1 OpenSSL - Frequently Asked Questions
2 --------------------------------------
4 * Which is the current version of OpenSSL?
5 * Where is the documentation?
6 * How can I contact the OpenSSL developers?
7 * Do I need patent licenses to use OpenSSL?
8 * Is OpenSSL thread-safe?
9 * Why do I get a "PRNG not seeded" error message?
10 * Why does the linker complain about undefined symbols?
11 * Where can I get a compiled version of OpenSSL?
12 * I've compiled a program under Windows and it crashes: why?
13 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
14 * I've called <some function> and it fails, why?
15 * I just get a load of numbers for the error output, what do they mean?
16 * Why do I get errors about unknown algorithms?
17 * How do I create certificates or certificate requests?
18 * Why can't I create certificate requests?
19 * Why does <SSL program> fail with a certificate verify error?
20 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
21 * How can I create DSA certificates?
22 * Why can't I make an SSL connection using a DSA certificate?
23 * How can I remove the passphrase on a private key?
24 * Why can't the OpenSSH configure script detect OpenSSL?
25 * Why does the OpenSSL test fail with "bc: command not found"?
26 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
27 * Why does the OpenSSL compilation fail on Alpha True64 Unix?
28 * Why does the OpenSSL compilation fail with "ar: command not found"?
31 * Which is the current version of OpenSSL?
33 The current version is available from <URL: http://www.openssl.org>.
34 OpenSSL 0.9.5a was released on April 1st, 2000.
36 In addition to the current stable release, you can also access daily
37 snapshots of the OpenSSL development version at <URL:
38 ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access.
41 * Where is the documentation?
43 OpenSSL is a library that provides cryptographic functionality to
44 applications such as secure web servers. Be sure to read the
45 documentation of the application you want to use. The INSTALL file
46 explains how to install this library.
48 OpenSSL includes a command line utility that can be used to perform a
49 variety of cryptographic functions. It is described in the openssl(1)
50 manpage. Documentation for developers is currently being written. A
51 few manual pages already are available; overviews over libcrypto and
52 libssl are given in the crypto(3) and ssl(3) manpages.
54 The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
55 different directory if you specified one as described in INSTALL).
56 In addition, you can read the most current versions at
57 <URL: http://www.openssl.org/docs/>.
59 For information on parts of libcrypto that are not yet documented, you
60 might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
61 predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much
62 of this still applies to OpenSSL.
64 There is some documentation about certificate extensions and PKCS#12
67 The original SSLeay documentation is included in OpenSSL as
68 doc/ssleay.txt. It may be useful when none of the other resources
69 help, but please note that it reflects the obsolete version SSLeay
73 * How can I contact the OpenSSL developers?
75 The README file describes how to submit bug reports and patches to
76 OpenSSL. Information on the OpenSSL mailing lists is available from
77 <URL: http://www.openssl.org>.
80 * Do I need patent licenses to use OpenSSL?
82 The patents section of the README file lists patents that may apply to
83 you if you want to use OpenSSL. For information on intellectual
84 property rights, please consult a lawyer. The OpenSSL team does not
87 You can configure OpenSSL so as not to use RC5 and IDEA by using
88 ./config no-rc5 no-idea
91 * Is OpenSSL thread-safe?
93 Yes (with limitations: an SSL connection may not concurrently be used
94 by multiple threads). On Windows and many Unix systems, OpenSSL
95 automatically uses the multi-threaded versions of the standard
96 libraries. If your platform is not one of these, consult the INSTALL
99 Multi-threaded applications must provide two callback functions to
100 OpenSSL. This is described in the threads(3) manpage.
103 * Why do I get a "PRNG not seeded" error message?
105 Cryptographic software needs a source of unpredictable data to work
106 correctly. Many open source operating systems provide a "randomness
107 device" that serves this purpose. On other systems, applications have
108 to call the RAND_add() or RAND_seed() function with appropriate data
109 before generating keys or performing public key encryption.
111 Some broken applications do not do this. As of version 0.9.5, the
112 OpenSSL functions that need randomness report an error if the random
113 number generator has not been seeded with at least 128 bits of
114 randomness. If this error occurs, please contact the author of the
115 application you are using. It is likely that it never worked
116 correctly. OpenSSL 0.9.5 and later make the error visible by refusing
117 to perform potentially insecure encryption.
119 On systems without /dev/urandom, it is a good idea to use the Entropy
120 Gathering Demon; see the RAND_egd() manpage for details.
122 Most components of the openssl command line tool try to use the
123 file $HOME/.rnd (or $RANDFILE, if this environment variable is set)
124 for seeding the PRNG. If this file does not exist or is too short,
125 the "PRNG not seeded" error message may occur.
127 [Note to OpenSSL 0.9.5 users: The command "openssl rsa" in version
128 0.9.5 does not do this and will fail on systems without /dev/urandom
129 when trying to password-encrypt an RSA key! This is a bug in the
130 library; try a later version instead.]
132 For Solaris 2.6, Tim Nibbe <tnibbe@sprint.net> and others have suggested
133 installing the SUNski package from Sun patch 105710-01 (Sparc) which
134 adds a /dev/random device and make sure it gets used, usually through
135 $RANDFILE. There are probably similar patches for the other Solaris
136 versions. However, be warned that /dev/random is usually a blocking
137 device, which may have som effects on OpenSSL.
140 * Why does the linker complain about undefined symbols?
142 Maybe the compilation was interrupted, and make doesn't notice that
143 something is missing. Run "make clean; make".
145 If you used ./Configure instead of ./config, make sure that you
146 selected the right target. File formats may differ slightly between
147 OS versions (for example sparcv8/sparcv9, or a.out/elf).
149 In case you get errors about the following symbols, use the config
150 option "no-asm", as described in INSTALL:
152 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
153 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
154 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
155 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
156 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
157 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
158 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
160 If none of these helps, you may want to try using the current snapshot.
161 If the problem persists, please submit a bug report.
164 * Where can I get a compiled version of OpenSSL?
166 Some applications that use OpenSSL are distributed in binary form.
167 When using such an application, you don't need to install OpenSSL
168 yourself; the application will include the required parts (e.g. DLLs).
170 If you want to install OpenSSL on a Windows system and you don't have
171 a C compiler, read the "Mingw32" section of INSTALL.W32 for information
172 on how to obtain and install the free GNU C compiler.
174 A number of Linux and *BSD distributions include OpenSSL.
177 * I've compiled a program under Windows and it crashes: why?
179 This is usually because you've missed the comment in INSTALL.W32. You
180 must link with the multithreaded DLL version of the VC++ runtime library
181 otherwise the conflict will cause a program to crash: typically on the
182 first BIO related read or write operation.
185 * I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
187 This usually happens when you try compiling something using the PKCS#12
188 macros with a C++ compiler. There is hardly ever any need to use the
189 PKCS#12 macros in a program, it is much easier to parse and create
190 PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions
191 documented in doc/openssl.txt and with examples in demos/pkcs12. The
192 'pkcs12' application has to use the macros because it prints out
193 debugging information.
196 * I've called <some function> and it fails, why?
198 Before submitting a report or asking in one of the mailing lists, you
199 should try to determine the cause. In particular, you should call
200 ERR_print_errors() or ERR_print_errors_fp() after the failed call
201 and see if the message helps. Note that the problem may occur earlier
202 than you think -- you should check for errors after every call where
203 it is possible, otherwise the actual problem may be hidden because
204 some OpenSSL functions clear the error state.
207 * I just get a load of numbers for the error output, what do they mean?
209 The actual format is described in the ERR_print_errors() manual page.
210 You should call the function ERR_load_crypto_strings() before hand and
211 the message will be output in text form. If you can't do this (for example
212 it is a pre-compiled binary) you can use the errstr utility on the error
213 code itself (the hex digits after the second colon).
216 * Why do I get errors about unknown algorithms?
218 This can happen under several circumstances such as reading in an
219 encrypted private key or attempting to decrypt a PKCS#12 file. The cause
220 is forgetting to load OpenSSL's table of algorithms with
221 OpenSSL_add_all_algorithms(). See the manual page for more information.
224 * How do I create certificates or certificate requests?
226 Check out the CA.pl(1) manual page. This provides a simple wrapper round
227 the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
228 out the manual pages for the individual utilities and the certificate
229 extensions documentation (currently in doc/openssl.txt).
232 * Why can't I create certificate requests?
234 You typically get the error:
236 unable to find 'distinguished_name' in config
237 problems making Certificate Request
239 This is because it can't find the configuration file. Check out the
240 DIAGNOSTICS section of req(1) for more information.
243 * Why does <SSL program> fail with a certificate verify error?
245 This problem is usually indicated by log messages saying something like
246 "unable to get local issuer certificate" or "self signed certificate".
247 When a certificate is verified its root CA must be "trusted" by OpenSSL
248 this typically means that the CA certificate must be placed in a directory
249 or file and the relevant program configured to read it. The OpenSSL program
250 'verify' behaves in a similar way and issues similar error messages: check
251 the verify(1) program manual page for more information.
254 * Why can I only use weak ciphers when I connect to a server using OpenSSL?
256 This is almost certainly because you are using an old "export grade" browser
257 which only supports weak encryption. Upgrade your browser to support 128 bit
261 * How can I create DSA certificates?
263 Check the CA.pl(1) manual page for a DSA certificate example.
266 * Why can't I make an SSL connection to a server using a DSA certificate?
268 Typically you'll see a message saying there are no shared ciphers when
269 the same setup works fine with an RSA certificate. There are two possible
270 causes. The client may not support connections to DSA servers most web
271 browsers (including Netscape and MSIE) only support connections to servers
272 supporting RSA cipher suites. The other cause is that a set of DH parameters
273 has not been supplied to the server. DH parameters can be created with the
274 dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
275 check the source to s_server in apps/s_server.c for an example.
278 * How can I remove the passphrase on a private key?
280 Firstly you should be really *really* sure you want to do this. Leaving
281 a private key unencrypted is a major security risk. If you decide that
282 you do have to do this check the EXAMPLES sections of the rsa(1) and
286 * Why can't the OpenSSH configure script detect OpenSSL?
288 There is a problem with OpenSSH 1.2.2p1, in that the configure script
289 can't find the installed OpenSSL libraries. The problem is actually
290 a small glitch that is easily solved with the following patch to be
291 applied to the OpenSSH distribution:
293 ----- snip:start -----
294 --- openssh-1.2.2p1/configure.in.orig Thu Mar 23 18:56:58 2000
295 +++ openssh-1.2.2p1/configure.in Thu Mar 23 18:55:05 2000
296 @@ -152,10 +152,10 @@
297 AC_MSG_CHECKING([for OpenSSL/SSLeay directory])
298 for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do
299 if test ! -z "$ssldir" ; then
300 - LIBS="$saved_LIBS -L$ssldir"
301 + LIBS="$saved_LIBS -L$ssldir/lib"
302 CFLAGS="$CFLAGS -I$ssldir/include"
303 if test "x$need_dash_r" = "x1" ; then
304 - LIBS="$LIBS -R$ssldir"
305 + LIBS="$LIBS -R$ssldir/lib"
308 LIBS="$LIBS -lcrypto"
309 --- openssh-1.2.2p1/configure.orig Thu Mar 23 18:55:02 2000
310 +++ openssh-1.2.2p1/configure Thu Mar 23 18:57:08 2000
311 @@ -1890,10 +1890,10 @@
312 echo "configure:1891: checking for OpenSSL/SSLeay directory" >&5
313 for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do
314 if test ! -z "$ssldir" ; then
315 - LIBS="$saved_LIBS -L$ssldir"
316 + LIBS="$saved_LIBS -L$ssldir/lib"
317 CFLAGS="$CFLAGS -I$ssldir/include"
318 if test "x$need_dash_r" = "x1" ; then
319 - LIBS="$LIBS -R$ssldir"
320 + LIBS="$LIBS -R$ssldir/lib"
323 LIBS="$LIBS -lcrypto"
327 * Why does the OpenSSL test fail with "bc: command not found"?
329 You didn't install "bc", the Unix calculator. If you want to run the
330 tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
333 * Why does the OpenSSL test fail with "bc: 1 no implemented"?
335 On some SCO installations or versions, bc has a bug that gets triggered when
336 you run the test suite (using "make test"). The message returned is "bc:
337 1 not implemented". The best way to deal with this is to find another
338 implementation of bc and compile/install it. For example, GNU bc (see
339 http://www.gnu.org/software/software.html for download instructions) can
343 * Why does the OpenSSL compilation fail on Alpha True64 Unix?
345 On some Alpha installations running True64 Unix and Compaq C, the compilation
346 of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual
347 memory to continue compilation.' As far as the tests have shown, this may be
348 a compiler bug. What happens is that it eats up a lot of resident memory
349 to build something, probably a table. The problem is clearly in the
350 optimization code, because if one eliminates optimization completely (-O0),
351 the compilation goes through (and the compiler consumes about 2MB of resident
352 memory instead of 240MB or whatever one's limit is currently).
354 There are three options to solve this problem:
356 1. set your current data segment size soft limit higher. Experience shows
357 that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do
358 this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
359 kbytes to set the limit to.
361 2. If you have a hard limit that is lower than what you need and you can't
362 get it changed, you can compile all of OpenSSL with -O0 as optimization
363 level. This is however not a very nice thing to do for those who expect to
364 get the best result from OpenSSL. A bit more complicated solution is the
367 ----- snip:start -----
368 make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \
369 sed -e 's/ -O[0-9] / -O0 /'`"
370 rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'`
374 This will only compile sha_dgst.c with -O0, the rest with the optimization
375 level chosen by the configuration process. When the above is done, do the
376 test and installation and you're set.
379 * Why does the OpenSSL compilation fail with "ar: command not found"?
381 Getting this message is quite usual on Solaris 2, because Sun has hidden
382 away 'ar' and other development commands in directories that aren't in
383 $PATH by default. One of those directories is '/usr/ccs/bin'. The
384 quickest way to fix this is to do the following (it assumes you use sh
385 or any sh-compatible shell):
387 ----- snip:start -----
388 PATH=${PATH}:/usr/ccs/bin; export PATH
391 and then redo the compilation. What you should really do is make sure
392 '/usr/ccs/bin' is permanently in your $PATH, for example through your
393 '.profile' (again, assuming you use a sh-compatible shell).