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?
+
+[LEGAL] Legal questions
+
* Do I need patent licenses to use OpenSSL?
-* Is OpenSSL thread-safe?
+* 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 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?
-* 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?
* 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?
+
+[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 compilation fail on Alpha True64 Unix?
+* Why does the OpenSSL compilation fail with "ar: command not found"?
+* Why does the OpenSSL compilation fail on Win32 with VC++?
+
+[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?
+* 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?
+===============================================================================
+
+[MISC] ========================================================================
* Which is the current version of OpenSSL?
The current version is available from <URL: http://www.openssl.org>.
-OpenSSL 0.9.5a was released on April 1st, 2000.
+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:
<URL: http://www.openssl.org>.
+* 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.
+
+
+* Why aren't tools like 'autoconf' and 'libtool' used?
+
+autoconf is a nice tool, but is unfortunately very Unix-centric.
+Although one can come up with solution to have ports keep in track,
+there's also some work needed for that, and can be quite painful at
+times. If there was a 'autoconf'-like tool that generated perl
+scripts or something similarly general, it would probably be used
+in OpenSSL much earlier.
+
+libtool has repeatadly been reported by some members of the OpenSSL
+development and others to be a pain to use. So far, those in the
+development team who have said anything about this have expressed
+a wish to avoid libtool for that reason.
+
+
+[LEGAL] =======================================================================
+
* Do I need patent licenses to use OpenSSL?
The patents section of the README file lists patents that may apply to
You can configure OpenSSL so as not to use RC5 and IDEA by using
./config no-rc5 no-idea
-Until the RSA patent expires, U.S. users may want to use
- ./config no-rc5 no-idea no-rsa
-Please note that you will *not* be able to communicate with most of
-the popular web browsers without RSA support.
+* 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).
-* Is OpenSSL thread-safe?
+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.
-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.
+If you develop open source software that uses OpenSSL, you may find it
+useful to choose an other license than the GPL, or state explicitely 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.
-Multi-threaded applications must provide two callback functions to
-OpenSSL. This is described in the threads(3) manpage.
+[USER] ========================================================================
* Why do I get a "PRNG not seeded" error message?
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.
+
+
+* 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.
+
+
+[BUILD] =======================================================================
* Why does the linker complain about undefined symbols?
If the problem persists, please submit a bug report.
-* Where can I get a compiled version of OpenSSL?
+* Why does the OpenSSL test fail with "bc: command not found"?
-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).
+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.
-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.
+* 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).
+
+
+* 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, one should run VCVARS32.BAT which is found in
+the 'bin' subdirectory of the VC++ installation directory (somewhere
+under 'Program Files'). This needs to be done prior to running NMAKE,
+and the changes are only valid for the current DOS session.
+
+
+[PROG] ========================================================================
+
+* 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.
* I've compiled a program under Windows and it crashes: why?
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
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
fi
LIBS="$LIBS -lcrypto"
----- snip:end -----
+
+
+* 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.
+
+
+===============================================================================
+
projects / openssl.git / blobdiff