...
Some of these causes are platform-dependent, and difficult to anticipate. Others are fairly easy to anticipate, such as reading data from a file. As a result, programs must not accept untrusted input in a manner that can cause the program to exhaust memory.
Noncompliant Code Example (readLine())
This noncompliant code example reads lines of text from a file and adds each one to a vector until a line with the word "quit" is encountered.
...
Any code that uses this method is susceptible to a resource exhaustion attack because the user can enter a string of any length.
Compliant Solution (Java 1.7, Limited File Size)
This compliant solution imposes a limit on the size of the file being read. This is accomplished with the Files.size() method, which is new to Java 1.7. If the file is within the limit, we can assume the standard readLine() method will not exhaust memory, nor will memory be exhausted by the while loop.
| Code Block | ||
|---|---|---|
| ||
class ShowHeapError {
static public final int fileSizeLimit = 1000000;
public ShowHeapError(String filename) throws IOException {
if (Files.size(Paths.get(filename)) > fileSizeLimit) {
throw new IOException("File too large");
}
this.input = new FileReader(filename);
this.reader = new BufferedReader(input);
}
// ...other methods
}
|
Compliant Solution (Limited Length Input)
This compliant solution imposes limits, both on the length of each line and on the total number of items to add to the vector. (It does not depend on any Java 1.7 features.)
...
The readLimitedLine() method defined above takes a numeric limit, indicating the total number of characters that may exist on one line. If a line contains more characters, the line is truncated, and they are returned on the next invocation. This prevents an attacker from exhausting memory by supplying input with no line breaks.
Noncompliant Code Example
| Wiki Markup |
|---|
In a server-class machine using a parallel garbage collector, the default initial and maximum heap sizes are as follows for Java SE 6 \[[Sun 2006|AA. Bibliography#Sun 06]\]: |
...
| Code Block | ||
|---|---|---|
| ||
/** Assuming the heap size as 512 MB (calculated as 1/4th of 2 GB RAM = 512 MB)
* Considering long values being entered (64 bits each, the max number of elements
* would be 512 MB/64bits = 67108864)
*/
public class ShowHeapError {
Vector<Long> names = new Vector<Long>(); // Accepts unknown number of records
long newID = 0L;
int count = 67108865;
int i = 0;
InputStreamReader input = new InputStreamReader(System.in);
Scanner reader = new Scanner(input);
public void addNames() {
try {
do {
// Adding unknown number of records to a list
// The user can enter more IDs than the heap can support and as a result
// exhaust the heap. Assume that the record ID is a 64 bit long value
System.out.print("Enter recordID (To quit, enter -1): ");
newID = reader.nextLong();
names.addElement(newID);
i++;
} while (i < count || newID != -1);
} finally {
input.close();
}
}
public static void main(String[] args) {
ShowHeapError demo = new ShowHeapError();
demo.addNames();
}
}
|
Compliant Solution
A simple compliant solution is to reduce the number of names to read.
| Code Block | ||
|---|---|---|
| ||
// ... int count = 10000000; // ... |
Compliant Solution
| Wiki Markup |
|---|
The {{OutOfMemoryError}} can be avoided by ensuring the absence of infinite loops, memory leaks, and unnecessary object retention. When memory requirements are known ahead of time, the heap size can be tailored to fit the requirements using the following runtime parameters \[[Java 2006|AA. Bibliography#Java 06]\]: |
...
This setting can be changed either using the Java Control Panel or from the command line. It cannot be adjusted through the application itself.
Risk Assessment
Assuming that infinite heap space is available can result in denial of service.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
MSC05-J | low | probable | medium | P4 | L3 |
Related Vulnerabilities
The Apache Geronimo bug described by GERONIMO-4224 results in an OutOfMemoryError exception thrown by the WebAccessLogViewer if the access log file size is too large, such as more than 200 MB.
Related Guidelines
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="a9a413be4e601eaf-5a6c2e80-4e574053-b978b9b5-bc7989d0f7fee7dd0ef44030"><ac:plain-text-body><![CDATA[ | [ISO/IEC TR 24772:2010 | http://www.aitcnet.org/isai/] | "Resource Exhaustion [XZP]" | ]]></ac:plain-text-body></ac:structured-macro> |
CWE-400, "Uncontrolled Resource Consumption ('Resource Exhaustion')" | ||||
| CWE-770, "Allocation of Resources Without Limits or Throttling" |
Bibliography
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="f62afdff5692900b-c9bba67f-48f04167-a286965f-515553ea4a50b208d184518b"><ac:plain-text-body><![CDATA[ | [[API 2006 | AA. Bibliography#API 06]] | Class ObjectInputStream and ObjectOutputStream | ]]></ac:plain-text-body></ac:structured-macro> | |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="8980debf51b2e7cf-1984d93e-42e345bd-8a8897d2-625dd8684343e2dfd0e27837"><ac:plain-text-body><![CDATA[ | [[Java 2006 | AA. Bibliography#Java 06]] | [java - the Java application launcher | http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html ], "Syntax for increasing the heap size" | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="8d898e6850fb0fe5-99f02d71-4f7748c8-8b2ab8af-a8c29582f0dda0483798e7a6"><ac:plain-text-body><![CDATA[ | [[SDN 2008 | AA. Bibliography#SDN 08]] | [Serialization FAQ | http://java.sun.com/javase/technologies/core/basic/serializationFAQ.jsp] | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="4c18a33c7af32ecd-b9de75a3-4eac4043-9018b8c4-6f2d2b317b5dd455bf7395a0"><ac:plain-text-body><![CDATA[ | [[Sun 2003 | AA. Bibliography#Sun 03]] | Chapter 5: Tuning the Java Runtime System, [Tuning the Java Heap | http://docs.sun.com/source/817-2180-10/pt_chap5.html#wp57027] | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="45d0049e231dfc5b-b45c5e22-4f6f428c-8175902d-83023aa5defe861b3b72f2b9"><ac:plain-text-body><![CDATA[ | [[Sun 2006 | AA. Bibliography#Sun 06]] | [Garbage Collection Ergonomics | http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html ], "Default values for the Initial and Maximum heap size" | ]]></ac:plain-text-body></ac:structured-macro> |
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