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[Backport 2.9] Add throw for empty strings in rules with modifier contains, startwith, and endswith #886

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Mar 12, 2024
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[Backport 2.9] Add throw for empty strings in rules with modifier contains, startwith, and endswith #886

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10 changes: 9 additions & 1 deletion src/main/java/org/opensearch/securityanalytics/rules/objects/SigmaDetectionItem.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import org.opensearch.securityanalytics.rules.modifiers.SigmaModifierFacade;
import org.opensearch.securityanalytics.rules.modifiers.SigmaValueModifier;
import org.opensearch.securityanalytics.rules.types.SigmaNull;
import org.opensearch.securityanalytics.rules.types.SigmaString;
import org.opensearch.securityanalytics.rules.types.SigmaType;
import org.opensearch.securityanalytics.rules.types.SigmaTypeFacade;
import org.opensearch.securityanalytics.rules.utils.AnyOneOf;
Expand Down Expand Up @@ -111,7 +112,14 @@ public static <T> SigmaDetectionItem fromMapping(String key, Either<T, List<T>>

List<SigmaType> sigmaTypes = new ArrayList<>();
for (T v: values) {
sigmaTypes.add(SigmaTypeFacade.sigmaType(v));
SigmaType sigmaType = SigmaTypeFacade.sigmaType(v);
// throws an error if sigmaType is an empty string and the modifier is "contains" or "startswith" or "endswith"
boolean invalidModifierWithEmptyString = modifierIds.contains("contains") || modifierIds.contains("startswith") || modifierIds.contains("endswith");
if (sigmaType.getClass().equals(SigmaString.class) && v.toString().isEmpty() && invalidModifierWithEmptyString) {
throw new SigmaValueError("Cannot create rule with empty string and given modifier(s): " + modifierIds);
} else {
sigmaTypes.add(sigmaType);
}
}

return new SigmaDetectionItem(field, modifiers, sigmaTypes, null, null, true);
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72 changes: 72 additions & 0 deletions src/test/java/org/opensearch/securityanalytics/rules/backend/QueryBackendTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -907,6 +907,78 @@ public void testConvertUnboundValuesAsWildcard() throws IOException, SigmaError
Assert.assertEquals("((mappedA: \"value1\") OR (mappedA: \"value2\") OR (mappedA: \"value3\")) OR (test*)", queries.get(0).toString());
}

public void testConvertSkipEmptyStringStartsWithModifier() throws IOException, SigmaError {
OSQueryBackend queryBackend = testBackend();
Assert.assertThrows(SigmaValueError.class, () -> {
queryBackend.convertRule(SigmaRule.fromYaml(
" title: Test\n" +
" id: 39f919f3-980b-4e6f-a975-8af7e507ef2b\n" +
" status: test\n" +
" level: critical\n" +
" description: Detects QuarksPwDump clearing access history in hive\n" +
" author: Florian Roth\n" +
" date: 2017/05/15\n" +
" logsource:\n" +
" category: test_category\n" +
" product: test_product\n" +
" detection:\n" +
" sel:\n" +
" fieldA1|startswith: \n" +
" - value1\n" +
" - value2\n" +
" - ''\n" +
" condition: sel", false));
});
}

public void testConvertSkipEmptyStringEndsWithModifier() throws IOException, SigmaError {
OSQueryBackend queryBackend = testBackend();
Assert.assertThrows(SigmaValueError.class, () -> {
queryBackend.convertRule(SigmaRule.fromYaml(
" title: Test\n" +
" id: 39f919f3-980b-4e6f-a975-8af7e507ef2b\n" +
" status: test\n" +
" level: critical\n" +
" description: Detects QuarksPwDump clearing access history in hive\n" +
" author: Florian Roth\n" +
" date: 2017/05/15\n" +
" logsource:\n" +
" category: test_category\n" +
" product: test_product\n" +
" detection:\n" +
" sel:\n" +
" fieldA1|endswith: \n" +
" - value1\n" +
" - value2\n" +
" - ''\n" +
" condition: sel", false));
});
}

public void testConvertSkipEmptyStringContainsModifier() throws IOException, SigmaError {
OSQueryBackend queryBackend = testBackend();
Assert.assertThrows(SigmaValueError.class, () -> {
queryBackend.convertRule(SigmaRule.fromYaml(
" title: Test\n" +
" id: 39f919f3-980b-4e6f-a975-8af7e507ef2b\n" +
" status: test\n" +
" level: critical\n" +
" description: Detects QuarksPwDump clearing access history in hive\n" +
" author: Florian Roth\n" +
" date: 2017/05/15\n" +
" logsource:\n" +
" category: test_category\n" +
" product: test_product\n" +
" detection:\n" +
" sel:\n" +
" fieldA1|contains: \n" +
" - value1\n" +
" - value2\n" +
" - ''\n" +
" condition: sel", false));
});
}

private OSQueryBackend testBackend() throws IOException {
return new OSQueryBackend(testFieldMapping, false, true);
}
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