FAQ revision 59191
1OpenSSL - Frequently Asked Questions 2-------------------------------------- 3 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 called <some function> and it fails, why? 14* I just get a load of numbers for the error output, what do they mean? 15* Why do I get errors about unknown algorithms? 16* How do I create certificates or certificate requests? 17* Why can't I create certificate requests? 18* Why does <SSL program> fail with a certificate verify error? 19* How can I create DSA certificates? 20* Why can't I make an SSL connection using a DSA certificate? 21* Why can't the OpenSSH configure script detect OpenSSL? 22 23 24* Which is the current version of OpenSSL? 25 26The current version is available from <URL: http://www.openssl.org>. 27OpenSSL 0.9.5a was released on April 1st, 2000. 28 29In addition to the current stable release, you can also access daily 30snapshots of the OpenSSL development version at <URL: 31ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. 32 33 34* Where is the documentation? 35 36OpenSSL is a library that provides cryptographic functionality to 37applications such as secure web servers. Be sure to read the 38documentation of the application you want to use. The INSTALL file 39explains how to install this library. 40 41OpenSSL includes a command line utility that can be used to perform a 42variety of cryptographic functions. It is described in the openssl(1) 43manpage. Documentation for developers is currently being written. A 44few manual pages already are available; overviews over libcrypto and 45libssl are given in the crypto(3) and ssl(3) manpages. 46 47The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a 48different directory if you specified one as described in INSTALL). 49In addition, you can read the most current versions at 50<URL: http://www.openssl.org/docs/>. 51 52For information on parts of libcrypto that are not yet documented, you 53might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's 54predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much 55of this still applies to OpenSSL. 56 57There is some documentation about certificate extensions and PKCS#12 58in doc/openssl.txt 59 60The original SSLeay documentation is included in OpenSSL as 61doc/ssleay.txt. It may be useful when none of the other resources 62help, but please note that it reflects the obsolete version SSLeay 630.6.6. 64 65 66* How can I contact the OpenSSL developers? 67 68The README file describes how to submit bug reports and patches to 69OpenSSL. Information on the OpenSSL mailing lists is available from 70<URL: http://www.openssl.org>. 71 72 73* Do I need patent licenses to use OpenSSL? 74 75The patents section of the README file lists patents that may apply to 76you if you want to use OpenSSL. For information on intellectual 77property rights, please consult a lawyer. The OpenSSL team does not 78offer legal advice. 79 80You can configure OpenSSL so as not to use RC5 and IDEA by using 81 ./config no-rc5 no-idea 82 83Until the RSA patent expires, U.S. users may want to use 84 ./config no-rc5 no-idea no-rsa 85 86Please note that you will *not* be able to communicate with most of 87the popular web browsers without RSA support. 88 89 90* Is OpenSSL thread-safe? 91 92Yes (with limitations: an SSL connection may not concurrently be used 93by multiple threads). On Windows and many Unix systems, OpenSSL 94automatically uses the multi-threaded versions of the standard 95libraries. If your platform is not one of these, consult the INSTALL 96file. 97 98Multi-threaded applications must provide two callback functions to 99OpenSSL. This is described in the threads(3) manpage. 100 101 102* Why do I get a "PRNG not seeded" error message? 103 104Cryptographic software needs a source of unpredictable data to work 105correctly. Many open source operating systems provide a "randomness 106device" that serves this purpose. On other systems, applications have 107to call the RAND_add() or RAND_seed() function with appropriate data 108before generating keys or performing public key encryption. 109 110Some broken applications do not do this. As of version 0.9.5, the 111OpenSSL functions that need randomness report an error if the random 112number generator has not been seeded with at least 128 bits of 113randomness. If this error occurs, please contact the author of the 114application you are using. It is likely that it never worked 115correctly. OpenSSL 0.9.5 and later make the error visible by refusing 116to perform potentially insecure encryption. 117 118On systems without /dev/urandom, it is a good idea to use the Entropy 119Gathering Demon; see the RAND_egd() manpage for details. 120 121Most components of the openssl command line tool try to use the 122file $HOME/.rnd (or $RANDFILE, if this environment variable is set) 123for seeding the PRNG. If this file does not exist or is too short, 124the "PRNG not seeded" error message may occur. 125 126[Note to OpenSSL 0.9.5 users: The command "openssl rsa" in version 1270.9.5 does not do this and will fail on systems without /dev/urandom 128when trying to password-encrypt an RSA key! This is a bug in the 129library; try a later version instead.] 130 131 132* Why does the linker complain about undefined symbols? 133 134Maybe the compilation was interrupted, and make doesn't notice that 135something is missing. Run "make clean; make". 136 137If you used ./Configure instead of ./config, make sure that you 138selected the right target. File formats may differ slightly between 139OS versions (for example sparcv8/sparcv9, or a.out/elf). 140 141In case you get errors about the following symbols, use the config 142option "no-asm", as described in INSTALL: 143 144 BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, 145 CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, 146 RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, 147 bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, 148 bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, 149 des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, 150 des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order 151 152If none of these helps, you may want to try using the current snapshot. 153If the problem persists, please submit a bug report. 154 155 156* Where can I get a compiled version of OpenSSL? 157 158Some applications that use OpenSSL are distributed in binary form. 159When using such an application, you don't need to install OpenSSL 160yourself; the application will include the required parts (e.g. DLLs). 161 162If you want to install OpenSSL on a Windows system and you don't have 163a C compiler, read the "Mingw32" section of INSTALL.W32 for information 164on how to obtain and install the free GNU C compiler. 165 166A number of Linux and *BSD distributions include OpenSSL. 167 168 169* I've compiled a program under Windows and it crashes: why? 170 171This is usually because you've missed the comment in INSTALL.W32. You 172must link with the multithreaded DLL version of the VC++ runtime library 173otherwise the conflict will cause a program to crash: typically on the 174first BIO related read or write operation. 175 176 177* I've called <some function> and it fails, why? 178 179Before submitting a report or asking in one of the mailing lists you 180should try to determine the cause. In particular you should call 181ERR_print_errors() or ERR_print_errors_fp() after the failed call 182and see if the message helps. 183 184 185* I just get a load of numbers for the error output, what do they mean? 186 187The actual format is described in the ERR_print_errors() manual page. 188You should call the function ERR_load_crypto_strings() before hand and 189the message will be output in text form. If you can't do this (for example 190it is a pre-compiled binary) you can use the errstr utility on the error 191code itself (the hex digits after the second colon). 192 193 194* Why do I get errors about unknown algorithms? 195 196This can happen under several circumstances such as reading in an 197encrypted private key or attempting to decrypt a PKCS#12 file. The cause 198is forgetting to load OpenSSL's table of algorithms with 199OpenSSL_add_all_algorithms(). See the manual page for more information. 200 201 202* How do I create certificates or certificate requests? 203 204Check out the CA.pl(1) manual page. This provides a simple wrapper round 205the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check 206out the manual pages for the individual utilities and the certificate 207extensions documentation (currently in doc/openssl.txt). 208 209 210* Why can't I create certificate requests? 211 212You typically get the error: 213 214 unable to find 'distinguished_name' in config 215 problems making Certificate Request 216 217This is because it can't find the configuration file. Check out the 218DIAGNOSTICS section of req(1) for more information. 219 220 221* Why does <SSL program> fail with a certificate verify error? 222 223This problem is usually indicated by log messages saying something like 224"unable to get local issuer certificate" or "self signed certificate". 225When a certificate is verified its root CA must be "trusted" by OpenSSL 226this typically means that the CA certificate must be placed in a directory 227or file and the relevant program configured to read it. The OpenSSL program 228'verify' behaves in a similar way and issues similar error messages: check 229the verify(1) program manual page for more information. 230 231 232* How can I create DSA certificates? 233 234Check the CA.pl(1) manual page for a DSA certificate example. 235 236 237* Why can't I make an SSL connection to a server using a DSA certificate? 238 239Typically you'll see a message saying there are no shared ciphers when 240the same setup works fine with an RSA certificate. There are two possible 241causes. The client may not support connections to DSA servers most web 242browsers only support connections to servers supporting RSA cipher suites. 243The other cause is that a set of DH parameters has not been supplied to 244the server. DH parameters can be created with the dhparam(1) command and 245loaded using the SSL_CTX_set_tmp_dh() for example: check the source to 246s_server in apps/s_server.c for an example. 247 248 249* Why can't the OpenSSH configure script detect OpenSSL? 250 251There is a problem with OpenSSH 1.2.2p1, in that the configure script 252can't find the installed OpenSSL libraries. The problem is actually 253a small glitch that is easily solved with the following patch to be 254applied to the OpenSSH distribution: 255 256----- snip:start ----- 257--- openssh-1.2.2p1/configure.in.orig Thu Mar 23 18:56:58 2000 258+++ openssh-1.2.2p1/configure.in Thu Mar 23 18:55:05 2000 259@@ -152,10 +152,10 @@ 260 AC_MSG_CHECKING([for OpenSSL/SSLeay directory]) 261 for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do 262 if test ! -z "$ssldir" ; then 263- LIBS="$saved_LIBS -L$ssldir" 264+ LIBS="$saved_LIBS -L$ssldir/lib" 265 CFLAGS="$CFLAGS -I$ssldir/include" 266 if test "x$need_dash_r" = "x1" ; then 267- LIBS="$LIBS -R$ssldir" 268+ LIBS="$LIBS -R$ssldir/lib" 269 fi 270 fi 271 LIBS="$LIBS -lcrypto" 272--- openssh-1.2.2p1/configure.orig Thu Mar 23 18:55:02 2000 273+++ openssh-1.2.2p1/configure Thu Mar 23 18:57:08 2000 274@@ -1890,10 +1890,10 @@ 275 echo "configure:1891: checking for OpenSSL/SSLeay directory" >&5 276 for ssldir in "" $tryssldir /usr /usr/local/openssl /usr/lib/openssl /usr/local/ssl /usr/lib/ssl /usr/local /usr/pkg /opt /opt/openssl ; do 277 if test ! -z "$ssldir" ; then 278- LIBS="$saved_LIBS -L$ssldir" 279+ LIBS="$saved_LIBS -L$ssldir/lib" 280 CFLAGS="$CFLAGS -I$ssldir/include" 281 if test "x$need_dash_r" = "x1" ; then 282- LIBS="$LIBS -R$ssldir" 283+ LIBS="$LIBS -R$ssldir/lib" 284 fi 285 fi 286 LIBS="$LIBS -lcrypto" 287----- snip:end ----- 288