Secure Software Contract Annex

Author: Jeff Williams




This contract Annex is intended to help software developers and their clients negotiate and capture important contractual terms and conditions related to the security of the software to be developed or delivered. The reason for this project is that most contracts are silent on these issues, and the parties frequently have dramatically different views on what has actually been agreed to. We believe that clearly articulating these terms is the best way to ensure that both parties can make informed decisions about how to proceed.

"The security of commercial software will improve when the market demands better security. At a minimum, every software request for proposal should ask vendors to detail how they test their products for security vulnerabilities. This step will start convincing vendors of off-the-shelf software and outsourced developers that enterprises value security." ` – As John Pescatore, research director with Gartner`

We urge Clients and Developers to use this document as a framework for discussing expectations and negotiating responsibilities. This Annex is intended to be appended to a software development contract. These terms are negotiable, meaning they can and should be discussed by the Client and Developer.


This document was created by The Open Web Application Security Project (OWASP) Foundation, a not-for-profit charitable organization dedicated to creating free and open tools and documentation related to secure software. To facilitate easy use in private contracting, this document is offered under the CC Share Alike 3.0 license. You may modify and use as you see fit. We welcome comment from both producers and consumers of software, as well as the legal community.

OWASP gratefully acknowledges the special contribution from Aspect Security for their role in the research and preparation of this document.


The following few pages cover some frequently heard objections to using this language in software development contracts:


This document should be considered a starting point for your agreement. You may not like all the activities, or may want to propose more. You may want to assign responsibilities differently. This document is not intended to exactly capture the needs of all software Clients and Developers. It is intended to provide a framework for discussing the key topics that are important to ensuring that software ends up secure. After you have a security discussion and reach agreement, you should tailor this agreement to match.


This contract is NOT about putting more burden on the software developer. The question is not whether there are costs associated with security – of course there are. Rather, the right question is what activities should be performed by both parties to minimize those costs, and when should they happen.

This annex is intentionally silent on the issue of who should pay for the activities described herein. While many of these activities should already be happening, and are expected by many Clients, they are not regularly practiced in the software industry. The question of who pays (and how much) should be part of the negotiation.

Calculating the costs of security is very difficult. While there are costs associated with performing security activities, there are also significant costs associated with ignoring them. We are convinced that the most cost-effective way to develop software is to reduce the likelihood that security flaws are introduced and to minimize the time between introducing a flaw and fixing it.

One important distinction to make when calculating costs is between building security mechanisms and the assurance activities that make sure those mechanisms are correct and effective. Attempting to add mechanisms at the end of the lifecycle can cause serious design issues and will increase costs dramatically. This agreement encourages early decisions on mechanisms to minimize these costs. Similarly, waiting until just before deployment to do assurance activities, such as code review and penetration testing, will also dramatically increase costs. We believe that the most cost-effective way to gain assurance is to put a constant level of effort into assurance throughout the lifecycle.


This agreement assumes that the software being developed is reasonably important to a large enterprise or government agency. We’ve selected a “level of rigor” for the agreement that is achievable by most software development organizations, and will identify and handle the most common risks.

However, for software that is going to be used in critical applications, such as medical, financial, or defense related software, you may want to increase the level of rigor. You may want to add additional reviews, documentation, and testing activities. You may want to enhance the processes for finding, diagnosing, and remediating vulnerabilities. For less sensitive applications, you may want to reduce or remove activities.


This agreement is intended to facilitate discussions about who will take the risk for security vulnerabilities in the software. At one end of the spectrum, the Client could take all the risk and the Developer could deliver code with lots of vulnerabilities. At the other extreme, the Developer could take all the risk and assume responsibility for delivering perfect code. Both of these extremes are unworkable.

Currently, in this agreement, the Developer takes the risk for problems that were covered in the requirements or should be covered by reasonable testing efforts. But remediation of “novel” security issues is to be paid for by the Client. We believe this is a useful balance, as the Developer can bound their risk, and encourages Client to get the security requirements correct up front. But there are many other possible solutions to this problem. Please let us know if you have alternative suggestions and we may include them in future versions of this document.

Note that the discussion here only covers the risk associated with fixing the security vulnerabilities in the code, and does not include the costs associated with recovering from any security incidents based on any exploits of these vulnerabilities. We are interested in best practices in this area.


Almost all software projects use a significant amount of third party code, such as libraries, frameworks, and products. This code is just as important from a security perspective as custom code developed specifically for your project. We believe that the responsibility for ensuring the security of this code is best borne by Developer, although they may not have the full capability themselves to guarantee this security. However, security must be a part of the “build or buy” decision, and this seems like the best way to encourage that.

Developer, of course, has the option of passing this responsibility through to the providers of third party software. Developer can also analyze the third party code themselves, or hire security experts to analyze it for them.


Ultimately, we believe that there is no alternative to making security a part of the software contracting process. Currently, we believe that there are serious misunderstandings about the security of code being delivered under many software development contracts. This can only lead to expensive litigation and a decision made by individuals with little software experience or understanding. Read the Secure software contracting hypothetical case study for a full discussion of this problem.

There are many benefits to working through this agreement. The principal one is that it will make expectations clear between the parties involved. In some cases it will help to prevent lawsuits when difficult security problems surface in the software. Also, these are the same activities that are required by many legal and regulatory compliance reasons.


OWASP does not encourage documentation for documentation’s sake. This agreement is focused on encouraging quality, not quantity. We believe that it would be possible (on some projects) to meet this contract with a short risk assessment, a few pages of requirements, a short security design document, a test plan, and some test results.

The goal of this documentation is simply to ensure, at each stage of the lifecycle, that appropriate attention has been paid to security. An additional benefit is that this documentation can be collected together to form a “certification package” that essentially lays out the argument for why this software should be trusted to do what it claims it does.



This Annex is made to _________ (“Agreement”) between Client and Developer. Client and Developer agree to maximize the security of the software according to the following terms.


This Annex is intended to clarify the security-related rights and obligations of all the parties to a software development relationship. At the highest level, the parties agree that:

(a) Security Decisions Will Be Based on Risk : Decisions about security will be made jointly by both Client and Developer based on a firm understanding of the risks involved.

(b) Security Activities Will Be Balanced : Security effort will be roughly evenly distributed across the entire software development lifecycle.

(c) Security Activities Will Be Integrated : All the activities and documentation discussed herein can and should be integrated into Developer’s software development lifecycle and not kept separate from the rest of the project. Nothing in this Annex implies any particular software development process.

(d) Vulnerabilities Are Expected : All software has bugs, and some of those will create security issues. Both Client and Developer will strive to identify vulnerabilities as early as possible in the lifecycle.

(e) Security Information Will Be Fully Disclosed : All security-relevant information will be shared between Client and Developer immediately and completely.

(f) Only Useful Security Documentation Is Required : Security documentation does not need to be extensive in order to clearly describe security design, risk analysis, or issues.


(a) Risk Understanding : Developer and Client agree to work together to understand and document the risks facing the application. This effort should identify the key risks to the important assets and functions provided by the application. Each of the topics listed in the requirements section should be considered.

(b) Requirements : Based on the risks, Developer and Client agree to work together to create detailed security requirements as a part of the specification of the software to be developed. Each of the topics listed in the requirements section of this Annex should be discussed and evaluated by both Developer and Client. These requirements may be satisfied by custom software, third party software, or the platform.

(c) Design : Developer agrees to provide documentation that clearly explains the design for achieving each of the security requirements. In most cases, this documentation will describe security mechanisms, where the mechanisms fit into the architecture, and all relevant design patterns to ensure their proper use. The design should clearly specify whether the support comes from custom software, third party software, or the platform.

(d) Implementation : Developer agrees to provide and follow a set of secure coding guidelines and to use a set of common security control programming interfaces (such as the OWASP Enterprise Security API (ESAPI)). Guidelines will indicate how code should be formatted, structured, and commented. Common security control programming interfaces will define how security controls must be called and how security controls shall function. All security-relevant code shall be thoroughly commented. Specific guidance on avoiding common security vulnerabilities shall be included. Also, all code shall be reviewed by at least one other Developer against the security requirements and coding guideline before it is considered ready for unit test.

(e) Security Analysis and Testing : Developer will perform application security analysis and testing (also called “verification”) according to the verification requirements of an agreed-upon standard (such as the OWASP Application Security Verification Standard (ASVS)). The Developer shall document verification findings according to the reporting requirements of the standard. The Developer shall provide the verification findings to Client.

(f) Secure Deployment : Developer agrees to provide secure configuration guidelines that fully describe all security relevant configuration options and their implications for the overall security of the software. The guideline shall include a full description of dependencies on the supporting platform, including operating system, web server, and application server, and how they should be configured for security. The default configuration of the software shall be secure.


The following topic areas must be considered during the risk understanding and requirements definition activities. This effort should produce a set of specific, tailored, and testable requirements Both Developer and Client should be involved in this process and must agree on the final set of requirements.

(a) Input Validation and Encoding : The requirements shall specify the rules for canonicalizing, validating, and encoding each input to the application, whether from users, file systems, databases, directories, or external systems. The default rule shall be that all input is invalid unless it matches a detailed specification of what is allowed. In addition, the requirements shall specify the action to be taken when invalid input is received. Specifically, the application shall not be susceptible to injection, overflow, tampering, or other corrupt input attacks.

(b) Authentication and Session Management : The requirements shall specify how authentication credentials and session identifiers will be protected throughout their lifecycle. Requirements for all related functions, including forgotten passwords, changing passwords, remembering passwords, logout, and multiple logins, shall be included.

(c) Access Control : The requirements shall include a detailed description of all roles (groups, privileges, authorizations) used in the application. The requirements shall also indicate all the assets and functions provided by the application. The requirements shall fully specify the exact access rights to each asset and function for each role. An access control matrix is the suggested format for these rules.

(d) Error Handling : The requirements shall detail how errors occurring during processing will be handled. Some applications should provide best effort results in the event of an error, whereas others should terminate processing immediately.

(e) Logging : The requirements shall specify what events are security-relevant and need to be logged, such as detected attacks, failed login attempts, and attempts to exceed authorization. The requirements shall also specify what information to log with each event, including time and date, event description, application details, and other information useful in forensic efforts.

(f) Connections to External Systems : The requirements shall specify how authentication and encryption will be handled for all external systems, such as databases, directories, and web services. All credentials required for communication with external systems shall be stored outside the code in a configuration file in encrypted form.

(g) Encryption : The requirements shall specify what data must be encrypted, how it is to be encrypted, and how all certificates and other credentials must be handled. The application shall use a standard algorithm implemented in a widely used and tested encryption library.

(h) Availability : The requirements shall specify how it will protect against denial of service attacks. All likely attacks on the application should be considered, including authentication lockout, connection exhaustion, and other resource exhaustion attacks.

(i) Secure Configuration : The requirements shall specify that the default values for all security relevant configuration options shall be secure. For audit purposes, the software should be able to produce an easily readable report showing all the security relevant configuration details.

__(j) Specific Vulnerabilities : The requirements shall include a set of specific vulnerabilities that shall not be found in the software. If not otherwise specified, then the software shall not include any of the flaws described in the current “OWASP Top Ten Most Critical Web Application Vulnerabilities.”


(a) Security Architect : Developer will assign responsibility for security to a single senior technical resource, to be known as the project Security Architect. The Security Architect will certify the security of each deliverable.

(b) Security Training : Developer will be responsible for verifying that all members of the developer team have been trained in secure programming techniques.

(c) Trustworthy Developers : Developer agrees to perform appropriate background investigation of all development team members.


(a) Secure Coding : Developer shall disclose what tools are used in the software development environment to encourage secure coding.

(b) Configuration Management : Developer shall use a source code control system that authenticates and logs the team member associated with all changes to the software baseline and all related configuration and build files.

(c) Distribution : Developer shall use a build process that reliably builds a complete distribution from source. This process shall include a method for verifying the integrity of the software delivered to Client.


(a) Disclosure : Developer shall disclose all third party software used in the software, including all libraries, frameworks, components, and other products, whether commercial, free, open-source, or closed-source.

(b) Evaluation : Developer shall make reasonable efforts to ensure that third party software meets all the terms of this agreement and is as secure as custom developed code developed under this agreement.


(a) Right to Review : Client has the right to have the software reviewed for security flaws at their expense at any time within 60 days of delivery. Developer agrees to provide reasonable support to the review team by providing source code and access to test environments.

(b) Review Coverage : Security reviews shall cover all aspects of the software delivered, including custom code, components, products, and system configuration.

(c) Scope of Review : At a minimum, the review shall cover all of the security requirements and should search for other common vulnerabilities. The review may include a combination of vulnerability scanning, penetration testing, static analysis of the source code, and expert code review.

(d) Issues Discovered : Security issues uncovered will be reported to both Client and Developer. All issues will be tracked and remediated as specified in the Security Issue Management section of this Annex.


(a) Identification : Developer will track all security issues uncovered during the entire lifecycle, whether a requirements, design, implementation, testing, deployment, or operational issue. The risk associated with each security issue will be evaluated, documented, and reported to Client as soon as possible after discovery.

(b) Protection : Developer will appropriately protect information regarding security issues and associated documentation, to help limit the likelihood that vulnerabilities in operational Client software are exposed.

(c) Remediation : Security issues that are identified before delivery shall be fixed by Developer. Security issues discovered after delivery shall be handled in the same manner as other bugs and issues as specified in this Agreement.


(a) Assurance : Developer will provide a “certification package” consisting of the security documentation created throughout the development process. The package should establish that the security requirements, design, implementation, and test results were properly completed and all security issues were resolved appropriately.

(b) Self-Certification : The Security Architect will certify that the software meets the security requirements, all security activities have been performed, and all identified security issues have been documented and resolved. Any exceptions to the certification status shall be fully documented with the delivery.

(c) No Malicious Code : Developer warrants that the software shall not contain any code that does not support a software requirement and weakens the security of the application, including computer viruses, worms, time bombs, back doors, Trojan horses, Easter eggs, and all other forms of malicious code.


(a) Acceptance : The software shall not be considered accepted until the certification package is complete and all security issues have been resolved.

(b) Investigating Security Issues : After acceptance, if security issues are discovered or reasonably suspected, Developer shall assist Client in performing an investigation to determine the nature of the issue. The issue shall be considered “novel” if it is not covered by the security requirements and is outside the reasonable scope of security testing.

(c) Novel Security Issues : Developer and Client agree to scope the effort required to resolve novel security issues, and to negotiate in good faith to achieve an agreement to perform the required work to address them.

(d) Other Security Issues : Developer shall use all commercially reasonable efforts consistent with sound software development practices, taking into account the severity of the risk, to resolve all security issues not considered novel as quickly as possible.