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JNI does provide methods that work with Modified UTF-8 (see [API 2013], Interface DataInput, section "Modified UTF-8"). The advantage of working with Modified UTF-8 is that it encodes \u0000 as 0xc0 0x80 instead of 0x00. This allows the use of C-style null-terminated strings that can be handled by C standard library string functions. However, arbitrary UTF-8 data cannot be expected to work correctly in JNI. Data passed to the NewStringUTF() function must be in Modified UTF-8 format. Character data read from a file or stream cannot be passed to the NewStringUTF() function without being filtered to convert the high-ASCII characters to Modified UTF-8. In other words, character data must be normalized to Modified UTF-8 before being passed to the NewStringUTF() function. (For more information about string normalization see IDS01-J. Normalize strings before validating them. Note, however, that that rule is mainly about UTF-16 normalization whereas what is of concern here is Modified UTF-8 normalization.)
Noncompliant Code Example
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Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
JNI04-J | Low | Probable | Medium | P4 | L3 |
Automated Detection
It may be possible to automatically detect whether character data from untrusted sources has been normalized before being passed to the NewStringUTF() function.
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