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merged 3 commits into from
Nov 3, 2025
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Merged

ext_authz: perform request header checks progressively #41766

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89f18fe
ext_authz: perform request header checks progressively
antoniovleonti Oct 29, 2025
4c5b261
fix fmt
antoniovleonti Oct 29, 2025
6f0dc27
const ref
antoniovleonti Nov 3, 2025
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36 changes: 30 additions & 6 deletions source/extensions/filters/http/ext_authz/ext_authz.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,11 @@ const envoy::extensions::filters::http::ext_authz::v3::CheckSettings& defaultChe
CONSTRUCT_ON_FIRST_USE(envoy::extensions::filters::http::ext_authz::v3::CheckSettings);
}

bool headersWithinLimits(const Http::HeaderMap& headers) {
return headers.size() <= headers.maxHeadersCount() &&
headers.byteSize() <= headers.maxHeadersKb() * 1024;
}

} // namespace

FilterConfig::FilterConfig(const envoy::extensions::filters::http::ext_authz::v3::ExtAuthz& config,
Expand Down Expand Up @@ -686,6 +691,11 @@ void Filter::onComplete(Filters::Common::ExtAuthz::ResponsePtr&& response) {
case CheckResult::OK:
ENVOY_STREAM_LOG(trace, "'{}':'{}'", *decoder_callbacks_, key, value);
request_headers_->setCopy(Http::LowerCaseString(key), value);
if (!headersWithinLimits(*request_headers_)) {
stats_.request_header_limits_reached_.inc();
rejectResponse();
return;
}
break;
case CheckResult::IGNORE:
ENVOY_STREAM_LOG(trace, "Ignoring invalid header to set '{}':'{}'.", *decoder_callbacks_,
Expand All @@ -705,6 +715,11 @@ void Filter::onComplete(Filters::Common::ExtAuthz::ResponsePtr&& response) {
case CheckResult::OK:
ENVOY_STREAM_LOG(trace, "'{}':'{}'", *decoder_callbacks_, key, value);
request_headers_->addCopy(Http::LowerCaseString(key), value);
if (!headersWithinLimits(*request_headers_)) {
stats_.request_header_limits_reached_.inc();
rejectResponse();
return;
}
break;
case CheckResult::IGNORE:
ENVOY_STREAM_LOG(trace, "Ignoring invalid header to add '{}':'{}'.", *decoder_callbacks_,
Expand Down Expand Up @@ -740,6 +755,11 @@ void Filter::onComplete(Filters::Common::ExtAuthz::ResponsePtr&& response) {
// into one entry. The value of that combined entry is separated by ",".
// TODO(dio): Consider to use addCopy instead.
request_headers_->appendCopy(lowercase_key, value);
if (!headersWithinLimits(*request_headers_)) {
stats_.request_header_limits_reached_.inc();
rejectResponse();
return;
}
}
break;
}
Expand Down Expand Up @@ -779,6 +799,11 @@ void Filter::onComplete(Filters::Common::ExtAuthz::ResponsePtr&& response) {
case CheckResult::OK:
ENVOY_STREAM_LOG(trace, "'{}'", *decoder_callbacks_, key);
request_headers_->remove(lowercase_key);
if (!headersWithinLimits(*request_headers_)) {
stats_.request_header_limits_reached_.inc();
rejectResponse();
return;
}
break;
case CheckResult::IGNORE:
ENVOY_STREAM_LOG(trace, "Ignoring disallowed header removal '{}'.", *decoder_callbacks_,
Expand Down Expand Up @@ -901,12 +926,11 @@ void Filter::onComplete(Filters::Common::ExtAuthz::ResponsePtr&& response) {
trace, "ext_authz filter modified query parameter(s), using new path for request: {}",
*decoder_callbacks_, new_path);
request_headers_->setPath(new_path);
}

if (request_headers_->size() > request_headers_->maxHeadersCount() ||
request_headers_->byteSize() > request_headers_->maxHeadersKb() * 1024) {
rejectResponse();
return;
if (!headersWithinLimits(*request_headers_)) {
stats_.request_header_limits_reached_.inc();
rejectResponse();
return;
}
}

if (cluster_) {
Expand Down
3 changes: 2 additions & 1 deletion source/extensions/filters/http/ext_authz/ext_authz.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,8 @@ namespace ExtAuthz {
COUNTER(invalid) \
COUNTER(ignored_dynamic_metadata) \
COUNTER(filter_state_name_collision) \
COUNTER(omitted_response_headers)
COUNTER(omitted_response_headers) \
COUNTER(request_header_limits_reached)

/**
* Wrapper struct for ext_authz filter stats. @see stats_macros.h
Expand Down
131 changes: 103 additions & 28 deletions test/extensions/filters/http/ext_authz/ext_authz_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -2105,17 +2105,47 @@ TEST_F(HttpFilterTest, DeniedResponseWithBodyNotTruncatedWhenLimitIsZero) {
EXPECT_EQ(1U, config_->stats().denied_.value());
}

// Verifies that the downstream request fails when the ext_authz response
// would cause the request headers to exceed their limit.
TEST_F(HttpFilterTest, DownstreamRequestFailsOnHeaderLimit) {
InSequence s;
class RequestHeaderLimitTest : public HttpFilterTest {
public:
RequestHeaderLimitTest() = default;

initialize(R"EOF(
grpc_service:
envoy_grpc:
cluster_name: "ext_authz_server"
)EOF");
void runTest(Http::RequestHeaderMap& request_headers,
Filters::Common::ExtAuthz::Response response) {
InSequence s;

initialize(R"EOF(
grpc_service:
envoy_grpc:
cluster_name: "ext_authz_server"
)EOF");

prepareCheck();

EXPECT_CALL(*client_, check(_, _, _, _))
.WillOnce(Invoke(
[&](Filters::Common::ExtAuthz::RequestCallbacks& callbacks,
const envoy::service::auth::v3::CheckRequest&, Tracing::Span&,
const StreamInfo::StreamInfo&) -> void { request_callbacks_ = &callbacks; }));

EXPECT_EQ(Http::FilterHeadersStatus::StopAllIterationAndWatermark,
filter_->decodeHeaders(request_headers, false));

// Now the test should fail, since we expect the downstream request to fail.
EXPECT_CALL(decoder_filter_callbacks_.stream_info_,
setResponseFlag(Envoy::StreamInfo::CoreResponseFlag::UnauthorizedExternalService));
EXPECT_CALL(decoder_filter_callbacks_, encodeHeaders_(_, _))
.WillOnce(Invoke([&](const Http::ResponseHeaderMap& headers, bool) -> void {
EXPECT_EQ(headers.getStatusValue(),
std::to_string(enumToInt(Http::Code::InternalServerError)));
}));
EXPECT_CALL(decoder_filter_callbacks_, continueDecoding()).Times(0);

request_callbacks_->onComplete(std::make_unique<Filters::Common::ExtAuthz::Response>(response));
EXPECT_EQ(1U, config_->stats().request_header_limits_reached_.value());
}
};

TEST_F(RequestHeaderLimitTest, HeadersToSetCount) {
// The total number of headers in the request header map is not allowed to
// exceed the limit.
Http::TestRequestHeaderMapImpl request_headers({}, /*max_headers_kb=*/99999,
Expand All @@ -2124,32 +2154,77 @@ TEST_F(HttpFilterTest, DownstreamRequestFailsOnHeaderLimit) {
request_headers.addCopy(Http::Headers::get().Path, "/");
request_headers.addCopy(Http::Headers::get().Method, "GET");

prepareCheck();
Filters::Common::ExtAuthz::Response response{};
response.status = Filters::Common::ExtAuthz::CheckStatus::OK;
response.headers_to_set = {{"foo", "bar"}, {"foo2", "bar2"}};

EXPECT_CALL(*client_, check(_, _, _, _))
.WillOnce(
Invoke([&](Filters::Common::ExtAuthz::RequestCallbacks& callbacks,
const envoy::service::auth::v3::CheckRequest&, Tracing::Span&,
const StreamInfo::StreamInfo&) -> void { request_callbacks_ = &callbacks; }));
runTest(request_headers, response);
}

EXPECT_EQ(Http::FilterHeadersStatus::StopAllIterationAndWatermark,
filter_->decodeHeaders(request_headers, false));
TEST_F(RequestHeaderLimitTest, HeadersToSetSize) {
// The total number of headers in the request header map is not allowed to
// exceed the limit.
Http::TestRequestHeaderMapImpl request_headers({}, /*max_headers_kb=*/1,
/*max_headers_count=*/9999);
request_headers.addCopy(Http::Headers::get().Host, "host");
request_headers.addCopy(Http::Headers::get().Path, "/");
request_headers.addCopy(Http::Headers::get().Method, "GET");

Filters::Common::ExtAuthz::Response response{};
response.status = Filters::Common::ExtAuthz::CheckStatus::OK;
response.headers_to_set = {{"foo", "bar"}, {"foo2", "bar2"}};
response.headers_to_set = {{"foo", "bar"}, {"foo2", std::string(9999, 'a')}};

// Now the test should fail, since we expect the downstream request to fail.
EXPECT_CALL(decoder_filter_callbacks_.stream_info_,
setResponseFlag(Envoy::StreamInfo::CoreResponseFlag::UnauthorizedExternalService));
EXPECT_CALL(decoder_filter_callbacks_, encodeHeaders_(_, _))
.WillOnce(Invoke([&](const Http::ResponseHeaderMap& headers, bool) -> void {
EXPECT_EQ(headers.getStatusValue(),
std::to_string(enumToInt(Http::Code::InternalServerError)));
}));
EXPECT_CALL(decoder_filter_callbacks_, continueDecoding()).Times(0);
runTest(request_headers, response);
}

request_callbacks_->onComplete(std::make_unique<Filters::Common::ExtAuthz::Response>(response));
// (headers to append can't add new headers, so it won't ever violate the count limit)
TEST_F(RequestHeaderLimitTest, HeadersToAppendSize) {
// The total number of headers in the request header map is not allowed to
// exceed the limit.
Http::TestRequestHeaderMapImpl request_headers({}, /*max_headers_kb=*/1,
/*max_headers_count=*/9999);
request_headers.addCopy(Http::Headers::get().Host, "host");
request_headers.addCopy(Http::Headers::get().Path, "/");
request_headers.addCopy(Http::Headers::get().Method, "GET");
request_headers.addCopy("foo", "original value");

Filters::Common::ExtAuthz::Response response{};
response.status = Filters::Common::ExtAuthz::CheckStatus::OK;
response.headers_to_append = {{"foo", std::string(9999, 'a')}};

runTest(request_headers, response);
}

TEST_F(RequestHeaderLimitTest, HeadersToAddCount) {
// The total number of headers in the request header map is not allowed to
// exceed the limit.
Http::TestRequestHeaderMapImpl request_headers({}, /*max_headers_kb=*/99999,
/*max_headers_count=*/4);
request_headers.addCopy(Http::Headers::get().Host, "host");
request_headers.addCopy(Http::Headers::get().Path, "/");
request_headers.addCopy(Http::Headers::get().Method, "GET");

Filters::Common::ExtAuthz::Response response{};
response.status = Filters::Common::ExtAuthz::CheckStatus::OK;
response.headers_to_add = {{"foo", "bar"}, {"foo2", "bar2"}};

runTest(request_headers, response);
}

TEST_F(RequestHeaderLimitTest, HeadersToAddSize) {
// The total number of headers in the request header map is not allowed to
// exceed the limit.
Http::TestRequestHeaderMapImpl request_headers({}, /*max_headers_kb=*/1,
/*max_headers_count=*/9999);
request_headers.addCopy(Http::Headers::get().Host, "host");
request_headers.addCopy(Http::Headers::get().Path, "/");
request_headers.addCopy(Http::Headers::get().Method, "GET");

Filters::Common::ExtAuthz::Response response{};
response.status = Filters::Common::ExtAuthz::CheckStatus::OK;
response.headers_to_add = {{"foo2", std::string(9999, 'a')}};

runTest(request_headers, response);
}

// Verifies that the downstream request fails when the ext_authz response
Expand Down