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fix: reject invalid JSON-RPC response versions #1162

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fix: reject invalid JSON-RPC response versions #1162

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1 change: 1 addition & 0 deletions mcp-core/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
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Original file line number Diff line number Diff line change
Expand Up @@ -320,6 +320,7 @@ public record JSONRPCResponse( // @formatter:off

public JSONRPCResponse {
Assert.hasText(jsonrpc, "jsonrpc must not be empty");
Assert.isTrue(JSONRPC_VERSION.equals(jsonrpc), "jsonrpc must be 2.0");
Assert.notNull(id, "MCP responses MUST include an ID - null IDs are not allowed");
Assert.isTrue(id instanceof String || id instanceof Integer || id instanceof Long,
"MCP responses MUST have an ID that is either a string or integer");
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23 changes: 23 additions & 0 deletions mcp-test/src/test/java/io/modelcontextprotocol/spec/JsonRpcDispatchTests.java
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Expand Up @@ -6,6 +6,7 @@

import static io.modelcontextprotocol.util.McpJsonMapperUtils.JSON_MAPPER;
import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;

import java.io.IOException;
import java.util.Map;
Expand Down Expand Up @@ -81,6 +82,28 @@ void dispatchesErrorResponse() throws IOException {
assertThat(resp.result()).isNull();
}

@Test
void rejectsSuccessResponseWithInvalidJsonRpcVersion() {
String json = """
{"jsonrpc":"1.0","id":"req-1","result":{"content":[{"type":"text","text":"hi"}]}}
""";

assertThatThrownBy(() -> McpSchema.deserializeJsonRpcMessage(mapper, json)).rootCause()
.isInstanceOf(IllegalArgumentException.class)
.hasMessage("jsonrpc must be 2.0");
}

@Test
void rejectsErrorResponseWithInvalidJsonRpcVersion() {
String json = """
{"jsonrpc":"1.0","id":"req-1","error":{"code":-32601,"message":"Method not found"}}
""";

assertThatThrownBy(() -> McpSchema.deserializeJsonRpcMessage(mapper, json)).rootCause()
.isInstanceOf(IllegalArgumentException.class)
.hasMessage("jsonrpc must be 2.0");
}

@Test
void paramsMapSurvivesConvertValue() throws IOException {
String json = """
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