cc01781c31
* Add kotlin to rule S6096 * Add Kotlin rule description, update Java SE name * Apply suggestions from code review Co-authored-by: Pierre-Loup <49131563+pierre-loup-tristant-sonarsource@users.noreply.github.com> --------- Co-authored-by: christophe-zurn-sonarsource <christophe-zurn-sonarsource@users.noreply.github.com> Co-authored-by: Christophe Zurn <christophe.zurn@sonarsource.com> Co-authored-by: Christophe Zürn <36889251+christophe-zurn-sonarsource@users.noreply.github.com> Co-authored-by: Pierre-Loup <49131563+pierre-loup-tristant-sonarsource@users.noreply.github.com>
91 lines
2.6 KiB
Plaintext
91 lines
2.6 KiB
Plaintext
== How to fix it in Java I/O API
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=== Code examples
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:canonicalization_function1: java.io.File.getCanonicalFile
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:canonicalization_function2: java.io.File.getCanonicalPath
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include::../../common/fix/code-rationale.adoc[]
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==== Noncompliant code example
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[source,kotlin,diff-id=1,diff-type=noncompliant]
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----
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class Example {
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companion object {
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private const val TARGET_DIRECTORY = "/example/directory/"
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}
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fun extractEntry(zipFile: ZipFile) {
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val entries = zipFile.entries()
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val entry = entries.nextElement()
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val inputStream = zipFile.getInputStream(entry)
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val file = File(TARGET_DIRECTORY + entry.name)
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inputStream.copyTo(file.outputStream())
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}
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}
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----
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==== Compliant solution
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[source,kotlin,diff-id=1,diff-type=compliant]
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----
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class Example {
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companion object {
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private const val TARGET_DIRECTORY = "/example/directory/"
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}
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fun extractEntry(zipFile: ZipFile) {
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val entries = zipFile.entries()
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val entry = entries.nextElement()
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val inputStream = zipFile.getInputStream(entry)
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val file = File(TARGET_DIRECTORY + entry.name)
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val canonicalDestinationPath = file.canonicalPath
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if (canonicalDestinationPath.startsWith(TARGET_DIRECTORY)) {
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inputStream.copyTo(file.outputStream())
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}
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}
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}
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----
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=== How does this work?
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include::../../common/fix/how-does-this-work.adoc[]
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=== Pitfalls
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include::../../common/pitfalls/partial-path-traversal.adoc[]
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For example, the following code is vulnerable to partial path injection. Note
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that the string `targetDirectory` does not end with a path separator:
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[source, kotlin]
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----
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companion object {
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private const val targetDirectory = "/Users/John"
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}
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fun ExtractEntry(zipFile: ZipFile) {
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val entries = zipFile.entries()
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val entry = entries.nextElement()
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val inputStream = zipFile.getInputStream(entry)
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val file = File(entry.name)
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val canonicalDestinationPath = file.canonicalPath
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if (canonicalDestinationPath.startsWith(targetDirectory)) {
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Files.copy(inputStream, file.toPath(), StandardCopyOption.REPLACE_EXISTING, LinkOption.NOFOLLOW_LINKS)
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}
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}
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----
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This check can be bypassed because `"/Users/Johnny".startsWith("/Users/John")`
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returns `true`. Thus, for validation, `"/Users/John"` should actually be
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`"/Users/John/"`.
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**Warning**: Some functions, such as `.getCanonicalPath`, remove the
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terminating path separator in their return value. +
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The validation code should be tested to ensure that it cannot be impacted by this
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issue.
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https://github.com/aws/aws-sdk-java/security/advisories/GHSA-c28r-hw5m-5gv3[Here is a real-life example of this vulnerability.]
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