+
+* Why does the OpenSSL compilation fail with "ar: command not found"?
+
+Getting this message is quite usual on Solaris 2, because Sun has hidden
+away 'ar' and other development commands in directories that aren't in
+$PATH by default. One of those directories is '/usr/ccs/bin'. The
+quickest way to fix this is to do the following (it assumes you use sh
+or any sh-compatible shell):
+
+----- snip:start -----
+ PATH=${PATH}:/usr/ccs/bin; export PATH
+----- snip:end -----
+
+and then redo the compilation. What you should really do is make sure
+'/usr/ccs/bin' is permanently in your $PATH, for example through your
+'.profile' (again, assuming you use a sh-compatible shell).
+
+
+* Why does the OpenSSL compilation fail on Win32 with VC++?
+
+Sometimes, you may get reports from VC++ command line (cl) that it
+can't find standard include files like stdio.h and other weirdnesses.
+One possible cause is that the environment isn't correctly set up.
+To solve that problem, one should run VCVARS32.BAT which is found in
+the 'bin' subdirectory of the VC++ installation directory (somewhere
+under 'Program Files'). This needs to be done prior to running NMAKE,
+and the changes are only valid for the current DOS session.
+
+
+[PROG] ========================================================================
+
+* Is OpenSSL thread-safe?
+
+Yes (with limitations: an SSL connection may not concurrently be used
+by multiple threads). On Windows and many Unix systems, OpenSSL
+automatically uses the multi-threaded versions of the standard
+libraries. If your platform is not one of these, consult the INSTALL
+file.
+
+Multi-threaded applications must provide two callback functions to
+OpenSSL. This is described in the threads(3) manpage.
+
+
+* I've compiled a program under Windows and it crashes: why?
+
+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.
+
+
+===============================================================================
+