vulnerabilities-workflow-1.md

Combined Vulnerability List

This document combines identified vulnerabilities from multiple lists into a single, deduplicated list.

Vulnerability: Filename Sanitization Bypass in SafeFileName

• Description:

  1. The SafeFileName function in utils.go aims to sanitize input strings to produce safe filenames.
  2. The function uses regular expressions to replace or remove characters considered unsafe in filenames.
  3. However, the current implementation of SafeFileName might not effectively sanitize filenames against all types of potentially harmful characters, specifically certain Unicode control characters like bidirectional override characters (e.g., RIGHT-TO-LEFT OVERRIDE - \u202E).
  4. An attacker could craft a filename containing these characters.
  5. When SafeFileName is used to sanitize this crafted filename, it may fail to remove or neutralize the harmful characters.
  6. An application using the govalidator library and relying on SafeFileName for security purposes might then inadvertently use the unsanitized filename.
  7. This could lead to filename spoofing or other unexpected behavior depending on how the filename is used by the application.

• Impact:

  • Filename spoofing: An attacker could create files with names that visually mimic other filenames, potentially leading to users executing unintended files or being tricked into downloading or interacting with malicious content.
  • Depending on the application's use of filenames, other security issues could arise from unexpected or unsanitized filenames.
  • The vulnerability is ranked as high because filename spoofing can be a significant phishing and social engineering vector, and bypasses intended security sanitization.

• Vulnerability Rank: high

• Currently implemented mitigations:

  • The SafeFileName function uses regular expressions to remove separators ([ &_=+:]) and illegal characters ([^[:alnum:]-.]).
  • It also handles double dashes (--) by replacing them with a single dash (-).
  • These mitigations are implemented in the SafeFileName function in /code/utils.go.

• Missing mitigations:

  • The current regular expressions do not specifically target or remove Unicode bidirectional override characters or other potentially harmful Unicode control characters.
  • Missing mitigation is a more comprehensive sanitization approach that considers a wider range of potentially unsafe Unicode characters in filenames.

• Preconditions:

  • An application uses the govalidator library, specifically the SafeFileName function, to sanitize filenames.
  • The application relies on SafeFileName to prevent filename-based vulnerabilities.
  • An attacker can control or influence the input string that is passed to SafeFileName.

• Source code analysis:

  1. File: /code/utils.go
  2. Function: SafeFileName(str string) string
  3. Code Snippet:

  func SafeFileName(str string) string {
      name := strings.ToLower(str)
      name = path.Clean(path.Base(name))
      name = strings.Trim(name, " ")
      separators, err := regexp.Compile(`[ &_=+:]`)
      if err == nil {
          name = separators.ReplaceAllString(name, "-")
      }
      legal, err := regexp.Compile(`[^[:alnum:]-.]`)
      if err == nil {
          name = legal.ReplaceAllString(name, "")
      }
      for strings.Contains(name, "--") {
          name = strings.Replace(name, "--", "-", -1)
      }
      return name
  }

  4. Vulnerability Point: The regular expression [^[:alnum:]-.] is intended to remove illegal characters. However, it focuses on ASCII alphanumeric characters, hyphens, and dots. It does not explicitly address Unicode control characters, such as bidirectional override characters.
  5. Example: Input string "test\u202Etxt.abc" contains the Unicode RIGHT-TO-LEFT OVERRIDE character (\u202E). When this string is processed by SafeFileName, the regex [^[:alnum:]-.] will not match and remove \u202E because [:alnum:] and the negated set [^...] might not cover or explicitly exclude this specific Unicode control character. The resulting filename might still contain \u202E, leading to potential spoofing issues.

• Security test case:

  1. Test Environment: Set up a Go development environment and include the govalidator library.
  2. Test Code: Write a Go test program that calls the SafeFileName function with a malicious input string containing a Unicode bidirectional override character.

  package main
  
  import (
      "fmt"
      "github.com/asaskevich/govalidator/v11"
  )
  
  func main() {
      maliciousFilename := "test\u202Etxt.abc"
      safeFilename := govalidator.SafeFileName(maliciousFilename)
      fmt.Printf("Original Filename: %s\n", maliciousFilename)
      fmt.Printf("Sanitized Filename: %s\n", safeFilename)
      if govalidator.Contains(safeFilename, "\u202E") {
          fmt.Println("Vulnerability Found: Sanitized filename still contains Unicode bidirectional override character.")
      } else {
          fmt.Println("Sanitization Successful: Unicode bidirectional override character removed.")
      }
  }

  3. Run Test: Execute the Go test program.
  4. Expected Result: The test should output that the "Sanitized Filename" still contains the Unicode bidirectional override character (\u202E), indicating a vulnerability. The output should show that safeFilename contains \u202E. For example, when running the test, the output might be similar to:

  Original Filename: test‏txt.abc
  Sanitized Filename: test‏txt.abc
  Vulnerability Found: Sanitized filename still contains Unicode bidirectional override character.
  

  5. Verification: Manually inspect the "Sanitized Filename" output to confirm if the Unicode bidirectional override character is still present. If it is, the vulnerability is confirmed.