From: Marcelo Magallon Date: Tue, 19 Oct 2021 16:50:47 +0000 (-0600) Subject: Add body_size_limit option to http module (#836) X-Git-Url: https://vcs.fsf.org/?a=commitdiff_plain;h=e86980961f8e463288e31cac03255701cb1a11d1;p=blackbox_exporter.git Add body_size_limit option to http module (#836) This option limits the maximum body length that will be read from the HTTP server. It's meant to prevent misconfigured servers from causing the probe to use too many resources, even if temporarily. It's not an additional check on the response, for that, use the resulting metrics (probe_http_content_length, probe_http_uncompressed_body_length, etc). Co-authored-by: Julien Pivotto --- diff --git a/CONFIGURATION.md b/CONFIGURATION.md index 2d83584..5a8608e 100644 --- a/CONFIGURATION.md +++ b/CONFIGURATION.md @@ -49,6 +49,14 @@ The other placeholders are specified separately. headers: [ : ... ] + # The maximum uncompressed body length in bytes that will be processed. A value of 0 means no limit. + # + # If the response includes a Content-Length header, it is NOT validated against this value. This + # setting is only meant to limit the amount of data that you are willing to read from the server. + # + # Example: 10MB + [ body_size_limit: | default = 0 ] + # The compression algorithm to use to decompress the response (gzip, br, deflate, identity). # # If an "Accept-Encoding" header is specified, it MUST be such that the compression algorithm diff --git a/config/config.go b/config/config.go index 07e84c0..03ac771 100644 --- a/config/config.go +++ b/config/config.go @@ -28,6 +28,7 @@ import ( yaml "gopkg.in/yaml.v3" + "github.com/alecthomas/units" "github.com/go-kit/kit/log" "github.com/go-kit/kit/log/level" "github.com/miekg/dns" @@ -207,6 +208,7 @@ type HTTPProbe struct { Body string `yaml:"body,omitempty"` HTTPClientConfig config.HTTPClientConfig `yaml:"http_client_config,inline"` Compression string `yaml:"compression,omitempty"` + BodySizeLimit units.Base2Bytes `yaml:"body_size_limit,omitempty"` } type HeaderMatch struct { @@ -287,6 +289,11 @@ func (s *HTTPProbe) UnmarshalYAML(unmarshal func(interface{}) error) error { if err := unmarshal((*plain)(s)); err != nil { return err } + + if s.BodySizeLimit <= 0 { + s.BodySizeLimit = math.MaxInt64 + } + if err := s.HTTPClientConfig.Validate(); err != nil { return err } diff --git a/config/testdata/blackbox-good.yml b/config/testdata/blackbox-good.yml index 4e044b4..59304d4 100644 --- a/config/testdata/blackbox-good.yml +++ b/config/testdata/blackbox-good.yml @@ -11,6 +11,7 @@ modules: basic_auth: username: "username" password: "mysecret" + body_size_limit: 1MB tcp_connect: prober: tcp timeout: 5s diff --git a/go.mod b/go.mod index ec2c3d9..daea731 100644 --- a/go.mod +++ b/go.mod @@ -1,6 +1,7 @@ module github.com/prometheus/blackbox_exporter require ( + github.com/alecthomas/units v0.0.0-20210912230133-d1bdfacee922 github.com/andybalholm/brotli v1.0.2 github.com/go-kit/kit v0.10.0 github.com/miekg/dns v1.1.41 diff --git a/go.sum b/go.sum index e0116f8..fe1ded8 100644 --- a/go.sum +++ b/go.sum @@ -11,8 +11,9 @@ github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 h1:JYp7IbQjafo github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc= github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0= github.com/alecthomas/units v0.0.0-20190717042225-c3de453c63f4/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0= -github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d h1:UQZhZ2O0vMHr2cI+DC1Mbh0TJxzA3RcLoMsFw+aXw7E= github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho= +github.com/alecthomas/units v0.0.0-20210912230133-d1bdfacee922 h1:8ypNbf5sd3Sm3cKJ9waOGoQv6dKAFiFty9L6NP1AqJ4= +github.com/alecthomas/units v0.0.0-20210912230133-d1bdfacee922/go.mod h1:OMCwj8VM1Kc9e19TLln2VL61YJF0x1XFtfdL4JdbSyE= github.com/andybalholm/brotli v1.0.2 h1:JKnhI/XQ75uFBTiuzXpzFrUriDPiZjlOSzh6wXogP0E= github.com/andybalholm/brotli v1.0.2/go.mod h1:loMXtMfwqflxFJPmdbJO0a3KNoPuLBgiu3qAvBg8x/Y= github.com/apache/thrift v0.12.0/go.mod h1:cp2SuWMxlEZw2r+iP2GNCdIi4C1qmUzdZFSVb+bacwQ= diff --git a/prober/http.go b/prober/http.go index 95c5353..d675452 100644 --- a/prober/http.go +++ b/prober/http.go @@ -499,6 +499,14 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr } } + // If there's a configured body_size_limit, wrap the body in the response in a http.MaxBytesReader. + // This will read up to BodySizeLimit bytes from the body, and return an error if the response is + // larger. It forwards the Close call to the original resp.Body to make sure the TCP connection is + // correctly shut down. The limit is applied _after decompression_ if applicable. + if httpConfig.BodySizeLimit > 0 { + resp.Body = http.MaxBytesReader(nil, resp.Body, int64(httpConfig.BodySizeLimit)) + } + byteCounter := &byteCounter{ReadCloser: resp.Body} if success && (len(httpConfig.FailIfBodyMatchesRegexp) > 0 || len(httpConfig.FailIfBodyNotMatchesRegexp) > 0) { diff --git a/prober/http_test.go b/prober/http_test.go index 6679b3c..56d65f2 100644 --- a/prober/http_test.go +++ b/prober/http_test.go @@ -513,6 +513,126 @@ func TestHandlingOfCompressionSetting(t *testing.T) { } } +func TestMaxResponseLength(t *testing.T) { + const max = 128 + + var shortGzippedPayload bytes.Buffer + enc := gzip.NewWriter(&shortGzippedPayload) + enc.Write(bytes.Repeat([]byte{'A'}, max-1)) + enc.Close() + + var longGzippedPayload bytes.Buffer + enc = gzip.NewWriter(&longGzippedPayload) + enc.Write(bytes.Repeat([]byte{'A'}, max+1)) + enc.Close() + + testcases := map[string]struct { + target string + compression string + expectedMetrics map[string]float64 + expectFailure bool + }{ + "short": { + target: "/short", + expectedMetrics: map[string]float64{ + "probe_http_uncompressed_body_length": float64(max - 1), + "probe_http_content_length": float64(max - 1), + }, + }, + "long": { + target: "/long", + expectFailure: true, + expectedMetrics: map[string]float64{ + "probe_http_content_length": float64(max + 1), + }, + }, + "short compressed": { + target: "/short-compressed", + compression: "gzip", + expectedMetrics: map[string]float64{ + "probe_http_content_length": float64(shortGzippedPayload.Len()), + "probe_http_uncompressed_body_length": float64(max - 1), + }, + }, + "long compressed": { + target: "/long-compressed", + compression: "gzip", + expectFailure: true, + expectedMetrics: map[string]float64{ + "probe_http_content_length": float64(longGzippedPayload.Len()), + "probe_http_uncompressed_body_length": max, // it should stop decompressing at max bytes + }, + }, + } + + ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { + var resp []byte + + switch r.URL.Path { + case "/short-compressed": + resp = shortGzippedPayload.Bytes() + w.Header().Add("Content-Encoding", "gzip") + + case "/long-compressed": + resp = longGzippedPayload.Bytes() + w.Header().Add("Content-Encoding", "gzip") + + case "/long": + resp = bytes.Repeat([]byte{'A'}, max+1) + + case "/short": + resp = bytes.Repeat([]byte{'A'}, max-1) + + default: + w.WriteHeader(http.StatusBadRequest) + return + } + + w.Header().Set("Content-Length", strconv.Itoa(len(resp))) + w.WriteHeader(http.StatusOK) + w.Write(resp) + })) + defer ts.Close() + + for name, tc := range testcases { + t.Run(name, func(t *testing.T) { + registry := prometheus.NewRegistry() + testCTX, cancel := context.WithTimeout(context.Background(), 10*time.Second) + defer cancel() + + result := ProbeHTTP( + testCTX, + ts.URL+tc.target, + config.Module{ + Timeout: time.Second, + HTTP: config.HTTPProbe{ + IPProtocolFallback: true, + BodySizeLimit: max, + HTTPClientConfig: pconfig.DefaultHTTPClientConfig, + Compression: tc.compression, + }, + }, + registry, + log.NewNopLogger(), + ) + + switch { + case tc.expectFailure && result: + t.Fatalf("test passed unexpectedly") + case !tc.expectFailure && !result: + t.Fatalf("test failed unexpectedly") + } + + mfs, err := registry.Gather() + if err != nil { + t.Fatal(err) + } + + checkRegistryResults(tc.expectedMetrics, mfs, t) + }) + } +} + func TestRedirectFollowed(t *testing.T) { ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { if r.URL.Path == "/" {