f4401cd869
alter des.h to be friendly with openssl/des.h (you can include both in the same file) make libkrb to depend on libdes. bump major. massage various portioin of heimdal to be friendly with openssl 0.9.7b.
767 lines
33 KiB
Plaintext
767 lines
33 KiB
Plaintext
OpenSSL - Frequently Asked Questions
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--------------------------------------
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[MISC] Miscellaneous questions
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* Which is the current version of OpenSSL?
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* Where is the documentation?
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* How can I contact the OpenSSL developers?
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* Where can I get a compiled version of OpenSSL?
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* Why aren't tools like 'autoconf' and 'libtool' used?
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* What is an 'engine' version?
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* How do I check the authenticity of the OpenSSL distribution?
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[LEGAL] Legal questions
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* Do I need patent licenses to use OpenSSL?
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* Can I use OpenSSL with GPL software?
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[USER] Questions on using the OpenSSL applications
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* Why do I get a "PRNG not seeded" error message?
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* Why do I get an "unable to write 'random state'" error message?
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* How do I create certificates or certificate requests?
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* Why can't I create certificate requests?
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* Why does <SSL program> fail with a certificate verify error?
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* Why can I only use weak ciphers when I connect to a server using OpenSSL?
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* How can I create DSA certificates?
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* Why can't I make an SSL connection using a DSA certificate?
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* How can I remove the passphrase on a private key?
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* Why can't I use OpenSSL certificates with SSL client authentication?
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* Why does my browser give a warning about a mismatched hostname?
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* How do I install a CA certificate into a browser?
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* Why is OpenSSL x509 DN output not conformant to RFC2253?
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[BUILD] Questions about building and testing OpenSSL
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* Why does the linker complain about undefined symbols?
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* Why does the OpenSSL test fail with "bc: command not found"?
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* Why does the OpenSSL test fail with "bc: 1 no implemented"?
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* Why does the OpenSSL test fail with "bc: stack empty"?
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* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
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* Why does the OpenSSL compilation fail with "ar: command not found"?
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* Why does the OpenSSL compilation fail on Win32 with VC++?
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* What is special about OpenSSL on Redhat?
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* Why does the OpenSSL compilation fail on MacOS X?
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* Why does the OpenSSL test suite fail on MacOS X?
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* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
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* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
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[PROG] Questions about programming with OpenSSL
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* Is OpenSSL thread-safe?
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* I've compiled a program under Windows and it crashes: why?
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* How do I read or write a DER encoded buffer using the ASN1 functions?
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* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
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* I've called <some function> and it fails, why?
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* I just get a load of numbers for the error output, what do they mean?
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* Why do I get errors about unknown algorithms?
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* Why can't the OpenSSH configure script detect OpenSSL?
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* Can I use OpenSSL's SSL library with non-blocking I/O?
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* Why doesn't my server application receive a client certificate?
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* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
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===============================================================================
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[MISC] ========================================================================
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* Which is the current version of OpenSSL?
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The current version is available from <URL: http://www.openssl.org>.
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OpenSSL 0.9.7b was released on April 10, 2003.
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In addition to the current stable release, you can also access daily
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snapshots of the OpenSSL development version at <URL:
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ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access.
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* Where is the documentation?
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OpenSSL is a library that provides cryptographic functionality to
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applications such as secure web servers. Be sure to read the
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documentation of the application you want to use. The INSTALL file
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explains how to install this library.
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OpenSSL includes a command line utility that can be used to perform a
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variety of cryptographic functions. It is described in the openssl(1)
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manpage. Documentation for developers is currently being written. A
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few manual pages already are available; overviews over libcrypto and
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libssl are given in the crypto(3) and ssl(3) manpages.
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The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
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different directory if you specified one as described in INSTALL).
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In addition, you can read the most current versions at
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<URL: http://www.openssl.org/docs/>.
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For information on parts of libcrypto that are not yet documented, you
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might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
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predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much
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of this still applies to OpenSSL.
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There is some documentation about certificate extensions and PKCS#12
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in doc/openssl.txt
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The original SSLeay documentation is included in OpenSSL as
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doc/ssleay.txt. It may be useful when none of the other resources
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help, but please note that it reflects the obsolete version SSLeay
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0.6.6.
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* How can I contact the OpenSSL developers?
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The README file describes how to submit bug reports and patches to
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OpenSSL. Information on the OpenSSL mailing lists is available from
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<URL: http://www.openssl.org>.
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* Where can I get a compiled version of OpenSSL?
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Some applications that use OpenSSL are distributed in binary form.
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When using such an application, you don't need to install OpenSSL
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yourself; the application will include the required parts (e.g. DLLs).
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If you want to install OpenSSL on a Windows system and you don't have
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a C compiler, read the "Mingw32" section of INSTALL.W32 for information
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on how to obtain and install the free GNU C compiler.
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A number of Linux and *BSD distributions include OpenSSL.
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* Why aren't tools like 'autoconf' and 'libtool' used?
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autoconf will probably be used in future OpenSSL versions. If it was
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less Unix-centric, it might have been used much earlier.
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* What is an 'engine' version?
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With version 0.9.6 OpenSSL was extended to interface to external crypto
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hardware. This was realized in a special release '0.9.6-engine'. With
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version 0.9.7 (not yet released) the changes were merged into the main
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development line, so that the special release is no longer necessary.
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* How do I check the authenticity of the OpenSSL distribution?
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We provide MD5 digests and ASC signatures of each tarball.
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Use MD5 to check that a tarball from a mirror site is identical:
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md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
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You can check authenticity using pgp or gpg. You need the OpenSSL team
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member public key used to sign it (download it from a key server). Then
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just do:
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pgp TARBALL.asc
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[LEGAL] =======================================================================
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* Do I need patent licenses to use OpenSSL?
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The patents section of the README file lists patents that may apply to
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you if you want to use OpenSSL. For information on intellectual
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property rights, please consult a lawyer. The OpenSSL team does not
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offer legal advice.
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You can configure OpenSSL so as not to use RC5 and IDEA by using
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./config no-rc5 no-idea
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* Can I use OpenSSL with GPL software?
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On many systems including the major Linux and BSD distributions, yes (the
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GPL does not place restrictions on using libraries that are part of the
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normal operating system distribution).
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On other systems, the situation is less clear. Some GPL software copyright
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holders claim that you infringe on their rights if you use OpenSSL with
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their software on operating systems that don't normally include OpenSSL.
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If you develop open source software that uses OpenSSL, you may find it
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useful to choose an other license than the GPL, or state explicitly that
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"This program is released under the GPL with the additional exemption that
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compiling, linking, and/or using OpenSSL is allowed." If you are using
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GPL software developed by others, you may want to ask the copyright holder
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for permission to use their software with OpenSSL.
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[USER] ========================================================================
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* Why do I get a "PRNG not seeded" error message?
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Cryptographic software needs a source of unpredictable data to work
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correctly. Many open source operating systems provide a "randomness
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device" (/dev/urandom or /dev/random) that serves this purpose.
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All OpenSSL versions try to use /dev/urandom by default; starting with
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version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not
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available.
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On other systems, applications have to call the RAND_add() or
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RAND_seed() function with appropriate data before generating keys or
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performing public key encryption. (These functions initialize the
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pseudo-random number generator, PRNG.) Some broken applications do
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not do this. As of version 0.9.5, the OpenSSL functions that need
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randomness report an error if the random number generator has not been
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seeded with at least 128 bits of randomness. If this error occurs and
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is not discussed in the documentation of the application you are
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using, please contact the author of that application; it is likely
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that it never worked correctly. OpenSSL 0.9.5 and later make the
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error visible by refusing to perform potentially insecure encryption.
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If you are using Solaris 8, you can add /dev/urandom and /dev/random
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devices by installing patch 112438 (Sparc) or 112439 (x86), which are
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available via the Patchfinder at <URL: http://sunsolve.sun.com>
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(Solaris 9 includes these devices by default). For /dev/random support
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for earlier Solaris versions, see Sun's statement at
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<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski>
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(the SUNWski package is available in patch 105710).
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On systems without /dev/urandom and /dev/random, it is a good idea to
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use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for
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details. Starting with version 0.9.7, OpenSSL will automatically look
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for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and
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/etc/entropy.
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Most components of the openssl command line utility automatically try
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to seed the random number generator from a file. The name of the
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default seeding file is determined as follows: If environment variable
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RANDFILE is set, then it names the seeding file. Otherwise if
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environment variable HOME is set, then the seeding file is $HOME/.rnd.
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If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will
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use file .rnd in the current directory while OpenSSL 0.9.6a uses no
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default seeding file at all. OpenSSL 0.9.6b and later will behave
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similarly to 0.9.6a, but will use a default of "C:\" for HOME on
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Windows systems if the environment variable has not been set.
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If the default seeding file does not exist or is too short, the "PRNG
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not seeded" error message may occur.
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The openssl command line utility will write back a new state to the
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default seeding file (and create this file if necessary) unless
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there was no sufficient seeding.
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Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work.
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Use the "-rand" option of the OpenSSL command line tools instead.
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The $RANDFILE environment variable and $HOME/.rnd are only used by the
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OpenSSL command line tools. Applications using the OpenSSL library
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provide their own configuration options to specify the entropy source,
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please check out the documentation coming the with application.
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* Why do I get an "unable to write 'random state'" error message?
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Sometimes the openssl command line utility does not abort with
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a "PRNG not seeded" error message, but complains that it is
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"unable to write 'random state'". This message refers to the
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default seeding file (see previous answer). A possible reason
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is that no default filename is known because neither RANDFILE
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nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the
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current directory in this case, but this has changed with 0.9.6a.)
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* How do I create certificates or certificate requests?
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Check out the CA.pl(1) manual page. This provides a simple wrapper round
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the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
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out the manual pages for the individual utilities and the certificate
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extensions documentation (currently in doc/openssl.txt).
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* Why can't I create certificate requests?
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You typically get the error:
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unable to find 'distinguished_name' in config
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problems making Certificate Request
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This is because it can't find the configuration file. Check out the
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DIAGNOSTICS section of req(1) for more information.
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* Why does <SSL program> fail with a certificate verify error?
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This problem is usually indicated by log messages saying something like
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"unable to get local issuer certificate" or "self signed certificate".
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When a certificate is verified its root CA must be "trusted" by OpenSSL
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this typically means that the CA certificate must be placed in a directory
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or file and the relevant program configured to read it. The OpenSSL program
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'verify' behaves in a similar way and issues similar error messages: check
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the verify(1) program manual page for more information.
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* Why can I only use weak ciphers when I connect to a server using OpenSSL?
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This is almost certainly because you are using an old "export grade" browser
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which only supports weak encryption. Upgrade your browser to support 128 bit
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ciphers.
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* How can I create DSA certificates?
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Check the CA.pl(1) manual page for a DSA certificate example.
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* Why can't I make an SSL connection to a server using a DSA certificate?
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Typically you'll see a message saying there are no shared ciphers when
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the same setup works fine with an RSA certificate. There are two possible
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causes. The client may not support connections to DSA servers most web
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browsers (including Netscape and MSIE) only support connections to servers
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supporting RSA cipher suites. The other cause is that a set of DH parameters
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has not been supplied to the server. DH parameters can be created with the
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dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
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check the source to s_server in apps/s_server.c for an example.
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* How can I remove the passphrase on a private key?
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Firstly you should be really *really* sure you want to do this. Leaving
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a private key unencrypted is a major security risk. If you decide that
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you do have to do this check the EXAMPLES sections of the rsa(1) and
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dsa(1) manual pages.
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* Why can't I use OpenSSL certificates with SSL client authentication?
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What will typically happen is that when a server requests authentication
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it will either not include your certificate or tell you that you have
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no client certificates (Netscape) or present you with an empty list box
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(MSIE). The reason for this is that when a server requests a client
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certificate it includes a list of CAs names which it will accept. Browsers
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will only let you select certificates from the list on the grounds that
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there is little point presenting a certificate which the server will
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reject.
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The solution is to add the relevant CA certificate to your servers "trusted
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CA list". How you do this depends on the server software in uses. You can
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print out the servers list of acceptable CAs using the OpenSSL s_client tool:
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openssl s_client -connect www.some.host:443 -prexit
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If your server only requests certificates on certain URLs then you may need
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to manually issue an HTTP GET command to get the list when s_client connects:
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GET /some/page/needing/a/certificate.html
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If your CA does not appear in the list then this confirms the problem.
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* Why does my browser give a warning about a mismatched hostname?
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Browsers expect the server's hostname to match the value in the commonName
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(CN) field of the certificate. If it does not then you get a warning.
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* How do I install a CA certificate into a browser?
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The usual way is to send the DER encoded certificate to the browser as
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MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
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link. On MSIE certain extensions such as .der or .cacert may also work, or you
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can import the certificate using the certificate import wizard.
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You can convert a certificate to DER form using the command:
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openssl x509 -in ca.pem -outform DER -out ca.der
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Occasionally someone suggests using a command such as:
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openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
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DO NOT DO THIS! This command will give away your CAs private key and
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reduces its security to zero: allowing anyone to forge certificates in
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whatever name they choose.
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* Why is OpenSSL x509 DN output not conformant to RFC2253?
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The ways to print out the oneline format of the DN (Distinguished Name) have
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been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex()
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interface, the "-nameopt" option could be introduded. See the manual
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page of the "openssl x509" commandline tool for details. The old behaviour
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has however been left as default for the sake of compatibility.
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[BUILD] =======================================================================
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* Why does the linker complain about undefined symbols?
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Maybe the compilation was interrupted, and make doesn't notice that
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something is missing. Run "make clean; make".
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If you used ./Configure instead of ./config, make sure that you
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selected the right target. File formats may differ slightly between
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OS versions (for example sparcv8/sparcv9, or a.out/elf).
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In case you get errors about the following symbols, use the config
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option "no-asm", as described in INSTALL:
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BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
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CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
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RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
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bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
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bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
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des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
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des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
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If none of these helps, you may want to try using the current snapshot.
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If the problem persists, please submit a bug report.
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* Why does the OpenSSL test fail with "bc: command not found"?
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You didn't install "bc", the Unix calculator. If you want to run the
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tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
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* Why does the OpenSSL test fail with "bc: 1 no implemented"?
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On some SCO installations or versions, bc has a bug that gets triggered
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when you run the test suite (using "make test"). The message returned is
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"bc: 1 not implemented".
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The best way to deal with this is to find another implementation of bc
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and compile/install it. GNU bc (see http://www.gnu.org/software/software.html
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for download instructions) can be safely used, for example.
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* Why does the OpenSSL test fail with "bc: stack empty"?
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On some DG/ux versions, bc seems to have a too small stack for calculations
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that the OpenSSL bntest throws at it. This gets triggered when you run the
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test suite (using "make test"). The message returned is "bc: stack empty".
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The best way to deal with this is to find another implementation of bc
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and compile/install it. GNU bc (see http://www.gnu.org/software/software.html
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for download instructions) can be safely used, for example.
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* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
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On some Alpha installations running Tru64 Unix and Compaq C, the compilation
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of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual
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memory to continue compilation.' As far as the tests have shown, this may be
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a compiler bug. What happens is that it eats up a lot of resident memory
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to build something, probably a table. The problem is clearly in the
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optimization code, because if one eliminates optimization completely (-O0),
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the compilation goes through (and the compiler consumes about 2MB of resident
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memory instead of 240MB or whatever one's limit is currently).
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There are three options to solve this problem:
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1. set your current data segment size soft limit higher. Experience shows
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that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do
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this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
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kbytes to set the limit to.
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2. If you have a hard limit that is lower than what you need and you can't
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get it changed, you can compile all of OpenSSL with -O0 as optimization
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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 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. For patent reasons, support for IDEA, RC5 and MDC2
|
|
is disabled 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.
|
|
|
|
FYI: Patent numbers and expiry dates of US patents:
|
|
MDC-2: 4,908,861 13/03/2007
|
|
IDEA: 5,214,703 25/05/2010
|
|
RC5: 5,724,428 03/03/2015
|
|
|
|
|
|
* 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.
|
|
|
|
[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?
|
|
|
|
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.
|
|
|
|
|
|
* 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.
|
|
|
|
|
|
* 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.
|
|
|
|
|
|
===============================================================================
|
|
|