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Escape HTML output in builtin /flags service #3529

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0cd03f2
Escape HTML output in builtin /flags service
Sep 6, 2026
668d2d1
Use FlagSaver in flags_escaping unittest
Sep 7, 2026
4619d7f
Scope req/res per sub-case in flags_escaping unittest
Sep 7, 2026
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9 changes: 6 additions & 3 deletions src/brpc/builtin/flags_service.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -117,11 +117,11 @@ void FlagsService::set_value_page(Controller* cntl,
const bool is_string = (info.type == "string");
os << "<!DOCTYPE html><html><body>"
"<form action='' method='get'>"
" Set `" << name << "' from ";
" Set `" << WebEscape(name) << "' from ";
if (is_string) {
os << '"';
}
os << info.current_value;
os << WebEscape(info.current_value);
if (is_string) {
os << '"';
}
Expand Down Expand Up @@ -177,9 +177,12 @@ void FlagsService::default_method(::google::protobuf::RpcController* cntl_base,
return;
}
butil::IOBufBuilder os;
os << "Set `" << constraint << "' to " << *value_str;
if (use_html) {
os << "Set `" << WebEscape(constraint) << "' to "
<< WebEscape(*value_str);
os << "<br><a href='/flags'>[back to flags]</a>";
} else {
os << "Set `" << constraint << "' to " << *value_str;
}
os.move_to(cntl->response_attachment());
return;
Expand Down
67 changes: 67 additions & 0 deletions test/brpc_builtin_service_unittest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,17 @@
DEFINE_bool(foo, false, "Flags for UT");
BRPC_VALIDATE_GFLAG(foo, brpc::PassValidate);

// A reloadable string gflag so that FlagsService is able to modify its
// value via ?setvalue=. String flags must register the validator manually,
// see comments in butil/reloadable_flags.h.
DEFINE_string(reloadable_string_flag_for_ut, "", "Flags for UT");
static bool PassValidateStringFlag(const char*, const std::string&) {
return true;
}
const bool ALLOW_UNUSED dummy_validate_reloadable_string_flag_for_ut =
GFLAGS_NAMESPACE::RegisterFlagValidator(
&FLAGS_reloadable_string_flag_for_ut, PassValidateStringFlag);

namespace brpc {
DECLARE_bool(enable_rpcz);
DECLARE_bool(rpcz_hex_log_id);
Expand Down Expand Up @@ -686,6 +697,62 @@ TEST_F(BuiltinServiceTest, flags) {
TestFlags(true);
}

TEST_F(BuiltinServiceTest, flags_escaping) {
// Save all flags and restore them on any exit of this test, since the
// /flags service below modifies `reloadable_string_flag_for_ut'.
GFLAGS_NAMESPACE::FlagSaver flag_saver;
brpc::FlagsService service;
const std::string payload = "<svg onload=alert(1)>&\"'";
const std::string escaped = brpc::WebEscape(payload);

// Reflected: the ?setvalue= value is echoed into the html page.
{
ClosureChecker done;
brpc::Controller cntl;
brpc::FlagsRequest req;
brpc::FlagsResponse res;
SetUpController(&cntl, true);
cntl.http_request()._unresolved_path = "reloadable_string_flag_for_ut";
cntl.http_request().uri().SetQuery(brpc::SETVALUE_STR, payload);
service.default_method(&cntl, &req, &res, &done);

@wwbmmm wwbmmm Sep 7, 2026

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Done in 4619d7f: req/res are now declared inside each { ... } block so every default_method invocation gets fresh, empty request/response objects. Full brpc_builtin_service_unittest suite still passes (20/20).

🤖 This reply was automatically generated by brpc-oncall

EXPECT_FALSE(cntl.Failed());
const std::string& body = cntl.response_attachment().to_string();
EXPECT_EQ(std::string::npos, body.find(payload))
<< "unescaped payload in html: " << body;
CheckContent(cntl, escaped.c_str());
}
// Stored: ?setvalue&withform renders the flag value stored above.
{
ClosureChecker done;
brpc::Controller cntl;
brpc::FlagsRequest req;
brpc::FlagsResponse res;
SetUpController(&cntl, true);
cntl.http_request()._unresolved_path = "reloadable_string_flag_for_ut";
cntl.http_request().uri().SetQuery(brpc::SETVALUE_STR, "");
cntl.http_request().uri().SetQuery("withform", "");
service.default_method(&cntl, &req, &res, &done);

@wwbmmm wwbmmm Sep 7, 2026

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Done in 4619d7f: req/res are now declared inside each { ... } block so every default_method invocation gets fresh, empty request/response objects. Full brpc_builtin_service_unittest suite still passes (20/20).

🤖 This reply was automatically generated by brpc-oncall

EXPECT_FALSE(cntl.Failed());
const std::string& body = cntl.response_attachment().to_string();
EXPECT_EQ(std::string::npos, body.find(payload))
<< "unescaped payload in html: " << body;
CheckContent(cntl, escaped.c_str());
}
// Plain text output is not html-escaped.
{
ClosureChecker done;
brpc::Controller cntl;
brpc::FlagsRequest req;
brpc::FlagsResponse res;
SetUpController(&cntl, false);
cntl.http_request()._unresolved_path = "reloadable_string_flag_for_ut";
cntl.http_request().uri().SetQuery(brpc::SETVALUE_STR, payload);
service.default_method(&cntl, &req, &res, &done);

@wwbmmm wwbmmm Sep 7, 2026

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Done in 4619d7f: req/res are now declared inside each { ... } block so every default_method invocation gets fresh, empty request/response objects. Full brpc_builtin_service_unittest suite still passes (20/20).

🤖 This reply was automatically generated by brpc-oncall

EXPECT_FALSE(cntl.Failed());
CheckContent(cntl, payload.c_str());
}
}

TEST_F(BuiltinServiceTest, bad_method) {
TestBadMethod(false);
TestBadMethod(true);
Expand Down
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