308 lines
12 KiB
Plaintext
308 lines
12 KiB
Plaintext
OpenSSL - Frequently Asked 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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* Do I need patent licenses to use OpenSSL?
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* Is OpenSSL thread-safe?
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* Why do I get a "PRNG not seeded" error message?
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* Why does the linker complain about undefined symbols?
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* Where can I get a compiled version of OpenSSL?
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* I've compiled a program under Windows and it crashes: 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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* 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 the OpenSSH configure script detect OpenSSL?
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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 0.9.5a was released on April 1st, 2000.
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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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* 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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Until the RSA patent expires, U.S. users may want to use
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./config no-rc5 no-idea no-rsa
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Please note that you will *not* be able to communicate with most of
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the popular web browsers without RSA support.
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* Is OpenSSL thread-safe?
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Yes (with limitations: an SSL connection may not concurrently be used
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by multiple threads). On Windows and many Unix systems, OpenSSL
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automatically uses the multi-threaded versions of the standard
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libraries. If your platform is not one of these, consult the INSTALL
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file.
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Multi-threaded applications must provide two callback functions to
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OpenSSL. This is described in the threads(3) manpage.
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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" that serves this purpose. On other systems, applications have
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to call the RAND_add() or RAND_seed() function with appropriate data
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before generating keys or performing public key encryption.
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Some broken applications do not do this. As of version 0.9.5, the
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OpenSSL functions that need randomness report an error if the random
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number generator has not been seeded with at least 128 bits of
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randomness. If this error occurs, please contact the author of the
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application you are using. It is likely that it never worked
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correctly. OpenSSL 0.9.5 and later make the error visible by refusing
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to perform potentially insecure encryption.
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On systems without /dev/urandom, it is a good idea to use the Entropy
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Gathering Demon; see the RAND_egd() manpage for details.
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Most components of the openssl command line tool try to use the
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file $HOME/.rnd (or $RANDFILE, if this environment variable is set)
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for seeding the PRNG. If this file does not exist or is too short,
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the "PRNG not seeded" error message may occur.
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[Note to OpenSSL 0.9.5 users: The command "openssl rsa" in version
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0.9.5 does not do this and will fail on systems without /dev/urandom
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when trying to password-encrypt an RSA key! This is a bug in the
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library; try a later version instead.]
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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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* 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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* I've compiled a program under Windows and it crashes: why?
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This is usually because you've missed the comment in INSTALL.W32. You
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must link with the multithreaded DLL version of the VC++ runtime library
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otherwise the conflict will cause a program to crash: typically on the
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first BIO related read or write operation.
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* I've called <some function> and it fails, why?
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Before submitting a report or asking in one of the mailing lists, you
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should try to determine the cause. In particular, you should call
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ERR_print_errors() or ERR_print_errors_fp() after the failed call
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and see if the message helps. Note that the problem may occur earlier
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than you think -- you should check for errors after every call where
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it is possible, otherwise the actual problem may be hidden because
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some OpenSSL functions clear the error state.
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* I just get a load of numbers for the error output, what do they mean?
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The actual format is described in the ERR_print_errors() manual page.
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You should call the function ERR_load_crypto_strings() before hand and
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the message will be output in text form. If you can't do this (for example
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it is a pre-compiled binary) you can use the errstr utility on the error
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code itself (the hex digits after the second colon).
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* Why do I get errors about unknown algorithms?
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This can happen under several circumstances such as reading in an
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encrypted private key or attempting to decrypt a PKCS#12 file. The cause
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is forgetting to load OpenSSL's table of algorithms with
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OpenSSL_add_all_algorithms(). See the manual page for more information.
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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 the OpenSSH configure script detect OpenSSL?
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There is a problem with OpenSSH 1.2.2p1, in that the configure script
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can't find the installed OpenSSL libraries. The problem is actually
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a small glitch that is easily solved with the following patch to be
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applied to the OpenSSH distribution:
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----- snip:start -----
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--- openssh-1.2.2p1/configure.in.orig Thu Mar 23 18:56:58 2000
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+++ openssh-1.2.2p1/configure.in Thu Mar 23 18:55:05 2000
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@@ -152,10 +152,10 @@
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AC_MSG_CHECKING([for OpenSSL/SSLeay directory])
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for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do
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if test ! -z "$ssldir" ; then
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- LIBS="$saved_LIBS -L$ssldir"
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+ LIBS="$saved_LIBS -L$ssldir/lib"
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CFLAGS="$CFLAGS -I$ssldir/include"
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if test "x$need_dash_r" = "x1" ; then
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- LIBS="$LIBS -R$ssldir"
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+ LIBS="$LIBS -R$ssldir/lib"
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fi
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fi
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LIBS="$LIBS -lcrypto"
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--- openssh-1.2.2p1/configure.orig Thu Mar 23 18:55:02 2000
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+++ openssh-1.2.2p1/configure Thu Mar 23 18:57:08 2000
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@@ -1890,10 +1890,10 @@
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echo "configure:1891: checking for OpenSSL/SSLeay directory" >&5
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for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do
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if test ! -z "$ssldir" ; then
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- LIBS="$saved_LIBS -L$ssldir"
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+ LIBS="$saved_LIBS -L$ssldir/lib"
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CFLAGS="$CFLAGS -I$ssldir/include"
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if test "x$need_dash_r" = "x1" ; then
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- LIBS="$LIBS -R$ssldir"
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+ LIBS="$LIBS -R$ssldir/lib"
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fi
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fi
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LIBS="$LIBS -lcrypto"
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----- snip:end -----
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