CloudEvents self-assessment

This assessment was created by community members as part of the Security Pals process and is currently pending changes from the maintainer team.

November 26, 2023

Authors: Igor Rodrigues (@Igor8mr), Matthew Gong (@MatthewZGong), Kushal Kothari (@Kushal-kothari) and Devyani Bairagya (@devyani-14).

Contributors/Reviewers: Pranava Kumar Vemula (@Rana-KV), Doug Davis (@duglin), Eddie Knight (@eddie-knight) and Ragashree (@ragashreeshekar).

This document was written to elaborate on and explore the design goals of CloudEvents through a limited security assessment of the software in collaboration with the project maintainer team. The information contained in this assessment was extracted from the CloudEvents GitHub Repository , and other channels maintained by the project, such as its website and Slack workspace .

Table of contents

• Table of contents
• Metadata
  • Security links
• Overview
  • Background
  • Actors
  • Actions
  • Goals
  • Non-goals
• Self-assessment use
• Security functions and features
  • Critical Security Components
  • Security Relevant Components
• Project compliance
• Secure development practices
  • Development Pipeline
  • Communications Channels
  • Ecosystem
• Security Issue Resolution
  • CloudEvents Specification
  • CloudEvents SDKs
• Lightweight Threat Modelling
  • Threat Modelling Notes
  • Threat Scenarios
  • Theoretical Threats
  • Potential threats
  • Conclusion
  • Recommendations
• Appendix
  • Known Issues Over Time
  • CII Best Practices
  • Action Item: Setup a system for automatically reviewing SDKs
  • Case Studies
  • Related Projects and Vendors
  • References

Metadata

Security links

Overview

CloudEvents is an open-source specification designed to articulate data events. While these events are widely employed in various industries, the absence of standardized guidelines for their composition has led to significant divergence among developers. This lack of uniformity makes programmers create distinct event-handling logic for each event source, impeding seamless communication between different systems. CloudEvents aims to streamline the process of declaring and delivering events, improving simplicity and interoperability across diverse services and platforms.

The project also provides software development kits (SDKs) for Go, JavaScript, Java, C#, Ruby, PHP, PowerShell, Rust, and Python. These can be used to build event routers, tracing systems, and other tools.

Background

Event

An event is a data entry that conveys an occurrence along with its surrounding context. Events are transmitted from an event producer (the origin) to interested event consumers. The transmission process may consider the information within the event, but the event itself does not specify a particular destination for routing. Events comprise two categories of information: Event Data, which represents the incident, and Context metadata, which furnishes additional contextual details about the incident. A single incident can generate more than one event.

There is no common language on events themselves. So when a new software is created developers have to write new event handling processes for different types of sources. This can become very chaotic and unorganized.

CloudEvents was developed to address the need for non-uniformity in event data formats in cloud and microservices environments. CloudEvents adopts a pragmatic approach instead of enforcing a universal event format. While it provides a structured layout, it acknowledges the diverse preferences in the industry. Users can include event data and context attributes in a single document, and the support for a binary format seamlessly integrates with existing event structures. Therefore, CloudEvents standardizes the location for retrieving shared metadata about an event without the need to parse the specific business logic of the event.

Actors

Event Consumer

The Event Consumer is the entity or system interested in subscribing to different events. Receiving Events from the producer will trigger further action that is up to the consumer. A “consumer” receives the event and acts upon it, which might lead to the occurrence of new events.

Event Producer

The Event Producer is the entity or system that produces the “events”. They are responsible for wrapping event data in the CloudEvents specification.

Event Mediator or Intermediary

Depending on the architecture of the system, the Event Mediator is the entity or system that is responsible for the distribution, processing and routing of events to consumers. The event broker ensures reliable delivery and may enforce security policies.

System Administrator

Responsible for incorporating CloudEvents support into their system to enable interoperability with other services and applications. The developer can use one of the CloudEvents SDKs to integrate CloudEvents functionality into their applications. Developers also collaborate to ensure the proper functioning of other actors within the CloudEvents ecosystem. They can also report issues they find to the CloudEvents maintainers, helping improve the specification and/or SDKs.

SDK Maintainers

Part of the CloudEvents ecosystem, they are responsible for the development, maintenance, and enhancement of CloudEvents Software Development Kits (SDKs). As stewards of the SDKs, their role is critical in ensuring that developers have reliable, up-to-date and safe tools to work with. They must triage issues, find and implement solutions to them and release security patches promptly.

CloudEvents Spec Maintainer

A CloudEvents specification maintainer is responsible for developing and maintaining the CloudEvents standard, ensuring consistency and interoperability for describing event data. They manage the roadmap, coordinate releases, and collaborate with the community to implement changes, improving the CloudEvents specification to facilitate event exchange in diverse cloud environments.

CloudEvents Administrator

These central figures in the ongoing development and governance of the CloudEvents ecosystem and specification. They are responsible for the management of critical aspects of the CloudEvents infrastructure. For example, the website, GitHub repos and moderate the meetings.

Actions

Event Formatting

Called by the producer and the consumer. An Event Format specifies how to serialize a CloudEvent as a sequence of bytes. Stand-alone event formats, such as the JSON format, specify serialization independent of any protocol or storage medium. The producer encodes the event, while the consumer decodes the event.

Protocol Binding

A protocol binding describes how events are sent and received over a given protocol. CloudEvents defines encoding modes such as binary and structured for serializing a CloudEvent during transmission.

• Binary Content Mode: The event data is placed in the message body, while the event attributes (metadata) are included in the message’s metadata. This mode is commonly employed when a CloudEvent producer wants to incorporate metadata into an existing event without affecting the message body. Binary encoding will maintain a receiver’s event processing since the message’s metadata often accommodates extension attributes.

• Structured Content Mode: The event data and attributes are encoded within the message body following a specific event format. This mode maintains event metadata and data in the payload, facilitating the straightforward forwarding of the same event across various routing hops and protocols.

Protocol bindings MAY choose to use an Event Format to map an event directly to the transport envelope body, or MAY provide additional formatting and structure to the envelope. For example, a wrapper around a structured-mode message might be used, or several messages could be batched together into a transport envelope body.

Goals

Listed below are the main goals of CloudEvents .

• Simplify event declaration and delivery across services, platforms and systems.
• Define interoperability of event systems that allow services to produce or consume events, where the producer and consumer can be developed and deployed independently.
• Establish a structured framework for the exchange of event data among services by standardizing the location for storing and retrieving common metadata related to events.
• Provide specifications for serializing events in different formats and protocols.

Non-goals

The following are considered as non-goals of CloudEvents :

• Function build and invocation process.
• Language-specific runtime APIs.
• Selecting a single identity/access control system.
• Inclusion of protocol-level routing information.
• Event persistence processes.
• Mechanism for Authorization, Data Integrity and Confidentiality.
• Change the implementation details of underlying communication protocols.
• Define the processing logic for events within different applications and systems.

Self-assessment use

This security assessment was created by Igor Rodrigues , Matthew Gong , Kushal Kothari , and Devyani Bairagya to perform an internal analysis of the CloudEvents project. The document was also reviewed by CloudEvents maintainers and members of the CNCF Security Technical Advisory Group (TAG) . It is meant to provide a current summary of the project and its security-related aspects. It is not intended to provide a security audit of CloudEvents, or function as an independent assessment or attestation of CloudEvents’s security health. For the latest state of the project please check the CloudEvents GitHub repository .

This document serves to provide CloudEvents users with an initial understanding of CloudEvents’s security, where to find existing security documentation, CloudEvents plans for security, and a general overview of CloudEvents security practices, both for the development of CloudEvents as well as security of CloudEvents.

This document provides the CNCF TAG-Security with an initial understanding of CloudEvents to assist in a joint assessment, necessary for projects under incubation. Taken together, this document and the joint assessment serve as a cornerstone as CloudEvents is under review for a Graduation status.

Security functions and features

Critical Security Components

Unlike similar projects in the past such as Simple Object Access Protocol (SOAP) , CloudEvents does not attempt to create new security protocols but relies on established, robust protocols. As emphasized earlier, the Specification exclusively concentrates on standardizing event creation and their representation across various protocols, avoiding defining how exactly they should be transported.

Event Identification

Every event within CloudEvents is uniquely identified by a specific combination of source and id . Producers must guarantee that each unique event’s concatenation of source and id remains distinctive. This practice aids in distinguishing events and preventing the processing of duplicate events.

Event Type

The type attribute holds a value that characterizes the nature of the event associated with the initial incident. This attribute is frequently utilized for routing, observability, policy enforcement, and similar purposes. The producer determines the format, which may contain details such as the version of the type.

Event Subject

The subject attribute explains the event’s subject within the context of the event producer. Clarifying the subject in contextual metadata proves particularly beneficial in scenarios involving generic subscription filtering, where middleware may lack the ability to interpret the content within the data attribute.

Event Data Integrity

CloudEvents does not focus on defining the methods for safeguarding data integrity. Therefore, it is the choice of the user/developer to address this aspect. One approach to enhance security is to apply encryption to event data specific to the domain, restricting visibility to trusted entities. The choice of the encryption mechanism is collaboratively determined by event producers and consumers, which is an implementation detail defined by the user.

Privacy and Sensitive Information Handling

Context attributes should not carry or represent sensitive information. CloudEvent producers, consumers, and intermediaries can inspect and log context attributes.

Security Relevant Components

Transport Security

Although CloudEvents does not prescribe specific transport security mechanisms, it is typically conveyed over secure protocols such as HTTPS, ensuring integrity and confidentiality.

Event Source Authentication

The source attribute within a CloudEvent provides context for the event occurrence, establishing reliable and secure source identification.

Data Schema Verification

The data attribute in a CloudEvent contains the actual event data, and its schema can be defined and validated for consistency and accuracy. This verification process helps to prevent issues arising from malformed or unexpected data.

Project compliance

As of the latest security assessment, CloudEvents does not explicitly document compliance with specific security standards such as PCI-DSS, COBIT, ISO, GDPR, etc.

Secure development practices

Development Pipeline

CloudEvents Membership

There are three project membership categories , which make it harder for a single individual to make bad changes to the repository.

• Member: Anyone participating in group activities across communication channels. No formal registration is required.
• Voting Member: Criteria for Voting Members are outlined in the Voting section of the governance page . They have equal influence as Members, with specific voting rights during formal processes.
• Admin: Members with extra privileges for administrative tasks like managing the website and GitHub repos. Admin actions require group knowledge and consent, including the ability to merge/close PRs, subject to group approval. Since the role of an ‘Admin’ is mainly administrative, the list of Members within this group should not need to change regularly but can be done with votes.

CloudEvents SDK Community

The CloudEvents SDK community is organized as follows:

• Every SDK has its own Github Team .
• The union of all the SDK maintainers assembles the SDK maintainers group.
• To propose a new SDK for the community, a PR should be opened in the spec repository with the documentation changes necessary to point to the new repository.

CloudEvents defines an SDK project as healthy if it meets the criteria below.

• It works with the latest version of the programming language;
• It supports the latest versions of the integrated libraries/frameworks;
• It receives security patches regularly;
• It supports the last N-1 major versions of CloudEvents spec, as defined in; Contribution Acceptance;
• Issues and PRs are triaged (labeled, commented, reviewed, etc) regularly.

Moreover, CloudEvents defines an SDK as not actively maintained if:

• Issues and/or PRs have not been triaged from the SDK maintainers for 2 months
• Security patches have not been released from the SDK maintainers for 1 month from CVE disclosures

If a project does not meet the criteria above, the community can decide to hand over the project to a new group of maintainers through a voting process. In such cases, the community may also decide to archive the project instead.

Contributing to CloudEvents

General Instructions

• Developers can either report a change or create a Github Issue, checking for existing issues first.
• All Proposed changes will be done through Github Pull Requests (PRs).
• All patches must be signed by the author, with the sign-off being a simple line at the end of the explanation for the patch.
• All commits should use the Conventional Commits Specification .
• Pull Requests will be reviewed during official meetings .
  • Off-line reviews are recommended before meetings.
  • Meetings happen every Thursday at 9 AM PT.
• Pull Requests will be resolved and merged during official meetings as a result of a motion.
  • Pull Requests should not be merged if substantial changes have been made in the past 2 days.

Pull Request process

Usually, CloudEvents Pull Requests are expected to meet the following criteria before being merged:

• The author of the PR asks for it to be discussed and reviewed in an upcoming meeting.
• All comments have been addressed.
• PRs that have objections/concerns will be discussed off-line by interested parties. A resolution and updated PR will be expected from those talks.

Versioning

The release process follows Semantic Versioning (semver) , grouping specifications for simultaneous release. Non-breaking changes use “patch” updates while breaking changes follow semver. Tags are applied to the main branch, and additional branches, like core-v2.0, may be created, and then deleted post-merger. Creating a release involves updating versions via Pull requests, merging, and announcing changes.

Communications Channels

CloudEvents use different types of communication channels for different purposes.

• Internal communications channels:
  • Meetings
  • Email
  • GitHub Issues
• Inbound communications channels:
  • CloudEvents CNCF Email Address
  • CNCF Slack workspace
  • CNCF Meeting Calendar
• Outgoing communications channels:
  • CloudEvents CNCF Subscription

Ecosystem

CloudEvents is integrated with different cloud-native technologies and services. Its goal is to create interoperability in event-driven architecture.

CloudEvents has many adopters , including:

• Adobe I/O Events
• Azure Event Grid
• European Commission
• Google Cloud Eventarc
• IBM Cloud Code Engine
• Oracle Cloud
• VMware Event Broker Appliance

Security Issue Resolution

CloudEvents currently addresses the reporting of security issues and the responsible parties for triaging and issuing security patches through documented processes, such as how to report issues and who should triage and solve them . The CloudEvents specification does not have centralized documentation of the Vulnerability and Issue Response Processes; instead, these processes are currently distributed across different documents, such as the SDK Governance and Contributing documents.

CloudEvents Specification

To report an issue regarding CloudEvents , contributors can open a new issue on the GitHub repository. However, they should check if a similar issue already exists.

CloudEvents also provides a dedicated email address and a Security Mailing List for reporting security concerns related to the specification or the SDKs.

CloudEvents SDKs

Responsible Disclosures Process

Similarly to the CloudEvents specification, to report an issue about one of the CloudEvents SDKs, contributors can open a new issue on the GitHub repository, as well as using the dedicated email address and the Security Mailing List .

Vulnerability Response Process

CloudEvets does not specify a strict way on how issues should be handled, but it defines that it is the responsibility of the CloudEvents SDK maintainers to triage issues and PRs from their respective repositories, as well as frequently release security patches to issues found. As mentioned in CloudEvents SDK Community , the maintainers cannot abstain from triaging issues and PRs for more than 2 months, or releasing security patches for more than 1 month. Otherwise, their project will be marked as not actively maintained, which can lead to them losing the management of the SDK repository.

Incident Response

Discussing the Issue

After an issue is reported, the maintainers of the SDK will contact the author of the issue, talking through it to understand whether it should be resolved, its priority, how a solution could be implemented, and who will implement it, which can be done through the GitHub issues page of the SDK, Slack, a meeting or any other CloudEvents communication channel.

Solving the Issue

Once a security patch is written, the contributor should make a Pull Request and mark it as ready to review. The PR will be reviewed, improved, and approved by the other maintainers of the SDK. With that, a security patch is released by following the process described in Contributing to CloudEvents .

Lightweight Threat Modelling

• Project data classification: Sensitive
• Owner(s) and/or maintainer(s):
  • Name: CloudEvents administrators and members
  • Representation: Cloud Native Computing Foundation (CNCF)
  • Contact: CloudEvents Website

Threat Modelling Notes

• Where does it store data?
  • CloudEvents primarily defines a specification and does not store data itself.
• Is encryption used for data in transit and at rest?
  • The specification recommends using secure protocols for data in transit.
• Is data from potentially untrusted sources subject to input validation?
  • Yes, validation is part of the SDK implementations.

Threat Scenarios

• An External Attacker: Could potentially send malformed or malicious event data to disrupt services that consume CloudEvents.
• An External Attacker with valid access: Could potentially inject false events to lead to incorrect actions being taken by consumers.
• An Internal Attacker: Might be able to alter event definitions or intercept event data in transit within systems that utilize CloudEvents.
• A Malicious Internal User: Could misuse the event system to trigger unauthorized actions or services.

Theoretical Threats

• Deployment Architecture (pod and namespace configuration): Not applicable to CloudEvents as a specification.

• Networking (internal and external): Networking controls are typically managed by the underlying infrastructure and transport protocols used for sending and receiving CloudEvents.

• Cryptography: CloudEvents does not provide encryption methods or cryptographic implementations, all implementations are left up to the users’ choice.

• Audit and logging: This is typically handled by the platforms and services that implement CloudEvents.

Potential threats

The SDK management teams may implement vulnerabilities while implementing SDKs

Trail Of Bits was able to identify security concerns regarding the different CloudEvents SDKs . While these issues have been addressed, the expanding number of SDKs raises the possibility of introducing additional vulnerabilities. These vulnerabilities could serve as potential weak points in systems utilizing CloudEvents.

Mitigations:

• Frequently triage and patch issues.
• Always check if the code can be trusted before merging a Pull Request.
• Perform security audits when possible.

Man in the middle acting as Event Mediator

If an attacker can act as a man in the middle for an event mediator, the intruder may be able to read the events from the event generator or modify them before they arrive at the event consumer.

Mitigations:

• Users should implement infrastructure around CloudEvents making it difficult for bad actors to get access to the systems using CloudEvents or the channels delivering the events.

CloudEvent Modification in Transit

If event data is not properly encrypted, it could be intercepted and modified by an attacker, leading to misinformation or unauthorized actions.

Mitigations:

• Users should encrypt, validate, and monitor all important data to reduce the impact of modifications during transit.
• User permissions should be routinely checked to ensure that only the authorized users have the required capabilities.

Improper encoding and decoding of data

A bad actor can send malicious or faulty data with a CloudEvent wrapper to the main producer. If the decoding of that data is not handled correctly it can lead to the system crashing.

Mitigations:

• All actors (event producer, event mediator event consumer) should check if the data is correctly formatted to the CloudEvents Specification, not passing the data forward in such scenarios, but discarding or properly handling it.
• All SDKs should help in handling these scenarios.

Committing vulnerable code

Although there are many checks before a Pull Request is accepted, a developer can still commit code to the source repository that has vulnerabilities if nobody notices it. This can be either because of malicious intent or because of mistakes like vulnerable libraries being used.

Mitigations:

• A risk assessment can be done to uncover any potential gaps in the security controls.
• All secure development practices established by CloudEvents and CNCF should be strictly followed to prevent vulnerabilities from being introduced.

Malicious CloudEvent Wrapper

An attacker could wrap malicious content in a CloudEvent to exploit vulnerabilities in event consumers.

Mitigations:

• Users should check for malicious content when receiving CloudEvent data, not trusting the source whenever possible.

Conclusion

Overall, CloudEvents has solid governance rules and management practices for the specification and the SDKs . These rules delineate procedures that prioritize security patching, with strict enforcement mechanisms. Clear articulation of goals and non-goals assists users in discerning the aspects they need to self-enforce.

A notable challenge within the project revolves around the numerous SDKs developed by the CloudEvents SDK communities. Certain SDKs, particularly the newer ones, are susceptible to security vulnerabilities. While governance rules play a crucial role in ensuring continuous patching and monitoring, some SDKs have experienced vulnerabilities in the past, highlighting an ongoing concern.

During a team meeting on November 30, 2023 , a CloudEvents administrator also mentioned plans to introduce bots for regularly assessing the health of each SDK . This proactive measure aims to address potential security concerns that may arise in the future, mitigating both technical and managerial aspects across various SDKs.

Recommendations

As mentioned by CloudEvents, the maintainers of SDKs must release security patches and fix issues frequently for the project to be marked as active. It is essential for the maintainers of each SDK to frequently triage and release patches to the security issues found, which can solve problems such as the ones found by Trail Of Bits. Moreover, it is important for users to frequently check and install updates to their CloudEvents SDK installation.

Appendix

Known Issues Over Time

Trail of Bits Security Assessment

CloudEvents underwent a Security Audit performed by Trail of Bits released on October 26, 2022.

Trail of Bits is a cybersecurity company based in the United States that specializes in various aspects of security services, including security assessments, penetration testing, and software security.

The audit focused on various CloudEvents Software Development Kits (SDKs) rather than the specification itself. All identified security issues have been addressed. The report highlighted specific findings for different SDKs, such as the Java SDK’s reliance on default encoding or the outdated and vulnerable dependencies in both Java and Go SDKs. All of the security issues found by Trail of Bits have already been addressed.

CII Best Practices

CloudEvents received a passing CII Best Practices badge on December 08, 2022, at 17:02:04.

The project aims to align with the Core Infrastructure Initiative (CII) Best Practices, focusing on:

• Security Response Process: Establishing a comprehensive process for reporting and addressing security vulnerabilities.
• Automated Testing: Implementing automated testing in the development pipeline for consistent security and vulnerability checks.
• Dependency Management: Regular auditing and updating of third-party dependencies to mitigate security risks.
• Documentation: Enhancing documentation to provide clear guidance on security considerations for developers. These efforts are part of CloudEvents' commitment to maintaining high standards in open-source software development.

Action Item: Setup a system for automatically reviewing SDKs

• GitHub Issue Link: Setup Snyk for SDKs

This is an action item that the Security Pals team discussed with CloudEvents, which can help identify security issues on their repositories, especially those similar to the issues found by Trail of Bits .

Action Item Objective

Improve the security of CloudEvents SDKs by integrating static application security testing (SAST) , Software composition analysis (SCA) and/or secret scanning services for automatic dependency assessments. This integration should both conduct comprehensive scans for vulnerabilities within the SDK and systematically search the internet for recently reported issues or vulnerabilities linked to the library dependencies used in the development of CloudEvents SDKs. The automated tool should alert the development team to threats, helping the implementation of proactive measures for identifying, addressing, and mitigating potential risks.

Action Item Steps

Develop and deploy an automated system to monitor the health of various SDKs by integrating a bot into the development workflow. Collaborate with the team to conceptualize the bot’s features, ensuring its capability to evaluate maintenance status, address issues, and implement patch updates following the rules outlined in the governance documents. Configure the bot to perform checks, ensuring comprehensive analysis of SDK dependencies. Investigate the feasibility and requirements for adding a dedicated security bot to scan for potential security issues. Document the integration process and provide guidelines for ongoing usage within the development environment.

The CloudEvents team created a GitHub Issue on October 10, 2023, to implement the Snyk bot for CloudEvents, which is a possible bot that could solve the issues mentioned above. The Security Pals team wrote a comment on possible steps to implement Snyk under the issue.

Case Studies

CloudEvents has the potential to revolutionize event-driven architectures in various sectors. Below are a couple of enhanced case studies demonstrating its applicability.

Healthcare Data Management

CloudEvents plays a pivotal role in a healthcare system for managing patient data. In this scenario, it is used to track and route events such as patient admissions, lab results, and medication orders. By standardizing event formats, CloudEvents ensures seamless integration between different hospital systems, including Electronic Health Records (EHRs) and Laboratory Information Management Systems (LIMS), enhancing patient care and operational efficiency.

Smart City Infrastructure Monitoring

In a smart city environment, CloudEvents is employed to aggregate and analyze data from a multitude of sensors and IoT devices across the city. This includes traffic flow sensors, public transport updates, and utility usage meters. By utilizing CloudEvents for real-time data processing and event routing, city administrators can make informed decisions about traffic management, public transport schedules, and resource allocation, leading to improved city services and resident satisfaction.

Related Projects and Vendors

OpenTelemetry

OpenTelemetry is a collection of APIs, SDKs, and tools. It can be used to instrument, generate, collect, and export telemetry data (metrics, logs, and traces) to help analyze software performance and behavior.

CloudEvents and OpenTelemetry have different purposes. CloudEvents standardizes event formats, making it easier for different services to communicate through events, while OpenTelemetry focuses on observability, allowing developers to collect and analyze traces and metrics consistently. It’s also normal for systems to use CloudEvents and OpenTelemetry together. Events generated by CloudEvents could be traced and monitored using OpenTelemetry, providing a comprehensive view of the system’s behavior. Moreover, both projects are CNCF Incubating projects .

AsyncAPI

AsyncAPI is an open-source initiative that seeks to improve the current state of Event-Driven Architecture (EDA). Their long-term goal is to make working with EDAs as easy as working with REST APIs. That goes from documentation to code generation, and from discovery to event management.

CloudEvents and AsyncAPI are both specifications designed to facilitate communication and interoperability in the realm of cloud computing, but they focus on different aspects of the messaging process. CloudEvents is a standard for commonly describing event data. It aims to provide a vendor-neutral format for event data that can be understood across different cloud platforms. On the other hand, AsyncAPI concentrates on defining standards for documenting asynchronous APIs. While CloudEvents is focused on standardizing the payload format of events, AsyncAPI is concerned with documenting the structure and behavior of APIs in asynchronous systems, helping developers understand how to interact with messaging services. Therefore, CloudEvents is about the format of events, while AsyncAPI is about the documentation and specification of asynchronous APIs.

Event-B

Event-B is a formal method for system-level modeling and analysis. Key features of Event-B are the use of set theory as a modeling notation, the use of refinement to represent systems at different abstraction levels and the use of mathematical proof to verify consistency between refinement levels.

CloudEvents and Event-B have different uses in event-driven systems. Event-B is a method designed for the modeling and analysis of systems. It operates at a high level of abstraction, focusing on refining events and proving properties about the modeled system. On the other hand, CloudEvents is a specification that addresses the standardization of event data format in cloud-native environments. Unlike Event-B, CloudEvents does not offer a formal method for system modeling or verification. Instead, it concentrates on creating a common standard for describing events. CloudEvents aims to improve interoperability among distributed systems and services by providing a consistent structure for event data.

Simple Object Access Protocol (SOAP)

SOAP is a messaging protocol specification designed for the exchange of structured information within the implementation of web services on computer networks.

This protocol utilizes XML Information Set as its message format and depends on application layer protocols, primarily Hypertext Transfer Protocol (HTTP), though certain legacy systems may communicate using Simple Mail Transfer Protocol (SMTP) for message negotiation and transmission.

According to a CloudEvents maintainer, one of the main distinctions between SOAP and CloudEvents is the fact that the latter does not aim to develop new security protocols. Instead, it relies on existing and resilient protocols. As mentioned before, the CloudEvents Specification focuses solely on standardizing the creation and representation of events across different protocols, intentionally steering clear of specifying methods for their transportation. Moreover, while CloudEvents is focused on lightweight and flexibility, SOAP is more associated with traditional and heavyweight web services, emphasizing standards and strict message formatting.

Apex Event Specification

The Apex Event Specification Guide (ESG) is a written document that contains all the details of an event. The ESG is used by event organizers to communicate information to venues and suppliers. The ESG is a three-part template that includes: Narrative, Schedule, and Function orders.

This is an older document used across many engineering fields, which is not restricted to computer science, making it different from the other examples. However, it is an example of event specification being widely used in industry, including more physical areas such as mechanical engineering and factories.

References

• CloudEvents Website
• CloudEvents GitHub
• CloudEvents Security Assessment by Trail of Bits
• Security Assessment Guide
• Sample Security Assessment
• Open and Secure Book