Change the memory leak FAQ entry to describe the levels of thread safety in each...

[openssl.git] / FAQ

diff --git a/FAQ b/FAQ
index bd40bcd243b767de08f139a65df6abba0780b9d7..dab94a0359c80602b2ee26d876c9802442ea527e 100644 (file)
--- a/FAQ
+++ b/FAQ
@@ -52,6 +52,7 @@ OpenSSL  -  Frequently Asked Questions
 * Is OpenSSL thread-safe?
 * 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?
+* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
 * 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?
@@ -60,6 +61,7 @@ OpenSSL  -  Frequently Asked Questions
 * Can I use OpenSSL's SSL library with non-blocking I/O?
 * Why doesn't my server application receive a client certificate?
 * Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
+* I think I've detected a memory leak, is this a bug?
 
 ===============================================================================
 
@@ -68,7 +70,7 @@ OpenSSL  -  Frequently Asked Questions
 * Which is the current version of OpenSSL?
 
 The current version is available from <URL: http://www.openssl.org>.
-OpenSSL 0.9.7c was released on September 30, 2003.
+OpenSSL 0.9.7f was released on March 22, 2005.
 
 In addition to the current stable release, you can also access daily
 snapshots of the OpenSSL development version at <URL:
@@ -116,11 +118,14 @@ OpenSSL.  Information on the OpenSSL mailing lists is available from
 
 * Where can I get a compiled version of OpenSSL?
 
+You can finder pointers to binary distributions in
+http://www.openssl.org/related/binaries.html .
+
 Some applications that use OpenSSL are distributed in binary form.
 When using such an application, you don't need to install OpenSSL
 yourself; the application will include the required parts (e.g. DLLs).
 
-If you want to install OpenSSL on a Windows system and you don't have
+If you want to build OpenSSL on a Windows system and you don't have
 a C compiler, read the "Mingw32" section of INSTALL.W32 for information
 on how to obtain and install the free GNU C compiler.
 
@@ -147,7 +152,8 @@ Use MD5 to check that a tarball from a mirror site is identical:
    md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
 
 You can check authenticity using pgp or gpg. You need the OpenSSL team
-member public key used to sign it (download it from a key server). Then
+member public key used to sign it (download it from a key server, see a
+list of keys at <URL: http://www.openssl.org/about/>). Then
 just do:
 
    pgp TARBALL.asc
@@ -161,8 +167,8 @@ you if you want to use OpenSSL.  For information on intellectual
 property rights, please consult a lawyer.  The OpenSSL team does not
 offer legal advice.
 
-You can configure OpenSSL so as not to use RC5 and IDEA by using
- ./config no-rc5 no-idea
+You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using
+ ./config no-idea no-mdc2 no-rc5
 
 
 * Can I use OpenSSL with GPL software?
@@ -467,6 +473,10 @@ This will only compile sha_dgst.c with -O0, the rest with the optimization
 level chosen by the configuration process.  When the above is done, do the
 test and installation and you're set.
 
+3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It 
+should not be used and is not used in SSL/TLS nor any other recognized
+protocol in either case.
+
 
 * Why does the OpenSSL compilation fail with "ar: command not found"?
 
@@ -680,6 +690,20 @@ and attempts to free the buffer will have unpredictable results
 because it no longer points to the same address.
 
 
+* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
+
+The short answer is yes, because DER is a special case of BER and OpenSSL
+ASN1 decoders can process BER.
+
+The longer answer is that ASN1 structures can be encoded in a number of
+different ways. One set of ways is the Basic Encoding Rules (BER) with various
+permissible encodings. A restriction of BER is the Distinguished Encoding
+Rules (DER): these uniquely specify how a given structure is encoded.
+
+Therefore, because DER is a special case of BER, DER is an acceptable encoding
+for BER.
+
+
 * 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
@@ -762,5 +786,28 @@ The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier.
 Change your code to use the new name when compiling against OpenSSL 0.9.7.
 
 
+* I think I've detected a memory leak, is this a bug?
+
+In most cases the cause of an apparent memory leak is an OpenSSL internal table
+that is allocated when an application starts up. Since such tables do not grow
+in size over time they are harmless.
+
+These internal tables can be freed up when an application closes using various
+functions.  Currently these include following:
+
+Thread-local cleanup functions:
+
+  ERR_remove_state()
+
+Application-global cleanup functions that are aware of usage (and therefore
+thread-safe):
+
+  ENGINE_cleanup() and CONF_modules_unload()
+
+"Brutal" (thread-unsafe) Application-global cleanup functions:
+
+  ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data().
+
+
 ===============================================================================