file and the relevant program configured to read it. The OpenSSL program 319'verify' behaves in a similar way and issues similar error messages: check 320the verify(1) program manual page for more information. 321 322 323* Why can I only use weak ciphers when I connect to a server using OpenSSL? 324 325This is almost certainly because you are using an old "export grade" browser 326which only supports weak encryption. Upgrade your browser to support 128 bit 327ciphers. 328 329 330* How can I create DSA certificates? 331 332Check the CA.pl(1) manual page for a DSA certificate example. 333 334 335* Why can't I make an SSL connection to a server using a DSA certificate? 336 337Typically you'll see a message saying there are no shared ciphers when 338the same setup works fine with an RSA certificate. There are two possible 339causes. The client may not support connections to DSA servers most web 340browsers (including Netscape and MSIE) only support connections to servers 341supporting RSA cipher suites. The other cause is that a set of DH parameters 342has not been supplied to the server. DH parameters can be created with the 343dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 344check the source to s_server in apps/s_server.c for an example. 345 346 347* How can I remove the passphrase on a private key? 348 349Firstly you should be really *really* sure you want to do this. Leaving 350a private key unencrypted is a major security risk. If you decide that 351you do have to do this check the EXAMPLES sections of the rsa(1) and 352dsa(1) manual pages. 353 354 355* Why can't I use OpenSSL certificates with SSL client authentication? 356 357What will typically happen is that when a server requests authentication 358it will either not include your certificate or tell you that you have 359no client certificates (Netscape) or present you with an empty list box 360(MSIE). The reason for this is that when a server requests a client 361certificate it includes a list of CAs names which it will accept. Browsers 362will only let you select certificates from the list on the grounds that 363there is little point presenting a certificate which the server will 364reject. 365 366The solution is to add the relevant CA certificate to your servers "trusted 367CA list". How you do this depends on the server software in uses. You can 368print out the servers list of acceptable CAs using the OpenSSL s_client tool: 369 370openssl s_client -connect www.some.host:443 -prexit 371 372If your server only requests certificates on certain URLs then you may need 373to manually issue an HTTP GET command to get the list when s_client connects: 374 375GET /some/page/needing/a/certificate.html 376 377If your CA does not appear in the list then this confirms the problem. 378 379 380* Why does my browser give a warning about a mismatched hostname? 381 382Browsers expect the server's hostname to match the value in the commonName 383(CN) field of the certificate. If it does not then you get a warning. 384 385 386* How do I install a CA certificate into a browser? 387 388The usual way is to send the DER encoded certificate to the browser as 389MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 390link. On MSIE certain extensions such as .der or .cacert may also work, or you 391can import the certificate using the certificate import wizard. 392 393You can convert a certificate to DER form using the command: 394 395openssl x509 -in ca.pem -outform DER -out ca.der 396 397Occasionally someone suggests using a command such as: 398 399openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 400 401DO NOT DO THIS! This command will give away your CAs private key and 402reduces its security to zero: allowing anyone to forge certificates in 403whatever name they choose. 404 405* Why is OpenSSL x509 DN output not conformant to RFC2253? 406 407The ways to print out the oneline format of the DN (Distinguished Name) have 408been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 409interface, the "-nameopt" option could be introduded. See the manual 410page of the "openssl x509" commandline tool for details. The old behaviour 411has however been left as default for the sake of compatibility. 412 413* What is a "128 bit certificate"? Can I create one with OpenSSL? 414 415The term "128 bit certificate" is a highly misleading marketing term. It does 416*not* refer to the size of the public key in the certificate! A certificate 417containing a 128 bit RSA key would have negligible security. 418 419There were various other names such as "magic certificates", "SGC 420certificates", "step up certificates" etc. 421 422You can't generally create such a certificate using OpenSSL but there is no 423need to any more. Nowadays web browsers using unrestricted strong encryption 424are generally available. 425 426When there were tight restrictions on the export of strong encryption 427software from the US only weak encryption algorithms could be freely exported 428(initially 40 bit and then 56 bit). It was widely recognised that this was 429inadequate. A relaxation of the rules allowed the use of strong encryption but 430only to an authorised server. 431 432Two slighly different techniques were developed to support this, one used by 433Netscape was called "step up", the other used by MSIE was called "Server Gated 434Cryptography" (SGC). When a browser initially connected to a server it would 435check to see if the certificate contained certain extensions and was issued by 436an authorised authority. If these test succeeded it would reconnect using 437strong encryption. 438 439Only certain (initially one) certificate authorities could issue the 440certificates and they generally cost more than ordinary certificates. 441 442Although OpenSSL can create certificates containing the appropriate extensions 443the certificate would not come from a permitted authority and so would not 444be recognized. 445 446The export laws were later changed to allow almost unrestricted use of strong 447encryption so these certificates are now obsolete. 448 449 450* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? 451 452It doesn't: this extension is often the cause of confusion. 453 454Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose 455certificate C contains AKID. 456 457The purpose of this extension is to identify the authority certificate B. This 458can be done either by including the subject key identifier of B or its issuer 459name and serial number. 460 461In this latter case because it is identifying certifcate B it must contain the 462issuer name and serial number of B. 463 464It is often wrongly assumed that it should contain the subject name of B. If it 465did this would be redundant information because it would duplicate the issuer 466name of C. 467 468 469* How can I set up a bundle of commercial root CA certificates? 470 471The OpenSSL software is shipped without any root CA certificate as the 472OpenSSL project does not have any policy on including or excluding 473any specific CA and does not intend to set up such a policy. Deciding 474about which CAs to support is up to application developers or 475administrators. 476 477Other projects do have other policies so you can for example extract the CA 478bundle used by Mozilla and/or modssl as described in this article: 479 480 <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html> 481 482 483[BUILD] ======================================================================= 484 485* Why does the linker complain about undefined symbols? 486 487Maybe the compilation was interrupted, and make doesn't notice that 488something is missing. Run "make clean; make". 489 490If you used ./Configure instead of ./config, make sure that you 491selected the right target. File formats may differ slightly between 492OS versions (for example sparcv8/sparcv9, or a.out/elf). 493 494In case you get errors about the following symbols, use the config 495option "no-asm", as described in INSTALL: 496 497 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 498 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 499 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 500 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 501 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 502 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 503 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 504 505If none of these helps, you may want to try using the current snapshot. 506If the problem persists, please submit a bug report. 507 508 509* Why does the OpenSSL test fail with "bc: command not found"? 510 511You didn't install "bc", the Unix calculator. If you want to run the 512tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 513 514 515* Why does the OpenSSL test fail with "bc: 1 no implemented"? 516 517On some SCO installations or versions, bc has a bug that gets triggered 518when you run the test suite (using "make test"). The message returned is 519"bc: 1 not implemented". 520 521The best way to deal with this is to find another implementation of bc 522and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> 523for download instructions) can be safely used, for example. 524 525 526* Why does the OpenSSL test fail with "bc: stack empty"? 527 528On some DG/ux versions, bc seems to have a too small stack for calculations 529that the OpenSSL bntest throws at it. This gets triggered when you run the 530test suite (using "make test"). The message returned is "bc: stack empty". 531 532The best way to deal with this is to find another implementation of bc 533and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> 534for download instructions) can be safely used, for example. 535 536 537* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 538 539On some Alpha installations running Tru64 Unix and Compaq C, the compilation 540of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 541memory to continue compilation.' As far as the tests have shown, this may be 542a compiler bug. What happens is that it eats up a lot of resident memory 543to build something, probably a table. The problem is clearly in the 544optimization code, because if one eliminates optimization completely (-O0), 545the compilation goes through (and the compiler consumes about 2MB of resident 546memory instead of 240MB or whatever one's limit is currently). 547 548There are three options to solve this problem: 549 5501. set your current data segment size soft limit higher. Experience shows 551that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 552this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 553kbytes to set the limit to. 554 5552. If you have a hard limit that is lower than what you need and you can't 556get it changed, you can compile all of OpenSSL with -O0 as optimization 557level. This is however not a very nice thing to do for those who expect to 558get the best result from OpenSSL. A bit more complicated solution is the 559following: 560 561----- snip:start ----- 562 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 563 sed -e 's/ -O[0-9] / -O0 /'`" 564 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 565 make 566----- snip:end ----- 567 568This will only compile sha_dgst.c with -O0, the rest with the optimization 569level chosen by the configuration process. When the above is done, do the 570test and installation and you're set. 571 5723. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 573should not be used and is not used in SSL/TLS nor any other recognized 574protocol in either case. 575 576 577* Why does the OpenSSL compilation fail with "ar: command not found"? 578 579Getting this message is quite usual on Solaris 2, because Sun has hidden 580away 'ar' and other development commands in directories that aren't in 581$PATH by default. One of those directories is '/usr/ccs/bin'. The 582quickest way to fix this is to do the following (it assumes you use sh 583or any sh-compatible shell): 584 585----- snip:start ----- 586 PATH=${PATH}:/usr/ccs/bin; export PATH 587----- snip:end ----- 588 589and then redo the compilation. What you should really do is make sure 590'/usr/ccs/bin' is permanently in your $PATH, for example through your 591'.profile' (again, assuming you use a sh-compatible shell). 592 593 594* Why does the OpenSSL compilation fail on Win32 with VC++? 595 596Sometimes, you may get reports from VC++ command line (cl) that it 597can't find standard include files like stdio.h and other weirdnesses. 598One possible cause is that the environment isn't correctly set up. 599To solve that problem for VC++ versions up to 6, one should run 600VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 601installation directory (somewhere under 'Program Files'). For VC++ 602version 7 (and up?), which is also called VS.NET, the file is called 603VSVARS32.BAT instead. 604This needs to be done prior to running NMAKE, and the changes are only 605valid for the current DOS session. 606 607 608* What is special about OpenSSL on Redhat? 609 610Red Hat Linux (release 7.0 and later) include a preinstalled limited 611version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 612is disabled in this version. The same may apply to other Linux distributions. 613Users may therefore wish to install more or all of the features left out. 614 615To do this you MUST ensure that you do not overwrite the openssl that is in 616/usr/bin on your Red Hat machine. Several packages depend on this file, 617including sendmail and ssh. /usr/local/bin is a good alternative choice. The 618libraries that come with Red Hat 7.0 onwards have different names and so are 619not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 620/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 621/lib/libcrypto.so.2 respectively). 622 623Please note that we have been advised by Red Hat attempting to recompile the 624openssl rpm with all the cryptography enabled will not work. All other 625packages depend on the original Red Hat supplied openssl package. It is also 626worth noting that due to the way Red Hat supplies its packages, updates to 627openssl on each distribution never change the package version, only the 628build number. For example, on Red Hat 7.1, the latest openssl package has 629version number 0.9.6 and build number 9 even though it contains all the 630relevant updates in packages up to and including 0.9.6b. 631 632A possible way around this is to persuade Red Hat to produce a non-US 633version of Red Hat Linux. 634 635FYI: Patent numbers and expiry dates of US patents: 636MDC-2: 4,908,861 13/03/2007 637IDEA: 5,214,703 25/05/2010 638RC5: 5,724,428 03/03/2015 639 640 641* Why does the OpenSSL compilation fail on MacOS X? 642 643If the failure happens when trying to build the "openssl" binary, with 644a large number of undefined symbols, it's very probable that you have 645OpenSSL 0.9.6b delivered with the operating system (you can find out by 646running '/usr/bin/openssl version') and that you were trying to build 647OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 648MacOS X has a misfeature that's quite difficult to go around. 649Look in the file PROBLEMS for a more detailed explanation and for possible 650solutions. 651 652 653* Why does the OpenSSL test suite fail on MacOS X? 654 655If the failure happens when running 'make test' and the RC4 test fails, 656it's very probable that you have OpenSSL 0.9.6b delivered with the 657operating system (you can find out by running '/usr/bin/openssl version') 658and that you were trying to build OpenSSL 0.9.6d. The problem is that 659the loader ('ld') in MacOS X has a misfeature that's quite difficult to 660go around and has linked the programs "openssl" and the test programs 661with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 662libraries you just built. 663Look in the file PROBLEMS for a more detailed explanation and for possible 664solutions. 665 666* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 667 668Failure in BN_sqr test is most likely caused by a failure to configure the 669toolkit for current platform or lack of support for the platform in question. 670Run './config -t' and './apps/openssl version -p'. Do these platform 671identifiers match? If they don't, then you most likely failed to run 672./config and you're hereby advised to do so before filing a bug report. 673If ./config itself fails to run, then it's most likely problem with your 674local environment and you should turn to your system administrator (or 675similar). If identifiers match (and/or no alternative identifier is 676suggested by ./config script), then the platform is unsupported. There might 677or might not be a workaround. Most notably on SPARC64 platforms with GNU 678C compiler you should be able to produce a working build by running 679'./config -m32'. I understand that -m32 might not be what you want/need, 680but the build should be operational. For further details turn to 681<openssl-dev@openssl.org>. 682 683* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 684 685As of 0.9.7 assembler routines were overhauled for position independence 686of the machine code, which is essential for shared library support. For 687some reason OpenBSD is equipped with an out-of-date GNU assembler which 688finds the new code offensive. To work around the problem, configure with 689no-asm (and sacrifice a great deal of performance) or patch your assembler 690according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 691For your convenience a pre-compiled replacement binary is provided at 692<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 693Reportedly elder *BSD a.out platforms also suffer from this problem and 694remedy should be same. Provided binary is statically linked and should be 695working across wider range of *BSD branches, not just OpenBSD. 696 697* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 698 699If the test program in question fails withs SIGILL, Illegal Instruction 700exception, then you more than likely to run SSE2-capable CPU, such as 701Intel P4, under control of kernel which does not support SSE2 702instruction extentions. See accompanying INSTALL file and 703OPENSSL_ia32cap(3) documentation page for further information. 704 705* Why does compiler fail to compile sha512.c? 706 707OpenSSL SHA-512 implementation depends on compiler support for 64-bit 708integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a 709couple] lack support for this and therefore are incapable of compiling 710the module in question. The recommendation is to disable SHA-512 by 711adding no-sha512 to ./config [or ./Configure] command line. Another 712possible alternative might be to switch to GCC. 713 714* Test suite still fails, what to do? 715 716Another common reason for failure to complete some particular test is 717simply bad code generated by a buggy component in toolchain or deficiency 718in run-time environment. There are few cases documented in PROBLEMS file, 719consult it for possible workaround before you beat the drum. Even if you 720don't find solution or even mention there, do reserve for possibility of 721a compiler bug. Compiler bugs might appear in rather bizarre ways, they 722never make sense, and tend to emerge when you least expect them. In order 723to identify one, drop optimization level, e.g. by editing CFLAG line in 724top-level Makefile, recompile and re-run the test. 725 726* I think I've found a bug, what should I do? 727 728If you are a new user then it is quite likely you haven't found a bug and 729something is happening you aren't familiar with. Check this FAQ, the associated 730documentation and the mailing lists for similar queries. If you are still 731unsure whether it is a bug or not submit a query to the openssl-users mailing 732list. 733 734 735* I'm SURE I've found a bug, how do I report it? 736 737Bug reports with no security implications should be sent to the request 738tracker. This can be done by mailing the report to <rt@openssl.org> (or its 739alias <openssl-bugs@openssl.org>), please note that messages sent to the 740request tracker also appear in the public openssl-dev mailing list. 741 742The report should be in plain text. Any patches should be sent as 743plain text attachments because some mailers corrupt patches sent inline. 744If your issue affects multiple versions of OpenSSL check any patches apply 745cleanly and, if possible include patches to each affected version. 746 747The report should be given a meaningful subject line briefly summarising the 748issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful. 749 750By sending reports to the request tracker the bug can then be given a priority 751and assigned to the appropriate maintainer. The history of discussions can be 752accessed and if the issue has been addressed or a reason why not. If patches 753are only sent to openssl-dev they can be mislaid if a team member has to 754wade through months of old messages to review the discussion. 755 756See also <URL: http://www.openssl.org/support/rt.html> 757 758 759* I've found a security issue, how do I report it? 760 761If you think your bug has security implications then please send it to 762openssl-security@openssl.org if you don't get a prompt reply at least 763acknowledging receipt then resend or mail it directly to one of the 764more active team members (e.g. Steve). 765 766Note that bugs only present in the openssl utility are not in general 767considered to be security issues. 768 769[PROG] ======================================================================== 770 771* Is OpenSSL thread-safe? 772 773Yes (with limitations: an SSL connection may not concurrently be used 774by multiple threads). On Windows and many Unix systems, OpenSSL 775automatically uses the multi-threaded versions of the standard 776libraries. If your platform is not one of these, consult the INSTALL 777file. 778 779Multi-threaded applications must provide two callback functions to 780OpenSSL by calling CRYPTO_set_locking_callback() and 781CRYPTO_set_id_callback(), for all versions of OpenSSL up to and 782including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback() 783and associated APIs are deprecated by CRYPTO_THREADID_set_callback() 784and friends. This is described in the threads(3) manpage. 785 786* I've compiled a program under Windows and it crashes: why? 787 788This is usually because you've missed the comment in INSTALL.W32. 789Your application must link against the same version of the Win32 790C-Runtime against which your openssl libraries were linked. The 791default version for OpenSSL is /MD - "Multithreaded DLL". 792 793If you are using Microsoft Visual C++'s IDE (Visual Studio), in 794many cases, your new project most likely defaulted to "Debug 795Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 796program will crash, typically on the first BIO related read or write 797operation. 798 799For each of the six possible link stage configurations within Win32, 800your application must link against the same by which OpenSSL was 801built. If you are using MS Visual C++ (Studio) this can be changed 802by: 803 804 1. Select Settings... from the Project Menu. 805 2. Select the C/C++ Tab. 806 3. Select "Code Generation from the "Category" drop down list box 807 4. Select the Appropriate library (see table below) from the "Use 808 run-time library" drop down list box. Perform this step for both 809 your debug and release versions of your application (look at the 810 top left of the settings panel to change between the two) 811 812 Single Threaded /ML - MS VC++ often defaults to 813 this for the release 814 version of a new project. 815 Debug Single Threaded /MLd - MS VC++ often defaults to 816 this for the debug version 817 of a new project. 818 Multithreaded /MT 819 Debug Multithreaded /MTd 820 Multithreaded DLL /MD - OpenSSL defaults to this. 821 Debug Multithreaded DLL /MDd 822 823Note that debug and release libraries are NOT interchangeable. If you 824built OpenSSL with /MD your application must use /MD and cannot use /MDd. 825 826As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL 827.DLLs compiled with some specific run-time option [we insist on the 828default /MD] can be deployed with application compiled with different 829option or even different compiler. But there is a catch! Instead of 830re-compiling OpenSSL toolkit, as you would have to with prior versions, 831you have to compile small C snippet with compiler and/or options of 832your choice. The snippet gets installed as 833<install-root>/include/openssl/applink.c and should be either added to 834your application project or simply #include-d in one [and only one] 835of your application source files. Failure to link this shim module 836into your application manifests itself as fatal "no OPENSSL_Applink" 837run-time error. An explicit reminder is due that in this situation 838[mixing compiler options] it is as important to add CRYPTO_malloc_init 839prior first call to OpenSSL. 840 841* How do I read or write a DER encoded buffer using the ASN1 functions? 842 843You have two options. You can either use a memory BIO in conjunction 844with the i2d_*_bio() or d2i_*_bio() functions or you can use the 845i2d_*(), d2i_*() functions directly. Since these are often the 846cause of grief here are some code fragments using PKCS7 as an example: 847 848 unsigned char *buf, *p; 849 int len; 850 851 len = i2d_PKCS7(p7, NULL); 852 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 853 p = buf; 854 i2d_PKCS7(p7, &p); 855 856At this point buf contains the len bytes of the DER encoding of 857p7. 858 859The opposite assumes we already have len bytes in buf: 860 861 unsigned char *p; 862 p = buf; 863 p7 = d2i_PKCS7(NULL, &p, len); 864 865At this point p7 contains a valid PKCS7 structure of NULL if an error 866occurred. If an error occurred ERR_print_errors(bio) should give more 867information. 868 869The reason for the temporary variable 'p' is that the ASN1 functions 870increment the passed pointer so it is ready to read or write the next 871structure. This is often a cause of problems: without the temporary 872variable the buffer pointer is changed to point just after the data 873that has been read or written. This may well be uninitialized data 874and attempts to free the buffer will have unpredictable results 875because it no longer points to the same address. 876 877 878* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 879 880The short answer is yes, because DER is a special case of BER and OpenSSL 881ASN1 decoders can process BER. 882 883The longer answer is that ASN1 structures can be encoded in a number of 884different ways. One set of ways is the Basic Encoding Rules (BER) with various 885permissible encodings. A restriction of BER is the Distinguished Encoding 886Rules (DER): these uniquely specify how a given structure is encoded. 887 888Therefore, because DER is a special case of BER, DER is an acceptable encoding 889for BER. 890 891 892* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 893 894This usually happens when you try compiling something using the PKCS#12 895macros with a C++ compiler. There is hardly ever any need to use the 896PKCS#12 macros in a program, it is much easier to parse and create 897PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 898documented in doc/openssl.txt and with examples in demos/pkcs12. The 899'pkcs12' application has to use the macros because it prints out 900debugging information. 901 902 903* I've called <some function> and it fails, why? 904 905Before submitting a report or asking in one of the mailing lists, you 906should try to determine the cause. In particular, you should call 907ERR_print_errors() or ERR_print_errors_fp() after the failed call 908and see if the message helps. Note that the problem may occur earlier 909than you think -- you should check for errors after every call where 910it is possible, otherwise the actual problem may be hidden because 911some OpenSSL functions clear the error state. 912 913 914* I just get a load of numbers for the error output, what do they mean? 915 916The actual format is described in the ERR_print_errors() manual page. 917You should call the function ERR_load_crypto_strings() before hand and 918the message will be output in text form. If you can't do this (for example 919it is a pre-compiled binary) you can use the errstr utility on the error 920code itself (the hex digits after the second colon). 921 922 923* Why do I get errors about unknown algorithms? 924 925The cause is forgetting to load OpenSSL's table of algorithms with 926OpenSSL_add_all_algorithms(). See the manual page for more information. This 927can cause several problems such as being unable to read in an encrypted 928PEM file, unable to decrypt a PKCS#12 file or signature failure when 929verifying certificates. 930 931* Why can't the OpenSSH configure script detect OpenSSL? 932 933Several reasons for problems with the automatic detection exist. 934OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 935Sometimes the distribution has installed an older version in the system 936locations that is detected instead of a new one installed. The OpenSSL 937library might have been compiled for another CPU or another mode (32/64 bits). 938Permissions might be wrong. 939 940The general answer is to check the config.log file generated when running 941the OpenSSH configure script. It should contain the detailed information 942on why the OpenSSL library was not detected or considered incompatible. 943 944 945* Can I use OpenSSL's SSL library with non-blocking I/O? 946 947Yes; make sure to read the SSL_get_error(3) manual page! 948 949A pitfall to avoid: Don't assume that SSL_read() will just read from 950the underlying transport or that SSL_write() will just write to it -- 951it is also possible that SSL_write() cannot do any useful work until 952there is data to read, or that SSL_read() cannot do anything until it 953is possible to send data. One reason for this is that the peer may 954request a new TLS/SSL handshake at any time during the protocol, 955requiring a bi-directional message exchange; both SSL_read() and 956SSL_write() will try to continue any pending handshake. 957 958 959* Why doesn't my server application receive a client certificate? 960 961Due to the TLS protocol definition, a client will only send a certificate, 962if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 963SSL_CTX_set_verify() function to enable the use of client certificates. 964 965 966* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 967 968For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 969versions, uniqueIdentifier was incorrectly used for X.509 certificates. 970The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 971Change your code to use the new name when compiling against OpenSSL 0.9.7. 972 973 974* I think I've detected a memory leak, is this a bug? 975 976In most cases the cause of an apparent memory leak is an OpenSSL internal table 977that is allocated when an application starts up. Since such tables do not grow 978in size over time they are harmless. 979 980These internal tables can be freed up when an application closes using various 981functions. Currently these include following: 982 983Thread-local cleanup functions: 984 985 ERR_remove_state() 986 987Application-global cleanup functions that are aware of usage (and therefore 988thread-safe): 989 990 ENGINE_cleanup() and CONF_modules_unload() 991 992"Brutal" (thread-unsafe) Application-global cleanup functions: 993 994 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). 995 996 997* Why does Valgrind complain about the use of uninitialized data? 998 999When OpenSSL's PRNG routines are called to generate random numbers the supplied 1000buffer contents are mixed into the entropy pool: so it technically does not 1001matter whether the buffer is initialized at this point or not. Valgrind (and 1002other test tools) will complain about this. When using Valgrind, make sure the 1003OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) 1004to get rid of these warnings. 1005 1006 1007* Why doesn't a memory BIO work when a file does? 1008 1009This can occur in several cases for example reading an S/MIME email message. 1010The reason is that a memory BIO can do one of two things when all the data 1011has been read from it. 1012 1013The default behaviour is to indicate that no more data is available and that 1014the call should be retried, this is to allow the application to fill up the BIO 1015again if necessary. 1016 1017Alternatively it can indicate that no more data is available and that EOF has 1018been reached. 1019 1020If a memory BIO is to behave in the same way as a file this second behaviour 1021is needed. This must be done by calling: 1022 1023 BIO_set_mem_eof_return(bio, 0); 1024 1025See the manual pages for more details. 1026 1027 1028* Where are the declarations and implementations of d2i_X509() etc? 1029 1030These are defined and implemented by macros of the form: 1031 1032 1033 DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509) 1034 1035The implementation passes an ASN1 "template" defining the structure into an 1036ASN1 interpreter using generalised functions such as ASN1_item_d2i(). 1037 1038 1039=============================================================================== 1040