Red Hat Security Advisory: git security update

1. Implementation · Output Encoding

   Use context-aware encoding. That is, understand which encoding is being used by the downstream component, and ensure that this encoding is used. If an encoding can be specified, do so, instead of assuming that the default encoding is the same as the default being assumed by the downstream component.

2. Architecture and Design · Output Encoding

   Where possible, use communications protocols or data formats that provide strict boundaries between control and data. If this is not feasible, ensure that the protocols or formats allow the communicating components to explicitly state which encoding/decoding method is being used.

3. Architecture and Design · Libraries or Frameworks

   Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

OWASP Cheat Sheets

• Content Security Policy (opens in a new tab)

OWASP ASVS 4.0.3

• V14.4.6 (opens in a new tab)
• V14.4.4 (opens in a new tab)
• V14.4.2 (opens in a new tab)

Attack patterns

• Generic Cross-Browser Cross-Domain Theft (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

1. Implementation · Input Validation

   Developers should anticipate that delimiters will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.

2. Implementation · Input Validation

   Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

3. Implementation · Output Encoding

   While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments.

OWASP Cheat Sheets

• Abuse Case (opens in a new tab)
• Deserialization (opens in a new tab)
• Server Side Request Forgery Prevention (opens in a new tab)
• Unvalidated Redirects and Forwards (opens in a new tab)
• Cross Site Scripting Prevention (opens in a new tab)

OWASP ASVS 4.0.3

• V1.5.1 (opens in a new tab)
• V5.2.2 (opens in a new tab)

Attack patterns

• Command Delimiters (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

1. Architecture and Design

   When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt".

2. Architecture and Design · Operation

   Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory.

3. Architecture and Design

   For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…

OWASP Cheat Sheets

• XML Security (opens in a new tab)
• Mass Assignment (opens in a new tab)
• Secure Design Principles (opens in a new tab)

OWASP ASVS 4.0.3

• V12.3.2 (opens in a new tab)
• V13.3.1 (opens in a new tab)
• V5.1.4 (opens in a new tab)

Attack patterns

• Subverting Environment Variable Values (opens in a new tab)
• Leverage Alternate Encoding (opens in a new tab)
• Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
• URL Encoding (opens in a new tab)
• Manipulating Web Input to File System Calls (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

1. Implementation · Parameterization

   Where possible, avoid building a single string that contains the command and its arguments. Some languages or frameworks have functions that support specifying independent arguments, e.g. as an array, which is used to automatically perform the appropriate quoting or escaping while building the command.

2. Architecture and Design · Input Validation

   Understand all the potential areas where untrusted inputs can enter your product: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application.

3. Implementation · Input Validation

   Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

OWASP Cheat Sheets

• Abuse Case (opens in a new tab)
• Deserialization (opens in a new tab)
• Injection Prevention (opens in a new tab)
• SQL Injection Prevention (opens in a new tab)
• Injection Prevention in Java (opens in a new tab)

OWASP ASVS 4.0.3

• V1.5.1 (opens in a new tab)

Attack patterns

• Flash Parameter Injection (opens in a new tab)
• Using Meta-characters in E-mail Headers to Inject Malicious Payloads (opens in a new tab)
• HTTP Parameter Pollution (HPP) (opens in a new tab)
• OS Command Injection (opens in a new tab)
• Parameter Injection (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

1. Implementation

   Avoid using CRLF as a special sequence.

2. Implementation

   Appropriately filter or quote CRLF sequences in user-controlled input.

OWASP Cheat Sheets

• Abuse Case (opens in a new tab)
• Deserialization (opens in a new tab)
• Injection Prevention (opens in a new tab)
• SQL Injection Prevention (opens in a new tab)
• Injection Prevention in Java (opens in a new tab)

OWASP ASVS 4.0.3

• V1.5.1 (opens in a new tab)

Attack patterns

• Command Delimiters (opens in a new tab)
• Web Server Logs Tampering (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

1. Architecture and Design

   If at all possible, use library calls rather than external processes to recreate the desired functionality.

2. Architecture and Design · Operation · Sandbox or Jail

   Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.

3. Architecture and Design · Attack Surface Reduction

   For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.

OWASP Cheat Sheets

• Injection Prevention (opens in a new tab)
• Injection Prevention in Java (opens in a new tab)
• OS Command Injection Defense (opens in a new tab)
• Abuse Case (opens in a new tab)
• Deserialization (opens in a new tab)

OWASP ASVS 4.0.3

• V12.3.5 (opens in a new tab)
• V5.3.8 (opens in a new tab)
• V1.5.1 (opens in a new tab)

Attack patterns

• Command Line Execution through SQL Injection (opens in a new tab)
• Command Delimiters (opens in a new tab)
• Exploiting Multiple Input Interpretation Layers (opens in a new tab)
• Argument Injection (opens in a new tab)
• OS Command Injection (opens in a new tab)

From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).