Tag: esp

Sounding the Alarm on Emergency Alert System Flaws

The Department of Homeland Security (DHS) is urging states and localities to beef up security around proprietary devices that connect to the Emergency Alert System — a national public warning system used to deliver important emergency information, such as severe weather and AMBER alerts. The DHS warning came in advance of a workshop to be held this weekend at the DEFCON security conference in Las Vegas, where a security researcher is slated to demonstrate multiple weaknesses in the nationwide alert system.

A Digital Alert Systems EAS encoder/decoder that Pyle said he acquired off eBay in 2019. It had the username and password for the system printed on the machine.

The DHS warning was prompted by security researcher Ken Pyle, a partner at security firm Cybir. Pyle said he started acquiring old EAS equipment off of eBay in 2019, and that he quickly identified a number of serious security vulnerabilities in a device that is broadly used by states and localities to encode and decode EAS alert signals.

“I found all kinds of problems back then, and reported it to the DHS, FBI and the manufacturer,” Pyle said in an interview with KrebsOnSecurity. “But nothing ever happened. I decided I wasn’t going to tell anyone about it yet because I wanted to give people time to fix it.”

Pyle said he took up the research again in earnest after an angry mob stormed the U.S. Capitol on Jan. 6, 2021.

“I was sitting there thinking, ‘Holy shit, someone could start a civil war with this thing,”’ Pyle recalled. “I went back to see if this was still a problem, and it turns out it’s still a very big problem. So I decided that unless someone actually makes this public and talks about it, clearly nothing is going to be done about it.”

The EAS encoder/decoder devices Pyle acquired were made by Lyndonville, NY-based Digital Alert Systems (formerly Monroe Electronics, Inc.), which issued a security advisory this month saying it released patches in 2019 to fix the flaws reported by Pyle, but that some customers are still running outdated versions of the device’s firmware. That may be because the patches were included in version 4 of the firmware for the EAS devices, and many older models apparently do not support the new software.

“The vulnerabilities identified present a potentially serious risk, and we believe both were addressed in software updates issued beginning Oct 2019,” EAS said in a written statement. “We also provided attribution for the researcher’s responsible disclosure, allowing us to rectify the matters before making any public statements. We are aware that some users have not taken corrective actions and updated their software and should immediately take action to update the latest software version to ensure they are not at risk. Anything lower than version 4.1 should be updated immediately. On July 20, 2022, the researcher referred to other potential issues, and we trust the researcher will provide more detail. We will evaluate and work to issue any necessary mitigations as quickly as possible.”

But Pyle said a great many EAS stakeholders are still ignoring basic advice from the manufacturer, such as changing default passwords and placing the devices behind a firewall, not directly exposing them to the Internet, and restricting access only to trusted hosts and networks.

Pyle, in a selfie that is heavily redacted because the EAS device behind him had its user credentials printed on the lid.

Pyle said the biggest threat to the security of the EAS is that an attacker would only need to compromise a single EAS station to send out alerts locally that can be picked up by other EAS systems and retransmitted across the nation.

“The process for alerts is automated in most cases, hence, obtaining access to a device will allow you to pivot around,” he said. “There’s no centralized control of the EAS because these devices are designed such that someone locally can issue an alert, but there’s no central control over whether I am the one person who can send or whatever. If you are a local operator, you can send out nationwide alerts. That’s how easy it is to do this.”

One of the Digital Alert Systems devices Pyle sourced from an electronics recycler earlier this year was non-functioning, but whoever discarded it neglected to wipe the hard drive embedded in the machine. Pyle soon discovered the device contained the private cryptographic keys and other credentials needed to send alerts through Comcast, the nation’s third-largest cable company.

“I can issue and create my own alert here, which has all the valid checks or whatever for being a real alert station,” Pyle said in an interview earlier this month. “I can create a message that will start propagating through the EAS.”

Comcast told KrebsOnSecurity that “a third-party device used to deliver EAS alerts was lost in transit by a trusted shipping provider between two Comcast locations and subsequently obtained by a cybersecurity researcher.

“We’ve conducted a thorough investigation of this matter and have determined that no customer data, and no sensitive Comcast data, were compromised,” Comcast spokesperson David McGuire said.

The company said it also confirmed that the information included on the device can no longer be used to send false messages to Comcast customers or used to compromise devices within Comcast’s network, including EAS devices.

“We are taking steps to further ensure secure transfer of such devices going forward,” McGuire said. “Separately, we have conducted a thorough audit of all EAS devices on our network and confirmed that they are updated with currently available patches and are therefore not vulnerable to recently reported security issues. We’re grateful for the responsible disclosure and to the security research community for continuing to engage and share information with our teams to make our products and technologies ever more secure. Mr. Pyle informed us promptly of his research and worked with us as we took steps to validate his findings and ensure the security of our systems.”

The user interface for an EAS device.

Unauthorized EAS broadcast alerts have happened enough that there is a chronicle of EAS compromises over at fandom.com. Thankfully, most of these incidents have involved fairly obvious hoaxes.

According to the EAS wiki, in February 2013, hackers broke into the EAS networks in Great Falls, Mt. and Marquette, Mich. to broadcast an alert that zombies had risen from their graves in several counties. In Feb. 2017, an EAS station in Indiana also was hacked, with the intruders playing the same “zombies and dead bodies” audio from the 2013 incidents.

“On February 20 and February 21, 2020, Wave Broadband’s EASyCAP equipment was hacked due to the equipment’s default password not being changed,” the Wiki states. “Four alerts were broadcasted, two of which consisted of a Radiological Hazard Warning and a Required Monthly Test playing parts of the Hip Hop song Hot by artist Young Thug.”

In January 2018, Hawaii sent out an alert to cell phones, televisions and radios, warning everyone in the state that a missile was headed their way. It took 38 minutes for Hawaii to let people know the alert was a misfire, and that a draft alert was inadvertently sent. The news video clip below about the 2018 event in Hawaii does a good job of walking through how the EAS works.

The Department of Homeland Security (DHS) is urging states and localities to beef up security around proprietary devices that connect to the Emergency Alert System — a national public warning system used to deliver important emergency information, such as severe weather and AMBER alerts. The DHS warning came in advance of a workshop to be held this weekend at the DEFCON security conference in Las Vegas, where a security researcher is slated to demonstrate multiple weaknesses in the nationwide alert system.Read More

Twitter Exposes Personal Information for 5.4 Million Accounts

Twitter accidentally exposed the personal information—including phone numbers and email addresses—for 5.4 million accounts. And someone was trying to sell this information.

In January 2022, we received a report through our bug bounty program of a vulnerability in Twitter’s systems. As a result of the vulnerability, if someone submitted an email address or phone number to Twitter’s systems, Twitter’s systems would tell the person what Twitter account the submitted email addresses or phone number was associated with, if any. This bug resulted from an update to our code in June 2021. When we learned about this, we immediately investigated and fixed it. At that time, we had no evidence to suggest someone had taken advantage of the vulnerability.

In July 2022, we learned through a press report that someone had potentially leveraged this and was offering to sell the information they had compiled. After reviewing a sample of the available data for sale, we confirmed that a bad actor had taken advantage of the issue before it was addressed.

This includes anonymous accounts.

This comment has it right:

So after forcing users to enter a phone number to continue using twitter, despite twitter having no need to know the users phone number, they then leak the phone numbers and associated accounts. Great.

But it gets worse… After being told of the leak in January, rather than disclosing the fact millions of users data had been open for anyone who looked, they quietly fixed it and hoped nobody else had found it.

It was only when the press started to notice they finally disclosed the leak.

That isn’t just one bug causing a security leak—it’s a chain of bad decisions and bad security culture, and if anything should attract government fines for lax data security, this is it.

Twitter’s blog post unhelpfully goes on to say:

If you operate a pseudonymous Twitter account, we understand the risks an incident like this can introduce and deeply regret that this happened. To keep your identity as veiled as possible, we recommend not adding a publicly known phone number or email address to your Twitter account.

Three news articles.

Twitter accidentally exposed the personal information—including phone numbers and email addresses—for 5.4 million accounts. And someone was trying to sell this information.
In January 2022, we received a report through our bug bounty program of a vulnerability in Twitter’s systems. As a result of the vulnerability, if someone submitted an email address or phone number to Twitter’s systems, Twitter’s systems would tell the person what Twitter account the submitted email addresses or phone number was associated with, if any. This bug resulted from an update to our code in June 2021. When we learned about this, we immediately investigated and fixed it. At that time, we had no evidence to suggest someone had taken advantage of the vulnerability. …Read More

Microsoft: We Don’t Want to Zero-Day Our Customers

The head of Microsoft’s Security Response Center defends keeping its initial vulnerability disclosures sparse — it is, she says, to protect customers.The head of Microsoft’s Security Response Center defends keeping its initial vulnerability disclosures sparse — it is, she says, to protect customers.Read More

It Might Be Our Data, But It’s Not Our Breach

Image: Shutterstock.

A cybersecurity firm says it has intercepted a large, unique stolen data set containing the names, addresses, email addresses, phone numbers, Social Security Numbers and dates of birth on nearly 23 million Americans. The firm’s analysis of the data suggests it corresponds to current and former customers of AT&T. The telecommunications giant stopped short of saying the data wasn’t theirs, but it maintains the records do not appear to have come from its systems and may be tied to a previous data incident at another company.

Milwaukee-based cybersecurity consultancy Hold Security said it intercepted a 1.6 gigabyte compressed file on a popular dark web file-sharing site. The largest item in the archive is a 3.6 gigabyte file called “dbfull,” and it contains 28.5 million records, including 22.8 million unique email addresses and 23 million unique SSNs. There are no passwords in the database.

Hold Security founder Alex Holden said a number of patterns in the data suggest it relates to AT&T customers. For starters, email addresses ending in “att.net” accounted for 13.7 percent of all addresses in the database, with addresses from SBCGLobal.net and Bellsouth.net — both AT&T companies — making up another seven percent. In contrast, Gmail users made up more than 30 percent of the data set, with Yahoo addresses accounting for 24 percent. More than 10,000 entries in the database list “none@att.com” in the email field.

Hold Security found these email domains account for 87% of all domains in the data set. Nearly 21% belonged to AT&T customers.

Holden’s team also examined the number of email records that included an alias in the username portion of the email, and found 293 email addresses with plus addressing. Of those, 232 included an alias that indicated the customer had signed up at some AT&T property; 190 of the aliased email addresses were “+att@”; 42 were “+uverse@,” an oddly specific reference to a DirecTV/AT&T entity that included broadband Internet. In September 2016, AT&T rebranded U-verse as AT&T Internet.

According to its website, AT&T Internet is offered in 21 states, including Alabama, Arkansas, California, Florida, Georgia, Indiana, Kansas, Kentucky, Louisiana, Michigan, Missouri, Nevada, North Carolina, Ohio, Oklahoma, Tennessee, Texas and Wisconsin. Nearly all of the records in the database that contain a state designation corresponded to those 21 states; all other states made up just 1.64 percent of the records, Hold Security found.

Image: Hold Security.

The vast majority of records in this database belong to consumers, but almost 13,000 of the entries are for corporate entities. Holden said 387 of those corporate names started with “ATT,” with various entries like “ATT PVT XLOW” appearing 81 times. And most of the addresses for these entities are AT&T corporate offices.

How old is this data? One clue may be in the dates of birth exposed in this database. There are very few records in this file with dates of birth after 2000.

“Based on these statistics, we see that the last significant number of subscribers born in March of 2000,” Holden told KrebsOnSecurity, noting that AT&T requires new account holders to be 18 years of age or older. “Therefore, it makes sense that the dataset was likely created close to March of 2018.”

There was also this anomaly: Holden said one of his analysts is an AT&T customer with a 13-letter last name, and that her AT&T bill has always had the same unique misspelling of her surname (they added yet another letter). He said the analyst’s name is identically misspelled in this database.

KrebsOnSecurity shared the large data set with AT&T, as well as Hold Security’s analysis of it. AT&T ultimately declined to say whether all of the people in the database are or were at some point AT&T customers. The company said the data appears to be several years old, and that “it’s not immediately possible to determine the percentage that may be customers.”

“This information does not appear to have come from our systems,” AT&T said in a written statement. “It may be tied to a previous data incident at another company. It is unfortunate that data can continue to surface over several years on the dark web. However, customers often receive notices after such incidents, and advice for ID theft is consistent and can be found online.”

The company declined to elaborate on what they meant by “a previous data incident at another company.”

But it seems likely that this database is related to one that went up for sale on a hacker forum on August 19, 2021. That auction ran with the title “AT&T Database +70M (SSN/DOB),” and was offered by ShinyHunters, a well-known threat actor with a long history of compromising websites and developer repositories to steal credentials or API keys.

Image: BleepingComputer

ShinyHunters established the starting price for the auction at $200,000, but set the “flash” or “buy it now” price at $1 million. The auction also included a small sampling of the stolen information, but that sample is no longer available. The hacker forum where the ShinyHunters sales thread existed was seized by the FBI in April, and its alleged administrator arrested.

But cached copies of the auction, as recorded by cyber intelligence firm Intel 471, show ShinyHunters received bids of up to $230,000 for the entire database before they suspended the sale.

“This thread has been deleted several times,” ShinyHunters wrote in their auction discussion on Sept. 6, 2021. “Therefore, the auction is suspended. AT&T will be available on WHM as soon as they accept new vendors.”

The WHM initialism was a reference to the White House Market, a dark web marketplace that shut down in October 2021.

“In many cases, when a database is not sold, ShinyHunters will release it for free on hacker forums,” wrote BleepingComputer’s Lawrence Abrams, who broke the news of the auction last year and confronted AT&T about the hackers’ claims.

AT&T gave Abrams a similar statement, saying the data didn’t come from their systems.

“When asked whether the data may have come from a third-party partner, AT&T chose not to speculate,” Abrams wrote. “‘Given this information did not come from us, we can’t speculate on where it came from or whether it is valid,’” AT&T told BleepingComputer.

Asked to respond to AT&T’s denial, ShinyHunters told BleepingComputer at the time, “I don’t care if they don’t admit. I’m just selling.”

On June 1, 2022, a 21-year-old Frenchman was arrested in Morocco for allegedly being a member of ShinyHunters. Databreaches.net reports the defendant was arrested on an Interpol “Red Notice” at the request of a U.S. federal prosecutor from Washington state.

Databreaches.net suggests the warrant could be tied to a ShinyHunters theft in May 2020, when the group announced they had exfiltrated 500 GB of Microsoft’s source code from Microsoft’s private GitHub repositories.

“Researchers assess that Shiny Hunters gained access to roughly 1,200 private repositories around March 28, 2020, which have since been secured,” reads a May 2020 alert posted by the New Jersey Cybersecurity & Communications Integration Cell, a component within the New Jersey Office of Homeland Security and Preparedness.

“Though the breach was largely dismissed as insignificant, some images of the directory listing appear to contain source code for Azure, Office, and some Windows runtimes, and concerns have been raised regarding access to private API keys or passwords that may have been mistakenly included in some private repositories,” the alert continues. “Additionally, Shiny Hunters is flooding dark web marketplaces with breached databases.”

Last month, T-Mobile agreed to pay $350 million to settle a consolidated class action lawsuit over a breach in 2021 that affected 40 million current and former customers. The breach came to light on Aug. 16, 2021, when someone starting selling tens of millions of SSN/DOB records from T-Mobile on the same hacker forum where the ShinyHunters would post their auction for the claimed AT&T database just three days later.

T-Mobile has not disclosed many details about the “how” of last year’s breach, but it said the intruder(s) “leveraged their knowledge of technical systems, along with specialized tools and capabilities, to gain access to our testing environments and then used brute force attacks and other methods to make their way into other IT servers that included customer data.”

A sales thread tied to the stolen T-Mobile customer data.

A cybersecurity firm says it has intercepted a large, unique stolen data set containing the names, addresses, email addresses, phone numbers, Social Security Numbers and dates of birth on nearly 23 million Americans. The firm’s analysis of the data suggests it corresponds to current and former customers of AT&T. The telecommunications giant stopped short of saying the data wasn’t theirs, but it maintains the records do not appear to have come from its systems and may be tied to a previous data incident at another company.Read More

Education hammered by exploits and backdoors in 2021 and 2022

In May of 2021, education underwent a siege of exploit attempts using the vulnerability CVE-2021-21551, which exploits a Dell system driver bug and helps attackers to gain access to a network. Considering that many schools across the United States use Dell hardware, it’s understandable to see such a large amount of this exploit. 

In fact, both Rockland Schools in Massachusetts and Visalia USD in California were hit with ransomware attacks during this period. The states that detected this threat the most were Minnesota and Michigan, with Detroit being the biggest target in the US. 

In September of 2021, there was a spike of the malicious setting, RiskwareTool.IFEOHijack, with detections having increased from July 2021 onward. This threat is flagged when malware modifies a registry setting that changes the default Windows debugger to a malware executable. It is a red flag that needs to be investigated immediately. Unfortunately, it doesn’t pinpoint which malware made the modification, but the increased presence of this threat, especially in Oklahoma and Washington State, calls for deeper threat hunting on the victims’ networks. During the same period, a spike in exploit detections was observed and Howard University was breached.

The Trojan TechSupportScam covers an array of applications all designed to fool users into calling a “tech support” number to solve a problem created by the application, such as a blue screen, error message, activation alert, etc. These tools started spiking in January of 2022.  Educational institutions in New Jersey have had to deal with this threat more than any other state, however the public school district of Albuquerque, NM suffered a breach during the same month that could have been influenced by this spike in scams. Students and staff likely encountered these threats when installing risky software and/or visiting shady sites.

Finally, Pennsylvania schools have been dealing with an active campaign of backdoors, specifically QBot, since March of 2022, which will likely result in greater infections during the rest of 2022.

Beyond spikes in detections, the education sector has dealt with an onslaught of attacks ranging from spyware and denial of service tools to ransomware.  Throughout the year, almost every month has a report of an educational institution under attack. The first half of 2021 saw attacks against schools in Florida, New York, Oregon, Massachusetts, and California, while the second half saw attacks against Texas, Washington D.C., Wisconsin, and Illinois. The biggest attack of 2022, so far, would be the breach of Austin Peay State University in April, though time will tell if that remains true.

The education industry has the largest userbase out of all industries, considering the constant rotation of students and faculty. Therefore, the greatest threat to these organizations are the users themselves, who may download their own applications, visit dangerous websites, and even make system modifications to get around monitoring tools.

Recommendations for education

Our recommendation for this sector includes keeping an eye out for all new exploits that might affect your organization, especially commonly used systems. In a lot of cases, organizations may have a difficult time updating quickly, because of operational needs, but in the case of schools, a single vulnerability might be duplicated across 99% of its endpoints, which turns each of those systems into backdoors for the bad guys. So, making vulnerability patching one of the highest priorities will reduce attacks and decrease malicious file installation.

Next, systems that have been infected may leave behind artifacts of its operations, for example the IFEOHijack registry setting. Additionally, threats that may be installed on day one, might not activate until a user does something specific, or a certain date comes around, allowing the threat to hide in the meantime. To combat this threat, consider creating a secure, default system image that can be easily duplicated to endpoints, returning them to a default state. While this is likely already done by many schools every year, consider increasing the frequency to every quarter, maybe even every month, and have students save their files on cloud-based storage solutions.

By utilizing a default image, an organization can erase hidden malware, reset modified settings, and provide confidence in quickly isolating or wiping out an infected system. For the education industry, it’s not so much about what threats are actively targeting schools, but rather what threats have been left behind, that open doors for other, future attacks.

Summer of exploitation leads to healthcare under fire

May 2021 was a tough month for the Healthcare and Medical sector–the most notable threat trend at the time was the heavy use of a new popular exploit against Dell systems, leading to immense effort by attackers to utilize the exploit before it became less effective due to patching.  

During this period, hospitals in central Florida were hit with malicious attacks that disrupted their operations and forced them to conduct business via pen and paper. In addition, a hospital system in Southern California was forced to modify how it did business due to a cyberattack. The San Diego-based health system quickly moved its information technology program offline, to reduce the damage done by the attack. However it also put a roadblock in the way of legitimate employees and customers trying access their medical information online.

Figure 1. United States Healthcare and Medical Threat Family Detections by Month

After the spike in May, CVE 2021-21551 detections dropped to about a quarter of the original numbers, and remained there throughout the year, except for another spike in February 2022. It seems the primary target for these attacks were healthcare and medical organizations in Pensacola, FL, but detections for New York, Wisconsin and New Jersey weren’t far behind.

Heavy detections of TrickBot were observed, especially against organizations in York, Pennsylvania during the first three months of 2021. But detections of this threat all over the United States quickly dropped beginning in April 2021 and steadily declined throughout the time period. TrickBot isn’t a stranger to healthcare organizations and has historically targeted them for the sake of launching ransomware or causing operational disruption.

This threat is even a concern to the US Government, which released an alert, through the CISA portal, back in October of 2020, about the danger of the TrickBot organization specifically targeting Healthcare organizations.

Figure 2. United States Healthcare & Medical Family Threat Detections Pie Chart

In August and September, we observed significant spikes of AI behavioral-based detections, which lines up with a series of newsworthy healthcare breaches during the same period. 

For example, a healthcare group in central Indiana was the victim of an attack that lead to a ransomware infection and the loss of information from patients and employees, then released on the dark web. The attack itself occurred in early August and forced organizations to turn away ambulances for several days, an action which led to the death of a person in Germany.

Another attack in early August, this time against a healthcare management firm in Dallas, Texas, resulted in the theft of valuable information, including patient information, health insurance and financial data. 

Securing healthcare and medical organizations

Our recommendations for securing healthcare and medical organizations start with acknowledging that securing these organizations from every possible threat is not possible. Therefore, when considering how to defend against a ransomware attack, be sure to account for getting operations back online after an attack. This includes having plans for operating the business without the use of computers, establishing secure backups of sensitive data off-site and off-line, while still following HIPPA protocol.

Beyond that, this industry has dealt with lots of heavy attacks originating from both attempts to exploit vulnerabilities, as well as spear phishing. Quickly patching vulnerabilities is a high priority, however given that quick patching isn’t always an option, times like these require risk reduction, such as removing non-patchable endpoints from direct Internet access, creating additional layers of authentication to access high value systems, and a thorough review of user accounts and permissions, to tighten up who has access to what.

Finally, many of these organizations utilize mobile stations for inputting or reviewing data. These systems should not be able to do things like using USB drives. They should have screen protectors to prevent unintended information disclosure, and these systems should be completely wiped with a new image on a regular basis, to ensure removal of any hidden rootkit-level threats. 

How to incorporate ACM PCA into your existing Windows Active Directory Certificate Services

Using certificates to authenticate and encrypt data is vital to any enterprise security. For example, companies rely on certificates to provide TLS encryption for web applications so that client data is protected. However, not all certificates need to be issued from a publicly trusted certificate authority (CA). A privately trusted CA can be leveraged to issue certificates to help protect data in transit on resources such as load-balancers and also device authentication for endpoints and IoT devices. Many organizations already have that privately trusted CA running in their Microsoft Active Directory architecture via Active Directory Certificate Services (ADCS).

This post outlines how you can use Microsoft’s Windows 2019 ADCS to sign an AWS Certificate Manager (ACM) Private Certificate Authority (Private CA) instance, extending your existing ADCS system into your AWS environment. This will allow you to issue certificates via ACM for resources like Application Load Balancer that are trusted by your Active Directory members. The ACM PCA documentation talks about how to use an external CA to sign the ACM PCA certificate. However, it leaves the details of the external CA outside of the documentation scope.

Why use ACM PCA?

AWS Certificate Manager Private Certificate Authority (ACM Private CA or ACM PCA) is a private CA service that extends ACM certificate management capabilities to both public and private certificates. ACM PCA provides a highly available private CA service without the upfront investment and ongoing maintenance costs of operating your own private CA. ACM PCA allows developers to be more agile by providing them with APIs to create and deploy private certificates programmatically. You also have the flexibility to create private certificates for applications that require custom certificate lifetimes or resource names.

Why use ACM PCA with Windows Active Directory?

Many enterprises already use Active Directory to manage their IT resources. Whether it is on-premises or built into your AWS accounts, Active Directory’s built-in CA can be extended by ACM PCA. Using your ADCS to sign an ACM PCA means that members of your Active Directory automatically trust certificates issued by that ACM PCA. Keep in mind that these are still private certificates, and they are intended to be used just like certificates from ADCS itself. They will not be trusted by unmanaged devices, because these are not signed by a publicly trusted external CA. Therefore, systems like Mac and Linux may require that you manually deploy the ADCS certificate chain in order to trust certificates issued by your new ACM PCA.

This means it is more efficient for you to rapidly deploy certificates to your endpoint workstations for authentication. Or you can protect internal-only workloads with certificates that are constrained to your internal domain namespace. These tasks can be done conveniently through AWS APIs and the AWS SDK.

Solution overview

In the following sections, we will configure Microsoft ADCS to be able to sign a subordinate CA, deploy and sign ACM PCA, and then test the solution using a private website that is protected by a TLS certificate issued from the ACM PCA.

Configure Microsoft ADCS

Microsoft ADCS is normally deployed as part of your Windows Active Directory architecture. It can be extended to do multiple different types of certificate signing depending on your environment’s needs. Each of these different types of certificates is defined by a template that you must enable and configure. Each template contains configuration information about how Microsoft ADCS will issue the certificate type. You can copy and configure templates differently depending on your environment’s requirements. The specifics of each type of template is outside the scope of this blog post.

To configure ADCS to sign subordinate CAs

On the CA server that will be signing the private CA certificate, open the Certification Authority Microsoft Management Console (MMC).
In the left-side tree view, expand the name of the server.
Open the context (right-click) menu for Certificate Templates and choose Manage.

Figure 1: Navigating to the Manage option for the certificate templates

This opens the Certificate Template Console, which is populated with the list of optional templates.

Scroll down, open the context (right-click) menu for Subordinate Certification Authority, and choose Duplicate Template, as shown in Figure 2. This will create a duplicate of the template that you can alter for your needs, while leaving the original template unaltered for future use. Selecting Duplicate Template immediately opens the configuration for the new template.

Figure 2: Select Duplicate Template to create a copy of the Subordinate Certification Authority template

To configure and use the new template

On the new template configuration page, choose the General tab, and change the template display name to something that uniquely identifies it. The example in this post uses the name Subordinate Certification Authority – Private CA.
Select the check box for Publish certificate in Active Directory, and then choose OK. The new template appears in the list of available templates. Close the Certificate Templates Console.
Return to the Certification Authority MMC. Open the context (right-click) menu for Certificate Templates again, but this time choose New -> Certificate Template to Issue.

Figure 3: Issue the new Certificate Template you created for subordinate Cas

In the dialog box that appears, choose the new template you created in Step 1 of this procedure, and then choose OK.

That’s all that’s needed! Your CA is now ready to issue certificates for subordinate CAs in your public key infrastructure. Open a browser from either the ADCS CA server itself or through a network connection to the ADCS CA server, and use the following URL to access the certificate server’s certificate signing interface.

http://<hostname-of-your-ca-with-domain>/certsrv/certrqxt.asp

Now you can see that in the Certificate Templates list, you can choose the Subordinate Certification Authority template that you created, as shown in Figure 4.

Figure 4: The interface to sign certificates on your CA now shows the new certificate template you created

Deploy and sign the ACM Private CA’s certificate

In this step, you will deploy the ACM PCA, which is the first step to create a subordinate CA to deploy in your AWS account. The process of deploying the ACM PCA is well documented, so this post will not go into depth about the deployment itself. Instead, this procedure focuses on the steps for taking the certificate signing request (CSR) and signing it against the ADCS, and then covers the additional steps to convert the certificates that ADCS produces into the certificate format that ACM PCA expects.

After the ACM PCA is initially deployed, it needs to have a certificate signed to authenticate it. ACM PCA offers two options for signing the new instance’s certificate. You can choose to sign either through another ACM PCA instance, or via an external CA. Since you are using ADCS in this walkthrough, you will use the process of an external CA. The ACM PCA deployment is now at a point where it needs its CSR signed by Microsoft ADCS. You should see that it is ready in the AWS Management Console for ACM PCA.

To deploy and sign the ACM PCA’s certificate

When the ACM PCA is ready, in the ACM PCA console, begin the Install subordinate CA certificate process by choosing External private CA for the CA type.

Figure 5: Options for signing the new instance’s certificate

You will then be provided the certificate signing request (CSR) for the ACM PCA. Copy and paste the CSR content into the ADCS CA signing URL you visited earlier on the CA server. Then choose Next. The next page is where you will paste in the new signed certificate and certchain in a later step.
From the ADCS CA URL, be sure that the new Subordinate Certification Authority template is selected, and then choose Submit. The new certificate will be issued to you. The ADCS issuing page provides two different formats for the certificate, either as Distinguished Encoding Rules (DER) or base64-encoded.
Copy the base64-encoded files for both the certificate and the certchain to your local computer. The certificate is already in Privacy Enhanced Mail (PEM) format, and its contents can be pasted into the ACM PCA certificate input in the console. However, you must convert the certchain into the format required by the ACM PCA by following these steps:
To convert the format of the certchain, use the openssl tool from the command line. The process of installing the openssl tool is outside the scope of this blog post. Refer to the OpenSSL site documentation for installation options for your operating system.
Use the following command to convert the certchain file from Public Key Cryptographic Standards #7 (PKCS7) to PEM.

openssl pkcs7 -print_certs -in certnew.p7b -out certchain.pem

Using a text editor, open the certchain.pem file and copy the last certificate block from the file, starting with —–BEGIN CERTIFICATE—– and ending with —–END CERTIFICATE—–. You will notice that the file begins with the signed certificate and includes subject= and issuer= statements. ACM PCA only accepts the content that is the certificate chain.

Return to the ACM PCA console page from Step 1, and paste the text the you just copied into the input area provided for the certificate chain. After this step is complete, the private CA is now signed by your corporate PKI.

Test the solution

Now that the ACM PCA is online, one of the things it can do is issue certificates via ACM that are trusted by your corporate Active Directory joined clients. These certificates can be used in services such as Application Load Balancers to provide TLS protected endpoints that are unique to your organization and trusted only by your internal clients.

From a client joined to our test Active Directory, Internet Explorer shows that it trusts the TLS certificate issued by AWS Certificate Manager and used on the Application Load Balancer for a private site.

Figure 6: Internet Explorer showing that it trusts the TLS certificate

For this demo, we created a test web server that is hosting an example webpage. The web server is behind an AWS Application Load Balancer. The TLS certificate attached to the Application Load Balancer is issued from the new ACM PCA.

Conclusion

Organizations that have Microsoft Active Directory deployed can use Active Directory’s Certificate Services to issue certificates for private resources. This blog post shows how you can extend that certificate trust to AWS Certificate Manager Private CA. This provides a way for your developers to issue private certificates automatically, which are trusted by your Active Directory domain-joined clients or clients that have the ADCS certificate chain installed.

For more information on hybrid public key infrastructure (PKI) on AWS, refer to these blog posts:

How to implement a hybrid PKI solution on AWS
Integrating Microsoft Active Directory with AWS Certificate Manager Private CA using Secardeo certEP

For more information on certificates for Mac and Linux, refer to the following resources:

Add certificates to a keychain using Keychain Access on Mac
Ubuntu – Installing a root CA certificate in the trust store
RedHat – Making CA certificates available to Linux command-line tools

 
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Geoff Sweet

Geoff has been in industry for over 20 years, and began his career in Electrical Engineering. Starting in IT during the dot-com boom, he has held a variety of diverse roles, such as systems architect, network architect, and, for the past several years, security architect. Geoff specializes in infrastructure security.

Using certificates to authenticate and encrypt data is vital to any enterprise security. For example, companies rely on certificates to provide TLS encryption for web applications so that client data is protected. However, not all certificates need to be issued from a publicly trusted certificate authority (CA). A privately trusted CA can be leveraged toRead More