diff options
author | Rich Salz <rsalz@akamai.com> | 2015-08-17 00:38:24 +0200 |
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committer | Rich Salz <rsalz@openssl.org> | 2015-08-17 01:02:29 +0200 |
commit | 4f46473a86c9e3741203b22d4d401a3763583494 (patch) | |
tree | 20d5a927cd9f28a4e3a50584bd4c7c7c51c8ab50 /FAQ | |
parent | PACKETise CertificateRequest (diff) | |
download | openssl-4f46473a86c9e3741203b22d4d401a3763583494.tar.xz openssl-4f46473a86c9e3741203b22d4d401a3763583494.zip |
Move FAQ to the web.
Best hope of keeping current.
Reviewed-by: Tim Hudson <tjh@openssl.org>
Diffstat (limited to 'FAQ')
-rw-r--r-- | FAQ | 1093 |
1 files changed, 2 insertions, 1091 deletions
@@ -1,1091 +1,2 @@ -OpenSSL - Frequently Asked Questions --------------------------------------- - -[MISC] Miscellaneous questions - -* Which is the current version of OpenSSL? -* Where is the documentation? -* How can I contact the OpenSSL developers? -* Where can I get a compiled version of OpenSSL? -* Why aren't tools like 'autoconf' and 'libtool' used? -* What is an 'engine' version? -* How do I check the authenticity of the OpenSSL distribution? -* How does the versioning scheme work? - -[LEGAL] Legal questions - -* Do I need patent licenses to use OpenSSL? -* Can I use OpenSSL with GPL software? - -[USER] Questions on using the OpenSSL applications - -* Why do I get a "PRNG not seeded" error message? -* Why do I get an "unable to write 'random state'" error message? -* How do I create certificates or certificate requests? -* Why can't I create certificate requests? -* Why does <SSL program> fail with a certificate verify error? -* Why can I only use weak ciphers when I connect to a server using OpenSSL? -* How can I create DSA certificates? -* Why can't I make an SSL connection using a DSA certificate? -* How can I remove the passphrase on a private key? -* Why can't I use OpenSSL certificates with SSL client authentication? -* Why does my browser give a warning about a mismatched hostname? -* How do I install a CA certificate into a browser? -* Why is OpenSSL x509 DN output not conformant to RFC2253? -* What is a "128 bit certificate"? Can I create one with OpenSSL? -* Why does OpenSSL set the authority key identifier extension incorrectly? -* How can I set up a bundle of commercial root CA certificates? -* Some secure servers 'hang' with OpenSSL 1.0.1, is this a bug? - -[BUILD] Questions about building and testing OpenSSL - -* Why does the linker complain about undefined symbols? -* Why does the OpenSSL test fail with "bc: command not found"? -* Why does the OpenSSL test fail with "bc: 1 no implemented"? -* Why does the OpenSSL test fail with "bc: stack empty"? -* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? -* Why does the OpenSSL compilation fail with "ar: command not found"? -* Why does the OpenSSL compilation fail on Win32 with VC++? -* What is special about OpenSSL on Redhat? -* Why does the OpenSSL compilation fail on MacOS X? -* Why does the OpenSSL test suite fail on MacOS X? -* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? -* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? -* Why does the OpenSSL test suite fail in sha512t on x86 CPU? -* Why does compiler fail to compile sha512.c? -* Test suite still fails, what to do? -* I think I've found a bug, what should I do? -* I'm SURE I've found a bug, how do I report it? -* I've found a security issue, how do I report it? - -[PROG] Questions about programming with OpenSSL - -* Is OpenSSL thread-safe? -* I've compiled a program under Windows and it crashes: why? -* How do I read or write a DER encoded buffer using the ASN1 functions? -* OpenSSL uses DER but I need BER format: does OpenSSL support BER? -* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? -* I've called <some function> and it fails, why? -* I just get a load of numbers for the error output, what do they mean? -* Why do I get errors about unknown algorithms? -* Why can't the OpenSSH configure script detect OpenSSL? -* Can I use OpenSSL's SSL library with non-blocking I/O? -* Why doesn't my server application receive a client certificate? -* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? -* I think I've detected a memory leak, is this a bug? -* Why does Valgrind complain about the use of uninitialized data? -* Why doesn't a memory BIO work when a file does? -* Where are the declarations and implementations of d2i_X509() etc? -* When debugging I observe SIGILL during OpenSSL initialization: why? - -=============================================================================== - -[MISC] ======================================================================== - -* Which is the current version of OpenSSL? - -The current version is available from <URL: http://www.openssl.org>. - -In addition to the current stable release, you can also access daily -snapshots of the OpenSSL development version at <URL: -ftp://ftp.openssl.org/snapshot/>, or get it by anonymous Git access. - - -* Where is the documentation? - -OpenSSL is a library that provides cryptographic functionality to -applications such as secure web servers. Be sure to read the -documentation of the application you want to use. The INSTALL file -explains how to install this library. - -OpenSSL includes a command line utility that can be used to perform a -variety of cryptographic functions. It is described in the openssl(1) -manpage. Documentation for developers is currently being written. Many -manual pages are available; overviews over libcrypto and -libssl are given in the crypto(3) and ssl(3) manpages. - -The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a -different directory if you specified one as described in INSTALL). -In addition, you can read the most current versions at -<URL: http://www.openssl.org/docs/>. Note that the online documents refer -to the very latest development versions of OpenSSL and may include features -not present in released versions. If in doubt refer to the documentation -that came with the version of OpenSSL you are using. The pod format -documentation is included in each OpenSSL distribution under the docs -directory. - -There is some documentation about certificate extensions and PKCS#12 -in doc/openssl.txt - -The original SSLeay documentation is included in OpenSSL as -doc/ssleay.txt. It may be useful when none of the other resources -help, but please note that it reflects the obsolete version SSLeay -0.6.6. - - -* How can I contact the OpenSSL developers? - -The README file describes how to submit bug reports and patches to -OpenSSL. Information on the OpenSSL mailing lists is available from -<URL: http://www.openssl.org>. - - -* Where can I get a compiled version of OpenSSL? - -You can finder pointers to binary distributions in -<URL: http://www.openssl.org/about/binaries.html> . - -Some applications that use OpenSSL are distributed in binary form. -When using such an application, you don't need to install OpenSSL -yourself; the application will include the required parts (e.g. DLLs). - -If you want to build OpenSSL on a Windows system and you don't have -a C compiler, read the "Mingw32" section of INSTALL.W32 for information -on how to obtain and install the free GNU C compiler. - -A number of Linux and *BSD distributions include OpenSSL. - - -* Why aren't tools like 'autoconf' and 'libtool' used? - -autoconf will probably be used in future OpenSSL versions. If it was -less Unix-centric, it might have been used much earlier. - -* What is an 'engine' version? - -With version 0.9.6 OpenSSL was extended to interface to external crypto -hardware. This was realized in a special release '0.9.6-engine'. With -version 0.9.7 the changes were merged into the main development line, -so that the special release is no longer necessary. - -* How do I check the authenticity of the OpenSSL distribution? - -We provide MD5 digests and ASC signatures of each tarball. -Use MD5 to check that a tarball from a mirror site is identical: - - md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 - -You can check authenticity using pgp or gpg. You need the OpenSSL team -member public key used to sign it (download it from a key server, see a -list of keys at <URL: http://www.openssl.org/about/>). Then -just do: - - pgp TARBALL.asc - -* How does the versioning scheme work? - -After the release of OpenSSL 1.0.0 the versioning scheme changed. Letter -releases (e.g. 1.0.1a) can only contain bug and security fixes and no -new features. Minor releases change the last number (e.g. 1.0.2) and -can contain new features that retain binary compatibility. Changes to -the middle number are considered major releases and neither source nor -binary compatibility is guaranteed. - -Therefore the answer to the common question "when will feature X be -backported to OpenSSL 1.0.0/0.9.8?" is "never" but it could appear -in the next minor release. - -* What happens when the letter release reaches z? - -It was decided after the release of OpenSSL 0.9.8y the next version should -be 0.9.8za then 0.9.8zb and so on. - - -[LEGAL] ======================================================================= - -* Do I need patent licenses to use OpenSSL? - -For information on intellectual property rights, please consult a lawyer. -The OpenSSL team does not offer legal advice. - -You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using - ./config no-idea no-mdc2 no-rc5 - - -* Can I use OpenSSL with GPL software? - -On many systems including the major Linux and BSD distributions, yes (the -GPL does not place restrictions on using libraries that are part of the -normal operating system distribution). - -On other systems, the situation is less clear. Some GPL software copyright -holders claim that you infringe on their rights if you use OpenSSL with -their software on operating systems that don't normally include OpenSSL. - -If you develop open source software that uses OpenSSL, you may find it -useful to choose an other license than the GPL, or state explicitly that -"This program is released under the GPL with the additional exemption that -compiling, linking, and/or using OpenSSL is allowed." If you are using -GPL software developed by others, you may want to ask the copyright holder -for permission to use their software with OpenSSL. - - -[USER] ======================================================================== - -* Why do I get a "PRNG not seeded" error message? - -Cryptographic software needs a source of unpredictable data to work -correctly. Many open source operating systems provide a "randomness -device" (/dev/urandom or /dev/random) that serves this purpose. -All OpenSSL versions try to use /dev/urandom by default; starting with -version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not -available. - -On other systems, applications have to call the RAND_add() or -RAND_seed() function with appropriate data before generating keys or -performing public key encryption. (These functions initialize the -pseudo-random number generator, PRNG.) Some broken applications do -not do this. As of version 0.9.5, the OpenSSL functions that need -randomness report an error if the random number generator has not been -seeded with at least 128 bits of randomness. If this error occurs and -is not discussed in the documentation of the application you are -using, please contact the author of that application; it is likely -that it never worked correctly. OpenSSL 0.9.5 and later make the -error visible by refusing to perform potentially insecure encryption. - -If you are using Solaris 8, you can add /dev/urandom and /dev/random -devices by installing patch 112438 (Sparc) or 112439 (x86), which are -available via the Patchfinder at <URL: http://sunsolve.sun.com> -(Solaris 9 includes these devices by default). For /dev/random support -for earlier Solaris versions, see Sun's statement at -<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> -(the SUNWski package is available in patch 105710). - -On systems without /dev/urandom and /dev/random, it is a good idea to -use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for -details. Starting with version 0.9.7, OpenSSL will automatically look -for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and -/etc/entropy. - -Most components of the openssl command line utility automatically try -to seed the random number generator from a file. The name of the -default seeding file is determined as follows: If environment variable -RANDFILE is set, then it names the seeding file. Otherwise if -environment variable HOME is set, then the seeding file is $HOME/.rnd. -If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will -use file .rnd in the current directory while OpenSSL 0.9.6a uses no -default seeding file at all. OpenSSL 0.9.6b and later will behave -similarly to 0.9.6a, but will use a default of "C:\" for HOME on -Windows systems if the environment variable has not been set. - -If the default seeding file does not exist or is too short, the "PRNG -not seeded" error message may occur. - -The openssl command line utility will write back a new state to the -default seeding file (and create this file if necessary) unless -there was no sufficient seeding. - -Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. -Use the "-rand" option of the OpenSSL command line tools instead. -The $RANDFILE environment variable and $HOME/.rnd are only used by the -OpenSSL command line tools. Applications using the OpenSSL library -provide their own configuration options to specify the entropy source, -please check out the documentation coming the with application. - - -* Why do I get an "unable to write 'random state'" error message? - - -Sometimes the openssl command line utility does not abort with -a "PRNG not seeded" error message, but complains that it is -"unable to write 'random state'". This message refers to the -default seeding file (see previous answer). A possible reason -is that no default filename is known because neither RANDFILE -nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the -current directory in this case, but this has changed with 0.9.6a.) - - -* How do I create certificates or certificate requests? - -Check out the CA.pl(1) manual page. This provides a simple wrapper round -the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check -out the manual pages for the individual utilities and the certificate -extensions documentation (in ca(1), req(1), x509v3_config(5) ) - - -* Why can't I create certificate requests? - -You typically get the error: - - unable to find 'distinguished_name' in config - problems making Certificate Request - -This is because it can't find the configuration file. Check out the -DIAGNOSTICS section of req(1) for more information. - - -* Why does <SSL program> fail with a certificate verify error? - -This problem is usually indicated by log messages saying something like -"unable to get local issuer certificate" or "self signed certificate". -When a certificate is verified its root CA must be "trusted" by OpenSSL -this typically means that the CA certificate must be placed in a directory -or file and the relevant program configured to read it. The OpenSSL program -'verify' behaves in a similar way and issues similar error messages: check -the verify(1) program manual page for more information. - - -* Why can I only use weak ciphers when I connect to a server using OpenSSL? - -This is almost certainly because you are using an old "export grade" browser -which only supports weak encryption. Upgrade your browser to support 128 bit -ciphers. - - -* How can I create DSA certificates? - -Check the CA.pl(1) manual page for a DSA certificate example. - - -* Why can't I make an SSL connection to a server using a DSA certificate? - -Typically you'll see a message saying there are no shared ciphers when -the same setup works fine with an RSA certificate. There are two possible -causes. The client may not support connections to DSA servers most web -browsers (including Netscape and MSIE) only support connections to servers -supporting RSA cipher suites. The other cause is that a set of DH parameters -has not been supplied to the server. DH parameters can be created with the -dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: -check the source to s_server in apps/s_server.c for an example. - - -* How can I remove the passphrase on a private key? - -Firstly you should be really *really* sure you want to do this. Leaving -a private key unencrypted is a major security risk. If you decide that -you do have to do this check the EXAMPLES sections of the rsa(1) and -dsa(1) manual pages. - - -* Why can't I use OpenSSL certificates with SSL client authentication? - -What will typically happen is that when a server requests authentication -it will either not include your certificate or tell you that you have -no client certificates (Netscape) or present you with an empty list box -(MSIE). The reason for this is that when a server requests a client -certificate it includes a list of CAs names which it will accept. Browsers -will only let you select certificates from the list on the grounds that -there is little point presenting a certificate which the server will -reject. - -The solution is to add the relevant CA certificate to your servers "trusted -CA list". How you do this depends on the server software in uses. You can -print out the servers list of acceptable CAs using the OpenSSL s_client tool: - -openssl s_client -connect www.some.host:443 -prexit - -If your server only requests certificates on certain URLs then you may need -to manually issue an HTTP GET command to get the list when s_client connects: - -GET /some/page/needing/a/certificate.html - -If your CA does not appear in the list then this confirms the problem. - - -* Why does my browser give a warning about a mismatched hostname? - -Browsers expect the server's hostname to match the value in the commonName -(CN) field of the certificate. If it does not then you get a warning. - - -* How do I install a CA certificate into a browser? - -The usual way is to send the DER encoded certificate to the browser as -MIME type application/x-x509-ca-cert, for example by clicking on an appropriate -link. On MSIE certain extensions such as .der or .cacert may also work, or you -can import the certificate using the certificate import wizard. - -You can convert a certificate to DER form using the command: - -openssl x509 -in ca.pem -outform DER -out ca.der - -Occasionally someone suggests using a command such as: - -openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem - -DO NOT DO THIS! This command will give away your CAs private key and -reduces its security to zero: allowing anyone to forge certificates in -whatever name they choose. - -* Why is OpenSSL x509 DN output not conformant to RFC2253? - -The ways to print out the oneline format of the DN (Distinguished Name) have -been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() -interface, the "-nameopt" option could be introduded. See the manual -page of the "openssl x509" command line tool for details. The old behaviour -has however been left as default for the sake of compatibility. - -* What is a "128 bit certificate"? Can I create one with OpenSSL? - -The term "128 bit certificate" is a highly misleading marketing term. It does -*not* refer to the size of the public key in the certificate! A certificate -containing a 128 bit RSA key would have negligible security. - -There were various other names such as "magic certificates", "SGC -certificates", "step up certificates" etc. - -You can't generally create such a certificate using OpenSSL but there is no -need to any more. Nowadays web browsers using unrestricted strong encryption -are generally available. - -When there were tight restrictions on the export of strong encryption -software from the US only weak encryption algorithms could be freely exported -(initially 40 bit and then 56 bit). It was widely recognised that this was -inadequate. A relaxation of the rules allowed the use of strong encryption but -only to an authorised server. - -Two slightly different techniques were developed to support this, one used by -Netscape was called "step up", the other used by MSIE was called "Server Gated -Cryptography" (SGC). When a browser initially connected to a server it would -check to see if the certificate contained certain extensions and was issued by -an authorised authority. If these test succeeded it would reconnect using -strong encryption. - -Only certain (initially one) certificate authorities could issue the -certificates and they generally cost more than ordinary certificates. - -Although OpenSSL can create certificates containing the appropriate extensions -the certificate would not come from a permitted authority and so would not -be recognized. - -The export laws were later changed to allow almost unrestricted use of strong -encryption so these certificates are now obsolete. - - -* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? - -It doesn't: this extension is often the cause of confusion. - -Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose -certificate C contains AKID. - -The purpose of this extension is to identify the authority certificate B. This -can be done either by including the subject key identifier of B or its issuer -name and serial number. - -In this latter case because it is identifying certifcate B it must contain the -issuer name and serial number of B. - -It is often wrongly assumed that it should contain the subject name of B. If it -did this would be redundant information because it would duplicate the issuer -name of C. - - -* How can I set up a bundle of commercial root CA certificates? - -The OpenSSL software is shipped without any root CA certificate as the -OpenSSL project does not have any policy on including or excluding -any specific CA and does not intend to set up such a policy. Deciding -about which CAs to support is up to application developers or -administrators. - -Other projects do have other policies so you can for example extract the CA -bundle used by Mozilla and/or modssl as described in this article: - - <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html> - - -* Some secure servers 'hang' with OpenSSL 1.0.1, is this a bug? - -OpenSSL 1.0.1 is the first release to support TLS 1.2, among other things, -this increases the size of the default ClientHello message to more than -255 bytes in length. Some software cannot handle this and hangs. For more -details and workarounds see: - - <URL: http://rt.openssl.org/Ticket/Display.html?user=guest&pass=guest&id=2771> - - -[BUILD] ======================================================================= - -* Why does the linker complain about undefined symbols? - -Maybe the compilation was interrupted, and make doesn't notice that -something is missing. Run "make clean; make". - -If you used ./Configure instead of ./config, make sure that you -selected the right target. File formats may differ slightly between -OS versions (for example sparcv8/sparcv9, or a.out/elf). - -In case you get errors about the following symbols, use the config -option "no-asm", as described in INSTALL: - - BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, - CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, - RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, - bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, - bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, - des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, - des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order - -If none of these helps, you may want to try using the current snapshot. -If the problem persists, please submit a bug report. - - -* Why does the OpenSSL test fail with "bc: command not found"? - -You didn't install "bc", the Unix calculator. If you want to run the -tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. - - -* Why does the OpenSSL test fail with "bc: 1 no implemented"? - -On some SCO installations or versions, bc has a bug that gets triggered -when you run the test suite (using "make test"). The message returned is -"bc: 1 not implemented". - -The best way to deal with this is to find another implementation of bc -and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> -for download instructions) can be safely used, for example. - - -* Why does the OpenSSL test fail with "bc: stack empty"? - -On some DG/ux versions, bc seems to have a too small stack for calculations -that the OpenSSL bntest throws at it. This gets triggered when you run the -test suite (using "make test"). The message returned is "bc: stack empty". - -The best way to deal with this is to find another implementation of bc -and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> -for download instructions) can be safely used, for example. - - -* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? - -On some Alpha installations running Tru64 Unix and Compaq C, the compilation -of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual -memory to continue compilation.' As far as the tests have shown, this may be -a compiler bug. What happens is that it eats up a lot of resident memory -to build something, probably a table. The problem is clearly in the -optimization code, because if one eliminates optimization completely (-O0), -the compilation goes through (and the compiler consumes about 2MB of resident -memory instead of 240MB or whatever one's limit is currently). - -There are three options to solve this problem: - -1. set your current data segment size soft limit higher. Experience shows -that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do -this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of -kbytes to set the limit to. - -2. If you have a hard limit that is lower than what you need and you can't -get it changed, you can compile all of OpenSSL with -O0 as optimization -level. This is however not a very nice thing to do for those who expect to -get the best result from OpenSSL. A bit more complicated solution is the -following: - ------ snip:start ----- - make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ - sed -e 's/ -O[0-9] / -O0 /'`" - rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` - make ------ snip:end ----- - -This will only compile sha_dgst.c with -O0, the rest with the optimization -level chosen by the configuration process. When the above is done, do the -test and installation and you're set. - -3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It -should not be used and is not used in SSL/TLS nor any other recognized -protocol in either case. - - -* Why does the OpenSSL compilation fail with "ar: command not found"? - -Getting this message is quite usual on Solaris 2, because Sun has hidden -away 'ar' and other development commands in directories that aren't in -$PATH by default. One of those directories is '/usr/ccs/bin'. The -quickest way to fix this is to do the following (it assumes you use sh -or any sh-compatible shell): - ------ snip:start ----- - PATH=${PATH}:/usr/ccs/bin; export PATH ------ snip:end ----- - -and then redo the compilation. What you should really do is make sure -'/usr/ccs/bin' is permanently in your $PATH, for example through your -'.profile' (again, assuming you use a sh-compatible shell). - - -* Why does the OpenSSL compilation fail on Win32 with VC++? - -Sometimes, you may get reports from VC++ command line (cl) that it -can't find standard include files like stdio.h and other weirdnesses. -One possible cause is that the environment isn't correctly set up. -To solve that problem for VC++ versions up to 6, one should run -VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ -installation directory (somewhere under 'Program Files'). For VC++ -version 7 (and up?), which is also called VS.NET, the file is called -VSVARS32.BAT instead. -This needs to be done prior to running NMAKE, and the changes are only -valid for the current DOS session. - - -* What is special about OpenSSL on Redhat? - -Red Hat Linux (release 7.0 and later) include a preinstalled limited -version of OpenSSL. Red Hat has chosen to disable support for IDEA, RC5 and -MDC2 in this version. The same may apply to other Linux distributions. -Users may therefore wish to install more or all of the features left out. - -To do this you MUST ensure that you do not overwrite the openssl that is in -/usr/bin on your Red Hat machine. Several packages depend on this file, -including sendmail and ssh. /usr/local/bin is a good alternative choice. The -libraries that come with Red Hat 7.0 onwards have different names and so are -not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and -/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and -/lib/libcrypto.so.2 respectively). - -Please note that we have been advised by Red Hat attempting to recompile the -openssl rpm with all the cryptography enabled will not work. All other -packages depend on the original Red Hat supplied openssl package. It is also -worth noting that due to the way Red Hat supplies its packages, updates to -openssl on each distribution never change the package version, only the -build number. For example, on Red Hat 7.1, the latest openssl package has -version number 0.9.6 and build number 9 even though it contains all the -relevant updates in packages up to and including 0.9.6b. - -A possible way around this is to persuade Red Hat to produce a non-US -version of Red Hat Linux. - - -* Why does the OpenSSL compilation fail on MacOS X? - -If the failure happens when trying to build the "openssl" binary, with -a large number of undefined symbols, it's very probable that you have -OpenSSL 0.9.6b delivered with the operating system (you can find out by -running '/usr/bin/openssl version') and that you were trying to build -OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in -MacOS X has a misfeature that's quite difficult to go around. -Look in the file PROBLEMS for a more detailed explanation and for possible -solutions. - - -* Why does the OpenSSL test suite fail on MacOS X? - -If the failure happens when running 'make test' and the RC4 test fails, -it's very probable that you have OpenSSL 0.9.6b delivered with the -operating system (you can find out by running '/usr/bin/openssl version') -and that you were trying to build OpenSSL 0.9.6d. The problem is that -the loader ('ld') in MacOS X has a misfeature that's quite difficult to -go around and has linked the programs "openssl" and the test programs -with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the -libraries you just built. -Look in the file PROBLEMS for a more detailed explanation and for possible -solutions. - -* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? - -Failure in BN_sqr test is most likely caused by a failure to configure the -toolkit for current platform or lack of support for the platform in question. -Run './config -t' and './apps/openssl version -p'. Do these platform -identifiers match? If they don't, then you most likely failed to run -./config and you're hereby advised to do so before filing a bug report. -If ./config itself fails to run, then it's most likely problem with your -local environment and you should turn to your system administrator (or -similar). If identifiers match (and/or no alternative identifier is -suggested by ./config script), then the platform is unsupported. There might -or might not be a workaround. Most notably on SPARC64 platforms with GNU -C compiler you should be able to produce a working build by running -'./config -m32'. I understand that -m32 might not be what you want/need, -but the build should be operational. For further details turn to -<openssl-dev@openssl.org>. - -* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? - -As of 0.9.7 assembler routines were overhauled for position independence -of the machine code, which is essential for shared library support. For -some reason OpenBSD is equipped with an out-of-date GNU assembler which -finds the new code offensive. To work around the problem, configure with -no-asm (and sacrifice a great deal of performance) or patch your assembler -according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. -For your convenience a pre-compiled replacement binary is provided at -<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. -Reportedly elder *BSD a.out platforms also suffer from this problem and -remedy should be same. Provided binary is statically linked and should be -working across wider range of *BSD branches, not just OpenBSD. - -* Why does the OpenSSL test suite fail in sha512t on x86 CPU? - -If the test program in question fails withs SIGILL, Illegal Instruction -exception, then you more than likely to run SSE2-capable CPU, such as -Intel P4, under control of kernel which does not support SSE2 -instruction extensions. See accompanying INSTALL file and -OPENSSL_ia32cap(3) documentation page for further information. - -* Why does compiler fail to compile sha512.c? - -OpenSSL SHA-512 implementation depends on compiler support for 64-bit -integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a -couple] lack support for this and therefore are incapable of compiling -the module in question. The recommendation is to disable SHA-512 by -adding no-sha512 to ./config [or ./Configure] command line. Another -possible alternative might be to switch to GCC. - -* Test suite still fails, what to do? - -Another common reason for test failures is bugs in the toolchain -or run-time environment. Known cases of this are documented in the -PROBLEMS file, please review it before you beat the drum. Even if you -don't find anything in that file, please do consider the possibility -of a compiler bug. Compiler bugs often appear in rather bizarre ways, -they never make sense, and tend to emerge when you least expect -them. One thing to try is to reduce the level of optimization (such -as by editing the CFLAG variable line in the top-level Makefile), -and then recompile and re-run the test. - -* I think I've found a bug, what should I do? - -If you are a new user then it is quite likely you haven't found a bug and -something is happening you aren't familiar with. Check this FAQ, the associated -documentation and the mailing lists for similar queries. If you are still -unsure whether it is a bug or not submit a query to the openssl-users mailing -list. - -If you think you have found a bug based on the output of static analysis tools -then please manually check the issue is genuine. Such tools can produce a -LOT of false positives. - - -* I'm SURE I've found a bug, how do I report it? - -To avoid duplicated reports check the mailing lists and release notes for the -relevant version of OpenSSL to see if the problem has been reported already. - -Bug reports with no security implications should be sent to the request -tracker. This can be done by mailing the report to <rt@openssl.org> (or its -alias <openssl-bugs@openssl.org>), please note that messages sent to the -request tracker also appear in the public openssl-dev mailing list. - -The report should be in plain text. Any patches should be sent as -plain text attachments because some mailers corrupt patches sent inline. -If your issue affects multiple versions of OpenSSL check any patches apply -cleanly and, if possible include patches to each affected version. - -The report should be given a meaningful subject line briefly summarising the -issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful. - -By sending reports to the request tracker the bug can then be given a priority -and assigned to the appropriate maintainer. The history of discussions can be -accessed and if the issue has been addressed or a reason why not. If patches -are only sent to openssl-dev they can be mislaid if a team member has to -wade through months of old messages to review the discussion. - -See also <URL: http://www.openssl.org/support/rt.html> - - -* I've found a security issue, how do I report it? - -If you think your bug has security implications then please send it to -openssl-security@openssl.org if you don't get a prompt reply at least -acknowledging receipt then resend or mail it directly to one of the -more active team members (e.g. Steve). If you wish to use PGP to send -in a report please use one or more of the keys of the team members listed -at <URL: http://www.openssl.org/about/> - -Note that bugs only present in the openssl utility are not in general -considered to be security issues. - -[PROG] ======================================================================== - -* Is OpenSSL thread-safe? - -Provided an application sets up the thread callback functions, the -answer is yes. There are limitations; for example, an SSL connection -cannot be used concurrently by multiple threads. This is true for -most OpenSSL objects. - -To do this, your application must call CRYPTO_set_locking_callback() -and one of the CRYPTO_THREADID_set...() API's. See the OpenSSL threads -manpage for details and "note on multi-threading" in the INSTALL file in -the source distribution. - -* I've compiled a program under Windows and it crashes: why? - -This is usually because you've missed the comment in INSTALL.W32. -Your application must link against the same version of the Win32 -C-Runtime against which your openssl libraries were linked. The -default version for OpenSSL is /MD - "Multithreaded DLL". - -If you are using Microsoft Visual C++'s IDE (Visual Studio), in -many cases, your new project most likely defaulted to "Debug -Singlethreaded" - /ML. This is NOT interchangeable with /MD and your -program will crash, typically on the first BIO related read or write -operation. - -For each of the six possible link stage configurations within Win32, -your application must link against the same by which OpenSSL was -built. If you are using MS Visual C++ (Studio) this can be changed -by: - - 1. Select Settings... from the Project Menu. - 2. Select the C/C++ Tab. - 3. Select "Code Generation from the "Category" drop down list box - 4. Select the Appropriate library (see table below) from the "Use - run-time library" drop down list box. Perform this step for both - your debug and release versions of your application (look at the - top left of the settings panel to change between the two) - - Single Threaded /ML - MS VC++ often defaults to - this for the release - version of a new project. - Debug Single Threaded /MLd - MS VC++ often defaults to - this for the debug version - of a new project. - Multithreaded /MT - Debug Multithreaded /MTd - Multithreaded DLL /MD - OpenSSL defaults to this. - Debug Multithreaded DLL /MDd - -Note that debug and release libraries are NOT interchangeable. If you -built OpenSSL with /MD your application must use /MD and cannot use /MDd. - -As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL -.DLLs compiled with some specific run-time option [we insist on the -default /MD] can be deployed with application compiled with different -option or even different compiler. But there is a catch! Instead of -re-compiling OpenSSL toolkit, as you would have to with prior versions, -you have to compile small C snippet with compiler and/or options of -your choice. The snippet gets installed as -<install-root>/include/openssl/applink.c and should be either added to -your application project or simply #include-d in one [and only one] -of your application source files. Failure to link this shim module -into your application manifests itself as fatal "no OPENSSL_Applink" -run-time error. An explicit reminder is due that in this situation -[mixing compiler options] it is as important to add CRYPTO_malloc_init -prior first call to OpenSSL. - -* How do I read or write a DER encoded buffer using the ASN1 functions? - -You have two options. You can either use a memory BIO in conjunction -with the i2d_*_bio() or d2i_*_bio() functions or you can use the -i2d_*(), d2i_*() functions directly. Since these are often the -cause of grief here are some code fragments using PKCS7 as an example: - ------ snip:start ----- - unsigned char *buf, *p; - int len = i2d_PKCS7(p7, NULL); - - buf = OPENSSL_malloc(len); /* error checking omitted */ - p = buf; - i2d_PKCS7(p7, &p); ------ snip:end ----- - -At this point buf contains the len bytes of the DER encoding of -p7. - -The opposite assumes we already have len bytes in buf: - ------ snip:start ----- - unsigned char *p = buf; - - p7 = d2i_PKCS7(NULL, &p, len); ------ snip:end ----- - -At this point p7 contains a valid PKCS7 structure or NULL if an error -occurred. If an error occurred ERR_print_errors(bio) should give more -information. - -The reason for the temporary variable 'p' is that the ASN1 functions -increment the passed pointer so it is ready to read or write the next -structure. This is often a cause of problems: without the temporary -variable the buffer pointer is changed to point just after the data -that has been read or written. This may well be uninitialized data -and attempts to free the buffer will have unpredictable results -because it no longer points to the same address. - -Memory allocation and encoding can also be combined in a single -operation by the ASN1 routines: - ------ snip:start ----- - unsigned char *buf = NULL; - int len = i2d_PKCS7(p7, &buf); - - if (len < 0) { - /* Error */ - } - /* Do some things with 'buf' */ - /* Finished with buf: free it */ - OPENSSL_free(buf); ------ snip:end ----- - -In this special case the "buf" parameter is *not* incremented, it points -to the start of the encoding. - - -* OpenSSL uses DER but I need BER format: does OpenSSL support BER? - -The short answer is yes, because DER is a special case of BER and OpenSSL -ASN1 decoders can process BER. - -The longer answer is that ASN1 structures can be encoded in a number of -different ways. One set of ways is the Basic Encoding Rules (BER) with various -permissible encodings. A restriction of BER is the Distinguished Encoding -Rules (DER): these uniquely specify how a given structure is encoded. - -Therefore, because DER is a special case of BER, DER is an acceptable encoding -for BER. - - -* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? - -This usually happens when you try compiling something using the PKCS#12 -macros with a C++ compiler. There is hardly ever any need to use the -PKCS#12 macros in a program, it is much easier to parse and create -PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions -documented in doc/openssl.txt and with examples in demos/pkcs12. The -'pkcs12' application has to use the macros because it prints out -debugging information. - - -* I've called <some function> and it fails, why? - -Before submitting a report or asking in one of the mailing lists, you -should try to determine the cause. In particular, you should call -ERR_print_errors() or ERR_print_errors_fp() after the failed call -and see if the message helps. Note that the problem may occur earlier -than you think -- you should check for errors after every call where -it is possible, otherwise the actual problem may be hidden because -some OpenSSL functions clear the error state. - - -* I just get a load of numbers for the error output, what do they mean? - -The actual format is described in the ERR_print_errors() manual page. -You should call the function ERR_load_crypto_strings() before hand and -the message will be output in text form. If you can't do this (for example -it is a pre-compiled binary) you can use the errstr utility on the error -code itself (the hex digits after the second colon). - - -* Why do I get errors about unknown algorithms? - -The cause is forgetting to load OpenSSL's table of algorithms with -OpenSSL_add_all_algorithms(). See the manual page for more information. This -can cause several problems such as being unable to read in an encrypted -PEM file, unable to decrypt a PKCS#12 file or signature failure when -verifying certificates. - -* Why can't the OpenSSH configure script detect OpenSSL? - -Several reasons for problems with the automatic detection exist. -OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. -Sometimes the distribution has installed an older version in the system -locations that is detected instead of a new one installed. The OpenSSL -library might have been compiled for another CPU or another mode (32/64 bits). -Permissions might be wrong. - -The general answer is to check the config.log file generated when running -the OpenSSH configure script. It should contain the detailed information -on why the OpenSSL library was not detected or considered incompatible. - - -* Can I use OpenSSL's SSL library with non-blocking I/O? - -Yes; make sure to read the SSL_get_error(3) manual page! - -A pitfall to avoid: Don't assume that SSL_read() will just read from -the underlying transport or that SSL_write() will just write to it -- -it is also possible that SSL_write() cannot do any useful work until -there is data to read, or that SSL_read() cannot do anything until it -is possible to send data. One reason for this is that the peer may -request a new TLS/SSL handshake at any time during the protocol, -requiring a bi-directional message exchange; both SSL_read() and -SSL_write() will try to continue any pending handshake. - - -* Why doesn't my server application receive a client certificate? - -Due to the TLS protocol definition, a client will only send a certificate, -if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the -SSL_CTX_set_verify() function to enable the use of client certificates. - - -* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? - -For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier -versions, uniqueIdentifier was incorrectly used for X.509 certificates. -The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. -Change your code to use the new name when compiling against OpenSSL 0.9.7. - - -* I think I've detected a memory leak, is this a bug? - -In most cases the cause of an apparent memory leak is an OpenSSL internal table -that is allocated when an application starts up. Since such tables do not grow -in size over time they are harmless. - -These internal tables can be freed up when an application closes using various -functions. Currently these include following: - -Thread-local cleanup functions: - - ERR_remove_state() - -Application-global cleanup functions that are aware of usage (and therefore -thread-safe): - - ENGINE_cleanup() and CONF_modules_unload() - -"Brutal" (thread-unsafe) Application-global cleanup functions: - - ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). - - -* Why does Valgrind complain about the use of uninitialized data? - -When OpenSSL's PRNG routines are called to generate random numbers the supplied -buffer contents are mixed into the entropy pool: so it technically does not -matter whether the buffer is initialized at this point or not. Valgrind (and -other test tools) will complain about this. When using Valgrind, make sure the -OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) -to get rid of these warnings. - - -* Why doesn't a memory BIO work when a file does? - -This can occur in several cases for example reading an S/MIME email message. -The reason is that a memory BIO can do one of two things when all the data -has been read from it. - -The default behaviour is to indicate that no more data is available and that -the call should be retried, this is to allow the application to fill up the BIO -again if necessary. - -Alternatively it can indicate that no more data is available and that EOF has -been reached. - -If a memory BIO is to behave in the same way as a file this second behaviour -is needed. This must be done by calling: - - BIO_set_mem_eof_return(bio, 0); - -See the manual pages for more details. - - -* Where are the declarations and implementations of d2i_X509() etc? - -These are defined and implemented by macros of the form: - - - DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509) - -The implementation passes an ASN1 "template" defining the structure into an -ASN1 interpreter using generalised functions such as ASN1_item_d2i(). - -* When debugging I observe SIGILL during OpenSSL initialization: why? - -OpenSSL adapts to processor it executes on and for this reason has to -query its capabilities. Unfortunately on some processors the only way -to achieve this for non-privileged code is to attempt instructions -that can cause Illegal Instruction exceptions. The initialization -procedure is coded to handle these exceptions to manipulate corresponding -bits in capabilities vector. This normally appears transparent, except -when you execute it under debugger, which stops prior delivering signal -to handler. Simply resuming execution does the trick, but when debugging -a lot it might feel counterproductive. Two options. Either set explicit -capability environment variable in order to bypass the capability query -(see corresponding crypto/*cap.c for details). Or configure debugger not -to stop upon SIGILL exception, e.g. in gdb case add 'handle SIGILL nostop' -to your .gdbinit. - -=============================================================================== +The FAQ is now maintained on the web: + https://www.openssl.org/docs/faq.html |