Methods can return values to communicate failure or success or to update local objects or fields. Security risks can arise when method return values are ignored or when the invoking method fails to take suitable action. Consequently, programs must not ignore method return values.
When getter methods are named after an action, a programmer could fail to realize that a return value is expected. For example, the only purpose of the ProcessBuilder.redirectErrorStream() method is to report via return value whether the process builder successfully merged standard error and standard output. The method that actually performs redirection of the error stream is the overloaded single-argument method ProcessBuilder.redirectErrorStream(boolean).
Noncompliant Code Example (File Deletion)
This noncompliant code example attempts to delete a file but fails to check whether the operation has succeeded:
| Code Block | ||
|---|---|---|
| ||
public void deleteFile(){
| ||
| Wiki Markup | ||
Methods return values to communicate failure or success and, at other times, to update local objects or fields. Security risks can arise when method return values are ignored or when the invoking method fails to take suitable action on its receipt. When getter methods are named after an action, such as {{ProcessBuilder.redirectErrorStream()}}, a programmer could fail to realize that a return value is expected. Note that the only purpose of the {{ProcessBuilder.redirectErrorStream()}} method is to report via return value whether the process builder successfully merges standard error and standard output. The method that actually performs redirection of the error stream is the overloaded single-argument version. It is important to read the API documentation so that return values are not ignored. {mc} Another example is ignoring the return value from add() on a HashSet. If duplicate, false will be returned. {mc} h2. Noncompliant Code Example (File Deletion) This noncompliant code example attempts to delete a file, but fails to check whether the operation has succeeded. {code:bgColor=#FFcccc} File someFile = new File("someFileName.txt"); // doDo something with someFile someFile.delete(); {code} h2. |
Compliant
...
Solution
...
This
...
compliant
...
solution
...
checks
...
the Boolean value returned by the delete()
...
method
...
and
...
handles any resulting errors:
| Code Block | ||
|---|---|---|
| ||
public void deleteFile(){ errors as appropriate. {code:bgColor=#ccccff} File someFile = new File("someFileName.txt"); // doDo something with someFile if (!someFile.delete()) { // handleHandle failure to delete the file } {code } h2. |
Noncompliant
...
Code
...
Example
...
(String
...
Replacement)
...
This
...
noncompliant
...
code
...
example
...
ignores
...
the
...
return
...
value
...
of
...
the
...
String.replace()
...
method,
...
failing
...
to
...
update
...
the
...
original
...
string.
...
The
...
String.replace()
...
method
...
cannot
...
modify
...
the
...
state
...
of
...
the
...
String
...
(because
...
String
...
objects
...
are
...
immutable);
...
rather,
...
it
...
returns
...
a
...
reference
...
to
...
a
...
new
...
String
...
object
...
containing the modified string.
| Code Block | ||
|---|---|---|
| ||
the desired result. {code:bgColor=#FFcccc} public class IgnoreReplace { public static void main(String[] args) { String original = "insecure"; original.replace( 'i', '9' ); System.out.println(original); } } {code} h2. Compliant |
It is especially important to process the return values of immutable object methods. Although many methods of mutable objects operate by changing some internal state of the object, methods of immutable objects cannot change the object and often return a mutated new object, leaving the original object unchanged.
Compliant Solution
This compliant solution correctly updates the String reference original with the return value from the String.replace() method:
| Code Block | ||
|---|---|---|
| ||
public class ReplaceSolution This compliant solution correctly updates the {{String}} reference {{original}} with the return value from the {{String.replace}} method. {code:bgColor=#ccccff} public class DoNotIgnore { public static void main(String[] args) { String original = "insecure"; original = original.replace( 'i', '9' ); System.out.println(original); } } {code} h2. Risk Assessment Ignoring method return values can lead to unanticipated program behavior. || Guideline || Severity || Likelihood || Remediation Cost || Priority || Level || | EXP00-J | medium | probable | medium | {color:#cc9900}{*}P8{*}{color} | {color:#cc9900}{*}L2{*}{color} | h3. Automated Detection The Coverity Prevent Version 5.0 *CHECKED_RETURN* checker can detect the instance where Value returned from a function is not checked for errors before being used. h3. Related Vulnerabilities Search for vulnerabilities resulting from the violation of this guideline on the [CERT website|https://www.kb.cert.org/vulnotes/bymetric?searchview&query=FIELD+KEYWORDS+contains+EXP02-J]. h2. Related Guidelines C Secure Coding Standard: [seccode:EXP12-C. Do not ignore values returned by functions] C+\+ Secure Coding Standard: [cplusplus:EXP12-CPP. Do not ignore values returned by functions or methods] h2. Related Guidelines [MITRE CWE|http://cwe.mitre.org/]: [CWE-252|http://cwe.mitre.org/data/definitions/252.html] "Unchecked Return Value" h2. Bibliography \[[API 2006|AA. Bibliography#API 06]\] method [delete()|http://java.sun.com/javase/6/docs/api/java/io/File.html#delete()] and method [replace()|http://java.sun.com/javase/6/docs/api/java/lang/String.html#replace(char,%20char)] \[[Green 2008|AA. Bibliography#Green 08]\] ["String.replace"|http://mindprod.com/jgloss/gotchas.html] \[[Pugh 2009|AA. Bibliography#Pugh 09]\] misusing putIfAbsent ---- [!The CERT Oracle Secure Coding Standard for Java^button_arrow_left.png!|04. Expressions (EXP)] [!The CERT Oracle Secure Coding Standard for Java^button_arrow_up.png!|04. Expressions (EXP)] [!The CERT Oracle Secure Coding Standard for Java^button_arrow_right.png!|EXP01-J. Do not confuse abstract object equality with reference equality] |
Risk Assessment
Ignoring method return values can lead to unexpected program behavior.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
EXP00-J | Medium | Probable | Medium | P8 | L2 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| CodeSonar |
| JAVA.NULL.RET.UNCHECKED | Call Might Return Null (Java) | ||||||
| Coverity | 7.5 | CHECKED_RETURN | Implemented | ||||||
| Parasoft Jtest |
| CERT.EXP00.NASSIG CERT.EXP00.AECB | Ensure method and constructor return values are used Avoid "try", "catch" and "finally" blocks with empty bodies | ||||||
| PVS-Studio |
| V6010, V6101 | |||||||
| SonarQube |
| Return values from functions without side effects should not be ignored Return values should not be ignored when they contain the operation status code | |||||||
| SpotBugs |
| RV_RETURN_VALUE_IGNORED | Implemented |
Related Guidelines
VOID EXP12-CPP. Do not ignore values returned by functions or methods | |
Passing Parameters and Return Values [CSJ] | |
CWE-252, Unchecked Return Value |
Bibliography
[API 2006] | |
Misusing | |
| [Seacord 2015] |
...