X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=FAQ;h=29acc8afdf5be9f58c0bce13c58259e6b522414b;hb=9ef9e78520eba0fb3d92b581dc4f895a5f464387;hp=6e34953c11ee19ca3d73f5ba6acf1a65e27cf85b;hpb=26b0d15628a63c452d53711df3e4f2891b288ae4;p=oweals%2Fopenssl.git

diff --git a/FAQ b/FAQ
index 6e34953c11..29acc8afdf 100644
--- a/FAQ
+++ b/FAQ
@@ -10,6 +10,8 @@ OpenSSL  -  Frequently Asked Questions
 * Why does the linker complain about undefined symbols?
 * Where can I get a compiled version of OpenSSL?
 * I've compiled a program under Windows and it crashes: why?
+* How do I read or write a DER encoded buffer using the ASN1 functions?
+* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
 * I've called <some function> and it fails, why?
 * I just get a load of numbers for the error output, what do they mean?
 * Why do I get errors about unknown algorithms?
@@ -30,7 +32,7 @@ OpenSSL  -  Frequently Asked Questions
 * Which is the current version of OpenSSL?
 
 The current version is available from <URL: http://www.openssl.org>.
-OpenSSL 0.9.5a was released on April 1st, 2000.
+OpenSSL 0.9.6 was released on September 24th, 2000.
 
 In addition to the current stable release, you can also access daily
 snapshots of the OpenSSL development version at <URL:
@@ -133,7 +135,7 @@ installing the SUNski package from Sun patch 105710-01 (Sparc) which
 adds a /dev/random device and make sure it gets used, usually through
 $RANDFILE.  There are probably similar patches for the other Solaris
 versions.  However, be warned that /dev/random is usually a blocking
-device, which may have som effects on OpenSSL.
+device, which may have some effects on OpenSSL.
 
 
 * Why does the linker complain about undefined symbols?
@@ -181,6 +183,54 @@ otherwise the conflict will cause a program to crash: typically on the
 first BIO related read or write operation.
 
 
+* 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