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CWE-378/CWE-379: Kotlin StdLib - Creation of Temporary File/Directory With Insecure Permissions

Moderate
JLLeitschuh published GHSA-5w9v-8x7x-rfqm Feb 3, 2022

Package

maven org.jetbrains.kotlin:kotlin-stdlib (Maven)

Affected versions

> 0

Patched versions

None

Description

Impact

Kotlin Stdlib is vulnerable to CWE-378 - Insecure Temporary File &  CWE-379 - Creation of Temporary File in Directory with Insecure Permissions.

These are the two vulnerable locations:

Here is a simple unit test that demonstrates the vulnerability.

package org.jlleitschuh.sandbox

import org.junit.jupiter.api.Test
import java.io.BufferedReader
import java.io.File
import java.io.IOException
import java.io.InputStreamReader
import java.nio.file.Files

class KotlinTempDirectoryPermissionCheck {
    @Test
    fun `kotlin check default directory permissions`() {
        val dir = createTempDir()
        runLS(dir.parentFile, dir) // Prints drwxr-xr-x
    }

    @Test
    fun `Files check default directory permissions`() {
        val dir = Files.createTempDirectory("random-directory")
        runLS(dir.toFile().parentFile, dir.toFile()) // Prints drwx------
    }

    @Test
    fun `kotlin check default file permissions`() {
        val file = createTempFile()
        runLS(file.parentFile, file) // Prints -rw-r--r--
    }

    @Test
    fun `Files check default file permissions`() {
        val file = Files.createTempFile("random-file", ".txt")
        runLS(file.toFile().parentFile, file.toFile()) // Prints -rw-------
    }

    private fun runLS(file: File, lookingFor: File) {
        val processBuilder = ProcessBuilder()
        processBuilder.command("ls", "-l", file.absolutePath)
        try {
            val process = processBuilder.start()
            val output = StringBuilder()
            val reader = BufferedReader(
                InputStreamReader(process.inputStream)
            )
            reader.lines().forEach { line ->
                if (line.contains("total")) {
                    output.append(line).append('\n')
                }
                if (line.contains(lookingFor.name)) {
                    output.append(line).append('\n')
                }
            }
            val exitVal = process.waitFor()
            if (exitVal == 0) {
                println("Success!")
                println(output)
            } else {
                //abnormal...
            }
        } catch (e: IOException) {
            e.printStackTrace()
        } catch (e: InterruptedException) {
            e.printStackTrace()
        }
    }
}

A Kotlin application using createTempDir or createTempFile and placing sensitive information within either of these locations would be leaking this information in a read-only way to other users also on this system.

Prerequisites

This vulnerability impacts Unix-like systems, and very old versions of Mac OSX and Windows as they all share the system temporary directory between all users.

Patches

There are no patched versions with this vulnerability fixed. All versions remain vulnerable. However, the impacted methods have been deprecated.

To fully mitigate this vulnerability, ensure your code and all dependencies don't use the createTempFile or createTempFile methods offered by the Kotlin standard library.

Workarounds

Setting the java.io.tmpdir system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability for all operating systems and all Kotlin versions.

Depending upon the version of android you are using, this may also impact you. See the following resource: google/guava#4011 (comment)

References

JetBrains does a really terrible job with fully disclosing the details of their own vulnerabilities unfortunately.

For more information

Reach out to Jetbrains: security@jetbrains.com

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVE ID

CVE-2020-29582

Credits