Tag Archives: SHA-1

TLS 1.0 and 1.1 Upcoming End of Support Announced

Early last week saw a coordinated effort from almost major browser vendor to follow the guidelines of the PCI-DSS standard and to end support for TLS 1.0 and 1.1

Why should this change be considered relevant?
Each of the browser vendors have worked together to create a definite timeline (starting in 2020 and complete by July 2020) for the end of support of these now obsolete security protocols. TLS 1.0 is almost 20 years old and is no longer PCI-DSS compliant.  Separately TLS 1.1 is more than 10 years old. They both contain known vulnerabilities e.g. BEAST (an attack), DROWN or FREAK (both downgrade attacks) etc. use insecure hash functions (e.g. MD5 and SHA-1) and receive very little use today:

0.4% from Apple Safari (<0.36% for all connections) (Source: WebKit)

0.5% for Google Chrome (Source: Google)

1.2% of Firefox Beta 62 during the time August-September 2018 (Source: Mozilla)

0.72% for Microsoft Edge (Source: Microsoft)

More modern standard e.g. TLS 1.2 offers improved performance when used with HTTP/2 and are PCI-DSS compliant. Moreover, it doesn’t suffer from all of the vulnerabilities affecting prior versions and includes stronger alternatives to older hash functions e.g. ECDHE_RSA_WITH_AES_128_GCM_SHA256 .

What does the future hold?
Following the recent deprecation of any standard of TLS older than 1.2 on the 30th of June this year due to the mandate set by the PCI Security Standard Council has steadily seen the increase of the recently ratified TLS 1.3 (in April 2018) but defined within (Request for Comments) RFC 8446 in August. This is in part due to a change by Mozilla to Firefox in April and the adoption of the newest standard by some popular websites e.g.:

Google’s Gmail (although the newer standard isn’t always enabled)

https://www.bleepingcomputer.com/

https://www.securityweek.com/

https://nakedsecurity.sophos.com

https://www.theregister.co.uk/

https://www.wordpress.com (which also includes this blog you are reading!)

The OpenSSL Foundation added full TLS 1.3 support to their popular cryptographic library OpenSSL with the release of version 1.1.1 in September 2018. OpenSSL are further driving adoption of the newest standard by ending support for the current long term support (LTS) version 1.0.2 by the end of 2019 (with it only receiving security updates after the 31st December 2018).

The increase in traffic is best illustrated by Mozilla showing approaching 6% usage for Firefox Beta 62 during the time August-September 2018. Such an increase is really good news for the security of the Internet specifically any online service that requests personal information and e-commerce websites in particular.

For more information on which web browsers support TLS 1.3, please see this link with a table from Salesforce illustrating browser support for TLS 1.2 here.

Thank you.

SHA-1 collision attack took two years to complete

Google security researchers Elie Bursztein, Ange Albertini, and Yarik Markov and researchers from Cryptology Group at Centrum Wiskunde and Informatica (CWI) in Amsterdam, Marc Stevens and Pierre Karpman last month detailed the results of two years of work to create a collision attack against the Secure Hash Algorithm (SHA)-1 (defined) algorithm.

They focused on an attack allowing the SHA-1 hash of one Adobe Portable Document Format (PDF) file to match the hash of a second PDF. The researchers divided the work into two phases; phase one used 6,500 years of Central Processing Unit (CPU)(defined) computation while phase 2 consumed 110 years of Graphics Processing Unit (GPU)(defined) computation time. The work appears to have cost between USD$75,000 and USD $120,000 to complete.

Theoretical attacks against SHA-1 have existed since 2005 with 2016 showcasing work estimating an attack could take as little as three months; this new attack marks the first practical attack. I previously detailed why you should migrate your website and code-signing certificates to SHA-2.

How can I protect myself from this vulnerability?
If you are responsible for website signing certificates and/or software signing certificates making use of SHA-1 algorithm you should continue your planned migration to SHA-2 signing certificates. Use of updated web browsers will correctly assign less trust to websites using SHA-1 certificates. While I agree with Linus Torvalds about the “sky not falling” with regard to SHA-1, use of a more secure hashing algorithm will be more important as time goes on. For example, the interruption of service of the WebKit SVN would not have occurred if SHA-2 was in use.

Thank you.

Blog Post Shout Out: SHA-1 Migration and Internet of Things (IoT)

With the transition to SHA-2 rapidly approaching (January 2017) if you have not already begun the migration process for your website or are having difficulties locating all of the certificates that need migrating; the following article that I wish to provide a respectful shout out to may be of assistance. The article includes advice on making the best use of the remaining time:

SHA-1 Time Bomb: One Third of Websites Have Yet to Upgrade by Phill Muncaster (Infosecurity Magazine)

This issue is also of note since Google (like the other browser vendors is moving away from SHA-1) will remove support for SHA-1 in Chrome version 56. Further details are provided in their blog post. The source of the statistics for the Infosecurity Magazine article was this blog post from Venafi, an organisation that provides cryptography related solutions and services to enterprises.

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With the DDoS attack (defined) against the DNS service Dyn last month attributed to Internet of Things (defined) devices further steps need to be taken to secure them. To assist with this, the US CERT have written a PDF document titled “Strategic Principles for Securing the IoT”. It is intended for consumers, operators and manufacturers of IoT devices. It is available from the link below:

Securing the Internet of Things (US-CERT)

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Thank you.

Mozilla Releases Firefox 43.0.2 and Firefox ESR 38.5.2

In late December 2015 Mozilla released security updates for Firefox bringing it to version 43.0.2 and Firefox ESR (Extended Support Release) 38.5.2.

At that time the release notes for these updates didn’t reference any further security issues resolved since the previous updates (described in a previous post of mine). The above mentioned Firefox version numbers were not present in late December. I was aware of these updates but since they didn’t contain further security related changes I didn’t create a post about them. In future I will need to re-check those pages again in the days following such updates in order to avoid such a delay in posting.

Since that time the security advisory pages for Firefox and Firefox ESR (linked to below) now include details of a moderate severity security issue (assigned 1 CVE number (defined)) resolved by these updates. The issue relates to the Network Security Services (NSS) component of Firefox still accepting TLS 1.2 ServerKeyExchange messages with MD5 digital signatures. As discussed here and here, the use of MD5 is discouraged and Mozilla has rectified this issue using these updates.

Full details of the security issues resolved by these updates are available in the following links:

Firefox 43.0.2
Firefox ESR 38.5.2

Details of how to install updates for Firefox are here. If Firefox is your web browser of choice, please update it as soon as possible to resolve this security issue.

Note: The most recent version of Firefox 43 at the time of writing is 43.0.4. It has since been updated following the release of 43.0.2. Please ensure you are using the most up to date version available. 43.0.4 re-enables SHA-1 certificates for “man-in-the-middle” (defined) devices. More details are provided here.

In general, Mozilla Firefox updates install without issues, however as always I would recommend backing up the data on any device for which you are installing updates in order to prevent data loss in the rare event that any update causes unexpected issues.

Thank you.

Why Your Organizations Website Should Migrate From SHA-1

Update: 15th March 2017:
The first practical attack against SHA-1 took place in February 2017 and is discussed in a more recent blog post.

Thank you.

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Update: 25th June 2016:
Microsoft have updated their SHA-1 deprecation roadmap to state that from the 12th of July changes described in that psot will be seen for Microsoft Edge, Microsoft Internet and Windows 10 (with the Anniversary update) with regard to how they display the status of SHA-1 certificates. Further details are available within that post.

Thank you.
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Update: 10th January 2016:
As mentioned in a recent blog post Mozilla have needed to re-enable SHA-1 certificates for “man-in-the-middle” (defined) devices due to issues being experienced by companies/organizations using such devices.

In addition, in mid-December Google announced their schedule for phasing out SHA-1. They too are considering moving the deadline forward to 1st July 2016 but have set a hard deadline of the 1st January 2017.

At the end of their blog post announcing this schedule they also provide advice on migrating from SHA-1. It is notable that within Step 2 of their plan they mention they took into account the issue Mozilla encountered (mentioned above; however, Google published that blog post before Mozilla Firefox users encountered that issue and worked around it in advance).

The migration from SHA-1 poses some very difficult issues for both users who cannot upgrade their web browsers before the imposed deadlines as well as corporate users who will be unable to make the transition in time (e.g. they are using custom applications that are critical to their business). These issues are discussed here with a possible work around being voted upon by the CA/Browser Forum discussed in a separate post.

Thank you.
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Update: 24th November 2015:
Since publishing this blog post last month Mozilla and Microsoft are considering moving forward the deadline for phasing out SHA-1 to the 1st of July 2016. Their decisions have come in light of the recent disclosure of potential attacks on SHA-1 previously discussed within this blog post. The final deadline has not yet been decided but this should be yet another reason to begin planning to move your organization’s website away from using SHA-1.

Thank you.

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Original Post:
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Earlier this month a report was published by a team of researchers which shows that a potential attack on a SHA-1 hash (defined) could take as little as 3 months and cost in the region of USD $75k to $125k. The time and cost necessary are significantly less than the previous 2012 estimates of $700k necessary in 2015 and $173k by 2018.

Why Should This Potential Attack Be Considered Important?
In October 2012 possible attacks on SHA-1 were discussed and estimates provided on how time such attacks would take to carry out. Migration away from SHA-1 at the time was suggested. With the publication of the new research this month the need for migration has become more important.

An attack against the MD5 hash algorithm in 2012 was used by malware known as Flame to allow the installation of the malware onto PCs by making it “look like” genuine Windows Updates from Microsoft.

This was accomplished by the malware authors making improper use of Microsoft’s Terminal Services licensing certificate authority (CA)(defined). The certificate used to sign the updates was created using the MD5 algorithm (defined). A hash collision attack (defined) was used by the malware authors to make a different signing certificate produce the same hash as that of the genuine signing certificate. This seemingly “genuine” certificate was then used to sign their malware making it look like those malware files were Windows Updates.

While weaknesses in the MD5 algorithm were used to accomplish this, the same method of attack could potentially be used with SHA-1 to once again make malware look like legitimate/non-malicious files. When I say this, I don’t mean that an attack of this kind could again be carried out against Windows Update but I am referring to the use of SHA-1 in general. It’s not uncommon to see SHA-1 hashes provided when downloading new software or software updates from a software vendor’s website. If those files could be replaced with malware that has an identical hash to that of the legitimate file, the same type of attack could be carried out. You could download the file which would be malware but it would have the same SHA-1 hash as the genuine software.

SHA-1 is not only used for code-signing certificates but also with TLS (defined) secured websites. For example, if a website e.g. example.com has a legitimate certificate, that certificate could potentially be used by an attacker to provide more trust to a website of their choice using a collision attack on SHA-1. Thus when you visit the attackers website, malware.com it would appear to have a legitimate/trusted certificate. If this fake certificate were used in combination with another attack e.g. pharming (defined)(also discussed further in this post), there is the potential for you to visit example.com and actually be taken to the attacker’s website but example.com would appear in your web browsers address bar (while at the same time having a seemingly legitimate TLS certificate making the website appear even more trustworthy).

How Can I Protect Against The Known Weaknesses in SHA-1?
If you would like to check if your website uses a SHA-1 certificate you can visit this website. That site also provides advice on obtaining a newer SHA-2 certificate.

In addition this link provides advice on generating a new TLS SHA-2 certificate. Moreover a list of compatible web browsers, operating systems, web servers, databases, firewalls etc. is provided here. Finally the current planned roll-out phases of SHA-2 is provided here. Moreover you may find that this article provides useful background information and advice. For TLS certificates, the deadline for transition to SHA-2 is currently January 2017.

However a ballot with the CA/Browser Forum wishes to extend the issuing of SHA-1 certificates throughout 2016 giving large organizations with too many certificates to switch over during 2016 more time to do so. It appears from this post that this 1 year extension was granted (please see the update below for clarification on this).

Update: 4th January 2016:
I have been contacted in relation to the CA/Browser forum vote and have been informed that Symantec withdrew their ballot and the Baseline Requirements section on SHA-1 are unchanged. Many thanks to Mr. E. Mill for this information.

Update: 7th February 2016:
Qualys in September 2014 published a thorough blog post detailing how to migrate from SHA-1 including what to do should you need to support devices that cannot migrate from SHA-1.

I hope that the above information is useful to any organization or individual wishing to migrate their websites TLS certificate from SHA-1 to SHA-2.

Thank you.