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Add throw for empty strings in rules with modifier contains, startwith, and endswith #860

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Mar 6, 2024
Merged

Add throw for empty strings in rules with modifier contains, startwith, and endswith #860

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6093bdb
add validation for empty strings with contains, startswith and endswi…
jowg-amazon Feb 16, 2024
460f406
throw exception if empty string with contains, startswith, or endswith
jowg-amazon Feb 17, 2024
db4a584
change var name
jowg-amazon Feb 17, 2024
b1bf251
add modifiers to log
jowg-amazon Feb 19, 2024
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11 changes: 10 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 +112,15 @@ 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);
// skips if sigmaType is an empty string and the modifier is "contains" or "startswith" or "endswith"
if (sigmaType.getClass().equals(SigmaString.class)) {
if (!(v.toString().isEmpty() && (modifierIds.contains("contains") || modifierIds.contains("startswith") || modifierIds.contains("endswith")))) {
sigmaTypes.add(sigmaType);
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}
} else {
sigmaTypes.add(sigmaType);
}
}

return new SigmaDetectionItem(field, modifiers, sigmaTypes, null, null, true);
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31 changes: 31 additions & 0 deletions src/test/java/org/opensearch/securityanalytics/TestHelpers.java
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Expand Up @@ -259,6 +259,37 @@ public static String randomRule() {
"level: high";
}

public static String randomRuleWithContainsAndEmptyString() {
return "title: Remote Encrypting File System Abuse\n" +
"id: 5f92fff9-82e2-48eb-8fc1-8b133556a551\n" +
"description: Detects remote RPC calls to possibly abuse remote encryption service via MS-EFSR\n" +
"references:\n" +
" - https://attack.mitre.org/tactics/TA0008/\n" +
" - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36942\n" +
" - https://github.com/jsecurity101/MSRPC-to-ATTACK/blob/main/documents/MS-EFSR.md\n" +
" - https://github.com/zeronetworks/rpcfirewall\n" +
" - https://zeronetworks.com/blog/stopping_lateral_movement_via_the_rpc_firewall/\n" +
"tags:\n" +
" - attack.defense_evasion\n" +
"status: experimental\n" +
"author: Sagie Dulce, Dekel Paz\n" +
"date: 2022/01/01\n" +
"modified: 2022/01/01\n" +
"logsource:\n" +
" product: rpc_firewall\n" +
" category: application\n" +
" definition: 'Requirements: install and apply the RPC Firewall to all processes with \"audit:true action:block uuid:df1941c5-fe89-4e79-bf10-463657acf44d or c681d488-d850-11d0-8c52-00c04fd90f7e'\n" +
"detection:\n" +
" selection:\n" +
" EventID|contains:\n" +
" 1996\n" +
" ''\n" +
" condition: selection\n" +
"falsepositives:\n" +
" - Legitimate usage of remote file encryption\n" +
"level: high";
}

public static String randomNullRule() {
return "title: null field\n" +
"id: 5f92fff9-82e2-48eb-8fc1-8b133556a551\n" +
Expand Down
52 changes: 52 additions & 0 deletions src/test/java/org/opensearch/securityanalytics/resthandler/RuleRestApiIT.java
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Expand Up @@ -46,6 +46,7 @@
import static org.opensearch.securityanalytics.TestHelpers.randomRuleForMappingView;
import static org.opensearch.securityanalytics.TestHelpers.randomRuleWithErrors;
import static org.opensearch.securityanalytics.TestHelpers.windowsIndexMapping;
import static org.opensearch.securityanalytics.TestHelpers.randomRuleWithContainsAndEmptyString;

public class RuleRestApiIT extends SecurityAnalyticsRestTestCase {

Expand Down Expand Up @@ -839,6 +840,57 @@ public void testGetAllRuleCategories() throws IOException {
assertTrue(categories.stream().anyMatch(e -> ((Map<String, Object>)e).get("key").equals("waf")));
}

public void testCreatingARuleWithContainsAndEmptyString() throws IOException {
String rule = randomRuleWithContainsAndEmptyString();

Response createResponse = makeRequest(client(), "POST", SecurityAnalyticsPlugin.RULE_BASE_URI, Collections.singletonMap("category", randomDetectorType()),
new StringEntity(rule), new BasicHeader("Content-Type", "application/json"));
Assert.assertEquals("Create rule failed", RestStatus.CREATED, restStatus(createResponse));

Map<String, Object> responseBody = asMap(createResponse);

String createdId = responseBody.get("_id").toString();
int createdVersion = Integer.parseInt(responseBody.get("_version").toString());
Assert.assertNotEquals("response is missing Id", Detector.NO_ID, createdId);
Assert.assertTrue("incorrect version", createdVersion > 0);
Assert.assertEquals("Incorrect Location header", String.format(Locale.getDefault(), "%s/%s", SecurityAnalyticsPlugin.RULE_BASE_URI, createdId), createResponse.getHeader("Location"));

String index = Rule.CUSTOM_RULES_INDEX;
String request = "{\n" +
" \"query\": {\n" +
" \"nested\": {\n" +
" \"path\": \"rule\",\n" +
" \"query\": {\n" +
" \"bool\": {\n" +
" \"must\": [\n" +
" { \"match\": {\"rule.category\": \"" + randomDetectorType().toLowerCase(Locale.ROOT) + "\"}}\n" +
" ]\n" +
" }\n" +
" }\n" +
" }\n" +
" }\n" +
"}";
List<SearchHit> hits = executeSearch(index, request);
Assert.assertEquals(1, hits.size());

request = "{\n" +
" \"query\": {\n" +
" \"nested\": {\n" +
" \"path\": \"rule\",\n" +
" \"query\": {\n" +
" \"bool\": {\n" +
" \"must\": [\n" +
" { \"match\": {\"rule.category\": \"application\"}}\n" +
" ]\n" +
" }\n" +
" }\n" +
" }\n" +
" }\n" +
"}";
hits = executeSearch(index, request);
Assert.assertEquals(0, hits.size());
}

@SuppressWarnings("unchecked")
public void testGetMappingsViewApiForFieldAliasesWithSameName() throws IOException {
String index = createTestIndex(randomIndex(), windowsIndexMapping());
Expand Down
69 changes: 69 additions & 0 deletions src/test/java/org/opensearch/securityanalytics/rules/backend/QueryBackendTests.java
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Expand Up @@ -907,6 +907,75 @@ 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();
List<Object> queries = 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));
Assert.assertEquals("(mappedA: value1*) OR (mappedA: value2*)", queries.get(0).toString());
}

public void testConvertSkipEmptyStringEndsWithModifier() throws IOException, SigmaError {
OSQueryBackend queryBackend = testBackend();
List<Object> queries = 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));
Assert.assertEquals("(mappedA: *value1) OR (mappedA: *value2)", queries.get(0).toString());
}

public void testConvertSkipEmptyStringContainsModifier() throws IOException, SigmaError {
OSQueryBackend queryBackend = testBackend();
List<Object> queries = 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));
Assert.assertEquals("(mappedA: *value1*) OR (mappedA: *value2*)", queries.get(0).toString());
}

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