FAQ revision 142425
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 50[PROG] Questions about programming with OpenSSL 51 52* Is OpenSSL thread-safe? 53* I've compiled a program under Windows and it crashes: why? 54* How do I read or write a DER encoded buffer using the ASN1 functions? 55* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 56* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 57* I've called <some function> and it fails, why? 58* I just get a load of numbers for the error output, what do they mean? 59* Why do I get errors about unknown algorithms? 60* Why can't the OpenSSH configure script detect OpenSSL? 61* Can I use OpenSSL's SSL library with non-blocking I/O? 62* Why doesn't my server application receive a client certificate? 63* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 64* I think I've detected a memory leak, is this a bug? 65 66=============================================================================== 67 68[MISC] ======================================================================== 69 70* Which is the current version of OpenSSL? 71 72The current version is available from <URL: http://www.openssl.org>. 73OpenSSL 0.9.7e was released on October 25, 2004. 74 75In addition to the current stable release, you can also access daily 76snapshots of the OpenSSL development version at <URL: 77ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 78 79 80* Where is the documentation? 81 82OpenSSL is a library that provides cryptographic functionality to 83applications such as secure web servers. Be sure to read the 84documentation of the application you want to use. The INSTALL file 85explains how to install this library. 86 87OpenSSL includes a command line utility that can be used to perform a 88variety of cryptographic functions. It is described in the openssl(1) 89manpage. Documentation for developers is currently being written. A 90few manual pages already are available; overviews over libcrypto and 91libssl are given in the crypto(3) and ssl(3) manpages. 92 93The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 94different directory if you specified one as described in INSTALL). 95In addition, you can read the most current versions at 96<URL: http://www.openssl.org/docs/>. 97 98For information on parts of libcrypto that are not yet documented, you 99might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 100predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 101of this still applies to OpenSSL. 102 103There is some documentation about certificate extensions and PKCS#12 104in doc/openssl.txt 105 106The original SSLeay documentation is included in OpenSSL as 107doc/ssleay.txt. It may be useful when none of the other resources 108help, but please note that it reflects the obsolete version SSLeay 1090.6.6. 110 111 112* How can I contact the OpenSSL developers? 113 114The README file describes how to submit bug reports and patches to 115OpenSSL. Information on the OpenSSL mailing lists is available from 116<URL: http://www.openssl.org>. 117 118 119* Where can I get a compiled version of OpenSSL? 120 121You can finder pointers to binary distributions in 122http://www.openssl.org/related/binaries.html . 123 124Some applications that use OpenSSL are distributed in binary form. 125When using such an application, you don't need to install OpenSSL 126yourself; the application will include the required parts (e.g. DLLs). 127 128If you want to build OpenSSL on a Windows system and you don't have 129a C compiler, read the "Mingw32" section of INSTALL.W32 for information 130on how to obtain and install the free GNU C compiler. 131 132A number of Linux and *BSD distributions include OpenSSL. 133 134 135* Why aren't tools like 'autoconf' and 'libtool' used? 136 137autoconf will probably be used in future OpenSSL versions. If it was 138less Unix-centric, it might have been used much earlier. 139 140* What is an 'engine' version? 141 142With version 0.9.6 OpenSSL was extended to interface to external crypto 143hardware. This was realized in a special release '0.9.6-engine'. With 144version 0.9.7 (not yet released) the changes were merged into the main 145development line, so that the special release is no longer necessary. 146 147* How do I check the authenticity of the OpenSSL distribution? 148 149We provide MD5 digests and ASC signatures of each tarball. 150Use MD5 to check that a tarball from a mirror site is identical: 151 152 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 153 154You can check authenticity using pgp or gpg. You need the OpenSSL team 155member public key used to sign it (download it from a key server). Then 156just do: 157 158 pgp TARBALL.asc 159 160[LEGAL] ======================================================================= 161 162* Do I need patent licenses to use OpenSSL? 163 164The patents section of the README file lists patents that may apply to 165you if you want to use OpenSSL. For information on intellectual 166property rights, please consult a lawyer. The OpenSSL team does not 167offer legal advice. 168 169You can configure OpenSSL so as not to use RC5 and IDEA by using 170 ./config no-rc5 no-idea 171 172 173* Can I use OpenSSL with GPL software? 174 175On many systems including the major Linux and BSD distributions, yes (the 176GPL does not place restrictions on using libraries that are part of the 177normal operating system distribution). 178 179On other systems, the situation is less clear. Some GPL software copyright 180holders claim that you infringe on their rights if you use OpenSSL with 181their software on operating systems that don't normally include OpenSSL. 182 183If you develop open source software that uses OpenSSL, you may find it 184useful to choose an other license than the GPL, or state explicitly that 185"This program is released under the GPL with the additional exemption that 186compiling, linking, and/or using OpenSSL is allowed." If you are using 187GPL software developed by others, you may want to ask the copyright holder 188for permission to use their software with OpenSSL. 189 190 191[USER] ======================================================================== 192 193* Why do I get a "PRNG not seeded" error message? 194 195Cryptographic software needs a source of unpredictable data to work 196correctly. Many open source operating systems provide a "randomness 197device" (/dev/urandom or /dev/random) that serves this purpose. 198All OpenSSL versions try to use /dev/urandom by default; starting with 199version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 200available. 201 202On other systems, applications have to call the RAND_add() or 203RAND_seed() function with appropriate data before generating keys or 204performing public key encryption. (These functions initialize the 205pseudo-random number generator, PRNG.) Some broken applications do 206not do this. As of version 0.9.5, the OpenSSL functions that need 207randomness report an error if the random number generator has not been 208seeded with at least 128 bits of randomness. If this error occurs and 209is not discussed in the documentation of the application you are 210using, please contact the author of that application; it is likely 211that it never worked correctly. OpenSSL 0.9.5 and later make the 212error visible by refusing to perform potentially insecure encryption. 213 214If you are using Solaris 8, you can add /dev/urandom and /dev/random 215devices by installing patch 112438 (Sparc) or 112439 (x86), which are 216available via the Patchfinder at <URL: http://sunsolve.sun.com> 217(Solaris 9 includes these devices by default). For /dev/random support 218for earlier Solaris versions, see Sun's statement at 219<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 220(the SUNWski package is available in patch 105710). 221 222On systems without /dev/urandom and /dev/random, it is a good idea to 223use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 224details. Starting with version 0.9.7, OpenSSL will automatically look 225for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 226/etc/entropy. 227 228Most components of the openssl command line utility automatically try 229to seed the random number generator from a file. The name of the 230default seeding file is determined as follows: If environment variable 231RANDFILE is set, then it names the seeding file. Otherwise if 232environment variable HOME is set, then the seeding file is $HOME/.rnd. 233If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 234use file .rnd in the current directory while OpenSSL 0.9.6a uses no 235default seeding file at all. OpenSSL 0.9.6b and later will behave 236similarly to 0.9.6a, but will use a default of "C:\" for HOME on 237Windows systems if the environment variable has not been set. 238 239If the default seeding file does not exist or is too short, the "PRNG 240not seeded" error message may occur. 241 242The openssl command line utility will write back a new state to the 243default seeding file (and create this file if necessary) unless 244there was no sufficient seeding. 245 246Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 247Use the "-rand" option of the OpenSSL command line tools instead. 248The $RANDFILE environment variable and $HOME/.rnd are only used by the 249OpenSSL command line tools. Applications using the OpenSSL library 250provide their own configuration options to specify the entropy source, 251please check out the documentation coming the with application. 252 253 254* Why do I get an "unable to write 'random state'" error message? 255 256 257Sometimes the openssl command line utility does not abort with 258a "PRNG not seeded" error message, but complains that it is 259"unable to write 'random state'". This message refers to the 260default seeding file (see previous answer). A possible reason 261is that no default filename is known because neither RANDFILE 262nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 263current directory in this case, but this has changed with 0.9.6a.) 264 265 266* How do I create certificates or certificate requests? 267 268Check out the CA.pl(1) manual page. This provides a simple wrapper round 269the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 270out the manual pages for the individual utilities and the certificate 271extensions documentation (currently in doc/openssl.txt). 272 273 274* Why can't I create certificate requests? 275 276You typically get the error: 277 278 unable to find 'distinguished_name' in config 279 problems making Certificate Request 280 281This is because it can't find the configuration file. Check out the 282DIAGNOSTICS section of req(1) for more information. 283 284 285* Why does <SSL program> fail with a certificate verify error? 286 287This problem is usually indicated by log messages saying something like 288"unable to get local issuer certificate" or "self signed certificate". 289When a certificate is verified its root CA must be "trusted" by OpenSSL 290this typically means that the CA certificate must be placed in a directory 291or file and the relevant program configured to read it. The OpenSSL program 292'verify' behaves in a similar way and issues similar error messages: check 293the verify(1) program manual page for more information. 294 295 296* Why can I only use weak ciphers when I connect to a server using OpenSSL? 297 298This is almost certainly because you are using an old "export grade" browser 299which only supports weak encryption. Upgrade your browser to support 128 bit 300ciphers. 301 302 303* How can I create DSA certificates? 304 305Check the CA.pl(1) manual page for a DSA certificate example. 306 307 308* Why can't I make an SSL connection to a server using a DSA certificate? 309 310Typically you'll see a message saying there are no shared ciphers when 311the same setup works fine with an RSA certificate. There are two possible 312causes. The client may not support connections to DSA servers most web 313browsers (including Netscape and MSIE) only support connections to servers 314supporting RSA cipher suites. The other cause is that a set of DH parameters 315has not been supplied to the server. DH parameters can be created with the 316dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 317check the source to s_server in apps/s_server.c for an example. 318 319 320* How can I remove the passphrase on a private key? 321 322Firstly you should be really *really* sure you want to do this. Leaving 323a private key unencrypted is a major security risk. If you decide that 324you do have to do this check the EXAMPLES sections of the rsa(1) and 325dsa(1) manual pages. 326 327 328* Why can't I use OpenSSL certificates with SSL client authentication? 329 330What will typically happen is that when a server requests authentication 331it will either not include your certificate or tell you that you have 332no client certificates (Netscape) or present you with an empty list box 333(MSIE). The reason for this is that when a server requests a client 334certificate it includes a list of CAs names which it will accept. Browsers 335will only let you select certificates from the list on the grounds that 336there is little point presenting a certificate which the server will 337reject. 338 339The solution is to add the relevant CA certificate to your servers "trusted 340CA list". How you do this depends on the server software in uses. You can 341print out the servers list of acceptable CAs using the OpenSSL s_client tool: 342 343openssl s_client -connect www.some.host:443 -prexit 344 345If your server only requests certificates on certain URLs then you may need 346to manually issue an HTTP GET command to get the list when s_client connects: 347 348GET /some/page/needing/a/certificate.html 349 350If your CA does not appear in the list then this confirms the problem. 351 352 353* Why does my browser give a warning about a mismatched hostname? 354 355Browsers expect the server's hostname to match the value in the commonName 356(CN) field of the certificate. If it does not then you get a warning. 357 358 359* How do I install a CA certificate into a browser? 360 361The usual way is to send the DER encoded certificate to the browser as 362MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 363link. On MSIE certain extensions such as .der or .cacert may also work, or you 364can import the certificate using the certificate import wizard. 365 366You can convert a certificate to DER form using the command: 367 368openssl x509 -in ca.pem -outform DER -out ca.der 369 370Occasionally someone suggests using a command such as: 371 372openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 373 374DO NOT DO THIS! This command will give away your CAs private key and 375reduces its security to zero: allowing anyone to forge certificates in 376whatever name they choose. 377 378* Why is OpenSSL x509 DN output not conformant to RFC2253? 379 380The ways to print out the oneline format of the DN (Distinguished Name) have 381been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 382interface, the "-nameopt" option could be introduded. See the manual 383page of the "openssl x509" commandline tool for details. The old behaviour 384has however been left as default for the sake of compatibility. 385 386[BUILD] ======================================================================= 387 388* Why does the linker complain about undefined symbols? 389 390Maybe the compilation was interrupted, and make doesn't notice that 391something is missing. Run "make clean; make". 392 393If you used ./Configure instead of ./config, make sure that you 394selected the right target. File formats may differ slightly between 395OS versions (for example sparcv8/sparcv9, or a.out/elf). 396 397In case you get errors about the following symbols, use the config 398option "no-asm", as described in INSTALL: 399 400 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 401 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 402 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 403 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 404 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 405 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 406 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 407 408If none of these helps, you may want to try using the current snapshot. 409If the problem persists, please submit a bug report. 410 411 412* Why does the OpenSSL test fail with "bc: command not found"? 413 414You didn't install "bc", the Unix calculator. If you want to run the 415tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 416 417 418* Why does the OpenSSL test fail with "bc: 1 no implemented"? 419 420On some SCO installations or versions, bc has a bug that gets triggered 421when you run the test suite (using "make test"). The message returned is 422"bc: 1 not implemented". 423 424The best way to deal with this is to find another implementation of bc 425and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 426for download instructions) can be safely used, for example. 427 428 429* Why does the OpenSSL test fail with "bc: stack empty"? 430 431On some DG/ux versions, bc seems to have a too small stack for calculations 432that the OpenSSL bntest throws at it. This gets triggered when you run the 433test suite (using "make test"). The message returned is "bc: stack empty". 434 435The best way to deal with this is to find another implementation of bc 436and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 437for download instructions) can be safely used, for example. 438 439 440* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 441 442On some Alpha installations running Tru64 Unix and Compaq C, the compilation 443of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 444memory to continue compilation.' As far as the tests have shown, this may be 445a compiler bug. What happens is that it eats up a lot of resident memory 446to build something, probably a table. The problem is clearly in the 447optimization code, because if one eliminates optimization completely (-O0), 448the compilation goes through (and the compiler consumes about 2MB of resident 449memory instead of 240MB or whatever one's limit is currently). 450 451There are three options to solve this problem: 452 4531. set your current data segment size soft limit higher. Experience shows 454that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 455this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 456kbytes to set the limit to. 457 4582. If you have a hard limit that is lower than what you need and you can't 459get it changed, you can compile all of OpenSSL with -O0 as optimization 460level. This is however not a very nice thing to do for those who expect to 461get the best result from OpenSSL. A bit more complicated solution is the 462following: 463 464----- snip:start ----- 465 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile | \ 466 sed -e 's/ -O[0-9] / -O0 /'`" 467 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 468 make 469----- snip:end ----- 470 471This will only compile sha_dgst.c with -O0, the rest with the optimization 472level chosen by the configuration process. When the above is done, do the 473test and installation and you're set. 474 475 476* Why does the OpenSSL compilation fail with "ar: command not found"? 477 478Getting this message is quite usual on Solaris 2, because Sun has hidden 479away 'ar' and other development commands in directories that aren't in 480$PATH by default. One of those directories is '/usr/ccs/bin'. The 481quickest way to fix this is to do the following (it assumes you use sh 482or any sh-compatible shell): 483 484----- snip:start ----- 485 PATH=${PATH}:/usr/ccs/bin; export PATH 486----- snip:end ----- 487 488and then redo the compilation. What you should really do is make sure 489'/usr/ccs/bin' is permanently in your $PATH, for example through your 490'.profile' (again, assuming you use a sh-compatible shell). 491 492 493* Why does the OpenSSL compilation fail on Win32 with VC++? 494 495Sometimes, you may get reports from VC++ command line (cl) that it 496can't find standard include files like stdio.h and other weirdnesses. 497One possible cause is that the environment isn't correctly set up. 498To solve that problem for VC++ versions up to 6, one should run 499VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 500installation directory (somewhere under 'Program Files'). For VC++ 501version 7 (and up?), which is also called VS.NET, the file is called 502VSVARS32.BAT instead. 503This needs to be done prior to running NMAKE, and the changes are only 504valid for the current DOS session. 505 506 507* What is special about OpenSSL on Redhat? 508 509Red Hat Linux (release 7.0 and later) include a preinstalled limited 510version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 511is disabled in this version. The same may apply to other Linux distributions. 512Users may therefore wish to install more or all of the features left out. 513 514To do this you MUST ensure that you do not overwrite the openssl that is in 515/usr/bin on your Red Hat machine. Several packages depend on this file, 516including sendmail and ssh. /usr/local/bin is a good alternative choice. The 517libraries that come with Red Hat 7.0 onwards have different names and so are 518not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 519/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 520/lib/libcrypto.so.2 respectively). 521 522Please note that we have been advised by Red Hat attempting to recompile the 523openssl rpm with all the cryptography enabled will not work. All other 524packages depend on the original Red Hat supplied openssl package. It is also 525worth noting that due to the way Red Hat supplies its packages, updates to 526openssl on each distribution never change the package version, only the 527build number. For example, on Red Hat 7.1, the latest openssl package has 528version number 0.9.6 and build number 9 even though it contains all the 529relevant updates in packages up to and including 0.9.6b. 530 531A possible way around this is to persuade Red Hat to produce a non-US 532version of Red Hat Linux. 533 534FYI: Patent numbers and expiry dates of US patents: 535MDC-2: 4,908,861 13/03/2007 536IDEA: 5,214,703 25/05/2010 537RC5: 5,724,428 03/03/2015 538 539 540* Why does the OpenSSL compilation fail on MacOS X? 541 542If the failure happens when trying to build the "openssl" binary, with 543a large number of undefined symbols, it's very probable that you have 544OpenSSL 0.9.6b delivered with the operating system (you can find out by 545running '/usr/bin/openssl version') and that you were trying to build 546OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 547MacOS X has a misfeature that's quite difficult to go around. 548Look in the file PROBLEMS for a more detailed explanation and for possible 549solutions. 550 551 552* Why does the OpenSSL test suite fail on MacOS X? 553 554If the failure happens when running 'make test' and the RC4 test fails, 555it's very probable that you have OpenSSL 0.9.6b delivered with the 556operating system (you can find out by running '/usr/bin/openssl version') 557and that you were trying to build OpenSSL 0.9.6d. The problem is that 558the loader ('ld') in MacOS X has a misfeature that's quite difficult to 559go around and has linked the programs "openssl" and the test programs 560with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 561libraries you just built. 562Look in the file PROBLEMS for a more detailed explanation and for possible 563solutions. 564 565* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 566 567Failure in BN_sqr test is most likely caused by a failure to configure the 568toolkit for current platform or lack of support for the platform in question. 569Run './config -t' and './apps/openssl version -p'. Do these platform 570identifiers match? If they don't, then you most likely failed to run 571./config and you're hereby advised to do so before filing a bug report. 572If ./config itself fails to run, then it's most likely problem with your 573local environment and you should turn to your system administrator (or 574similar). If identifiers match (and/or no alternative identifier is 575suggested by ./config script), then the platform is unsupported. There might 576or might not be a workaround. Most notably on SPARC64 platforms with GNU 577C compiler you should be able to produce a working build by running 578'./config -m32'. I understand that -m32 might not be what you want/need, 579but the build should be operational. For further details turn to 580<openssl-dev@openssl.org>. 581 582* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 583 584As of 0.9.7 assembler routines were overhauled for position independence 585of the machine code, which is essential for shared library support. For 586some reason OpenBSD is equipped with an out-of-date GNU assembler which 587finds the new code offensive. To work around the problem, configure with 588no-asm (and sacrifice a great deal of performance) or patch your assembler 589according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 590For your convenience a pre-compiled replacement binary is provided at 591<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 592Reportedly elder *BSD a.out platforms also suffer from this problem and 593remedy should be same. Provided binary is statically linked and should be 594working across wider range of *BSD branches, not just OpenBSD. 595 596[PROG] ======================================================================== 597 598* Is OpenSSL thread-safe? 599 600Yes (with limitations: an SSL connection may not concurrently be used 601by multiple threads). On Windows and many Unix systems, OpenSSL 602automatically uses the multi-threaded versions of the standard 603libraries. If your platform is not one of these, consult the INSTALL 604file. 605 606Multi-threaded applications must provide two callback functions to 607OpenSSL. This is described in the threads(3) manpage. 608 609 610* I've compiled a program under Windows and it crashes: why? 611 612This is usually because you've missed the comment in INSTALL.W32. 613Your application must link against the same version of the Win32 614C-Runtime against which your openssl libraries were linked. The 615default version for OpenSSL is /MD - "Multithreaded DLL". 616 617If you are using Microsoft Visual C++'s IDE (Visual Studio), in 618many cases, your new project most likely defaulted to "Debug 619Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 620program will crash, typically on the first BIO related read or write 621operation. 622 623For each of the six possible link stage configurations within Win32, 624your application must link against the same by which OpenSSL was 625built. If you are using MS Visual C++ (Studio) this can be changed 626by: 627 6281. Select Settings... from the Project Menu. 6292. Select the C/C++ Tab. 6303. Select "Code Generation from the "Category" drop down list box 6314. Select the Appropriate library (see table below) from the "Use 632 run-time library" drop down list box. Perform this step for both 633 your debug and release versions of your application (look at the 634 top left of the settings panel to change between the two) 635 636 Single Threaded /ML - MS VC++ often defaults to 637 this for the release 638 version of a new project. 639 Debug Single Threaded /MLd - MS VC++ often defaults to 640 this for the debug version 641 of a new project. 642 Multithreaded /MT 643 Debug Multithreaded /MTd 644 Multithreaded DLL /MD - OpenSSL defaults to this. 645 Debug Multithreaded DLL /MDd 646 647Note that debug and release libraries are NOT interchangeable. If you 648built OpenSSL with /MD your application must use /MD and cannot use /MDd. 649 650 651* How do I read or write a DER encoded buffer using the ASN1 functions? 652 653You have two options. You can either use a memory BIO in conjunction 654with the i2d_XXX_bio() or d2i_XXX_bio() functions or you can use the 655i2d_XXX(), d2i_XXX() functions directly. Since these are often the 656cause of grief here are some code fragments using PKCS7 as an example: 657 658unsigned char *buf, *p; 659int len; 660 661len = i2d_PKCS7(p7, NULL); 662buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 663p = buf; 664i2d_PKCS7(p7, &p); 665 666At this point buf contains the len bytes of the DER encoding of 667p7. 668 669The opposite assumes we already have len bytes in buf: 670 671unsigned char *p; 672p = buf; 673p7 = d2i_PKCS7(NULL, &p, len); 674 675At this point p7 contains a valid PKCS7 structure of NULL if an error 676occurred. If an error occurred ERR_print_errors(bio) should give more 677information. 678 679The reason for the temporary variable 'p' is that the ASN1 functions 680increment the passed pointer so it is ready to read or write the next 681structure. This is often a cause of problems: without the temporary 682variable the buffer pointer is changed to point just after the data 683that has been read or written. This may well be uninitialized data 684and attempts to free the buffer will have unpredictable results 685because it no longer points to the same address. 686 687 688* OpenSSL uses DER but I need BER format: does OpenSSL support BER? 689 690The short answer is yes, because DER is a special case of BER and OpenSSL 691ASN1 decoders can process BER. 692 693The longer answer is that ASN1 structures can be encoded in a number of 694different ways. One set of ways is the Basic Encoding Rules (BER) with various 695permissible encodings. A restriction of BER is the Distinguished Encoding 696Rules (DER): these uniquely specify how a given structure is encoded. 697 698Therefore, because DER is a special case of BER, DER is an acceptable encoding 699for BER. 700 701 702* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 703 704This usually happens when you try compiling something using the PKCS#12 705macros with a C++ compiler. There is hardly ever any need to use the 706PKCS#12 macros in a program, it is much easier to parse and create 707PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 708documented in doc/openssl.txt and with examples in demos/pkcs12. The 709'pkcs12' application has to use the macros because it prints out 710debugging information. 711 712 713* I've called <some function> and it fails, why? 714 715Before submitting a report or asking in one of the mailing lists, you 716should try to determine the cause. In particular, you should call 717ERR_print_errors() or ERR_print_errors_fp() after the failed call 718and see if the message helps. Note that the problem may occur earlier 719than you think -- you should check for errors after every call where 720it is possible, otherwise the actual problem may be hidden because 721some OpenSSL functions clear the error state. 722 723 724* I just get a load of numbers for the error output, what do they mean? 725 726The actual format is described in the ERR_print_errors() manual page. 727You should call the function ERR_load_crypto_strings() before hand and 728the message will be output in text form. If you can't do this (for example 729it is a pre-compiled binary) you can use the errstr utility on the error 730code itself (the hex digits after the second colon). 731 732 733* Why do I get errors about unknown algorithms? 734 735This can happen under several circumstances such as reading in an 736encrypted private key or attempting to decrypt a PKCS#12 file. The cause 737is forgetting to load OpenSSL's table of algorithms with 738OpenSSL_add_all_algorithms(). See the manual page for more information. 739 740 741* Why can't the OpenSSH configure script detect OpenSSL? 742 743Several reasons for problems with the automatic detection exist. 744OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 745Sometimes the distribution has installed an older version in the system 746locations that is detected instead of a new one installed. The OpenSSL 747library might have been compiled for another CPU or another mode (32/64 bits). 748Permissions might be wrong. 749 750The general answer is to check the config.log file generated when running 751the OpenSSH configure script. It should contain the detailed information 752on why the OpenSSL library was not detected or considered incompatible. 753 754 755* Can I use OpenSSL's SSL library with non-blocking I/O? 756 757Yes; make sure to read the SSL_get_error(3) manual page! 758 759A pitfall to avoid: Don't assume that SSL_read() will just read from 760the underlying transport or that SSL_write() will just write to it -- 761it is also possible that SSL_write() cannot do any useful work until 762there is data to read, or that SSL_read() cannot do anything until it 763is possible to send data. One reason for this is that the peer may 764request a new TLS/SSL handshake at any time during the protocol, 765requiring a bi-directional message exchange; both SSL_read() and 766SSL_write() will try to continue any pending handshake. 767 768 769* Why doesn't my server application receive a client certificate? 770 771Due to the TLS protocol definition, a client will only send a certificate, 772if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 773SSL_CTX_set_verify() function to enable the use of client certificates. 774 775 776* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 777 778For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 779versions, uniqueIdentifier was incorrectly used for X.509 certificates. 780The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 781Change your code to use the new name when compiling against OpenSSL 0.9.7. 782 783 784* I think I've detected a memory leak, is this a bug? 785 786In most cases the cause of an apparent memory leak is an OpenSSL internal table 787that is allocated when an application starts up. Since such tables do not grow 788in size over time they are harmless. 789 790These internal tables can be freed up when an application closes using various 791functions. Currently these include: EVP_cleanup(), ERR_remove_state(), 792ERR_free_strings(), ENGINE_cleanup(), CONF_modules_unload() and 793CRYPTO_cleanup_all_ex_data(). 794 795 796=============================================================================== 797 798