Android default (weak) signing configuration for the developer certificates

Some months ago I created a couple of Android applications.  As every Android developer  knows, in order to deploy applications on Android devices, these need to be signed. In other platforms like IOS, Symbian, Java or Windows Mobile, the signing process is a method used to prove the source of an application. Once an application is signed by a known certification authority, the platform will grant different execution permissions. Android  used code signing slightly different. The developer creates its own self signed certificate and uses this to sign any application he releases. This allows the platforms to recognize updates and also allow secure inter application communication.  The reason is simple, if there was no way to relate an application to its owner it would be trivial to impersonate him or her and deliver fake applications updates.

Without wanting to dig into the controversy between open and closed models, IOS vs Android, the part that caught my attention was that the developer would create a self signed certificate on his own and that that the only requirement is that the certificate must be valid until 2034. Today we all know that MD5 is proven to be weak and that key sizes should be at least 2048b, especially if we need to use it for a few years. On the other hand the default Android tools I used to create the certificate suggested to use a 1024b key and MD5 which is not a good idea, especially if that would be my identification until 2033!!

With that in mind I was curious to see how the digital certificates used to sign Android applications would look like. I analyzed nearly 4.000 applications, extracted the certificates and put together some statistics. For this I used unique certificates, which means that if two applications (in most cases these were updates) were signed with the same certificate I only took into consideration one occurrence.

First lets have a look at the algorithms being used:

As you can see the most used algorithm is RSA with SHA1 as a hashing algorithm but nearly one every 5 uses MD5 as a hashing algorithm. 

The strongest hashing algorithm found was SHA256 (1 occurrence, removed from the char) and the weakest MD5. It´s remarkable to see a 6% of DSA which is a n algorithm rarely used for X509 certificates, although perfectly valid.

Regarding key sizes for RSA we have the following distribution:

The most used key size is 1024b. Although I removed them from the pie charts, the weakest key size was 1023b (9 occurrences) and the strongest 8192b (1 occurrence). 

Developers, and some sysadmins too, tend to see digital certificates, and everything else around it, private keys, Root CAs, CRLs, etc as an annoyance and in the best cases as another “configuration” file.   Having in mind that Android forces you to use selfsigned certificates valid until 2033 it would be good to invest some time explaining developers the importance of the certificate/key and even more important enforce the use by default of stronger algorithms. Seeing the capabilities of the platform I don´t understand why Google did not enforce a minimum key length of 2048b and SHA1 or even better SHA256, instead of using default weaker settings especially when forcing developers to generate certificates valid for so long.

Android embeded certificates

Testing an application I wanted to verify the Root CAs embedded in an Android phone. After some searches the procedure has been easier than suspected. (For this test I used a WinXP SP3 with Java version 1.6.0_13). This what you should do to repeat it:

1) Install the Android USB Driver:
Download the Android SDK Starter package at http://developer.android.com/sdk/index.html, execute it, uncheck al components and mark the "USB Drives". Now you should have a new folder called "usb_driver"

2) In your Android phone go to Settings => Applications => Development and check "USB Debugging"

3) Connect the phone to the computer and when requested to install the required drivers choose the folder "usb_driver"

4) Go to the folder tools and in a console run
adb devices
That should display the serial number of the device you have connected. If that fails unplug and plug the device (you are in a Windows box my friend!)
5) Run
adb pull /system/etc/security/cacerts.bks cacerts.bks
to get the Root CA keystore in your computer
6) To be able to deal with that keystore you need the jar http://bouncycastle.org/download/bcprov-jdk16-141.jar on $JAVA_HOME/jre/lib/ext/
Now you can just run:
keytool -keystore cacerts.bks -storetype BKS -provider org.bouncycastle.jce.provider.BouncyCastleProvider -storepass changeit -list -v
to display the installed Root CAs

If you want to skip it I copy below the ones I found in the Nexus One and Magic:

Nexus One Root CAs:
Issuer: C=US,O=VeriSign\, Inc.,OU=Class 3 Public Primary Certification Authority
Issuer: C=US,O=Equifax Secure Inc.,CN=Equifax Secure Global eBusiness CA-1
Issuer: C=US,O=VeriSign\, Inc.,OU=Class 3 Public Primary Certification Authority - G2,OU=(c) 1998 VeriSign\, Inc. - For authorized use only,OU=VeriSign Trust Network
Issuer: C=IL,O=StartCom Ltd.,OU=StartCom Certification Authority,CN=StartCom Extended Validation Server CA
Issuer: C=PL,O=Unizeto Sp. z o.o.,CN=Certum CA
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert Assured ID Root CA
Issuer: C=HU,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Expressz (Class C) Tanusitvanykiado
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN-USERFirst-Hardware
Issuer: C=BM,O=QuoVadis Limited,OU=Root Certification Authority,CN=QuoVadis Root Certification Authority
Issuer: C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=(c) 2006 VeriSign\, Inc. - For authorized use only,CN=VeriSign Class 3 Public Primary Certification Authority - G5
Issuer: C=HU,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Uzleti (Class B) Tanusitvanykiado
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 1 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: C=US,O=Equifax,OU=Equifax Secure Certificate Authority
Issuer: C=EU,O=AC Camerfirma SA CIF A82743287,OU=http://www.chambersign.org,CN=Chambers of Commerce Root
Issuer: C=US,O=Entrust.net,OU=www.entrust.net/CPS incorp. by ref. (limits liab.),OU=(c) 1999 Entrust.net Limited,CN=Entrust.net Secure Server Certification Authority
Issuer: C=US,O=Equifax Secure Inc.,CN=Equifax Secure eBusiness CA-1
Issuer: C=DE,ST=Hamburg,L=Hamburg,O=TC TrustCenter for Security in Data Networks GmbH,OU=TC TrustCenter Class 2 CA,E=certificate@trustcenter.de
Issuer: C=US,O=Starfield Technologies\, Inc.,OU=Starfield Class 2 Certification Authority
Issuer: C=DE,ST=Hamburg,L=Hamburg,O=TC TrustCenter for Security in Data Networks GmbH,OU=TC TrustCenter Class 3 CA,E=certificate@trustcenter.de
Issuer: C=US,O=The Go Daddy Group\, Inc.,OU=Go Daddy Class 2 Certification Authority
Issuer: C=DE,O=TC TrustCenter GmbH,OU=TC TrustCenter Universal CA,CN=TC TrustCenter Universal CA I
Issuer: C=TW,O=Government Root Certification Authority
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN - DATACorp SGC
Issuer: C=ch,O=Swisscom,OU=Digital Certificate Services,CN=Swisscom Root CA 1
Issuer: C=ES,O=FNMT,OU=FNMT Clase 2 CA
Issuer: C=DE,O=Deutsche Telekom AG,OU=T-TeleSec Trust Center,CN=Deutsche Telekom Root CA 2
Issuer: C=ZA,ST=Western Cape,L=Cape Town,O=Thawte Consulting cc,OU=Certification Services Division,CN=Thawte Server CA,E=server-certs@thawte.com
Issuer: C=US,O=Digital Signature Trust,OU=DST ACES,CN=DST ACES CA X6
Issuer: C=US,O=GTE Corporation,OU=GTE CyberTrust Solutions\, Inc.,CN=GTE CyberTrust Global Root
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN-USERFirst-Network Applications
Issuer: C=FR,O=Certplus,CN=Class 2 Primary CA
Issuer: O=Entrust.net,OU=www.entrust.net/CPS_2048 incorp. by ref. (limits liab.),OU=(c) 1999 Entrust.net Limited,CN=Entrust.net Certification Authority (2048)
Issuer: C=JP,O=Japan Certification Services\, Inc.,CN=SecureSign RootCA1
Issuer: C=DK,O=TDC Internet,OU=TDC Internet Root CA
Issuer: C=ES,L=C/ Muntaner 244 Barcelona,CN=Autoridad de Certificacion Firmaprofesional CIF A62634068,E=ca@firmaprofesional.com
Issuer: C=SE,O=AddTrust AB,OU=AddTrust External TTP Network,CN=AddTrust External CA Root
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert Global Root CA
Issuer: OU=GlobalSign Root CA - R2,O=GlobalSign,CN=GlobalSign
Issuer: C=NL,O=Staat der Nederlanden,CN=Staat der Nederlanden Root CA
Issuer: C=ZA,ST=Western Cape,L=Cape Town,O=Thawte Consulting cc,OU=Certification Services Division,CN=Thawte Premium Server CA,E=premium-server@thawte.com
Issuer: OU=Copyright (c) 1997 Microsoft Corp.,OU=Microsoft Corporation,CN=Microsoft Root Authority
Issuer: C=IL,O=StartCom Ltd.,OU=Secure Digital Certificate Signing,CN=StartCom Certification Authority
Issuer: C=US,O=Entrust\, Inc.,OU=www.entrust.net/CPS is incorporated by reference,OU=(c) 2006 Entrust\, Inc.,CN=Entrust Root Certification Authority
Issuer: C=DE,O=TC TrustCenter GmbH,OU=TC TrustCenter Class 2 CA,CN=TC TrustCenter Class 2 CA II
Issuer: C=US,O=America Online Inc.,CN=America Online Root Certification Authority 1
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 2 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=Terms of use at https://www.verisign.com/rpa (c)06,CN=VeriSign Class 3 Extended Validation SSL SGC CA
Issuer: C=BE,O=GlobalSign nv-sa,OU=Root CA,CN=GlobalSign Root CA
Issuer: C=HU,ST=Hungary,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Kozjegyzoi (Class A) Tanusitvanykiado
Issuer: C=US,O=Entrust\, Inc.,OU=AND ADDITIONAL TERMS GOVERNING USE AND RELIANCE,OU=CPS CONTAINS IMPORTANT LIMITATIONS OF WARRANTIES AND LIABILITY,OU=www.entrust.net/CPS is incorporated by reference,OU=(c) 2008 Entrust\, Inc.,CN=Entrust Certification Authority - L1B
Issuer: C=FI,O=Sonera,CN=Sonera Class2 CA
Issuer: C=JP,O=SECOM Trust.net,OU=Security Communication RootCA1
Issuer: C=BM,O=QuoVadis Limited,CN=QuoVadis Root CA 3
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert High Assurance EV Root CA
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 3 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: C=BM,O=QuoVadis Limited,CN=QuoVadis Root CA 2

Magic:
Issuer: C=HU,ST=Hungary,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Kozjegyzoi (Class A) Tanusitvanykiado
Issuer: C=FI,O=Sonera,CN=Sonera Class2 CA
Issuer: C=JP,O=SECOM Trust.net,OU=Security Communication RootCA1
Issuer: C=US,O=GTE Corporation,CN=GTE CyberTrust Root
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert High Assurance EV Root CA
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 3 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: C=US,O=VeriSign\, Inc.,OU=Class 3 Public Primary Certification Authority
Issuer: C=US,O=Equifax Secure Inc.,CN=Equifax Secure Global eBusiness CA-1
Issuer: C=US,O=VeriSign\, Inc.,OU=Class 3 Public Primary Certification Authority - G2,OU=(c) 1998 VeriSign\, Inc. - For authorized use only,OU=VeriSign Trust Network
Issuer: C=PL,O=Unizeto Sp. z o.o.,CN=Certum CA
Issuer: C=DE,ST=Hamburg,L=Hamburg,O=TC TrustCenter for Security in Data Networks GmbH,OU=TC TrustCenter Class 2 CA,E=certificate@trustcenter.de
Issuer: C=US,O=Starfield Technologies\, Inc.,OU=Starfield Class 2 Certification Authority
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert Assured ID Root CA
Issuer: C=US,O=The Go Daddy Group\, Inc.,OU=Go Daddy Class 2 Certification Authority
Issuer: C=HU,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Expressz (Class C) Tanusitvanykiado
Issuer: C=TW,O=Government Root Certification Authority
Issuer: C=HU,L=Budapest,O=NetLock Halozatbiztonsagi Kft.,OU=Tanusitvanykiadok,CN=NetLock Uzleti (Class B) Tanusitvanykiado
Issuer: C=ES,O=FNMT,OU=FNMT Clase 2 CA
Issuer: C=US,O=Equifax,OU=Equifax Secure Certificate Authority
Issuer: C=US,O=Digital Signature Trust,OU=DST ACES,CN=DST ACES CA X6
Issuer: C=DE,ST=Hamburg,L=Hamburg,O=TC TrustCenter for Security in Data Networks GmbH,OU=TC TrustCenter Class 3 CA,E=certificate@trustcenter.de
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN-USERFirst-Hardware
Issuer: C=FR,O=Certplus,CN=Class 2 Primary CA
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN - DATACorp SGC
Issuer: C=US,O=RSA Data Security\, Inc.,OU=Secure Server Certification Authority
Issuer: C=ES,L=C/ Muntaner 244 Barcelona,CN=Autoridad de Certificacion Firmaprofesional CIF A62634068,E=ca@firmaprofesional.com
Issuer: C=DE,O=Deutsche Telekom AG,OU=T-TeleSec Trust Center,CN=Deutsche Telekom Root CA 2
Issuer: C=ES,ST=BARCELONA,L=BARCELONA,O=IPS Seguridad CA,OU=Certificaciones,CN=IPS SERVIDORES,E=ips@mail.ips.es
Issuer: OU=GlobalSign Root CA - R2,O=GlobalSign,CN=GlobalSign
Issuer: C=US,O=GTE Corporation,OU=GTE CyberTrust Solutions\, Inc.,CN=GTE CyberTrust Global Root
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 1 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: OU=Copyright (c) 1997 Microsoft Corp.,OU=Microsoft Corporation,CN=Microsoft Root Authority
Issuer: C=SE,O=AddTrust AB,OU=AddTrust External TTP Network,CN=AddTrust External CA Root
Issuer: C=EU,O=AC Camerfirma SA CIF A82743287,OU=http://www.chambersign.org,CN=Chambers of Commerce Root
Issuer: C=US,O=Entrust.net,OU=www.entrust.net/CPS incorp. by ref. (limits liab.),OU=(c) 1999 Entrust.net Limited,CN=Entrust.net Secure Server Certification Authority
Issuer: C=US,O=DigiCert Inc,OU=www.digicert.com,CN=DigiCert Global Root CA
Issuer: C=US,O=Equifax Secure Inc.,CN=Equifax Secure eBusiness CA-1
Issuer: C=ch,O=Swisscom,OU=Digital Certificate Services,CN=Swisscom Root CA 1
Issuer: C=ZA,ST=Western Cape,L=Cape Town,O=Thawte Consulting cc,OU=Certification Services Division,CN=Thawte Server CA,E=server-certs@thawte.com
Issuer: C=US,ST=UT,L=Salt Lake City,O=The USERTRUST Network,OU=http://www.usertrust.com,CN=UTN-USERFirst-Network Applications
Issuer: C=JP,O=Japan Certification Services\, Inc.,CN=SecureSign RootCA1
Issuer: C=DK,O=TDC Internet,OU=TDC Internet Root CA
Issuer: C=NL,O=Staat der Nederlanden,CN=Staat der Nederlanden Root CA
Issuer: C=IL,ST=Israel,L=Eilat,O=StartCom Ltd.,OU=CA Authority Dep.,CN=Free SSL Certification Authority,E=admin@startcom.org
Issuer: C=ZA,ST=Western Cape,L=Cape Town,O=Thawte Consulting cc,OU=Certification Services Division,CN=Thawte Premium Server CA,E=premium-server@thawte.com
Issuer: C=US,O=America Online Inc.,CN=America Online Root Certification Authority 1
Issuer: L=ValiCert Validation Network,O=ValiCert\, Inc.,OU=ValiCert Class 2 Policy Validation Authority,CN=http://www.valicert.com/,E=info@valicert.com
Issuer: C=BE,O=GlobalSign nv-sa,OU=Root CA,CN=GlobalSign Root CA


Main sources:
http://wiki.cacert.org/ImportRootCert#Android_Phones
http://developer.android.com/sdk/index.html

802.1x TLS authentication with Android, iPhones and iPads

In my last post I explained how to deploy the necessary infrastructure in order to connect macs to a 802.1x TLS protected network. In that post I´ll explain how to connect an Android or iPhone. The first thing you need is to add the device object in Active Directory and create certificate with the same characteristics as the one for the mac. Make sure you add "host/" at the beginning of the CN field preceding the name of the device as added in Active Directory.

Once you have the PKCS12 containers (.pfx file) with the device certificate, the key and the related certificates chains import it to the device and configure the WLAN interface as follows:

Android 2.1:
For Android, the first think you have to do is enable the credentials store. Go to "Settings", "Location and Security", and set password. Put the PKCS12 file in the root of the SD Card and come back to the security menu. Click on "Install from SD Card" and choose the appropriate file. You´ll be promoted to install the certificate, key and Root CAs. Once installed you can try to connect to the 802.1x TLS protected WLAN. Connect to the 802.1x TLS protected WLAN. As the network will request TLS authentication, the Android would request you to unblock your credentials storage. Enter the password and click Accept. In the configuration screen add the following parameters:
- EAP_ TLS
- No second phase authentication
- Choose the CA certificate (you should have only one)
- Choose the user certificate (you should have only one)
- In the identity entry add the same you added in the CN of the certificate. It should be something like: "host/machine-name"

I have successfully tested it with Android 2.1. The draw back is that you most probably will require a proxy to access the Internet and that can´t be configured in Android (unless you use a Cyanogen build)

iPhone 3, iPhone 4 and iPad:
Send the PKCS12 file by email and open it from the mail application. Follow the same instructions as the ones to connect an Android device to the WLAN. Remember to manually add the CN as the Identity with the "host/" at the beginning.