Red Hat Security Advisory: kernel security update

1. Implementation

   Change the code's logic so that the resource is only closed once. This might require simplifying or refactoring. This fix can be simple to do in small code blocks, but more difficult when multiple closes are buried within complex conditionals.

2. Implementation · Refactoring

   It can be effective to implement a flag that is (1) set when the resource is opened, (2) cleared when it is closed, and (3) checked before closing. This approach can be useful when there are disparate cases in which closes must be performed.

3. Implementation · Refactoring

   When closing a resource, set the resource's associated variable to NULL or equivalent value for the given language. Some APIs will ignore this null value without causing errors.

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

Attack patterns

• Forced Deadlock (opens in a new tab)

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

1. Implementation

   The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.

2. Implementation

   When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.

3. Architecture and Design

   Limit the interleaving of operations on files from multiple processes.

OWASP Cheat Sheets

• Abuse Case (opens in a new tab)

OWASP ASVS 4.0.3

• V1.11.3 (opens in a new tab)
• V11.1.6 (opens in a new tab)
• V1.11.2 (opens in a new tab)

Attack patterns

• Leveraging Race Conditions via Symbolic Links (opens in a new tab)
• Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)

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

1. Requirements · Language Selection

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

2. Architecture and Design

   Design signal handlers to only set flags, rather than perform complex functionality. These flags can then be checked and acted upon within the main program loop.

3. Implementation

   Only use reentrant functions within signal handlers. Also, use validation to ensure that state is consistent while performing asynchronous actions that affect the state of execution.

OWASP Cheat Sheets

• Abuse Case (opens in a new tab)

OWASP ASVS 4.0.3

• V1.11.2 (opens in a new tab)

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

1. Requirements · Language Selection

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

2. 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.

3. Operation · Build and Compilation · Environment Hardening

   Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…

OWASP Cheat Sheets

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

OWASP ASVS 4.0.3

• V13.3.1 (opens in a new tab)
• V5.1.4 (opens in a new tab)
• V5.1.3 (opens in a new tab)

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

1. 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

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

OWASP ASVS 4.0.3

• V13.3.1 (opens in a new tab)
• V5.1.4 (opens in a new tab)
• V5.1.3 (opens in a new tab)

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

1. Implementation

   When allocating a buffer for the purpose of transforming, converting, or encoding an input, allocate enough memory to handle the largest possible encoding. For example, in a routine that converts "&" characters to "&" for HTML entity encoding, the output buffer needs to be at least 5 times as large as the input…

2. Implementation

   Understand the programming language's underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how the language handles…

3. Implementation · Input Validation

   Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.

Attack patterns

• Overflow Buffers (opens in a new tab)
• Buffer Overflow via Parameter Expansion (opens in a new tab)

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