SslHelper has been removed, and its functionality has been transferred
into TrustedSocketFactory. The added layer of indirection wasn't really
simplifying anything. It's now easier to see what happens when
createSocket() is invoked.
A new instance of SecureRandom is no longer passed to SSLContext.init().
Instead, null is passed.
The (default) provider of the TLS SSLContext used is OpenSSLProvider,
which provides an SSLSocket instance of type OpenSSLSocketImpl. The only
use of SecureRandom is in OpenSSLSocketImpl.startHandshake(), where it is
used to seed the OpenSSL PRNG with additional random data. But if
SecureRandom is null, then /dev/urandom is used for seeding instead.
Meanwhile, the default provider for the SecureRandom service is
OpenSSLRandom, which uses the OpenSSL PRNG as its data source. So we were
effectively seeding the OpenSSL PRNG with itself. That's probably okay
(we trust that the OpenSSL PRNG was properly initialized with random data
before first use), but using /dev/urandom would seem like a better source
(or at least as good a source) for the additional seed data added with
each new connection.
Note that our PRNGFixes class replaces the default SecureRandom service
with one whose data source is /dev/urandom for certain vulnerable API
levels anyway. (It also makes sure that the OpenSSL PRNG is properly
seeded before first use for certain vulnerable API levels.)
This is done when the SASL EXTERNAL mechanism isn't advertised (indicating
the possibility that the server did not accept the client certificate) or
when the command for authenticating with SASL EXTERNAL fails.
The CertificateValidationException will trigger a notification to the user
that there's an authentication problem that needs addressing.
Also, there were instances where CertificateValidationException was being
thrown with a new CertificateException as the cause for the purpose of
notifying the user when STARTTLS is not available. This has been slightly
simplified by eliminating the need to include a new CertificateException
as a cause.
Instead of interpreting a "-" at the beginning of a line as
an error response, consider the absence of a "+" at the
beginning of a line as an error response.
This is what Thunderbird does.
http://hg.mozilla.org/releases/comm-esr24/file/55e96a433bd1/mailnews/local/src/nsPop3Protocol.cpp#l1177
The problem arises with godaddy servers spewing additional
lines of data upon login failure. The login was being
interpreted as successful, and a STAT commanded was subsequently
being sent, resulting in a dialog saying 'Cannot connect to
server. (Invalid int: "auth_error:")'.
$ openssl s_client -quiet -crlf -connect pop.secureserver.net:995
...
+OK <24984.1394317012@pop.secureserver.net>
user testuser
+OK
pass testpass
testuser not found in the auth database
warning: auth_error: authorization failed (no such object)
-ERR authorization failed Check your server settings.
These options originated in the AOSP email client from which K-9 Mail was
forked. They provide an odd combination of 2 features:
1. Don't bother to authenticate the server's certificate (applies to both
SSL/TLS and STARTTLS); i.e., blindly accept all certificates. This is
generally a bad security policy which is susceptible to MITM attacks.
2. If STARTTLS is selected but the server doesn't claim to support
STARTTLS, then proceed without using encryption. This, too, is a bad
security policy which is susceptible to MITM attacks.
Since the time that K-9 Mail was forked, a couple things have changed:
> K-9 Mail has implemented the ability for users to review and permanently
accept individual certificates that would otherwise fail authentication.
With this ability, there is no need for a user to subject themselves to
the ongoing risks of feature 1. above. Hence, this commit removes feature
1.
> The AOSP email client has changed its behavior and no longer permits a
security downgrade to an unencrypted connection if the server doesn't
claim to support STARTTLS (i.e., they eliminated feature 2. above). K-9
Mail should do the same. It's unlikely that a server is going to provide
STARTTLS on an intermittent basis, so providing a contingency for such
unusual behavior is an unnecessary risk. Hence, this commit removes that
feature as well.
Effect on existing users:
If the old connection security setting was "SSL/TLS (if available)" (which
now gets remapped to "SSL/TLS"), and the server does not provide a
certificate that can be authenticated, then a "Certificate error for
<account name>" notification is generated telling the user to check their
server settings. Tapping the notification takes the user to the relevant
server settings, where the user can tap "Next" to review the certificate
and choose to permanently accept it. This process would occur during the
first syncing of folders after application upgrade or (in the case of
SMTP) during the first attempt to send a message.
If the connection security setting was "STARTTLS (if available)" (which
now gets remapped to "STARTTLS"), and the server does not provide a
certificate that can be authenticated, then the same process as above
would occur.
If the old connection security setting was "STARTTLS (if available)", and
the server doesn't claim to support STARTTLS, then the user would get a
certificate error notification which would lead them to the server's
settings. There they would need to choose a different connection security
-- most likely "NONE". If they didn't change anything but instead just
tapped "Next", the server settings would be checked again and a dialog
would pop up saying, "Cannot connect to server. (STARTTLS connection
security not available)". (The implementation of notifications when
STARTTLS is not available is not actually included here -- it's in the
commit that follows.)
Regarding the changes to providers.xml: in cases where the scheme ended
with "+ssl", the schemes were simply updated by appending "+". In cases
where the scheme ended with "+tls", a check of the server was made to
assure that STARTTLS was available before appending "+" to the scheme.
Domains paran.com and nate.com failed the check and were removed because
no current information could be found. Domains me.com and mac.com also
failed and were updated based on http://support.apple.com/kb/ht4864.
Applicable for strings not intended for user consumption.
A %d string format code can generate eastern-arabic numerals
for users with an arabic locale.
V/k9 (20763): conn1103774136>>> 5 UID SEARCH ٦٤٦:٦٧٠ NOT DELETED
V/k9 (20763): conn1103774136<<<#5# [BAD, Invalid Search criteria]
E/k9 (20763): synchronizeMailbox
E/k9 (20763): com.fsck.k9.mail.store.ImapStore$ImapException: Command: UID SEARCH ٦٤٦:٦٧٠ NOT DELETED; response: #5# [BAD, Invalid Search criteria]
AUTOMATIC = "Automatic"
PLAIN = "Normal password"
CRAM_MD5 = "Encrypted password"
SMTP also uses LOGIN. No localized text was associated with that because
a future commit will remove that option.
(The text is similar to that of Thunderbird's)
Changes:
Extract code and create login() and authCramMD5() methods.
Implement the SASL PLAIN authentication mechanism. Its primary benefit is
the explicit support for UTF-8. If the user has configured "PLAIN"
authentication, then SASL PLAIN will be used, if available, otherwise
login() will be used.
Implement POP3 APOP authentication (issue 3218). If the user has
configured "CRAM_MD5" authentication (a future commit will change this
user option to a localized string "Encrypted password"), then SASL
CRAM-MD5 will be used, if available, otherwise the availability of POP3
APOP will be checked and used (per RFC 2449, there is no APOP
"capability").
Extend getCapabilities() to check for available authentication methods by
sending the "AUTH" command with no arguments
(http://tools.ietf.org/html/draft-myers-sasl-pop3-05). This never became
a standard, but there are servers that support it, and Thunderbird
includes this check.
The SASL PLAIN and CRAM-MD5 authentication methods are not attempted
unless the server professes to have the appropriate capability.
(Previously, CRAM-MD5 was tried regardless of capability.) No check is
made for the USER capability prior to use of that method. All this is the
same behavior as in Thunderbird.
Eliminate the testing for capabilities in cases where the test results are
never used (PIPELINING, USER).
Change when getCapabilities() is called. It is called once upon
connection. If STARTTLS is negotiated (POP3 STLS), then
getCapabilities() is called again after the connection is encrypted (and
the server is authenticated), but before user authentication is attempted.
In AccountSetupCheckSettings.onCreate(Bundle), the account settings are
checked.
If an AuthenticationFailedException occurs, A dialog saying "Username or
password incorrect." pops up. We don't want to say this if the cause is
not related to an incorrect user name or password. Instead we want to say
the more generic "Cannot connect to server" which pops up for other
exception types.
This commit attempts to eliminate the use of AuthenticationFailedException
in instances where it could not be due to "Username or password
incorrect."
The classes are just as much related to com.fsck.k9.mail.transport
as com.fsck.k9.mail.store, so having them in
com.fsck.k9.mail.store doesn't seem appropriate.
Move LocalKeyStore to com.fsck.k9.security
Move TrustManagerFactory and TrustedSocketFactory to com.fsck.k9.net.ssl
Proper host name validation was not being performed for certificates
kept in the local keystore. If an attacker could convince a user to
accept and store an attacker's certificate, then that certificate
could be used for MITM attacks, giving the attacker access to all
connections to all servers in all accounts in K-9.
This commit changes how the certificates are stored. Previously, an
entire certificate chain was stored for a server (and any of those
certificates in the chain were available for validating signatures on
certificates received when connecting). Now just the single
certificate for the server is stored.
This commit changes how locally stored certificates are retrieved.
They can only be retrieved using the host:port that the user
configured for the server.
This also fixes issue 1326. Users can now use different certificates
for different servers on the same host (listening to different ports).
The above changes mean that users might have to re-accept certificates
that they had previously accepted and are still using (but only if the
certificate's Subject doesn't match the host that they are connecting
to).
This commit modifies AccountSetupBasics so that it now calls
AccountSetupCheckSettings twice -- once for checking the incoming
settings and once for the outgoing settings. Otherwise, an exception
could occur while checking incoming settings, the user could say
continue (or the user could accept a certificate key), and the
outgoing settings would not be checked. This also helps with
determining if a certificate exception was for the incoming or
outgoing server, which is needed if the user decides to add the
certificate to the keystore.
The TrustedSocketFactory, which provides goodies like better cipher suites and
TLSv1.2, was only being used for tunnelled connections. Use it for STARTTLS
connections as well.
As Georg Lukas wrote in his blog post about how Android handles TLS
handshake (http://op-co.de/blog/posts/android_ssl_downgrade/), an
explicit order of cipher suites and TLS versions must be supplied to
avoid having the weak (presumably broken) RC4 cipher at the top of the
preference list.
This commit adds the list included in the blog post to every TLS socket
creation, including IMAP, POP3 and SMTP, see Wireshark screenshots done
during testing at http://vsza.hu/k9mail-tls-hardening/
The commit that introduced those notifications also introduced a rather
... interesting design pattern: The CertificateValidationException
notified the user of its pure existance - it's no longer a 'message'
only, but defines policy. As this is more than unusual, replace this
pattern by the MessagingController treating
CertificateValidationException specially when accessing remote folders.
Also make clear which account failed when constructing the notification.
With this fix, a CertPathValidatorException or CertificateException will
create a "Certificate error: Check your server settings" notification
in the status bar. When the user clicks on the notification, they are
taken to the appropriate server settings screen where they can review their
settings and can accept a different server certificate.
