ASP.NET Web API安全深度解析与实践

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"Apress.Pro ASP.NET Web API Security.pdf" 是一本深入探讨ASP.NET Web API安全性的专业书籍，旨在帮助开发者理解和应用最新的安全实践和技术。全书共分为15章，内容覆盖了从入门到高级的主题。第1章"Welcome to ASP.NET Web API" 引导读者快速了解ASP.NET Web API的基础概念，为后续的安全实践奠定基础。第2章"Building RESTful Services" 关注RESTful服务的构建，强调了设计原则与如何通过Web API实现高效、简洁的通信接口。第3章"Extensibility Points" 讨论了API的可扩展性，包括如何通过自定义中间件和扩展方法来增强API的功能和安全性。第4章"HTTP Anatomy and Security" 深入解析HTTP协议的各个方面，并讨论如何识别和处理常见的安全威胁，如跨站脚本攻击(CSSP)和跨站请求伪造(CSRF)。第5章"Identity Management" 重点关注身份管理，包括用户认证、授权和会话管理，如何确保API对合法用户开放且数据安全。第6章"Encryption and Signing" 针对数据加密和签名技术进行详尽讲解，涵盖了对称加密、非对称加密以及哈希函数在API安全中的应用。第7章至第13章深入研究OAuth 2.0的各种实现方式，包括通过Windows Identity Foundation (WIF)定制身份提供商、使用Live Connect API以及借助DotNetOpenAuth库。第14章"Two-Factor Authentication" 探讨二步验证在Web API中的实施，增强账户保护，抵御更高级别的攻击。第15章"Security Vulnerabilities" 介绍常见的安全漏洞及其防范措施，帮助开发者识别并修复潜在风险。附录"ASP.NET Web API Security Distilled" 总结了全书的关键点和最佳实践，为读者提供了简洁实用的安全指南。本书不仅适合经验丰富的开发人员提升对Web API安全的理解，也适合新手了解现代API设计中不可或缺的安全元素。通过阅读这本书，读者可以掌握如何创建更安全、可靠的ASP.NET Web API服务。

CHAPTER 1 ■ WELCOME TO ASP.NET WEB API

• Platform for Internet of Things (IOT): IOT devices with Ethernet controllers or a Global

System for Mobile Communications (GSM) modem, for example, can speak to ASP.NET Web

API services through HTTP. A platform built on .NET can receive the data and do business. Not

just IOT devices, but other HTTP-capable devices such as radio frequency ID (RFID) readers

can communicate with ASP.NET Web API.

Caution ■ ASP.NET Web API is meant for developing web APIs. In other words, although it can technically work,

it is not the right candidate for supplementing your web application’s AJAX needs, especially when the AJAX use cases

are very few.

ASP.NET Web API as a service layer or tier need not always be the optimum solution from a performance

standpoint, because there is an HTTP overhead with every call. For a service tier that is used by the presentation tier,

with both tiers in the same network within the safety of firewalls, TCP or Named Pipes could be better choices and

WCF can outshine a web API in this area.

A typical service tier or layer in a .NET technology stack gets realized through WCF. Such WCF services are

consumed by a front-end application such as a web application (ASP.NET WebForms or MVC) or thick client

application (WPF or WinForms). With the exception of Silverlight apps that consume WCF services, a majority of the

typical architecture scenarios see WCF services sitting comfortably behind the firewall outside of the DMZ, whereas

web servers running the front end or the web application sit within the DMZ and are more prone to attacks. The web

API tends to be similar to web applications, as they get typically consumed over the Internet just like an Internet web

application and hence get hosted in the servers in the DMZ.

Figure 1-1 illustrates a typical deployment associated with ASP.NET Web API. It is worth noting that ASP.NET Web

API is well suited for communication across the firewall, especially given the friendly relationship port 80 enjoys with

corporate firewall policies. Native mobile apps, browsers, and other devices are typically outside the firewall and this

basically boils down to the fact that ASP.NET Web API has to live outside the protection corporate firewalls offer and

be exposed to the Internet. Security will be a major factor in architecting and designing ASP.NET Web API.

CHAPTER 1 ■ WELCOME TO ASP.NET WEB API

Confidentiality, which means preserving authorized restrictions on access and disclosure, •

including the means for protecting personal privacy and proprietary information.

Integrity, which means guarding against improper information modification or destruction, •

and includes ensuring information nonrepudiation and authenticity.

Availability, which means ensuring timely and reliable access to and use of information.•

Confidentiality is about preventing the disclosure of information to unauthorized entities. Encrypting sensitive

data and storing hashed passwords are examples of ensuring confidentiality. We look at encryption in Chapter 6 and

hashing in Chapter 15.

Integrity is about preventing modifications to the data by unauthorized entities (an entity is a user or an external

system that uses the application). This means, first and the foremost, that an entity must be identified. Identification

is the process of simply identifying the entity. It is different from authentication, which is about ensuring that the user

really has the identity that she claims to have.

As an example, consider an application where a user, John Q. Human, with a user ID of jqhuman and some

password is trying to log in to the application. As soon as the application gets the user-entered identifier of jqhuman,

it can identify the user. At that point, the user is an identified user, but not yet authenticated. Once John enters

the password, the application compares the user-entered password with the one in its records; if they match, the

identified user is considered an authentic user. It is important to note that identification must precede authentication,

because only after the user is identified can the application retrieve the password from the data store for comparison

against the user-entered password to complete the authentication process.

Authentication can be based on three factors: knowledge, ownership, and inherence. In the preceding example,

the user John uses his user ID and password. The password is something the user knows or remembers and hence the

password is a knowledge factor. Authentication can be based on things a user owns or possesses, such as a security

token or a client certificate, which are ownership factors. The third factor, the inherence factor, is something a user is,

such as a fingerprint or DNA sequence. It is also possible to combine one or more of these factors for authentication.

If two factors are involved, it is a two-factor authentication (TFA or 2FA). An example of TFA would be authentication

based on an X.509 client certificate and a user ID–password combination. We cover knowledge-factor-based security

in Chapter 8 and ownership-factor-based security in Chapters 9 and 10. Two-factor security is covered in Chapter 14.

Once an entity is authenticated, actions that the entity wishes to perform on the application can be access

controlled. Authorization is the process that ensures only those entities with permission to perform a task do perform

the task. We look at identity management in depth, mainly from the point of view of the .NET Framework and the

concepts of authentication and authorization, in Chapter 5.

Authorization ensures entities get to see and operate on what they are allowed to access, but there are cases

where an entity would like to open up its own data or information in one application to another application, mostly on

a temporary basis. There are standards available in this area, such as OAuth, which we look at in depth in Chapters 11,

12, and 13.

Authentication and authorization are important for ensuring integrity, but those two factors alone do not

constitute the exhaustive list of things needed to ensure integrity. There are other requirements, too. For example, let’s

say our application is a web application and a user posts an HTML form with data based on which application data

store will be updated. Of course, the application enforces authentication and authorization, but what if someone in

the middle tampers with the data in transit? Then, integrity is said to be compromised.

It is common to handle situations like this by securing the layer that transports the data; in the case of web

applications, this means using transport security through HTTPS/TLS. We look at HTTPS in depth in Chapter 4. An

alternative to transport security is message security, where the message is protected without protecting the transport

layer. Message security typically involves encryption and signing of messages or the data transmitted, which are

covered in depth in Chapter 6.

Similar to man-in-the-middle attacks, where an adversary in the middle attempts to tamper with data, there are

multiple other forms of attacks and associated security risks. The Open Web Application Security Project (OWASP)

is a worldwide, not-for-profit organization that publishes a list of the top ten current security risks. Risks from this list

that are relevant to ASP.NET Web API are covered in Chapter 15.

CHAPTER 1 ■ WELCOME TO ASP.NET WEB API

So far, we have focused on the confidentiality and integrity aspects of the CIA triad. The third aspect, availability,

is about an application being available for legitimate users. There are forms of attacks such as denial-of-service

attacks, which are all about making an application unavailable for users. DoS and brute-force attacks are covered

in Chapter 15, but availability from a security standpoint is mostly attributed to IT administration and operation

activities involving specialized hardware and software, and is not typically related to application programming.

Related to that point, security is a team effort among the IT administration, operations, and development teams.

All the areas need to be covered to call a system or an application secure. You might painstakingly architect, design,

and implement a secure application, but if the platform running the software is not hardened or patched diligently,

you are opening your system to attacks. Similarly, if you have a sound and secure platform and infrastructure, yet you

don’t design or code the right way, you are equally vulnerable. One coding bug related to SQL injection is all it takes to

open up your application to attacks, even if your design, architecture, and infrastructure are top notch. However, this

book is for software developers, designers, and architects, and throughout its chapters, you will see that the focus is on

integrity and confidentiality aspects of the CIA triad from a programming perspective.

From an IT operations perspective auditing is an important aspect. We have authentication, authorization, and

other protection mechanisms in place, but there could be legal or business requirements to keep track of activities in

the application, in terms of who does what. This is called security auditing, covered in Chapter 15.

Finally, a short note on nonrepudiation, a term that is typically seen in a legal context. To repudiate is to deny,

so nonrepudiation is basically ensuring that someone cannot deny something. A digital signature based on an X.509

certificate is very common to ensure nonrepudiation. Signing and encryption using certificates are covered in Chapter 6,

but there is no coverage specific to nonrepudiation, as the legal requirements can vary. Figure 1-2 provides an

overview of the security topics discussed throughout the book, along with the chapters in which they are covered.

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