FAQ revision 111147
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* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 56* I've called <some function> and it fails, why? 57* I just get a load of numbers for the error output, what do they mean? 58* Why do I get errors about unknown algorithms? 59* Why can't the OpenSSH configure script detect OpenSSL? 60* Can I use OpenSSL's SSL library with non-blocking I/O? 61* Why doesn't my server application receive a client certificate? 62* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 63 64=============================================================================== 65 66[MISC] ======================================================================== 67 68* Which is the current version of OpenSSL? 69 70The current version is available from <URL: http://www.openssl.org>. 71OpenSSL 0.9.7a was released on February 19, 2003. 72 73In addition to the current stable release, you can also access daily 74snapshots of the OpenSSL development version at <URL: 75ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 76 77 78* Where is the documentation? 79 80OpenSSL is a library that provides cryptographic functionality to 81applications such as secure web servers. Be sure to read the 82documentation of the application you want to use. The INSTALL file 83explains how to install this library. 84 85OpenSSL includes a command line utility that can be used to perform a 86variety of cryptographic functions. It is described in the openssl(1) 87manpage. Documentation for developers is currently being written. A 88few manual pages already are available; overviews over libcrypto and 89libssl are given in the crypto(3) and ssl(3) manpages. 90 91The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 92different directory if you specified one as described in INSTALL). 93In addition, you can read the most current versions at 94<URL: http://www.openssl.org/docs/>. 95 96For information on parts of libcrypto that are not yet documented, you 97might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 98predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 99of this still applies to OpenSSL. 100 101There is some documentation about certificate extensions and PKCS#12 102in doc/openssl.txt 103 104The original SSLeay documentation is included in OpenSSL as 105doc/ssleay.txt. It may be useful when none of the other resources 106help, but please note that it reflects the obsolete version SSLeay 1070.6.6. 108 109 110* How can I contact the OpenSSL developers? 111 112The README file describes how to submit bug reports and patches to 113OpenSSL. Information on the OpenSSL mailing lists is available from 114<URL: http://www.openssl.org>. 115 116 117* Where can I get a compiled version of OpenSSL? 118 119Some applications that use OpenSSL are distributed in binary form. 120When using such an application, you don't need to install OpenSSL 121yourself; the application will include the required parts (e.g. DLLs). 122 123If you want to install OpenSSL on a Windows system and you don't have 124a C compiler, read the "Mingw32" section of INSTALL.W32 for information 125on how to obtain and install the free GNU C compiler. 126 127A number of Linux and *BSD distributions include OpenSSL. 128 129 130* Why aren't tools like 'autoconf' and 'libtool' used? 131 132autoconf will probably be used in future OpenSSL versions. If it was 133less Unix-centric, it might have been used much earlier. 134 135* What is an 'engine' version? 136 137With version 0.9.6 OpenSSL was extended to interface to external crypto 138hardware. This was realized in a special release '0.9.6-engine'. With 139version 0.9.7 (not yet released) the changes were merged into the main 140development line, so that the special release is no longer necessary. 141 142* How do I check the authenticity of the OpenSSL distribution? 143 144We provide MD5 digests and ASC signatures of each tarball. 145Use MD5 to check that a tarball from a mirror site is identical: 146 147 md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 148 149You can check authenticity using pgp or gpg. You need the OpenSSL team 150member public key used to sign it (download it from a key server). Then 151just do: 152 153 pgp TARBALL.asc 154 155[LEGAL] ======================================================================= 156 157* Do I need patent licenses to use OpenSSL? 158 159The patents section of the README file lists patents that may apply to 160you if you want to use OpenSSL. For information on intellectual 161property rights, please consult a lawyer. The OpenSSL team does not 162offer legal advice. 163 164You can configure OpenSSL so as not to use RC5 and IDEA by using 165 ./config no-rc5 no-idea 166 167 168* Can I use OpenSSL with GPL software? 169 170On many systems including the major Linux and BSD distributions, yes (the 171GPL does not place restrictions on using libraries that are part of the 172normal operating system distribution). 173 174On other systems, the situation is less clear. Some GPL software copyright 175holders claim that you infringe on their rights if you use OpenSSL with 176their software on operating systems that don't normally include OpenSSL. 177 178If you develop open source software that uses OpenSSL, you may find it 179useful to choose an other license than the GPL, or state explicitly that 180"This program is released under the GPL with the additional exemption that 181compiling, linking, and/or using OpenSSL is allowed." If you are using 182GPL software developed by others, you may want to ask the copyright holder 183for permission to use their software with OpenSSL. 184 185 186[USER] ======================================================================== 187 188* Why do I get a "PRNG not seeded" error message? 189 190Cryptographic software needs a source of unpredictable data to work 191correctly. Many open source operating systems provide a "randomness 192device" (/dev/urandom or /dev/random) that serves this purpose. 193All OpenSSL versions try to use /dev/urandom by default; starting with 194version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not 195available. 196 197On other systems, applications have to call the RAND_add() or 198RAND_seed() function with appropriate data before generating keys or 199performing public key encryption. (These functions initialize the 200pseudo-random number generator, PRNG.) Some broken applications do 201not do this. As of version 0.9.5, the OpenSSL functions that need 202randomness report an error if the random number generator has not been 203seeded with at least 128 bits of randomness. If this error occurs and 204is not discussed in the documentation of the application you are 205using, please contact the author of that application; it is likely 206that it never worked correctly. OpenSSL 0.9.5 and later make the 207error visible by refusing to perform potentially insecure encryption. 208 209If you are using Solaris 8, you can add /dev/urandom and /dev/random 210devices by installing patch 112438 (Sparc) or 112439 (x86), which are 211available via the Patchfinder at <URL: http://sunsolve.sun.com> 212(Solaris 9 includes these devices by default). For /dev/random support 213for earlier Solaris versions, see Sun's statement at 214<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> 215(the SUNWski package is available in patch 105710). 216 217On systems without /dev/urandom and /dev/random, it is a good idea to 218use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for 219details. Starting with version 0.9.7, OpenSSL will automatically look 220for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and 221/etc/entropy. 222 223Most components of the openssl command line utility automatically try 224to seed the random number generator from a file. The name of the 225default seeding file is determined as follows: If environment variable 226RANDFILE is set, then it names the seeding file. Otherwise if 227environment variable HOME is set, then the seeding file is $HOME/.rnd. 228If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will 229use file .rnd in the current directory while OpenSSL 0.9.6a uses no 230default seeding file at all. OpenSSL 0.9.6b and later will behave 231similarly to 0.9.6a, but will use a default of "C:\" for HOME on 232Windows systems if the environment variable has not been set. 233 234If the default seeding file does not exist or is too short, the "PRNG 235not seeded" error message may occur. 236 237The openssl command line utility will write back a new state to the 238default seeding file (and create this file if necessary) unless 239there was no sufficient seeding. 240 241Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. 242Use the "-rand" option of the OpenSSL command line tools instead. 243The $RANDFILE environment variable and $HOME/.rnd are only used by the 244OpenSSL command line tools. Applications using the OpenSSL library 245provide their own configuration options to specify the entropy source, 246please check out the documentation coming the with application. 247 248 249* Why do I get an "unable to write 'random state'" error message? 250 251 252Sometimes the openssl command line utility does not abort with 253a "PRNG not seeded" error message, but complains that it is 254"unable to write 'random state'". This message refers to the 255default seeding file (see previous answer). A possible reason 256is that no default filename is known because neither RANDFILE 257nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the 258current directory in this case, but this has changed with 0.9.6a.) 259 260 261* How do I create certificates or certificate requests? 262 263Check out the CA.pl(1) manual page. This provides a simple wrapper round 264the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 265out the manual pages for the individual utilities and the certificate 266extensions documentation (currently in doc/openssl.txt). 267 268 269* Why can't I create certificate requests? 270 271You typically get the error: 272 273 unable to find 'distinguished_name' in config 274 problems making Certificate Request 275 276This is because it can't find the configuration file. Check out the 277DIAGNOSTICS section of req(1) for more information. 278 279 280* Why does <SSL program> fail with a certificate verify error? 281 282This problem is usually indicated by log messages saying something like 283"unable to get local issuer certificate" or "self signed certificate". 284When a certificate is verified its root CA must be "trusted" by OpenSSL 285this typically means that the CA certificate must be placed in a directory 286or file and the relevant program configured to read it. The OpenSSL program 287'verify' behaves in a similar way and issues similar error messages: check 288the verify(1) program manual page for more information. 289 290 291* Why can I only use weak ciphers when I connect to a server using OpenSSL? 292 293This is almost certainly because you are using an old "export grade" browser 294which only supports weak encryption. Upgrade your browser to support 128 bit 295ciphers. 296 297 298* How can I create DSA certificates? 299 300Check the CA.pl(1) manual page for a DSA certificate example. 301 302 303* Why can't I make an SSL connection to a server using a DSA certificate? 304 305Typically you'll see a message saying there are no shared ciphers when 306the same setup works fine with an RSA certificate. There are two possible 307causes. The client may not support connections to DSA servers most web 308browsers (including Netscape and MSIE) only support connections to servers 309supporting RSA cipher suites. The other cause is that a set of DH parameters 310has not been supplied to the server. DH parameters can be created with the 311dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: 312check the source to s_server in apps/s_server.c for an example. 313 314 315* How can I remove the passphrase on a private key? 316 317Firstly you should be really *really* sure you want to do this. Leaving 318a private key unencrypted is a major security risk. If you decide that 319you do have to do this check the EXAMPLES sections of the rsa(1) and 320dsa(1) manual pages. 321 322 323* Why can't I use OpenSSL certificates with SSL client authentication? 324 325What will typically happen is that when a server requests authentication 326it will either not include your certificate or tell you that you have 327no client certificates (Netscape) or present you with an empty list box 328(MSIE). The reason for this is that when a server requests a client 329certificate it includes a list of CAs names which it will accept. Browsers 330will only let you select certificates from the list on the grounds that 331there is little point presenting a certificate which the server will 332reject. 333 334The solution is to add the relevant CA certificate to your servers "trusted 335CA list". How you do this depends on the server software in uses. You can 336print out the servers list of acceptable CAs using the OpenSSL s_client tool: 337 338openssl s_client -connect www.some.host:443 -prexit 339 340If your server only requests certificates on certain URLs then you may need 341to manually issue an HTTP GET command to get the list when s_client connects: 342 343GET /some/page/needing/a/certificate.html 344 345If your CA does not appear in the list then this confirms the problem. 346 347 348* Why does my browser give a warning about a mismatched hostname? 349 350Browsers expect the server's hostname to match the value in the commonName 351(CN) field of the certificate. If it does not then you get a warning. 352 353 354* How do I install a CA certificate into a browser? 355 356The usual way is to send the DER encoded certificate to the browser as 357MIME type application/x-x509-ca-cert, for example by clicking on an appropriate 358link. On MSIE certain extensions such as .der or .cacert may also work, or you 359can import the certificate using the certificate import wizard. 360 361You can convert a certificate to DER form using the command: 362 363openssl x509 -in ca.pem -outform DER -out ca.der 364 365Occasionally someone suggests using a command such as: 366 367openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem 368 369DO NOT DO THIS! This command will give away your CAs private key and 370reduces its security to zero: allowing anyone to forge certificates in 371whatever name they choose. 372 373* Why is OpenSSL x509 DN output not conformant to RFC2253? 374 375The ways to print out the oneline format of the DN (Distinguished Name) have 376been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() 377interface, the "-nameopt" option could be introduded. See the manual 378page of the "openssl x509" commandline tool for details. The old behaviour 379has however been left as default for the sake of compatibility. 380 381[BUILD] ======================================================================= 382 383* Why does the linker complain about undefined symbols? 384 385Maybe the compilation was interrupted, and make doesn't notice that 386something is missing. Run "make clean; make". 387 388If you used ./Configure instead of ./config, make sure that you 389selected the right target. File formats may differ slightly between 390OS versions (for example sparcv8/sparcv9, or a.out/elf). 391 392In case you get errors about the following symbols, use the config 393option "no-asm", as described in INSTALL: 394 395 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 396 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 397 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 398 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 399 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 400 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 401 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 402 403If none of these helps, you may want to try using the current snapshot. 404If the problem persists, please submit a bug report. 405 406 407* Why does the OpenSSL test fail with "bc: command not found"? 408 409You didn't install "bc", the Unix calculator. If you want to run the 410tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. 411 412 413* Why does the OpenSSL test fail with "bc: 1 no implemented"? 414 415On some SCO installations or versions, bc has a bug that gets triggered 416when you run the test suite (using "make test"). The message returned is 417"bc: 1 not implemented". 418 419The best way to deal with this is to find another implementation of bc 420and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 421for download instructions) can be safely used, for example. 422 423 424* Why does the OpenSSL test fail with "bc: stack empty"? 425 426On some DG/ux versions, bc seems to have a too small stack for calculations 427that the OpenSSL bntest throws at it. This gets triggered when you run the 428test suite (using "make test"). The message returned is "bc: stack empty". 429 430The best way to deal with this is to find another implementation of bc 431and compile/install it. GNU bc (see http://www.gnu.org/software/software.html 432for download instructions) can be safely used, for example. 433 434 435* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? 436 437On some Alpha installations running Tru64 Unix and Compaq C, the compilation 438of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual 439memory to continue compilation.' As far as the tests have shown, this may be 440a compiler bug. What happens is that it eats up a lot of resident memory 441to build something, probably a table. The problem is clearly in the 442optimization code, because if one eliminates optimization completely (-O0), 443the compilation goes through (and the compiler consumes about 2MB of resident 444memory instead of 240MB or whatever one's limit is currently). 445 446There are three options to solve this problem: 447 4481. set your current data segment size soft limit higher. Experience shows 449that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do 450this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of 451kbytes to set the limit to. 452 4532. If you have a hard limit that is lower than what you need and you can't 454get it changed, you can compile all of OpenSSL with -O0 as optimization 455level. This is however not a very nice thing to do for those who expect to 456get the best result from OpenSSL. A bit more complicated solution is the 457following: 458 459----- snip:start ----- 460 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ 461 sed -e 's/ -O[0-9] / -O0 /'`" 462 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` 463 make 464----- snip:end ----- 465 466This will only compile sha_dgst.c with -O0, the rest with the optimization 467level chosen by the configuration process. When the above is done, do the 468test and installation and you're set. 469 470 471* Why does the OpenSSL compilation fail with "ar: command not found"? 472 473Getting this message is quite usual on Solaris 2, because Sun has hidden 474away 'ar' and other development commands in directories that aren't in 475$PATH by default. One of those directories is '/usr/ccs/bin'. The 476quickest way to fix this is to do the following (it assumes you use sh 477or any sh-compatible shell): 478 479----- snip:start ----- 480 PATH=${PATH}:/usr/ccs/bin; export PATH 481----- snip:end ----- 482 483and then redo the compilation. What you should really do is make sure 484'/usr/ccs/bin' is permanently in your $PATH, for example through your 485'.profile' (again, assuming you use a sh-compatible shell). 486 487 488* Why does the OpenSSL compilation fail on Win32 with VC++? 489 490Sometimes, you may get reports from VC++ command line (cl) that it 491can't find standard include files like stdio.h and other weirdnesses. 492One possible cause is that the environment isn't correctly set up. 493To solve that problem for VC++ versions up to 6, one should run 494VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ 495installation directory (somewhere under 'Program Files'). For VC++ 496version 7 (and up?), which is also called VS.NET, the file is called 497VSVARS32.BAT instead. 498This needs to be done prior to running NMAKE, and the changes are only 499valid for the current DOS session. 500 501 502* What is special about OpenSSL on Redhat? 503 504Red Hat Linux (release 7.0 and later) include a preinstalled limited 505version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 506is disabled in this version. The same may apply to other Linux distributions. 507Users may therefore wish to install more or all of the features left out. 508 509To do this you MUST ensure that you do not overwrite the openssl that is in 510/usr/bin on your Red Hat machine. Several packages depend on this file, 511including sendmail and ssh. /usr/local/bin is a good alternative choice. The 512libraries that come with Red Hat 7.0 onwards have different names and so are 513not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and 514/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and 515/lib/libcrypto.so.2 respectively). 516 517Please note that we have been advised by Red Hat attempting to recompile the 518openssl rpm with all the cryptography enabled will not work. All other 519packages depend on the original Red Hat supplied openssl package. It is also 520worth noting that due to the way Red Hat supplies its packages, updates to 521openssl on each distribution never change the package version, only the 522build number. For example, on Red Hat 7.1, the latest openssl package has 523version number 0.9.6 and build number 9 even though it contains all the 524relevant updates in packages up to and including 0.9.6b. 525 526A possible way around this is to persuade Red Hat to produce a non-US 527version of Red Hat Linux. 528 529FYI: Patent numbers and expiry dates of US patents: 530MDC-2: 4,908,861 13/03/2007 531IDEA: 5,214,703 25/05/2010 532RC5: 5,724,428 03/03/2015 533 534 535* Why does the OpenSSL compilation fail on MacOS X? 536 537If the failure happens when trying to build the "openssl" binary, with 538a large number of undefined symbols, it's very probable that you have 539OpenSSL 0.9.6b delivered with the operating system (you can find out by 540running '/usr/bin/openssl version') and that you were trying to build 541OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in 542MacOS X has a misfeature that's quite difficult to go around. 543Look in the file PROBLEMS for a more detailed explanation and for possible 544solutions. 545 546 547* Why does the OpenSSL test suite fail on MacOS X? 548 549If the failure happens when running 'make test' and the RC4 test fails, 550it's very probable that you have OpenSSL 0.9.6b delivered with the 551operating system (you can find out by running '/usr/bin/openssl version') 552and that you were trying to build OpenSSL 0.9.6d. The problem is that 553the loader ('ld') in MacOS X has a misfeature that's quite difficult to 554go around and has linked the programs "openssl" and the test programs 555with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the 556libraries you just built. 557Look in the file PROBLEMS for a more detailed explanation and for possible 558solutions. 559 560* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? 561 562Failure in BN_sqr test is most likely caused by a failure to configure the 563toolkit for current platform or lack of support for the platform in question. 564Run './config -t' and './apps/openssl version -p'. Do these platform 565identifiers match? If they don't, then you most likely failed to run 566./config and you're hereby advised to do so before filing a bug report. 567If ./config itself fails to run, then it's most likely problem with your 568local environment and you should turn to your system administrator (or 569similar). If identifiers match (and/or no alternative identifier is 570suggested by ./config script), then the platform is unsupported. There might 571or might not be a workaround. Most notably on SPARC64 platforms with GNU 572C compiler you should be able to produce a working build by running 573'./config -m32'. I understand that -m32 might not be what you want/need, 574but the build should be operational. For further details turn to 575<openssl-dev@openssl.org>. 576 577* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? 578 579As of 0.9.7 assembler routines were overhauled for position independence 580of the machine code, which is essential for shared library support. For 581some reason OpenBSD is equipped with an out-of-date GNU assembler which 582finds the new code offensive. To work around the problem, configure with 583no-asm (and sacrifice a great deal of performance) or patch your assembler 584according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. 585For your convenience a pre-compiled replacement binary is provided at 586<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. 587Reportedly elder *BSD a.out platforms also suffer from this problem and 588remedy should be same. Provided binary is statically linked and should be 589working across wider range of *BSD branches, not just OpenBSD. 590 591[PROG] ======================================================================== 592 593* Is OpenSSL thread-safe? 594 595Yes (with limitations: an SSL connection may not concurrently be used 596by multiple threads). On Windows and many Unix systems, OpenSSL 597automatically uses the multi-threaded versions of the standard 598libraries. If your platform is not one of these, consult the INSTALL 599file. 600 601Multi-threaded applications must provide two callback functions to 602OpenSSL. This is described in the threads(3) manpage. 603 604 605* I've compiled a program under Windows and it crashes: why? 606 607This is usually because you've missed the comment in INSTALL.W32. 608Your application must link against the same version of the Win32 609C-Runtime against which your openssl libraries were linked. The 610default version for OpenSSL is /MD - "Multithreaded DLL". 611 612If you are using Microsoft Visual C++'s IDE (Visual Studio), in 613many cases, your new project most likely defaulted to "Debug 614Singlethreaded" - /ML. This is NOT interchangeable with /MD and your 615program will crash, typically on the first BIO related read or write 616operation. 617 618For each of the six possible link stage configurations within Win32, 619your application must link against the same by which OpenSSL was 620built. If you are using MS Visual C++ (Studio) this can be changed 621by: 622 6231. Select Settings... from the Project Menu. 6242. Select the C/C++ Tab. 6253. Select "Code Generation from the "Category" drop down list box 6264. Select the Appropriate library (see table below) from the "Use 627 run-time library" drop down list box. Perform this step for both 628 your debug and release versions of your application (look at the 629 top left of the settings panel to change between the two) 630 631 Single Threaded /ML - MS VC++ often defaults to 632 this for the release 633 version of a new project. 634 Debug Single Threaded /MLd - MS VC++ often defaults to 635 this for the debug version 636 of a new project. 637 Multithreaded /MT 638 Debug Multithreaded /MTd 639 Multithreaded DLL /MD - OpenSSL defaults to this. 640 Debug Multithreaded DLL /MDd 641 642Note that debug and release libraries are NOT interchangeable. If you 643built OpenSSL with /MD your application must use /MD and cannot use /MDd. 644 645 646* How do I read or write a DER encoded buffer using the ASN1 functions? 647 648You have two options. You can either use a memory BIO in conjunction 649with the i2d_XXX_bio() or d2i_XXX_bio() functions or you can use the 650i2d_XXX(), d2i_XXX() functions directly. Since these are often the 651cause of grief here are some code fragments using PKCS7 as an example: 652 653unsigned char *buf, *p; 654int len; 655 656len = i2d_PKCS7(p7, NULL); 657buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ 658p = buf; 659i2d_PKCS7(p7, &p); 660 661At this point buf contains the len bytes of the DER encoding of 662p7. 663 664The opposite assumes we already have len bytes in buf: 665 666unsigned char *p; 667p = buf; 668p7 = d2i_PKCS7(NULL, &p, len); 669 670At this point p7 contains a valid PKCS7 structure of NULL if an error 671occurred. If an error occurred ERR_print_errors(bio) should give more 672information. 673 674The reason for the temporary variable 'p' is that the ASN1 functions 675increment the passed pointer so it is ready to read or write the next 676structure. This is often a cause of problems: without the temporary 677variable the buffer pointer is changed to point just after the data 678that has been read or written. This may well be uninitialized data 679and attempts to free the buffer will have unpredictable results 680because it no longer points to the same address. 681 682 683* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? 684 685This usually happens when you try compiling something using the PKCS#12 686macros with a C++ compiler. There is hardly ever any need to use the 687PKCS#12 macros in a program, it is much easier to parse and create 688PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions 689documented in doc/openssl.txt and with examples in demos/pkcs12. The 690'pkcs12' application has to use the macros because it prints out 691debugging information. 692 693 694* I've called <some function> and it fails, why? 695 696Before submitting a report or asking in one of the mailing lists, you 697should try to determine the cause. In particular, you should call 698ERR_print_errors() or ERR_print_errors_fp() after the failed call 699and see if the message helps. Note that the problem may occur earlier 700than you think -- you should check for errors after every call where 701it is possible, otherwise the actual problem may be hidden because 702some OpenSSL functions clear the error state. 703 704 705* I just get a load of numbers for the error output, what do they mean? 706 707The actual format is described in the ERR_print_errors() manual page. 708You should call the function ERR_load_crypto_strings() before hand and 709the message will be output in text form. If you can't do this (for example 710it is a pre-compiled binary) you can use the errstr utility on the error 711code itself (the hex digits after the second colon). 712 713 714* Why do I get errors about unknown algorithms? 715 716This can happen under several circumstances such as reading in an 717encrypted private key or attempting to decrypt a PKCS#12 file. The cause 718is forgetting to load OpenSSL's table of algorithms with 719OpenSSL_add_all_algorithms(). See the manual page for more information. 720 721 722* Why can't the OpenSSH configure script detect OpenSSL? 723 724Several reasons for problems with the automatic detection exist. 725OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. 726Sometimes the distribution has installed an older version in the system 727locations that is detected instead of a new one installed. The OpenSSL 728library might have been compiled for another CPU or another mode (32/64 bits). 729Permissions might be wrong. 730 731The general answer is to check the config.log file generated when running 732the OpenSSH configure script. It should contain the detailed information 733on why the OpenSSL library was not detected or considered incompatible. 734 735* Can I use OpenSSL's SSL library with non-blocking I/O? 736 737Yes; make sure to read the SSL_get_error(3) manual page! 738 739A pitfall to avoid: Don't assume that SSL_read() will just read from 740the underlying transport or that SSL_write() will just write to it -- 741it is also possible that SSL_write() cannot do any useful work until 742there is data to read, or that SSL_read() cannot do anything until it 743is possible to send data. One reason for this is that the peer may 744request a new TLS/SSL handshake at any time during the protocol, 745requiring a bi-directional message exchange; both SSL_read() and 746SSL_write() will try to continue any pending handshake. 747 748 749* Why doesn't my server application receive a client certificate? 750 751Due to the TLS protocol definition, a client will only send a certificate, 752if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the 753SSL_CTX_set_verify() function to enable the use of client certificates. 754 755 756* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? 757 758For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier 759versions, uniqueIdentifier was incorrectly used for X.509 certificates. 760The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. 761Change your code to use the new name when compiling against OpenSSL 0.9.7. 762 763 764=============================================================================== 765 766