h2non#422 add support for returning source image response headers and…

… giving them precedence over cache-control

README.md

@@ -322,6 +322,7 @@ Usage:
   imaginary -enable-url-source -placeholder ./placeholder.jpg
   imaginary -enable-url-signature -url-signature-key 4f46feebafc4b5e988f131c4ff8b5997
   imaginary -enable-url-source -forward-headers X-Custom,X-Token
+  imaginary -enable-url-source -source-response-headers cache-control,etag
   imaginary -h | -help
   imaginary -v | -version
 
@@ -343,6 +344,7 @@ Options:
   -enable-placeholder       Enable image response placeholder to be used in case of error [default: false]
   -enable-auth-forwarding   Forwards X-Forward-Authorization or Authorization header to the image source server. -enable-url-source flag must be defined. Tip: secure your server from public access to prevent attack vectors
   -forward-headers          Forwards custom headers to the image source server. -enable-url-source flag must be defined.
+  -source-response-headers  Returns selected headers from the source image server response. Has precedence over -http-cache-ttl when cache-control is specified. Missing headers are ignored. -enable-url-source flag must be defined.
   -enable-url-signature     Enable URL signature (URL-safe Base64-encoded HMAC digest) [default: false]
   -url-signature-key        The URL signature key (32 characters minimum)
   -allowed-origins <urls>   Restrict remote image source processing to certain origins (separated by commas). Note: Origins are validated against host *AND* path.

controllers.go

@@ -45,7 +45,7 @@ func imageController(o ServerOptions, operation Operation) func(http.ResponseWri
 			return
 		}
 
-		buf, err := imageSource.GetImage(req)
+		buf, srcResponseHeaders, err := imageSource.GetImage(req)
 		if err != nil {
 			if xerr, ok := err.(Error); ok {
 				ErrorReply(req, w, xerr, o)
@@ -60,10 +60,23 @@ func imageController(o ServerOptions, operation Operation) func(http.ResponseWri
 			return
 		}
 
+		if len(o.SrcResponseHeaders) > 0 {
+			setSrcResponseHeaders(w, srcResponseHeaders, o.SrcResponseHeaders)
+		}
 		imageHandler(w, req, buf, operation, o)
 	}
 }
 
+func setSrcResponseHeaders(w http.ResponseWriter, responseHeaders http.Header, wantedHeaders []string) {
+	for _, wanted := range wantedHeaders {
+		v := responseHeaders.Get(wanted)
+		if len(v) > 0 {
+			w.Header().Set(wanted, v)
+		}
+	}
+
+}
+
 func determineAcceptMimeType(accept string) string {
 	for _, v := range strings.Split(accept, ",") {
 		mediaType, _, _ := mime.ParseMediaType(v)

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/garyburd/redigo v1.6.0 // indirect
 	github.com/h2non/bimg v1.1.7
 	github.com/h2non/filetype v1.1.0
-	github.com/hashicorp/golang-lru v0.0.0-20160813221303-0a025b7e63ad // indirect
 	github.com/rs/cors v0.0.0-20170727213201-7af7a1e09ba3
+	github.com/throttled/throttled/v2 v2.12.0
 	gopkg.in/throttled/throttled.v2 v2.0.3
 )

go.sum

@@ -1,12 +1,108 @@
+github.com/bsm/ginkgo/v2 v2.7.0/go.mod h1:AiKlXPm7ItEHNc/2+OkrNG4E0ITzojb9/xWzvQ9XZ9w=
+github.com/bsm/gomega v1.26.0/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
+github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
+github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=
 github.com/garyburd/redigo v1.6.0 h1:0VruCpn7yAIIu7pWVClQC8wxCJEcG3nyzpMSHKi1PQc=
 github.com/garyburd/redigo v1.6.0/go.mod h1:NR3MbYisc3/PwhQ00EMzDiPmrwpPxAn5GI05/YaO1SY=
+github.com/go-redis/redis v6.15.8+incompatible/go.mod h1:NAIEuMOZ/fxfXJIrKDQDz8wamY7mA7PouImQ2Jvg6kA=
+github.com/go-redis/redis/v8 v8.4.2/go.mod h1:A1tbYoHSa1fXwN+//ljcCYYJeLmVrwL9hbQN45Jdy0M=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
+github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:xKAWHe0F5eneWXFV3EuXVDTCmh+JuBKY0li0aMyXATA=
+github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
+github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
+github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
+github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
+github.com/gomodule/redigo v1.8.9/go.mod h1:7ArFNvsTjH8GMMzB4uy1snslv2BwmginuMs06a1uzZE=
+github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/h2non/bimg v1.1.7 h1:JKJe70nDNMWp2wFnTLMGB8qJWQQMaKRn56uHmC/4+34=
 github.com/h2non/bimg v1.1.7/go.mod h1:R3+UiYwkK4rQl6KVFTOFJHitgLbZXBZNFh2cv3AEbp8=
 github.com/h2non/filetype v1.1.0 h1:Or/gjocJrJRNK/Cri/TDEKFjAR+cfG6eK65NGYB6gBA=
 github.com/h2non/filetype v1.1.0/go.mod h1:319b3zT68BvV+WRj7cwy856M2ehB3HqNOt6sy1HndBY=
 github.com/hashicorp/golang-lru v0.0.0-20160813221303-0a025b7e63ad h1:eMxs9EL0PvIGS9TTtxg4R+JxuPGav82J8rA+GFnY7po=
 github.com/hashicorp/golang-lru v0.0.0-20160813221303-0a025b7e63ad/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
+github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
+github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
+github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/nxadm/tail v1.4.4/go.mod h1:kenIhsEOeOJmVchQTgglprH7qJGnHDVpk1VPCcaMI8A=
+github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
+github.com/onsi/ginkgo v1.12.1/go.mod h1:zj2OWP4+oCPe1qIXoGWkgMRwljMUYCdkwsT2108oapk=
+github.com/onsi/ginkgo v1.14.2/go.mod h1:iSB4RoI2tjJc9BBv4NKIKWKya62Rps+oPG/Lv9klQyY=
+github.com/onsi/gomega v1.7.1/go.mod h1:XdKZgCCFLUoM/7CFJVPcG8C1xQ1AJ0vpAezJrB7JYyY=
+github.com/onsi/gomega v1.10.1/go.mod h1:iN09h71vgCQne3DLsj+A5owkum+a2tYe+TOCB1ybHNo=
+github.com/onsi/gomega v1.10.3/go.mod h1:V9xEwhxec5O8UDM77eCW8vLymOMltsqPVYWrpDsH8xc=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/redis/go-redis/v9 v9.0.5/go.mod h1:WqMKv5vnQbRuZstUwxQI195wHy+t4PuXDOjzMvcuQHk=
 github.com/rs/cors v0.0.0-20170727213201-7af7a1e09ba3 h1:86ukAHRTa2CXdBnWJHcjjPPGTyLGEF488OFRsbBAuFs=
 github.com/rs/cors v0.0.0-20170727213201-7af7a1e09ba3/go.mod h1:gFx+x8UowdsKA9AchylcLynDq+nNFfI8FkUZdN/jGCU=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/throttled/throttled/v2 v2.12.0 h1:IezKE1uHlYC/0Al05oZV6Ar+uN/znw3cy9J8banxhEY=
+github.com/throttled/throttled/v2 v2.12.0/go.mod h1:+EAvrG2hZAQTx8oMpBu8fq6Xmm+d1P2luKK7fIY1Esc=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+go.opentelemetry.io/otel v0.14.0/go.mod h1:vH5xEuwy7Rts0GNtsCW3HYQoZDY+OmBJ6t1bFGGlxgw=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200520004742-59133d7f0dd7/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
+golang.org/x/net v0.0.0-20201006153459-a7d1128ccaa0/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
+golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190904154756-749cb33beabd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200519105757-fe76b779f299/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
+google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=
+google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=
+google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miEFZTKqfCUM6K7xSMQL9OKL/b6hQv+e19PK+JZNE=
+google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
+google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
 gopkg.in/throttled/throttled.v2 v2.0.3 h1:PGm7nfjjexecEyI2knw1akeLcrjzqxuYSU9a04R8rfU=
 gopkg.in/throttled/throttled.v2 v2.0.3/go.mod h1:L4cTNZO77XKEXtn8HNFRCMNGZPtRRKAhyuJBSvK/T90=
+gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
+gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

imaginary.go

@@ -40,6 +40,7 @@ var (
 	aKeyFile            = flag.String("keyfile", "", "TLS private key file path")
 	aAuthorization      = flag.String("authorization", "", "Defines a constant Authorization header value passed to all the image source servers. -enable-url-source flag must be defined. This overwrites authorization headers forwarding behavior via X-Forward-Authorization")
 	aForwardHeaders     = flag.String("forward-headers", "", "Forwards custom headers to the image source server. -enable-url-source flag must be defined.")
+	aSrcResponseHeaders = flag.String("source-response-headers", "", "Returns selected headers from the source image server response. Has precedence over -http-cache-ttl when cache-control is specified. -enable-url-source flag must be defined.")
 	aPlaceholder        = flag.String("placeholder", "", "Image path to image custom placeholder to be used in case of error. Recommended minimum image size is: 1200x1200")
 	aPlaceholderStatus  = flag.Int("placeholder-status", 0, "HTTP status returned when use -placeholder flag")
 	aDisableEndpoints   = flag.String("disable-endpoints", "", "Comma separated endpoints to disable. E.g: form,crop,rotate,health")
@@ -157,7 +158,8 @@ func main() {
 		HTTPReadTimeout:    *aReadTimeout,
 		HTTPWriteTimeout:   *aWriteTimeout,
 		Authorization:      *aAuthorization,
-		ForwardHeaders:     parseForwardHeaders(*aForwardHeaders),
+		ForwardHeaders:     parseHeadersList(*aForwardHeaders),
+		SrcResponseHeaders: parseHeadersList(*aSrcResponseHeaders),
 		AllowedOrigins:     parseOrigins(*aAllowedOrigins),
 		MaxAllowedSize:     *aMaxAllowedSize,
 		MaxAllowedPixels:   *aMaxAllowedPixels,
@@ -286,13 +288,13 @@ func checkHTTPCacheTTL(ttl int) {
 	}
 }
 
-func parseForwardHeaders(forwardHeaders string) []string {
+func parseHeadersList(headerString string) []string {
 	var headers []string
-	if forwardHeaders == "" {
+	if headerString == "" {
 		return headers
 	}
 
-	for _, header := range strings.Split(forwardHeaders, ",") {
+	for _, header := range strings.Split(headerString, ",") {
 		if norm := strings.TrimSpace(header); norm != "" {
 			headers = append(headers, norm)
 		}

middleware.go

@@ -31,7 +31,7 @@ func Middleware(fn func(http.ResponseWriter, *http.Request), o ServerOptions) ht
 		next = authorizeClient(next, o)
 	}
 	if o.HTTPCacheTTL >= 0 {
-		next = setCacheHeaders(next, o.HTTPCacheTTL)
+		next = setCacheHeaders(next, o.HTTPCacheTTL, o.SrcResponseHeaders)
 	}
 
 	return validate(defaultHeaders(next), o)
@@ -136,13 +136,26 @@ func defaultHeaders(next http.Handler) http.Handler {
 	})
 }
 
-func setCacheHeaders(next http.Handler, ttl int) http.Handler {
+func insensitiveArrayContains(haystack []string, needle string) bool {
+	for _, value := range haystack {
+		if strings.ToLower(value) == strings.ToLower(needle) {
+			return true
+		}
+	}
+	return false
+}
+
+func setCacheHeaders(next http.Handler, ttl int, srcResponseHeaders []string) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		defer next.ServeHTTP(w, r)
 
 		if r.Method != http.MethodGet || isPublicPath(r.URL.Path) {
 			return
 		}
+		// ignore the http-cache-ttl value if it's being set by a source image response header
+		if insensitiveArrayContains(srcResponseHeaders, "cache-control") && len(w.Header().Get("cache-control")) > 0 {
+			return
+		}
 
 		ttlDiff := time.Duration(ttl) * time.Second
 		expires := time.Now().Add(ttlDiff)

server.go

@@ -40,6 +40,7 @@ type ServerOptions struct {
 	Placeholder        string
 	PlaceholderStatus  int
 	ForwardHeaders     []string
+	SrcResponseHeaders []string
 	PlaceholderImage   []byte
 	Endpoints          Endpoints
 	AllowedOrigins     []*url.URL

source.go

@@ -9,21 +9,22 @@ type ImageSourceType string
 type ImageSourceFactoryFunction func(*SourceConfig) ImageSource
 
 type SourceConfig struct {
-	AuthForwarding bool
-	Authorization  string
-	MountPath      string
-	Type           ImageSourceType
-	ForwardHeaders []string
-	AllowedOrigins []*url.URL
-	MaxAllowedSize int
+	AuthForwarding     bool
+	Authorization      string
+	MountPath          string
+	Type               ImageSourceType
+	ForwardHeaders     []string
+	SrcResponseHeaders []string
+	AllowedOrigins     []*url.URL
+	MaxAllowedSize     int
 }
 
 var imageSourceMap = make(map[ImageSourceType]ImageSource)
 var imageSourceFactoryMap = make(map[ImageSourceType]ImageSourceFactoryFunction)
 
 type ImageSource interface {
 	Matches(*http.Request) bool
-	GetImage(*http.Request) ([]byte, error)
+	GetImage(*http.Request) ([]byte, http.Header, error)
 }
 
 func RegisterSource(sourceType ImageSourceType, factory ImageSourceFactoryFunction) {
@@ -33,13 +34,14 @@ func RegisterSource(sourceType ImageSourceType, factory ImageSourceFactoryFuncti
 func LoadSources(o ServerOptions) {
 	for name, factory := range imageSourceFactoryMap {
 		imageSourceMap[name] = factory(&SourceConfig{
-			Type:           name,
-			MountPath:      o.Mount,
-			AuthForwarding: o.AuthForwarding,
-			Authorization:  o.Authorization,
-			AllowedOrigins: o.AllowedOrigins,
-			MaxAllowedSize: o.MaxAllowedSize,
-			ForwardHeaders: o.ForwardHeaders,
+			Type:               name,
+			MountPath:          o.Mount,
+			AuthForwarding:     o.AuthForwarding,
+			Authorization:      o.Authorization,
+			AllowedOrigins:     o.AllowedOrigins,
+			MaxAllowedSize:     o.MaxAllowedSize,
+			ForwardHeaders:     o.ForwardHeaders,
+			SrcResponseHeaders: o.SrcResponseHeaders,
 		})
 	}
 }

source_body.go

@@ -23,11 +23,16 @@ func (s *BodyImageSource) Matches(r *http.Request) bool {
 	return r.Method == http.MethodPost || r.Method == http.MethodPut
 }
 
-func (s *BodyImageSource) GetImage(r *http.Request) ([]byte, error) {
+func (s *BodyImageSource) GetImage(r *http.Request) ([]byte, http.Header, error) {
+	var buf []byte
+	var err error
+
 	if isFormBody(r) {
-		return readFormBody(r)
+		buf, err = readFormBody(r)
+	} else {
+		buf, err = readRawBody(r)
 	}
-	return readRawBody(r)
+	return buf, make(http.Header), err
 }
 
 func isFormBody(r *http.Request) bool {