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 35[BUILD] Questions about building and testing OpenSSL 36 37* Why does the linker complain about undefined symbols? 38* Why does the OpenSSL test fail with "bc: command not found"? 39* Why does the OpenSSL test fail with "bc: 1 no implemented"? 40* Why does the OpenSSL test fail with "bc: stack empty"? 41* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 42* Why does the OpenSSL compilation fail with "ar: command not found"? 43* Why does the OpenSSL compilation fail on Win32 with VC++? 44* What is special about OpenSSL on Redhat? 45* Why does the OpenSSL compilation fail on MacOS X? 46* Why does the OpenSSL test suite fail on MacOS X? 47* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 48* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 49* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 50* Why does compiler fail to compile sha512.c? 51 52[PROG] Questions about programming with OpenSSL 53 54* Is OpenSSL thread-safe? 55* I've compiled a program under Windows and it crashes: why? 56* How do I read or write a DER encoded buffer using the ASN1 functions? 57* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 58* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 59* I've called <some function> and it fails, why? 60* I just get a load of numbers for the error output, what do they mean? 61* Why do I get errors about unknown algorithms? 62* Why can't the OpenSSH configure script detect OpenSSL? 63* Can I use OpenSSL's SSL library with non-blocking I/O? 64* Why doesn't my server application receive a client certificate? 65* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 66* I think I've detected a memory leak, is this a bug? 67 68=============================================================================== 69 70[MISC] ======================================================================== 71 72* Which is the current version of OpenSSL? 73 74The current version is available from <URL: http://www.openssl.org>. 75OpenSSL 0.9.8a was released on October 11th, 2005. 76 77In addition to the current stable release, you can also access daily 78snapshots of the OpenSSL development version at <URL: 79ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 80 81 82* Where is the documentation? 83 84OpenSSL is a library that provides cryptographic functionality to 85applications such as secure web servers. Be sure to read the 86documentation of the application you want to use. The INSTALL file 87explains how to install this library. 88 89OpenSSL includes a command line utility that can be used to perform a 90variety of cryptographic functions. It is described in the openssl(1) 91manpage. Documentation for developers is currently being written. A 92few manual pages already are available; overviews over libcrypto and 93libssl are given in the crypto(3) and ssl(3) manpages. 94 95The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 96different directory if you specified one as described in INSTALL). 97In addition, you can read the most current versions at 98<URL: http://www.openssl.org/docs/>. 99 100For information on parts of libcrypto that are not yet documented, you 101might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 102predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 103of this still applies to OpenSSL. 104 105There is some documentation about certificate extensions and PKCS#12 106in doc/openssl.txt 107 108The original SSLeay documentation is included in OpenSSL as 109doc/ssleay.txt. It may be useful when none of the other resources 110help, but please note that it reflects the obsolete version SSLeay 1110.6.6. 112 113 114* How can I contact the OpenSSL developers? 115 116The README file describes how to submit bug reports and patches to 117OpenSSL. Information on the OpenSSL mailing lists is available from 118<URL: http://www.openssl.org>. 119 120 121* Where can I get a compiled version of OpenSSL? 122 123You can finder pointers to binary distributions in 124http://www.openssl.org/related/binaries.html . 125 126Some applications that use OpenSSL are distributed in binary form. 127When using such an application, you don't need to install OpenSSL 128yourself; the application will include the required parts (e.g. DLLs). 129 130If you want to build OpenSSL on a Windows system and you don't have 131a C compiler, read the "Mingw32" section of INSTALL.W32 for information 132on how to obtain and install the free GNU C compiler. 133 134A number of Linux and *BSD distributions include OpenSSL. 135 136 137* Why aren't tools like 'autoconf' and 'libtool' used? 138 139autoconf will probably be used in future OpenSSL versions. If it was 140less Unix-centric, it might have been used much earlier. 141 142* What is an 'engine' version? 143 144With version 0.9.6 OpenSSL was extended to interface to external crypto 145hardware. This was realized in a special release '0.9.6-engine'. With 146version 0.9.7 the changes were merged into the main development line, 147so that the special release is no longer necessary. 148 149* How do I check the authenticity of the OpenSSL distribution? 150 151We provide MD5 digests and ASC signatures of each tarball. 152Use MD5 to check that a tarball from a mirror site is identical: 153 154 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 155 156You can check authenticity using pgp or gpg. You need the OpenSSL team 157member public key used to sign it (download it from a key server, see a 158list of keys at <URL: http://www.openssl.org/about/>). Then 159just do: 160 161 pgp TARBALL.asc 162 163[LEGAL] ======================================================================= 164 165* Do I need patent licenses to use OpenSSL? 166 167The patents section of the README file lists patents that may apply to 168you if you want to use OpenSSL. For information on intellectual 169property rights, please consult a lawyer. The OpenSSL team does not 170offer legal advice. 171 172You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using 173 ./config no-idea no-mdc2 no-rc5 174 175 176* Can I use OpenSSL with GPL software? 177 178On many systems including the major Linux and BSD distributions, yes (the 179GPL does not place restrictions on using libraries that are part of the 180normal operating system distribution). 181 182On other systems, the situation is less clear. Some GPL software copyright 183holders claim that you infringe on their rights if you use OpenSSL with 184their software on operating systems that don't normally include OpenSSL. 185 186If you develop open source software that uses OpenSSL, you may find it 187useful to choose an other license than the GPL, or state explicitly that 188"This program is released under the GPL with the additional exemption that 189compiling, linking, and/or using OpenSSL is allowed." If you are using 190GPL software developed by others, you may want to ask the copyright holder 191for permission to use their software with OpenSSL. 192 193 194[USER] ======================================================================== 195 196* Why do I get a "PRNG not seeded" error message? 197 198Cryptographic software needs a source of unpredictable data to work 199correctly. Many open source operating systems provide a "randomness 200device" (/dev/urandom or /dev/random) that serves this purpose. 201All OpenSSL versions try to use /dev/urandom by default; starting with 202version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 203available. 204 205On other systems, applications have to call the RAND_add() or 206RAND_seed() function with appropriate data before generating keys or 207performing public key encryption. (These functions initialize the 208pseudo-random number generator, PRNG.) Some broken applications do 209not do this. As of version 0.9.5, the OpenSSL functions that need 210randomness report an error if the random number generator has not been 211seeded with at least 128 bits of randomness. If this error occurs and 212is not discussed in the documentation of the application you are 213using, please contact the author of that application; it is likely 214that it never worked correctly. OpenSSL 0.9.5 and later make the 215error visible by refusing to perform potentially insecure encryption. 216 217If you are using Solaris 8, you can add /dev/urandom and /dev/random 218devices by installing patch 112438 (Sparc) or 112439 (x86), which are 219available via the Patchfinder at <URL: http://sunsolve.sun.com> 220(Solaris 9 includes these devices by default). For /dev/random support 221for earlier Solaris versions, see Sun's statement at 222<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 223(the SUNWski package is available in patch 105710). 224 225On systems without /dev/urandom and /dev/random, it is a good idea to 226use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 227details. Starting with version 0.9.7, OpenSSL will automatically look 228for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 229/etc/entropy. 230 231Most components of the openssl command line utility automatically try 232to seed the random number generator from a file. The name of the 233default seeding file is determined as follows: If environment variable 234RANDFILE is set, then it names the seeding file. Otherwise if 235environment variable HOME is set, then the seeding file is $HOME/.rnd. 236If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 237use file .rnd in the current directory while OpenSSL 0.9.6a uses no 238default seeding file at all. OpenSSL 0.9.6b and later will behave 239similarly to 0.9.6a, but will use a default of "C:\" for HOME on 240Windows systems if the environment variable has not been set. 241 242If the default seeding file does not exist or is too short, the "PRNG 243not seeded" error message may occur. 244 245The openssl command line utility will write back a new state to the 246default seeding file (and create this file if necessary) unless 247there was no sufficient seeding. 248 249Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 250Use the "-rand" option of the OpenSSL command line tools instead. 251The $RANDFILE environment variable and $HOME/.rnd are only used by the 252OpenSSL command line tools. Applications using the OpenSSL library 253provide their own configuration options to specify the entropy source, 254please check out the documentation coming the with application. 255 256 257* Why do I get an "unable to write 'random state'" error message? 258 259 260Sometimes the openssl command line utility does not abort with 261a "PRNG not seeded" error message, but complains that it is 262"unable to write 'random state'". This message refers to the 263default seeding file (see previous answer). A possible reason 264is that no default filename is known because neither RANDFILE 265nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 266current directory in this case, but this has changed with 0.9.6a.) 267 268 269* How do I create certificates or certificate requests? 270 271Check out the CA.pl(1) manual page. This provides a simple wrapper round 272the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 273out the manual pages for the individual utilities and the certificate 274extensions documentation (currently in doc/openssl.txt). 275 276 277* Why can't I create certificate requests? 278 279You typically get the error: 280 281 unable to find 'distinguished_name' in config 282 problems making Certificate Request 283 284This is because it can't find the configuration file. Check out the 285DIAGNOSTICS section of req(1) for more information. 286 287 288* Why does <SSL program> fail with a certificate verify error? 289 290This problem is usually indicated by log messages saying something like 291"unable to get local issuer certificate" or "self signed certificate". 292When a certificate is verified its root CA must be "trusted" by OpenSSL 293this typically means that the CA certificate must be placed in a directory 294or file and the relevant program configured to read it. The OpenSSL program 295'verify' behaves in a similar way and issues similar error messages: check 296the verify(1) program manual page for more information. 297 298 299* Why can I only use weak ciphers when I connect to a server using OpenSSL? 300 301This is almost certainly because you are using an old "export grade" browser 302which only supports weak encryption. Upgrade your browser to support 128 bit 303ciphers. 304 305 306* How can I create DSA certificates? 307 308Check the CA.pl(1) manual page for a DSA certificate example. 309 310 311* Why can't I make an SSL connection to a server using a DSA certificate? 312 313Typically you'll see a message saying there are no shared ciphers when 314the same setup works fine with an RSA certificate. There are two possible 315causes. The client may not support connections to DSA servers most web 316browsers (including Netscape and MSIE) only support connections to servers 317supporting RSA cipher suites. The other cause is that a set of DH parameters 318has not been supplied to the server. DH parameters can be created with the 319dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 320check the source to s_server in apps/s_server.c for an example. 321 322 323* How can I remove the passphrase on a private key? 324 325Firstly you should be really *really* sure you want to do this. Leaving 326a private key unencrypted is a major security risk. If you decide that 327you do have to do this check the EXAMPLES sections of the rsa(1) and 328dsa(1) manual pages. 329 330 331* Why can't I use OpenSSL certificates with SSL client authentication? 332 333What will typically happen is that when a server requests authentication 334it will either not include your certificate or tell you that you have 335no client certificates (Netscape) or present you with an empty list box 336(MSIE). The reason for this is that when a server requests a client 337certificate it includes a list of CAs names which it will accept. Browsers 338will only let you select certificates from the list on the grounds that 339there is little point presenting a certificate which the server will 340reject. 341 342The solution is to add the relevant CA certificate to your servers "trusted 343CA list". How you do this depends on the server software in uses. You can 344print out the servers list of acceptable CAs using the OpenSSL s_client tool: 345 346openssl s_client -connect www.some.host:443 -prexit 347 348If your server only requests certificates on certain URLs then you may need 349to manually issue an HTTP GET command to get the list when s_client connects: 350 351GET /some/page/needing/a/certificate.html 352 353If your CA does not appear in the list then this confirms the problem. 354 355 356* Why does my browser give a warning about a mismatched hostname? 357 358Browsers expect the server's hostname to match the value in the commonName 359(CN) field of the certificate. If it does not then you get a warning. 360 361 362* How do I install a CA certificate into a browser? 363 364The usual way is to send the DER encoded certificate to the browser as 365MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 366link. On MSIE certain extensions such as .der or .cacert may also work, or you 367can import the certificate using the certificate import wizard. 368 369You can convert a certificate to DER form using the command: 370 371openssl x509 -in ca.pem -outform DER -out ca.der 372 373Occasionally someone suggests using a command such as: 374 375openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 376 377DO NOT DO THIS! This command will give away your CAs private key and 378reduces its security to zero: allowing anyone to forge certificates in 379whatever name they choose. 380 381* Why is OpenSSL x509 DN output not conformant to RFC2253? 382 383The ways to print out the oneline format of the DN (Distinguished Name) have 384been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 385interface, the "-nameopt" option could be introduded. See the manual 386page of the "openssl x509" commandline tool for details. The old behaviour 387has however been left as default for the sake of compatibility. 388 389[BUILD] ======================================================================= 390 391* Why does the linker complain about undefined symbols? 392 393Maybe the compilation was interrupted, and make doesn't notice that 394something is missing. Run "make clean; make". 395 396If you used ./Configure instead of ./config, make sure that you 397selected the right target. File formats may differ slightly between 398OS versions (for example sparcv8/sparcv9, or a.out/elf). 399 400In case you get errors about the following symbols, use the config 401option "no-asm", as described in INSTALL: 402 403 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 404 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 405 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 406 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 407 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 408 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 409 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 410 411If none of these helps, you may want to try using the current snapshot. 412If the problem persists, please submit a bug report. 413 414 415* Why does the OpenSSL test fail with "bc: command not found"? 416 417You didn't install "bc", the Unix calculator. If you want to run the 418tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 419 420 421* Why does the OpenSSL test fail with "bc: 1 no implemented"? 422 423On some SCO installations or versions, bc has a bug that gets triggered 424when you run the test suite (using "make test"). The message returned is 425"bc: 1 not implemented". 426 427The best way to deal with this is to find another implementation of bc 428and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 429for download instructions) can be safely used, for example. 430 431 432* Why does the OpenSSL test fail with "bc: stack empty"? 433 434On some DG/ux versions, bc seems to have a too small stack for calculations 435that the OpenSSL bntest throws at it. This gets triggered when you run the 436test suite (using "make test"). The message returned is "bc: stack empty". 437 438The best way to deal with this is to find another implementation of bc 439and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 440for download instructions) can be safely used, for example. 441 442 443* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 444 445On some Alpha installations running Tru64 Unix and Compaq C, the compilation 446of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 447memory to continue compilation.' As far as the tests have shown, this may be 448a compiler bug. What happens is that it eats up a lot of resident memory 449to build something, probably a table. The problem is clearly in the 450optimization code, because if one eliminates optimization completely (-O0), 451the compilation goes through (and the compiler consumes about 2MB of resident 452memory instead of 240MB or whatever one's limit is currently). 453 454There are three options to solve this problem: 455 4561. set your current data segment size soft limit higher. Experience shows 457that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 458this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 459kbytes to set the limit to. 460 4612. If you have a hard limit that is lower than what you need and you can't 462get it changed, you can compile all of OpenSSL with -O0 as optimization 463level. This is however not a very nice thing to do for those who expect to 464get the best result from OpenSSL. A bit more complicated solution is the 465following: 466 467----- snip:start ----- 468 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 469 sed -e 's/ -O[0-9] / -O0 /'`" 470 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 471 make 472----- snip:end ----- 473 474This will only compile sha_dgst.c with -O0, the rest with the optimization 475level chosen by the configuration process. When the above is done, do the 476test and installation and you're set. 477 4783. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 479should not be used and is not used in SSL/TLS nor any other recognized 480protocol in either case. 481 482 483* Why does the OpenSSL compilation fail with "ar: command not found"? 484 485Getting this message is quite usual on Solaris 2, because Sun has hidden 486away 'ar' and other development commands in directories that aren't in 487$PATH by default. One of those directories is '/usr/ccs/bin'. The 488quickest way to fix this is to do the following (it assumes you use sh 489or any sh-compatible shell): 490 491----- snip:start ----- 492 PATH=${PATH}:/usr/ccs/bin; export PATH 493----- snip:end ----- 494 495and then redo the compilation. What you should really do is make sure 496'/usr/ccs/bin' is permanently in your $PATH, for example through your 497'.profile' (again, assuming you use a sh-compatible shell). 498 499 500* Why does the OpenSSL compilation fail on Win32 with VC++? 501 502Sometimes, you may get reports from VC++ command line (cl) that it 503can't find standard include files like stdio.h and other weirdnesses. 504One possible cause is that the environment isn't correctly set up. 505To solve that problem for VC++ versions up to 6, one should run 506VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 507installation directory (somewhere under 'Program Files'). For VC++ 508version 7 (and up?), which is also called VS.NET, the file is called 509VSVARS32.BAT instead. 510This needs to be done prior to running NMAKE, and the changes are only 511valid for the current DOS session. 512 513 514* What is special about OpenSSL on Redhat? 515 516Red Hat Linux (release 7.0 and later) include a preinstalled limited 517version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 518is disabled in this version. The same may apply to other Linux distributions. 519Users may therefore wish to install more or all of the features left out. 520 521To do this you MUST ensure that you do not overwrite the openssl that is in 522/usr/bin on your Red Hat machine. Several packages depend on this file, 523including sendmail and ssh. /usr/local/bin is a good alternative choice. The 524libraries that come with Red Hat 7.0 onwards have different names and so are 525not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 526/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 527/lib/libcrypto.so.2 respectively). 528 529Please note that we have been advised by Red Hat attempting to recompile the 530openssl rpm with all the cryptography enabled will not work. All other 531packages depend on the original Red Hat supplied openssl package. It is also 532worth noting that due to the way Red Hat supplies its packages, updates to 533openssl on each distribution never change the package version, only the 534build number. For example, on Red Hat 7.1, the latest openssl package has 535version number 0.9.6 and build number 9 even though it contains all the 536relevant updates in packages up to and including 0.9.6b. 537 538A possible way around this is to persuade Red Hat to produce a non-US 539version of Red Hat Linux. 540 541FYI: Patent numbers and expiry dates of US patents: 542MDC-2: 4,908,861 13/03/2007 543IDEA: 5,214,703 25/05/2010 544RC5: 5,724,428 03/03/2015 545 546 547* Why does the OpenSSL compilation fail on MacOS X? 548 549If the failure happens when trying to build the "openssl" binary, with 550a large number of undefined symbols, it's very probable that you have 551OpenSSL 0.9.6b delivered with the operating system (you can find out by 552running '/usr/bin/openssl version') and that you were trying to build 553OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 554MacOS X has a misfeature that's quite difficult to go around. 555Look in the file PROBLEMS for a more detailed explanation and for possible 556solutions. 557 558 559* Why does the OpenSSL test suite fail on MacOS X? 560 561If the failure happens when running 'make test' and the RC4 test fails, 562it's very probable that you have OpenSSL 0.9.6b delivered with the 563operating system (you can find out by running '/usr/bin/openssl version') 564and that you were trying to build OpenSSL 0.9.6d. The problem is that 565the loader ('ld') in MacOS X has a misfeature that's quite difficult to 566go around and has linked the programs "openssl" and the test programs 567with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 568libraries you just built. 569Look in the file PROBLEMS for a more detailed explanation and for possible 570solutions. 571 572* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 573 574Failure in BN_sqr test is most likely caused by a failure to configure the 575toolkit for current platform or lack of support for the platform in question. 576Run './config -t' and './apps/openssl version -p'. Do these platform 577identifiers match? If they don't, then you most likely failed to run 578./config and you're hereby advised to do so before filing a bug report. 579If ./config itself fails to run, then it's most likely problem with your 580local environment and you should turn to your system administrator (or 581similar). If identifiers match (and/or no alternative identifier is 582suggested by ./config script), then the platform is unsupported. There might 583or might not be a workaround. Most notably on SPARC64 platforms with GNU 584C compiler you should be able to produce a working build by running 585'./config -m32'. I understand that -m32 might not be what you want/need, 586but the build should be operational. For further details turn to 587<openssl-dev@openssl.org>. 588 589* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 590 591As of 0.9.7 assembler routines were overhauled for position independence 592of the machine code, which is essential for shared library support. For 593some reason OpenBSD is equipped with an out-of-date GNU assembler which 594finds the new code offensive. To work around the problem, configure with 595no-asm (and sacrifice a great deal of performance) or patch your assembler 596according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 597For your convenience a pre-compiled replacement binary is provided at 598<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 599Reportedly elder *BSD a.out platforms also suffer from this problem and 600remedy should be same. Provided binary is statically linked and should be 601working across wider range of *BSD branches, not just OpenBSD. 602 603* Why does the OpenSSL test suite fail in sha512t on x86 CPU? 604 605If the test program in question fails withs SIGILL, Illegal Instruction 606exception, then you more than likely to run SSE2-capable CPU, such as 607Intel P4, under control of kernel which does not support SSE2 608instruction extentions. See accompanying INSTALL file and 609OPENSSL_ia32cap(3) documentation page for further information. 610 611* Why does compiler fail to compile sha512.c? 612 613OpenSSL SHA-512 implementation depends on compiler support for 64-bit 614integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a 615couple] lack support for this and therefore are incapable of compiling 616the module in question. The recommendation is to disable SHA-512 by 617adding no-sha512 to ./config [or ./Configure] command line. Another 618possible alternative might be to switch to GCC. 619 620[PROG] ======================================================================== 621 622* Is OpenSSL thread-safe? 623 624Yes (with limitations: an SSL connection may not concurrently be used 625by multiple threads). On Windows and many Unix systems, OpenSSL 626automatically uses the multi-threaded versions of the standard 627libraries. If your platform is not one of these, consult the INSTALL 628file. 629 630Multi-threaded applications must provide two callback functions to 631OpenSSL. This is described in the threads(3) manpage. 632 633 634* I've compiled a program under Windows and it crashes: why? 635 636This is usually because you've missed the comment in INSTALL.W32. 637Your application must link against the same version of the Win32 638C-Runtime against which your openssl libraries were linked. The 639default version for OpenSSL is /MD - "Multithreaded DLL". 640 641If you are using Microsoft Visual C++'s IDE (Visual Studio), in 642many cases, your new project most likely defaulted to "Debug 643Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 644program will crash, typically on the first BIO related read or write 645operation. 646 647For each of the six possible link stage configurations within Win32, 648your application must link against the same by which OpenSSL was 649built. If you are using MS Visual C++ (Studio) this can be changed 650by: 651 6521. Select Settings... from the Project Menu. 6532. Select the C/C++ Tab. 6543. Select "Code Generation from the "Category" drop down list box 6554. Select the Appropriate library (see table below) from the "Use 656 run-time library" drop down list box. Perform this step for both 657 your debug and release versions of your application (look at the 658 top left of the settings panel to change between the two) 659 660 Single Threaded /ML - MS VC++ often defaults to 661 this for the release 662 version of a new project. 663 Debug Single Threaded /MLd - MS VC++ often defaults to 664 this for the debug version 665 of a new project. 666 Multithreaded /MT 667 Debug Multithreaded /MTd 668 Multithreaded DLL /MD - OpenSSL defaults to this. 669 Debug Multithreaded DLL /MDd 670 671Note that debug and release libraries are NOT interchangeable. If you 672built OpenSSL with /MD your application must use /MD and cannot use /MDd. 673 674As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL 675.DLLs compiled with some specific run-time option [we recommend the 676default /MD] can be deployed with application compiled with different 677option or even different compiler. But there is a catch! Instead of 678re-compiling OpenSSL toolkit, as you would have to with prior versions, 679you have to compile small C snippet with compiler and/or options of 680your choice. The snippet gets installed as 681<install-root>/include/openssl/applink.c and should be either added to 682your project or simply #include-d in one [and only one] of your source 683files. Failure to do either manifests itself as fatal "no 684OPENSSL_Applink" error. 685 686* How do I read or write a DER encoded buffer using the ASN1 functions? 687 688You have two options. You can either use a memory BIO in conjunction 689with the i2d_*_bio() or d2i_*_bio() functions or you can use the 690i2d_*(), d2i_*() functions directly. Since these are often the 691cause of grief here are some code fragments using PKCS7 as an example: 692 693 unsigned char *buf, *p; 694 int len; 695 696 len = i2d_PKCS7(p7, NULL); 697 buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 698 p = buf; 699 i2d_PKCS7(p7, &p); 700 701At this point buf contains the len bytes of the DER encoding of 702p7. 703 704The opposite assumes we already have len bytes in buf: 705 706 unsigned char *p; 707 p = buf; 708 p7 = d2i_PKCS7(NULL, &p, len); 709 710At this point p7 contains a valid PKCS7 structure of NULL if an error 711occurred. If an error occurred ERR_print_errors(bio) should give more 712information. 713 714The reason for the temporary variable 'p' is that the ASN1 functions 715increment the passed pointer so it is ready to read or write the next 716structure. This is often a cause of problems: without the temporary 717variable the buffer pointer is changed to point just after the data 718that has been read or written. This may well be uninitialized data 719and attempts to free the buffer will have unpredictable results 720because it no longer points to the same address. 721 722 723* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 724 725The short answer is yes, because DER is a special case of BER and OpenSSL 726ASN1 decoders can process BER. 727 728The longer answer is that ASN1 structures can be encoded in a number of 729different ways. One set of ways is the Basic Encoding Rules (BER) with various 730permissible encodings. A restriction of BER is the Distinguished Encoding 731Rules (DER): these uniquely specify how a given structure is encoded. 732 733Therefore, because DER is a special case of BER, DER is an acceptable encoding 734for BER. 735 736 737* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 738 739This usually happens when you try compiling something using the PKCS#12 740macros with a C++ compiler. There is hardly ever any need to use the 741PKCS#12 macros in a program, it is much easier to parse and create 742PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 743documented in doc/openssl.txt and with examples in demos/pkcs12. The 744'pkcs12' application has to use the macros because it prints out 745debugging information. 746 747 748* I've called <some function> and it fails, why? 749 750Before submitting a report or asking in one of the mailing lists, you 751should try to determine the cause. In particular, you should call 752ERR_print_errors() or ERR_print_errors_fp() after the failed call 753and see if the message helps. Note that the problem may occur earlier 754than you think -- you should check for errors after every call where 755it is possible, otherwise the actual problem may be hidden because 756some OpenSSL functions clear the error state. 757 758 759* I just get a load of numbers for the error output, what do they mean? 760 761The actual format is described in the ERR_print_errors() manual page. 762You should call the function ERR_load_crypto_strings() before hand and 763the message will be output in text form. If you can't do this (for example 764it is a pre-compiled binary) you can use the errstr utility on the error 765code itself (the hex digits after the second colon). 766 767 768* Why do I get errors about unknown algorithms? 769 770This can happen under several circumstances such as reading in an 771encrypted private key or attempting to decrypt a PKCS#12 file. The cause 772is forgetting to load OpenSSL's table of algorithms with 773OpenSSL_add_all_algorithms(). See the manual page for more information. 774 775 776* Why can't the OpenSSH configure script detect OpenSSL? 777 778Several reasons for problems with the automatic detection exist. 779OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 780Sometimes the distribution has installed an older version in the system 781locations that is detected instead of a new one installed. The OpenSSL 782library might have been compiled for another CPU or another mode (32/64 bits). 783Permissions might be wrong. 784 785The general answer is to check the config.log file generated when running 786the OpenSSH configure script. It should contain the detailed information 787on why the OpenSSL library was not detected or considered incompatible. 788 789 790* Can I use OpenSSL's SSL library with non-blocking I/O? 791 792Yes; make sure to read the SSL_get_error(3) manual page! 793 794A pitfall to avoid: Don't assume that SSL_read() will just read from 795the underlying transport or that SSL_write() will just write to it -- 796it is also possible that SSL_write() cannot do any useful work until 797there is data to read, or that SSL_read() cannot do anything until it 798is possible to send data. One reason for this is that the peer may 799request a new TLS/SSL handshake at any time during the protocol, 800requiring a bi-directional message exchange; both SSL_read() and 801SSL_write() will try to continue any pending handshake. 802 803 804* Why doesn't my server application receive a client certificate? 805 806Due to the TLS protocol definition, a client will only send a certificate, 807if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 808SSL_CTX_set_verify() function to enable the use of client certificates. 809 810 811* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 812 813For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 814versions, uniqueIdentifier was incorrectly used for X.509 certificates. 815The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 816Change your code to use the new name when compiling against OpenSSL 0.9.7. 817 818 819* I think I've detected a memory leak, is this a bug? 820 821In most cases the cause of an apparent memory leak is an OpenSSL internal table 822that is allocated when an application starts up. Since such tables do not grow 823in size over time they are harmless. 824 825These internal tables can be freed up when an application closes using various 826functions. Currently these include following: 827 828Thread-local cleanup functions: 829 830 ERR_remove_state() 831 832Application-global cleanup functions that are aware of usage (and therefore 833thread-safe): 834 835 ENGINE_cleanup() and CONF_modules_unload() 836 837"Brutal" (thread-unsafe) Application-global cleanup functions: 838 839 ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). 840 841 842=============================================================================== 843 844