security: sanitize Perplexity API error messages (CWE-200; re-impl of #103)

src/index.test.ts

@@ -418,7 +418,7 @@ describe("Perplexity MCP Server", () => {
       );
     });
 
-    it("should handle error text parse failures", async () => {
+    it("should handle error text parse failures with a generic message", async () => {
       global.fetch = vi.fn().mockResolvedValue({
         ok: false,
         status: 500,
@@ -430,8 +430,70 @@ describe("Perplexity MCP Server", () => {
 
       const messages = [{ role: "user", content: "test" }];
 
+      // Sanitized: the client should only see the status + statusText, never
+      // the underlying "Unable to parse error response" or raw exception text.
       await expect(performChatCompletion(messages)).rejects.toThrow(
-        "Unable to parse error response"
+        "Perplexity API error: 500 Internal Server Error"
+      );
+      await expect(performChatCompletion(messages)).rejects.not.toThrow(
+        "Cannot read error"
+      );
+    });
+
+    // CWE-200 regression: thrown error must not contain JSON-parser exception text.
+    it("should not expose JSON parse error details", async () => {
+      global.fetch = vi.fn().mockResolvedValue({
+        ok: true,
+        json: async () => {
+          throw new Error("Invalid JSON containing secret_token=abc123");
+        },
+      } as unknown as Response);
+
+      const messages = [{ role: "user", content: "test" }];
+
+      await expect(performChatCompletion(messages)).rejects.toThrow(
+        "Failed to parse JSON response from Perplexity API"
+      );
+      await expect(performChatCompletion(messages)).rejects.not.toThrow(
+        "secret_token=abc123"
+      );
+    });
+
+    // CWE-200 regression: thrown error must not contain network exception text.
+    it("should not expose network error details", async () => {
+      global.fetch = vi.fn().mockRejectedValue(
+        new Error("Network failure with credential=private-token")
+      );
+
+      const messages = [{ role: "user", content: "test" }];
+
+      await expect(performChatCompletion(messages)).rejects.toThrow(
+        "Network error while calling Perplexity API"
+      );
+      await expect(performChatCompletion(messages)).rejects.not.toThrow(
+        "credential=private-token"
+      );
+    });
+
+    // CWE-200 regression: thrown error must not contain the upstream response body.
+    it("should not expose upstream error response details", async () => {
+      global.fetch = vi.fn().mockResolvedValue({
+        ok: false,
+        status: 500,
+        statusText: "Internal Server Error",
+        text: async () => "internal_trace=abc123; account=private-tier",
+      } as Response);
+
+      const messages = [{ role: "user", content: "test" }];
+
+      await expect(performChatCompletion(messages)).rejects.toThrow(
+        "Perplexity API error: 500 Internal Server Error"
+      );
+      await expect(performChatCompletion(messages)).rejects.not.toThrow(
+        "internal_trace=abc123"
+      );
+      await expect(performChatCompletion(messages)).rejects.not.toThrow(
+        "private-tier"
       );
     });
 

src/server.ts

@@ -10,6 +10,7 @@ import type {
   UndiciRequestOptions
 } from "./types.js";
 import { ChatCompletionResponseSchema, SearchResponseSchema } from "./validation.js";
+import { logger } from "./logger.js";
 
 const PERPLEXITY_API_KEY = process.env.PERPLEXITY_API_KEY;
 const PERPLEXITY_BASE_URL = process.env.PERPLEXITY_BASE_URL || "https://api.perplexity.ai";
@@ -99,7 +100,10 @@ async function makeApiRequest(
     if (error instanceof Error && error.name === "AbortError") {
       throw new Error(`Request timeout: Perplexity API did not respond within ${TIMEOUT_MS}ms. Consider increasing PERPLEXITY_TIMEOUT_MS.`);
     }
-    throw new Error(`Network error while calling Perplexity API: ${error}`);
+    // CWE-200: do not leak raw exception text to MCP clients. Log server-side
+    // for operator diagnostics, return a stable generic message to the caller.
+    logger.error("Network error while calling Perplexity API", { error: String(error) });
+    throw new Error("Network error while calling Perplexity API");
   }
   clearTimeout(timeoutId);
 
@@ -110,8 +114,15 @@ async function makeApiRequest(
     } catch (parseError) {
       errorText = "Unable to parse error response";
     }
+    // CWE-200: keep upstream response body out of the client-facing error.
+    // Operators still see the full body in structured server logs.
+    logger.error("Perplexity API error", {
+      status: response.status,
+      statusText: response.statusText,
+      body: errorText,
+    });
     throw new Error(
-      `Perplexity API error: ${response.status} ${response.statusText}\n${errorText}`
+      `Perplexity API error: ${response.status} ${response.statusText}`
     );
   }
 
@@ -228,7 +239,9 @@ export async function performChatCompletion(
         throw new Error("Invalid API response: missing or empty choices array");
       }
     }
-    throw new Error(`Failed to parse JSON response from Perplexity API: ${error}`);
+    // CWE-200: do not leak parser exception text (may include partial body).
+    logger.error("Failed to parse JSON response from Perplexity API", { error: String(error) });
+    throw new Error("Failed to parse JSON response from Perplexity API");
   }
 
   const firstChoice = data.choices[0];
@@ -292,7 +305,9 @@ export async function performSearch(
     const json = await response.json();
     data = SearchResponseSchema.parse(json);
   } catch (error) {
-    throw new Error(`Failed to parse JSON response from Perplexity Search API: ${error}`);
+    // CWE-200: do not leak parser exception text (may include partial body).
+    logger.error("Failed to parse JSON response from Perplexity Search API", { error: String(error) });
+    throw new Error("Failed to parse JSON response from Perplexity Search API");
   }
 
   return formatSearchResults(data);