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This rule is a specific instance of the more general rule MSC11-J. Do not assume infinite heap space.
Noncompliant Code Example
This noncompliant code fails to check the resource consumption of the file that is being unzipped. It permits the operation to run to completion or until local resources are exhausted.
| Code Block | ||
|---|---|---|
| ||
static final int BUFFER = 512;
// ...
// external data source: filename
BufferedOutputStream dest = null;
FileInputStream fis = new FileInputStream(filename);
ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
ZipEntry entry;
while((entry = zis.getNextEntry()) != null) {
System.out.println("Extracting: " +entry);
int count;
byte data[] = new byte[BUFFER];
// write the files to the disk
FileOutputStream fos = new FileOutputStream(entry.getName());
dest = new BufferedOutputStream(fos, BUFFER);
while ((count = zis.read(data, 0, BUFFER)) != -1) {
dest.write(data, 0, count);
}
dest.flush();
dest.close();
}
zis.close();
|
Compliant Solution
In this compliant solution, the code inside the while loop uses the ZipEntry.getSize() to find the uncompressed filesize of each entry in a zip archive before extracting the entry. It throws an exception if the entry to be extracted is too large — 100MB in this case.
| Code Block | ||
|---|---|---|
| ||
static final int TOOBIG = 0x6400000; // 100MB
// ...
// write the files to the disk, but only if file is not insanely big
if (entry.getSize() > TOOBIG) {
throw new IllegalStateException("File to be unzipped is huge.");
}
if (entry.getSize() == -1) {
throw new IllegalStateException("File to be unzipped might be huge.");
}
FileOutputStream fos = new FileOutputStream(entry.getName());
dest = new BufferedOutputStream(fos, BUFFER);
while ((count = zis.read(data, 0, BUFFER)) != -1) {
dest.write(data, 0, count);
}
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Risk Assessment
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
IDS22-J | low | probable | high | P2 | L3 |
Related Guidelines
Bibliography
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