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SSL/TLS Strong Encryption: FAQ
The wise man doesn't give the right answers, he poses the right questions.
-- Claude Levi-Strauss
This chapter is a collection of frequently asked questions (FAQ) and
corresponding answers following the popular USENET tradition. Most of these
questions occurred on the Newsgroup comp.infosystems.www.servers.unix or the mod_ssl Support
Mailing List modssl-users@modssl.org. They are collected at this place
to avoid answering the same questions over and over.
Please read this chapter at least once when installing mod_ssl or at least search for your problem here before submitting a problem report to the author.
About The Module
- What is the history of mod_ssl?
- mod_ssl and Year 2000?
- mod_ssl and Wassenaar Arrangement?
What is the history of mod_ssl?
The mod_ssl v1 package was initially created in April 1998 by Ralf S. Engelschall via porting Ben Laurie's Apache-SSL 1.17 source patches for Apache 1.2.6 to Apache 1.3b6. Because of conflicts with Ben Laurie's development cycle it then was re-assembled from scratch for Apache 1.3.0 by merging the old mod_ssl 1.x with the newer Apache-SSL 1.18. From this point on mod_ssl lived its own life as mod_ssl v2. The first publicly released version was mod_ssl 2.0.0 from August 10th, 1998.
After US export restrictions on cryptographic software were
loosened, mod_ssl became part of the Apache HTTP
Server with the release of Apache httpd 2.
Is mod_ssl affected by the Wassenaar Arrangement?
First, let us explain what Wassenaar and its Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies is: This is a international regime, established in 1995, to control trade in conventional arms and dual-use goods and technology. It replaced the previous CoCom regime. Further details on both the Arrangement and its signatories are available at http://www.wassenaar.org/.
In short, the aim of the Wassenaar Arrangement is to prevent the build up of military capabilities that threaten regional and international security and stability. The Wassenaar Arrangement controls the export of cryptography as a dual-use good, that is, something that has both military and civilian applications. However, the Wassenaar Arrangement also provides an exemption from export controls for mass-market software and free software.
In the current Wassenaar List of Dual Use Goods and Technologies And
Munitions, under GENERAL SOFTWARE NOTE (GSN)
it says
The Lists do not control "software" which is either: 1. [...] 2. "in
the public domain".
And under DEFINITIONS OF TERMS USED IN
THESE LISTS
we find In the public
domain
defined as "technology" or "software" which has been made
available without restrictions upon its further dissemination. Note:
Copyright restrictions do not remove "technology" or "software" from being
"in the public domain".
So, both mod_ssl and OpenSSL are in the public domain
for the purposes
of the Wassenaar Arrangement and its List of Dual Use Goods and
Technologies And Munitions List
, and thus not affected by its provisions.
Installation
- Why do I get permission errors related to SSLMutex when I start Apache?
- Why does mod_ssl stop with the error "Failed to generate temporary 512 bit RSA private key", when I start Apache?
Why do I get permission errors related to SSLMutex when I start Apache?
Errors such as "mod_ssl: Child could not open
SSLMutex lockfile /opt/apache/logs/ssl_mutex.18332 (System error follows)
[...] System: Permission denied (errno: 13)" are usually
caused by overly restrictive permissions on the parent directories.
Make sure that all parent directories (here /opt,
/opt/apache和/opt/apache/logs) have the x-bit
set for, at minimum, the UID under which Apache's children are running (see
the User directive).
Why does mod_ssl stop with the error "Failed to generate temporary 512 bit RSA private key", when I start Apache?
Cryptographic software needs a source of unpredictable data
to work correctly. Many open source operating systems provide
a "randomness device" that serves this purpose (usually named
/dev/random). On other systems, applications have to
seed the OpenSSL Pseudo Random Number Generator (PRNG) manually with
appropriate data before generating keys or performing public key
encryption. As of version 0.9.5, the OpenSSL functions that need
randomness report an error if the PRNG has not been seeded with
at least 128 bits of randomness.
To prevent this error, mod_ssl has to provide
enough entropy to the PRNG to allow it to work correctly. This can
be done via the SSLRandomSeed
directives.
Configuration
- Is it possible to provide HTTP and HTTPS from the same server?
- Which port does HTTPS use?
- How do I speak HTTPS manually for testing purposes?
- Why does the connection hang when I connect to my SSL-aware Apache server
- Why do I get "Connection Refused" errors, when trying to access my newly installed Apache+mod_ssl server via HTTPS?
- Why are the
SSL_XXXvariables not available to my CGI & SSI scripts? - How can I switch between HTTP and HTTPS in relative hyperlinks?
Is it possible to provide HTTP and HTTPS from the same server?
Yes. HTTP and HTTPS use different server ports (HTTP binds to port 80, HTTPS to port 443), so there is no direct conflict between them. You can either run two separate server instances bound to these ports, or use Apache's elegant virtual hosting facility to create two virtual servers over one instance of Apache - one responding to requests on port 80 and speaking HTTP and the other responding to requests on port 443 speaking HTTPS.
Which port does HTTPS use?
You can run HTTPS on any port, but the standards specify port 443, which
is where any HTTPS compliant browser will look by default. You can force
your browser to look on a different port by specifying it in the URL like
this (for port 666): https://secure.server.dom:666/
How do I speak HTTPS manually for testing purposes?
While you usually just use
$ telnet localhost 80
GET / HTTP/1.0
for simple testing of Apache via HTTP, it's not so easy for
HTTPS because of the SSL protocol between TCP and HTTP. With the
help of OpenSSL's s_client command, however, you can
do a similar check for HTTPS:
$ openssl s_client -connect localhost:443 -state -debug
GET / HTTP/1.0
Before the actual HTTP response you will receive detailed information about the SSL handshake. For a more general command line client which directly understands both HTTP and HTTPS, can perform GET and POST operations, can use a proxy, supports byte ranges, etc. you should have a look at the nifty cURL tool. Using this, you can check that Apache is responding correctly on ports 80 and 443 as follows:
$ curl http://localhost/
$ curl https://localhost/
Why does the connection hang when I connect to my SSL-aware Apache server?
Because you connected with HTTP to the HTTPS port, i.e. you used an URL of
the form "http://" instead of "https://".
This also happens the other way round when you connect via HTTPS to a HTTP
port, i.e. when you try to use "https://" on a server that
doesn't support SSL (on this port). Make sure you are connecting to a
virtual server that supports SSL, which is probably the IP associated with
your hostname, not localhost (127.0.0.1).
Why do I get "Connection Refused" messages, when trying to access my newly installed Apache+mod_ssl server via HTTPS?
This can happen for various reasons. The most common mistakes
include starting Apache with just apachectl start (or
httpd) instead of apachectl startssl (or
httpd -DSSL). Your configuration may also be incorrect.
Please make sure that your Listen directives match your
<VirtualHost>
directives. If all else fails, please start afresh, using the default
configuration provided by mod_ssl.
Why are the SSL_XXX variables
not available to my CGI & SSI scripts?
Please make sure you have "SSLOptions +StdEnvVars"
enabled for the context of your CGI/SSI requests.
How can I switch between HTTP and HTTPS in relative hyperlinks?
Usually, to switch between HTTP and HTTPS, you have to use
fully-qualified hyperlinks (because you have to change the URL
scheme). Using mod_rewrite however, you can
manipulate relative hyperlinks, to achieve the same effect.
RewriteEngine on
RewriteRule ^/(.*):SSL$ https://%{SERVER_NAME}/$1 [R,L]
RewriteRule ^/(.*):NOSSL$ http://%{SERVER_NAME}/$1 [R,L]
This rewrite ruleset lets you use hyperlinks of the form
<a href="document.html:SSL">, to switch to HTTPS
in a relative link.
Certificates
- What are RSA Private Keys, CSRs and Certificates?
- Is there a difference on startup between the original Apache and an SSL-aware Apache?
- How do I create a self-signed SSL Certificate for testing purposes?
- How do I create a real SSL Certificate?
- How do I create and use my own Certificate Authority (CA)?
- How can I change the pass-phrase on my private key file?
- How can I get rid of the pass-phrase dialog at Apache startup time?
- How do I verify that a private key matches its Certificate?
- Why do connections fail with an "alert bad certificate" error?
- Why does my 2048-bit private key not work?
- Why is client authentication broken after upgrading from SSLeay version 0.8 to 0.9?
- How can I convert a certificate from PEM to DER format?
- Why can't I find the
getca或getverisignprograms mentioned by Verisign, for installing my Verisign certificate? - Can I use the Server Gated Cryptography (SGC) facility (aka Verisign Global ID) with mod_ssl?
- Why do browsers complain that they cannot verify my Verisign Global ID server certificate?
What are RSA Private Keys, CSRs and Certificates?
An RSA private key file is a digital file that you can use to decrypt messages sent to you. It has a public component which you distribute (via your Certificate file) which allows people to encrypt those messages to you.
A Certificate Signing Request (CSR) is a digital file which contains your public key and your name. You send the CSR to a Certifying Authority (CA), who will convert it into a real Certificate, by signing it.
A Certificate contains your RSA public key, your name, the name of the CA, and is digitally signed by the CA. Browsers that know the CA can verify the signature on that Certificate, thereby obtaining your RSA public key. That enables them to send messages which only you can decrypt.
See the 简介 chapter for a general description of the SSL protocol.
Is there a difference on startup between the original Apache and an SSL-aware Apache?
Yes. In general, starting Apache with
mod_ssl built-in is just like starting Apache
without it. However, if you have a passphrase on your SSL private
key file, a startup dialog will pop up which asks you to enter the
pass phrase.
Having to manually enter the passphrase when starting the server can be problematic - for example, when starting the server from the system boot scripts. In this case, you can follow the steps below to remove the passphrase from your private key.
How do I create a self-signed SSL Certificate for testing purposes?
- Make sure OpenSSL is installed and in your
PATH.
- Run the following command, to create
server.key和server.crtfiles:$ openssl req -new -x509 -nodes -out server.crt -keyout server.key
These can be used as follows in yourhttpd.conffile:SSLCertificateFile /path/to/this/server.crt SSLCertificateKeyFile /path/to/this/server.key - It is important that you are aware that this
server.keydoes not have any passphrase. To add a passphrase to the key, you should run the following command, and enter & verify the passphrase as requested.
Please backup the$ openssl rsa -des3 -in server.key -out server.key.new$ mv server.key.new server.keyserver.keyfile, and the passphrase you entered, in a secure location.
How do I create a real SSL Certificate?
Here is a step-by-step description:
- Make sure OpenSSL is installed and in your
PATH.
- Create a RSA private key for your Apache server
(will be Triple-DES encrypted and PEM formatted):
$ openssl genrsa -des3 -out server.key 1024
Please backup thisserver.keyfile and the pass-phrase you entered in a secure location. You can see the details of this RSA private key by using the command:$ openssl rsa -noout -text -in server.key
If necessary, you can also create a decrypted PEM version (not recommended) of this RSA private key with:$ openssl rsa -in server.key -out server.key.unsecure
- Create a Certificate Signing Request (CSR) with the server RSA private
key (output will be PEM formatted):
$ openssl req -new -key server.key -out server.csr
Make sure you enter the FQDN ("Fully Qualified Domain Name") of the server when OpenSSL prompts you for the "CommonName", i.e. when you generate a CSR for a website which will be later accessed viahttps://www.foo.dom/, enter "www.foo.dom" here. You can see the details of this CSR by using$ openssl req -noout -text -in server.csr
- You now have to send this Certificate Signing Request (CSR) to
a Certifying Authority (CA) to be signed. Once the CSR has been
signed, you will have a real Certificate, which can be used by
Apache. You can have a CSR signed by a commercial CA, or you can
create your own CA to sign it.
Commercial CAs usually ask you to post the CSR into a web form, pay for the signing, and then send a signed Certificate, which you can store in a server.crt file. For more information about commercial CAs see the following locations:- Verisign
http://digitalid.verisign.com/server/apacheNotice.htm - Thawte
http://www.thawte.com/ - CertiSign Certificadora Digital Ltda.
http://www.certisign.com.br - IKS GmbH
http://www.iks-jena.de/leistungen/ca/ - Uptime Commerce Ltd.
http://www.uptimecommerce.com - BelSign NV/SA
http://www.belsign.be
Once your CSR has been signed, you can see the details of the Certificate as follows:$ openssl x509 -noout -text -in server.crt
- Verisign
- You should now have two files:
server.key和server.crt. These can be used as follows in yourhttpd.conffile:SSLCertificateFile /path/to/this/server.crt SSLCertificateKeyFile /path/to/this/server.keyTheserver.csrfile is no longer needed.
How do I create and use my own Certificate Authority (CA)?
The short answer is to use the CA.sh或CA.pl
script provided by OpenSSL. Unless you have a good reason not to,
you should use these for preference. If you cannot, you can create a
self-signed Certificate as follows:
- Create a RSA private key for your server
(will be Triple-DES encrypted and PEM formatted):
$ openssl genrsa -des3 -out server.key 1024
Please backup thishost.keyfile and the pass-phrase you entered in a secure location. You can see the details of this RSA private key by using the command:$ openssl rsa -noout -text -in server.key
If necessary, you can also create a decrypted PEM version (not recommended) of this RSA private key with:$ openssl rsa -in server.key -out server.key.unsecure
- Create a self-signed Certificate (X509 structure)
with the RSA key you just created (output will be PEM formatted):
$ openssl req -new -x509 -nodes -sha1 -days 365 -key server.key -out server.crt
This signs the server CSR and results in aserver.crtfile.
You can see the details of this Certificate using:$ openssl x509 -noout -text -in server.crt
How can I change the pass-phrase on my private key file?
You simply have to read it with the old pass-phrase and write it again, specifying the new pass-phrase. You can accomplish this with the following commands:
$ openssl rsa -des3 -in server.key -out server.key.new$ mv server.key.new server.key
The first time you're asked for a PEM pass-phrase, you should enter the old pass-phrase. After that, you'll be asked again to enter a pass-phrase - this time, use the new pass-phrase. If you are asked to verify the pass-phrase, you'll need to enter the new pass-phrase a second time.
How can I get rid of the pass-phrase dialog at Apache startup time?
The reason this dialog pops up at startup and every re-start is that the RSA private key inside your server.key file is stored in encrypted format for security reasons. The pass-phrase is needed decrypt this file, so it can be read and parsed. Removing the pass-phrase removes a layer of security from your server - proceed with caution!
- Remove the encryption from the RSA private key (while
keeping a backup copy of the original file):
$ cp server.key server.key.org$ openssl rsa -in server.key.org -out server.key
- Make sure the server.key file is only readable by root:
$ chmod 400 server.key
Now server.key contains an unencrypted copy of the key.
If you point your server at this file, it will not prompt you for a
pass-phrase. HOWEVER, if anyone gets this key they will be able to
impersonate you on the net. PLEASE make sure that the permissions on this
file are such that only root or the web server user can read it
(preferably get your web server to start as root but run as another
user, and have the key readable only by root).
As an alternative approach you can use the "SSLPassPhraseDialog
exec:/path/to/program" facility. Bear in mind that this is
neither more nor less secure, of course.
How do I verify that a private key matches its Certificate?
A private key contains a series of numbers. Two of these numbers form the "public key", the others are part of the "private key". The "public key" bits are included when you generate a CSR, and subsequently form part of the associated Certificate.
To check that the public key in your Certificate matches the public portion of your private key, you simply need to compare these numbers. To view the Certificate and the key run the commands:
$ openssl x509 -noout -text -in server.crt$ openssl rsa -noout -text -in server.key
The 'modulus' and the 'public exponent' portions in the key and the Certificate must match. As the public exponent is usually 65537 and it's difficult to visually check that the long modulus numbers are the same, you can use the following approach:
$ openssl x509 -noout -modulus -in server.crt | openssl md5$ openssl rsa -noout -modulus -in server.key | openssl md5
This leaves you with two rather shorter numbers to compare. It is, in theory, possible that these numbers may be the same, without the modulus numbers being the same, but the chances of this are overwhelmingly remote.
Should you wish to check to which key or certificate a particular CSR belongs you can perform the same calculation on the CSR as follows:
$ openssl req -noout -modulus -in server.csr | openssl md5
Why do connections fail with an "alert bad certificate" error?
Errors such as OpenSSL: error:14094412: SSL
routines:SSL3_READ_BYTES:sslv3 alert bad certificate in the SSL
logfile, are usually caused a browser which is unable to handle the server
certificate/private-key. For example, Netscape Navigator 3.x is
unable to handle RSA key lengths not equal to 1024 bits.
Why does my 2048-bit private key not work?
The private key sizes for SSL must be either 512 or 1024 bits, for compatibility with certain web browsers. A keysize of 1024 bits is recommended because keys larger than 1024 bits are incompatible with some versions of Netscape Navigator and Microsoft Internet Explorer, and with other browsers that use RSA's BSAFE cryptography toolkit.
Why is client authentication broken after upgrading from SSLeay version 0.8 to 0.9?
The CA certificates under the path you configured with
SSLCACertificatePath are found by SSLeay through hash
symlinks. These hash values are generated by the 'openssl x509 -noout
-hash' command. However, the algorithm used to calculate the hash for a
certificate changed between SSLeay 0.8 and 0.9. You will need to remove
all old hash symlinks and create new ones after upgrading. Use the
Makefile provided by mod_ssl.
How can I convert a certificate from PEM to DER format?
The default certificate format for SSLeay/OpenSSL is PEM, which is simply
Base64 encoded DER, with header and footer lines. For some applications
(e.g. Microsoft Internet Explorer) you need the certificate in plain DER
format. You can convert a PEM file cert.pem into the
corresponding DER file cert.der using the following command:
$ openssl x509 -in cert.pem -out cert.der -outform DER
Why can't I find the
getca或getverisign programs mentioned by
Verisign, for installing my Verisign certificate?
Verisign has never provided specific instructions for Apache+mod_ssl. The instructions provided are for C2Net's Stronghold (a commercial Apache based server with SSL support).
To install your certificate, all you need to do is to save the
certificate to a file, and give the name of that file to the
SSLCertificateFile directive.
You will also need to give it the key file. For more information,
see the SSLCertificateKeyFile
directive.
Can I use the Server Gated Cryptography (SGC) facility (aka Verisign Global ID) with mod_ssl?
Yes. mod_ssl has included support for the SGC
facility since version 2.1. No special configuration is required -
just use the Global ID as your server certificate. The
step up of the clients is then automatically handled by
mod_ssl at run-time.
Why do browsers complain that they cannot verify my Verisign Global ID server certificate?
Verisign uses an intermediate CA certificate between the root CA
certificate (which is installed in the browsers) and the server
certificate (which you installed on the server). You should have
received this additional CA certificate from Verisign.
If not, complain to them. Then, configure this certificate with the
SSLCertificateChainFile
directive. This ensures that the intermediate CA certificate is
sent to the browser, filling the gap in the certificate chain.
The SSL Protocol
- Why do I get lots of random SSL protocol errors under heavy server load?
- Why does my webserver have a higher load, now that it serves SSL encrypted traffic?
- Why do HTTPS connections to my server sometimes take up to 30 seconds to establish a connection?
- What SSL Ciphers are supported by mod_ssl?
- Why do I get "no shared cipher" errors, when trying to use Anonymous Diffie-Hellman (ADH) ciphers?
- Why do I get a 'no shared ciphers' error when connecting to my newly installed server?
- Why can't I use SSL with name-based/non-IP-based virtual hosts?
- Why is it not possible to use Name-Based Virtual Hosting to identify different SSL virtual hosts?
- How do I get SSL compression working?
- When I use Basic Authentication over HTTPS the lock icon in Netscape browsers stays unlocked when the dialog pops up. Does this mean the username/password is being sent unencrypted?
- Why do I get I/O errors when connecting via HTTPS to an Apache+mod_ssl server with Microsoft Internet Explorer (MSIE)?
- Why do I get I/O errors, or the message "Netscape has encountered bad data from the server", when connecting via HTTPS to an Apache+mod_ssl server with Netscape Navigator?
Why do I get lots of random SSL protocol errors under heavy server load?
There can be a number of reasons for this, but the main one
is problems with the SSL session Cache specified by the
SSLSessionCache directive. The DBM session
cache is the most likely source of the problem, so using the SHM session cache (or
no cache at all) may help.
Why does my webserver have a higher load, now that it serves SSL encrypted traffic?
SSL uses strong cryptographic encryption, which necessitates a lot of number crunching. When you request a webpage via HTTPS, everything (even the images) is encrypted before it is transferred. So increased HTTPS traffic leads to load increases.
Why do HTTPS connections to my server sometimes take up to 30 seconds to establish a connection?
This is usually caused by a /dev/random device for
SSLRandomSeed which blocks the
read(2) call until enough entropy is available to service the
request. More information is available in the reference
manual for the SSLRandomSeed
directive.
What SSL Ciphers are supported by mod_ssl?
Usually, any SSL ciphers supported by the version of OpenSSL in use,
are also supported by mod_ssl. Which ciphers are
available can depend on the way you built OpenSSL. Typically, at
least the following ciphers are supported:
- RC4 with MD5
- RC4 with MD5 (export version restricted to 40-bit key)
- RC2 with MD5
- RC2 with MD5 (export version restricted to 40-bit key)
- IDEA with MD5
- DES with MD5
- Triple-DES with MD5
To determine the actual list of ciphers available, you should run the following:
$ openssl ciphers -v
Why do I get "no shared cipher" errors, when trying to use Anonymous Diffie-Hellman (ADH) ciphers?
By default, OpenSSL does not allow ADH ciphers, for security reasons. Please be sure you are aware of the potential side-effects if you choose to enable these ciphers.
In order to use Anonymous Diffie-Hellman (ADH) ciphers, you must
build OpenSSL with "-DSSL_ALLOW_ADH", and then add
"ADH" into your SSLCipherSuite.
Why do I get a 'no shared ciphers' error when connecting to my newly installed server?
Either you have made a mistake with your
SSLCipherSuite
directive (compare it with the pre-configured example in
httpd.conf-dist) or you chose to use DSA/DH
algorithms instead of RSA when you generated your private key
and ignored or overlooked the warnings. If you have chosen
DSA/DH, then your server cannot communicate using RSA-based SSL
ciphers (at least until you configure an additional RSA-based
certificate/key pair). Modern browsers like NS or IE can only
communicate over SSL using RSA ciphers. The result is the
"no shared ciphers" error. To fix this, regenerate your server
certificate/key pair, using the RSA algorithm.
Why can't I use SSL with name-based/non-IP-based virtual hosts?
The reason is very technical, and a somewhat "chicken and egg" problem.
The SSL protocol layer stays below the HTTP protocol layer and
encapsulates HTTP. When an SSL connection (HTTPS) is established
Apache/mod_ssl has to negotiate the SSL protocol parameters with the
client. For this, mod_ssl has to consult the configuration of the virtual
server (for instance it has to look for the cipher suite, the server
certificate, etc.). But in order to go to the correct virtual server
Apache has to know the Host HTTP header field. To do this, the
HTTP request header has to be read. This cannot be done before the SSL
handshake is finished, but the information is needed in order to
complete the SSL handshake phase. Bingo!
Why is it not possible to use Name-Based Virtual Hosting to identify different SSL virtual hosts?
Name-Based Virtual Hosting is a very popular method of identifying different virtual hosts. It allows you to use the same IP address and the same port number for many different sites. When people move on to SSL, it seems natural to assume that the same method can be used to have lots of different SSL virtual hosts on the same server.
It comes as rather a shock to learn that it is impossible.
The reason is that the SSL protocol is a separate layer which encapsulates the HTTP protocol. So the SSL session is a separate transaction, that takes place before the HTTP session has begun. The server receives an SSL request on IP address X and port Y (usually 443). Since the SSL request does not contain any Host: field, the server has no way to decide which SSL virtual host to use. Usually, it will just use the first one it finds, which matches the port and IP address specified.
You can, of course, use Name-Based Virtual Hosting to identify many non-SSL virtual hosts (all on port 80, for example) and then have a single SSL virtual host (on port 443). But if you do this, you must make sure to put the non-SSL port number on the NameVirtualHost directive, e.g.
NameVirtualHost 192.168.1.1:80
Other workaround solutions include:
Using separate IP addresses for different SSL hosts. Using different port numbers for different SSL hosts.
How do I get SSL compression working?
Although SSL compression negotiation was defined in the specification of SSLv2 and TLS, it took until May 2004 for RFC 3749 to define DEFLATE as a negotiable standard compression method.
OpenSSL 0.9.8 started to support this by default when compiled with the
zlib option. If both the client and the server support compression,
it will be used. However, most clients still try to initially connect with an
SSLv2 Hello. As SSLv2 did not include an array of prefered compression algorithms
in its handshake, compression cannot be negotiated with these clients.
If the client disables support for SSLv2, either an SSLv3 or TLS Hello
may be sent, depending on which SSL library is used, and compression may
be set up. You can verify whether clients make use of SSL compression by
logging the %{SSL_COMPRESS_METHOD}x variable.
When I use Basic Authentication over HTTPS the lock icon in Netscape browsers stays unlocked when the dialog pops up. Does this mean the username/password is being sent unencrypted?
No, the username/password is transmitted encrypted. The icon in Netscape browsers is not actually synchronized with the SSL/TLS layer. It only toggles to the locked state when the first part of the actual webpage data is transferred, which may confuse people. The Basic Authentication facility is part of the HTTP layer, which is above the SSL/TLS layer in HTTPS. Before any HTTP data communication takes place in HTTPS, the SSL/TLS layer has already completed its handshake phase, and switched to encrypted communication. So don't be confused by this icon.
Why do I get I/O errors when connecting via HTTPS to an Apache+mod_ssl server with Microsoft Internet Explorer (MSIE)?
The first reason is that the SSL implementation in some MSIE versions has some subtle bugs related to the HTTP keep-alive facility and the SSL close notify alerts on socket connection close. Additionally the interaction between SSL and HTTP/1.1 features are problematic in some MSIE versions. You can work around these problems by forcing Apache not to use HTTP/1.1, keep-alive connections or send the SSL close notify messages to MSIE clients. This can be done by using the following directive in your SSL-aware virtual host section:
SetEnvIf User-Agent ".*MSIE.*" \
nokeepalive ssl-unclean-shutdown \
downgrade-1.0 force-response-1.0
Further, some MSIE versions have problems with particular ciphers.
Unfortunately, it is not possible to implement a MSIE-specific
workaround for this, because the ciphers are needed as early as the
SSL handshake phase. So a MSIE-specific
SetEnvIf won't solve these
problems. Instead, you will have to make more drastic
adjustments to the global parameters. Before you decide to do
this, make sure your clients really have problems. If not, do not
make these changes - they will affect all your clients, MSIE
or otherwise.
The next problem is that 56bit export versions of MSIE 5.x browsers have a broken SSLv3 implementation, which interacts badly with OpenSSL versions greater than 0.9.4. You can accept this and require your clients to upgrade their browsers, you can downgrade to OpenSSL 0.9.4 (not advised), or you can work around this, accepting that your workaround will affect other browsers too:
SSLProtocol all -SSLv3
will completely disables the SSLv3 protocol and allow those browsers to work. A better workaround is to disable only those ciphers which cause trouble.
SSLCipherSuite
ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP
This also allows the broken MSIE versions to work, but only removes the newer 56bit TLS ciphers.
Another problem with MSIE 5.x clients is that they refuse to connect to
URLs of the form https://12.34.56.78/ (where IP-addresses are used
instead of the hostname), if the server is using the Server Gated
Cryptography (SGC) facility. This can only be avoided by using the fully
qualified domain name (FQDN) of the website in hyperlinks instead, because
MSIE 5.x has an error in the way it handles the SGC negotiation.
And finally there are versions of MSIE which seem to require that
an SSL session can be reused (a totally non standard-conforming
behaviour, of course). Connecting with those MSIE versions only work
if a SSL session cache is used. So, as a work-around, make sure you
are using a session cache (see the SSLSessionCache directive).
Why do I get I/O errors, or the message "Netscape has encountered bad data from the server", when connecting via HTTPS to an Apache+mod_ssl server with Netscape Navigator?
This usually occurs when you have created a new server certificate for a given domain, but had previously told your browser to always accept the old server certificate. Once you clear the entry for the old certificate from your browser, everything should be fine. Netscape's SSL implementation is correct, so when you encounter I/O errors with Netscape Navigator it is usually caused by the configured certificates.
mod_ssl Support
- What information resources are available in case of mod_ssl problems?
- What support contacts are available in case of mod_ssl problems?
- What information should I provide when writing a bug report?
- I had a core dump, can you help me?
- How do I get a backtrace, to help find the reason for my core dump?
What information resources are available in case of mod_ssl problems?
The following information resources are available. In case of problems you should search here first.
- Answers in the User Manual's F.A.Q. List (this)
-
http://httpd.apache.org/docs/2.2/ssl/ssl_faq.html
First check the F.A.Q. (this text). If your problem is a common one, it may have been answered several times before, and been included in this doc. - Postings from the modssl-users Support Mailing List http://www.modssl.org/support/
- Search for your problem in the archives of the modssl-users mailing list. You're probably not the first person to have had this problem!
What support contacts are available in case of mod_ssl problems?
The following lists all support possibilities for mod_ssl, in order of preference. Please go through these possibilities in this order - don't just pick the one you like the look of.
-
Send a Problem Report to the modssl-users Support Mailing List
modssl-users@modssl.org
This is the preferred way of submitting your problem report, because this way, others can see the problem, and learn from any answers. You must subscribe to the list first, but you can then easily discuss your problem with both the author and the whole mod_ssl user community. -
Send a Problem Report to the Apache httpd Users Support Mailing List
users@httpd.apache.org
This is the second way of submitting your problem report. Again, you must subscribe to the list first, but you can then easily discuss your problem with the whole Apache httpd user community. -
Write a Problem Report in the Bug Database
http://httpd.apache.org/bug_report.html
This is the last way of submitting your problem report. You should only do this if you've already posted to the mailing lists, and had no success. Please follow the instructions on the above page carefully.
What information should I provide when writing a bug report?
You should always provide at least the following information:
- Apache and OpenSSL version information
- The Apache version can be determined
by running
httpd -v. The OpenSSL version can be determined by runningopenssl version. Alternatively, if you have Lynx installed, you can run the commandlynx -mime_header http://localhost/ | grep Serverto gather this information in a single step. - The details on how you built and installed Apache+mod_ssl+OpenSSL
- For this you can provide a logfile of your terminal session which shows
the configuration and install steps. If this is not possible, you
should at least provide the
configurecommand line you used. - In case of core dumps please include a Backtrace
- If your Apache+mod_ssl+OpenSSL dumps its core, please attach a stack-frame "backtrace" (see below for information on how to get this). Without this information, the reason for your core dump cannot be found
- A detailed description of your problem
- Don't laugh, we really mean it! Many problem reports don't include a description of what the actual problem is. Without this, it's very difficult for anyone to help you. So, it's in your own interest (you want the problem be solved, don't you?) to include as much detail as possible, please. Of course, you should still include all the essentials above too.
I had a core dump, can you help me?
In general no, at least not unless you provide more details about the code location where Apache dumped core. What is usually always required in order to help you is a backtrace (see next question). Without this information it is mostly impossible to find the problem and help you in fixing it.
How do I get a backtrace, to help find the reason for my core dump?
Following are the steps you will need to complete, to get a backtrace:
- Make sure you have debugging symbols available, at least
in Apache. On platforms where you use GCC/GDB, you will have to build
Apache+mod_ssl with "
OPTIM="-g -ggdb3"" to get this. On other platforms at least "OPTIM="-g"" is needed. - Start the server and try to reproduce the core-dump. For this you may
want to use a directive like "
CoreDumpDirectory /tmp" to make sure that the core-dump file can be written. This should result in a/tmp/core或/tmp/httpd.corefile. If you don't get one of these, try running your server under a non-root UID. Many modern kernels do not allow a process to dump core after it has done asetuid()(unless it does anexec()) for security reasons (there can be privileged information left over in memory). If necessary, you can run/path/to/httpd -Xmanually to force Apache to not fork. - Analyze the core-dump. For this, run
gdb /path/to/httpd /tmp/httpd.coreor a similar command. In GDB, all you have to do then is to enterbt, and voila, you get the backtrace. For other debuggers consult your local debugger manual.