proxy_set_ja3_spoof

Instructions

Implementation Reference

• src/tools/tls.ts:112-141 (registration)

  Tool registration for 'proxy_set_ja3_spoof' via server.tool() — a legacy/deprecated MCP tool that accepts ja3 (ignored), user_agent, and host_patterns parameters.

  server.tool(
    "proxy_set_ja3_spoof",
    "Legacy: enable fingerprint spoofing (deprecated, use proxy_set_fingerprint_spoof with a preset). The ja3 parameter is accepted but ignored — the default Chrome preset is used.",
    {
      ja3: z.string().describe("JA3 fingerprint string (ignored — use proxy_set_fingerprint_spoof with a preset instead)"),
      user_agent: z.string().optional().describe("User-Agent header to use with spoofed requests"),
      host_patterns: z.array(z.string()).optional().describe("Only spoof requests to hostnames containing these substrings. Empty = spoof all HTTPS."),
    },
    async ({ ja3: _ja3, user_agent, host_patterns }) => {
      try {
        await proxyManager.setJa3Spoof({
          userAgent: user_agent,
          hostPatterns: host_patterns,
        });
  
        return {
          content: [{
            type: "text" as const,
            text: JSON.stringify({
              status: "success",
              message: "Fingerprint spoofing enabled with default Chrome preset. Use proxy_set_fingerprint_spoof with a preset for explicit control.",
              config: { userAgent: user_agent, hostPatterns: host_patterns ?? [] },
            }),
          }],
        };
      } catch (e) {
        return { content: [{ type: "text" as const, text: JSON.stringify({ status: "error", error: String(e) }) }] };
      }
    },
  );

• src/tools/tls.ts:120-141 (handler)

  Handler function that receives { ja3, user_agent, host_patterns }, ignores ja3, and calls proxyManager.setJa3Spoof() with user_agent and host_patterns.

    async ({ ja3: _ja3, user_agent, host_patterns }) => {
      try {
        await proxyManager.setJa3Spoof({
          userAgent: user_agent,
          hostPatterns: host_patterns,
        });
  
        return {
          content: [{
            type: "text" as const,
            text: JSON.stringify({
              status: "success",
              message: "Fingerprint spoofing enabled with default Chrome preset. Use proxy_set_fingerprint_spoof with a preset for explicit control.",
              config: { userAgent: user_agent, hostPatterns: host_patterns ?? [] },
            }),
          }],
        };
      } catch (e) {
        return { content: [{ type: "text" as const, text: JSON.stringify({ status: "error", error: String(e) }) }] };
      }
    },
  );

• src/tools/tls.ts:115-119 (schema)

  Input schema for proxy_set_ja3_spoof: ja3 (required string, but ignored), user_agent (optional string), host_patterns (optional string array).

  {
    ja3: z.string().describe("JA3 fingerprint string (ignored — use proxy_set_fingerprint_spoof with a preset instead)"),
    user_agent: z.string().optional().describe("User-Agent header to use with spoofed requests"),
    host_patterns: z.array(z.string()).optional().describe("Only spoof requests to hostnames containing these substrings. Empty = spoof all HTTPS."),
  },

• src/state.ts:1068-1070 (helper)

  ProxyManager.setJa3Spoof() — delegates to setFingerprintSpoof() which stores the config and triggers a mockttp rule rebuild.

  async setJa3Spoof(config: FingerprintSpoofConfig): Promise<void> {
    return this.setFingerprintSpoof(config);
  }

• src/state.ts:1063-1066 (helper)

  ProxyManager.setFingerprintSpoof() — stores the FingerprintSpoofConfig and if running, rebuilds mockttp rules to apply the spoofing.

  async setFingerprintSpoof(config: FingerprintSpoofConfig): Promise<void> {
    this._ja3SpoofConfig = config;
    if (this._running) await this.rebuildMockttpRules();
  }