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@@ -0,0 +1,432 @@ +OpenSSL - Frequently Asked Questions +-------------------------------------- + +* Which is the current version of OpenSSL? +* Where is the documentation? +* How can I contact the OpenSSL developers? +* Do I need patent licenses to use OpenSSL? +* Is OpenSSL thread-safe? +* Why do I get a "PRNG not seeded" error message? +* Why does the linker complain about undefined symbols? +* Where can I get a compiled version of OpenSSL? +* 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? +* 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? +* 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 the OpenSSH configure script detect OpenSSL? +* 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 compilation fail on Alpha True64 Unix? +* Why does the OpenSSL compilation fail with "ar: command not found"? + + +* Which is the current version of OpenSSL? + +The current version is available from <URL: http://www.openssl.org>. +OpenSSL 0.9.6 was released on September 24th, 2000. + +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 CVS 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. A +few manual pages already 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/>. + +For information on parts of libcrypto that are not yet documented, you +might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's +predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much +of this still applies to OpenSSL. + +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>. + + +* Do I need patent licenses to use OpenSSL? + +The patents section of the README file lists patents that may apply to +you if you want 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 RC5 and IDEA by using + ./config no-rc5 no-idea + + +* Is OpenSSL thread-safe? + +Yes (with limitations: an SSL connection may not concurrently be used +by multiple threads). On Windows and many Unix systems, OpenSSL +automatically uses the multi-threaded versions of the standard +libraries. If your platform is not one of these, consult the INSTALL +file. + +Multi-threaded applications must provide two callback functions to +OpenSSL. This is described in the threads(3) manpage. + + +* 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" that serves this purpose. 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. + +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, please contact the author of the +application you are using. 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. + +On systems without /dev/urandom, it is a good idea to use the Entropy +Gathering Demon; see the RAND_egd() manpage for details. + +Most components of the openssl command line tool try to use the +file $HOME/.rnd (or $RANDFILE, if this environment variable is set) +for seeding the PRNG. If this file does not exist or is too short, +the "PRNG not seeded" error message may occur. + +[Note to OpenSSL 0.9.5 users: The command "openssl rsa" in version +0.9.5 does not do this and will fail on systems without /dev/urandom +when trying to password-encrypt an RSA key! This is a bug in the +library; try a later version instead.] + +For Solaris 2.6, Tim Nibbe <tnibbe@sprint.net> and others have suggested +installing the SUNski package from Sun patch 105710-01 (Sparc) which +adds a /dev/random device and make sure it gets used, usually through +$RANDFILE. There are probably similar patches for the other Solaris +versions. However, be warned that /dev/random is usually a blocking +device, which may have some effects on OpenSSL. + + +* 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. + + +* Where can I get a compiled version of OpenSSL? + +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 install 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. + + +* I've compiled a program under Windows and it crashes: why? + +This is usually because you've missed the comment in INSTALL.W32. You +must link with the multithreaded DLL version of the VC++ runtime library +otherwise the conflict will cause a program to crash: typically on the +first BIO related read or write operation. + + +* 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_XXX_bio() or d2i_XXX_bio() functions or you can use the +i2d_XXX(), d2i_XXX() functions directly. Since these are often the +cause of grief here are some code fragments using PKCS7 as an example: + +unsigned char *buf, *p; +int len; + +len = i2d_PKCS7(p7, NULL); +buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ +p = buf; +i2d_PKCS7(p7, &p); + +At this point buf contains the len bytes of the DER encoding of +p7. + +The opposite assumes we already have len bytes in buf: + +unsigned char *p; +p = buf; +p7 = d2i_PKCS7(NULL, &p, len); + +At this point p7 contains a valid PKCS7 structure of 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. + + +* 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? + +This can happen under several circumstances such as reading in an +encrypted private key or attempting to decrypt a PKCS#12 file. The cause +is forgetting to load OpenSSL's table of algorithms with +OpenSSL_add_all_algorithms(). See the manual page for more information. + + +* 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 (currently in doc/openssl.txt). + + +* 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 the OpenSSH configure script detect OpenSSL? + +There is a problem with OpenSSH 1.2.2p1, in that the configure script +can't find the installed OpenSSL libraries. The problem is actually +a small glitch that is easily solved with the following patch to be +applied to the OpenSSH distribution: + +----- snip:start ----- +--- openssh-1.2.2p1/configure.in.orig Thu Mar 23 18:56:58 2000 ++++ openssh-1.2.2p1/configure.in Thu Mar 23 18:55:05 2000 +@@ -152,10 +152,10 @@ + AC_MSG_CHECKING([for OpenSSL/SSLeay directory]) + for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do + if test ! -z "$ssldir" ; then +- LIBS="$saved_LIBS -L$ssldir" ++ LIBS="$saved_LIBS -L$ssldir/lib" + CFLAGS="$CFLAGS -I$ssldir/include" + if test "x$need_dash_r" = "x1" ; then +- LIBS="$LIBS -R$ssldir" ++ LIBS="$LIBS -R$ssldir/lib" + fi + fi + LIBS="$LIBS -lcrypto" +--- openssh-1.2.2p1/configure.orig Thu Mar 23 18:55:02 2000 ++++ openssh-1.2.2p1/configure Thu Mar 23 18:57:08 2000 +@@ -1890,10 +1890,10 @@ + echo "configure:1891: checking for OpenSSL/SSLeay directory" >&5 + for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do + if test ! -z "$ssldir" ; then +- LIBS="$saved_LIBS -L$ssldir" ++ LIBS="$saved_LIBS -L$ssldir/lib" + CFLAGS="$CFLAGS -I$ssldir/include" + if test "x$need_dash_r" = "x1" ; then +- LIBS="$LIBS -R$ssldir" ++ LIBS="$LIBS -R$ssldir/lib" + fi + fi + LIBS="$LIBS -lcrypto" +----- snip:end ----- + + +* 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. For example, GNU bc (see +http://www.gnu.org/software/software.html for download instructions) can +be safely used. + + +* Why does the OpenSSL compilation fail on Alpha True64 Unix? + +On some Alpha installations running True64 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. + + +* 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). + |