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object: checkETag compares quoted ETags properly (#1997)

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Previously, checkETag didn't handle ETags with leading and trailing
double quotes. e.g "abcdef1234" == "\"abcdef1234\"" would return false.
Now, checkETag function canonicalizes the ETags passed as arguments by
removing one leading/trailing double quote.
This commit is contained in:
Krishnan Parthasarathi 2016-06-26 18:10:08 -07:00 committed by Harshavardhana
parent 1e52759c3c
commit d0be09fdd3
1 changed files with 35 additions and 23 deletions
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58
object-handlers.go
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@ -107,16 +107,6 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
return
}
// Verify 'If-Modified-Since' and 'If-Unmodified-Since'.
lastModified := objInfo.ModTime
if checkLastModified(w, r, lastModified) {
return
}
// Verify 'If-Match' and 'If-None-Match'.
if checkETag(w, r) {
return
}
var hrange *httpRange
hrange, err = getRequestedRange(r.Header.Get("Range"), objInfo.Size)
if err != nil {
@ -130,6 +120,16 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
// Set any additional requested response headers.
setGetRespHeaders(w, r.URL.Query())
// Verify 'If-Modified-Since' and 'If-Unmodified-Since'.
lastModified := objInfo.ModTime
if checkLastModified(w, r, lastModified) {
return
}
// Verify 'If-Match' and 'If-None-Match'.
if checkETag(w, r) {
return
}
// Get the object.
startOffset := hrange.start
length := hrange.length
@ -191,25 +191,40 @@ func checkLastModified(w http.ResponseWriter, r *http.Request, modtime time.Time
return false
}
// canonicalizeETag returns ETag with leading and trailing double-quotes removed,
// if any present
func canonicalizeETag(etag string) string {
canonicalETag := strings.TrimPrefix(etag, "\"")
return strings.TrimSuffix(canonicalETag, "\"")
}
// isETagEqual return true if the canonical representations of two ETag strings
// are equal, false otherwise
func isETagEqual(left, right string) bool {
return canonicalizeETag(left) == canonicalizeETag(right)
}
// checkETag implements If-None-Match and If-Match checks.
//
// The ETag must have been previously set in the ResponseWriter's
// headers. The return value is whether this request is now considered
// done.
func checkETag(w http.ResponseWriter, r *http.Request) bool {
// writer always has quoted string
// transform reader's etag to
if r.Method != "GET" && r.Method != "HEAD" {
return false
}
etag := w.Header().Get("ETag")
// Must know ETag.
if etag == "" {
return false
}
if inm := r.Header.Get("If-None-Match"); inm != "" {
if inm := r.Header.Get("If-None-Match"); !isETagEqual(inm, "") {
// Return the object only if its entity tag (ETag) is
// different from the one specified; otherwise, return a 304
// (not modified).
if r.Method != "GET" && r.Method != "HEAD" {
return false
}
if inm == etag || inm == "*" {
if isETagEqual(inm, etag) || isETagEqual(inm, "*") {
h := w.Header()
// Remove following headers if already set.
delete(h, "Content-Type")
@ -218,13 +233,10 @@ func checkETag(w http.ResponseWriter, r *http.Request) bool {
w.WriteHeader(http.StatusNotModified)
return true
}
} else if im := r.Header.Get("If-Match"); im != "" {
} else if im := r.Header.Get("If-Match"); !isETagEqual(im, "") {
// Return the object only if its entity tag (ETag) is the same
// as the one specified; otherwise, return a 412 (precondition failed).
if r.Method != "GET" && r.Method != "HEAD" {
return false
}
if im != etag {
if !isETagEqual(im, etag) {
h := w.Header()
// Remove following headers if already set.
delete(h, "Content-Type")
@ -275,6 +287,9 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
return
}
// Set standard object headers.
setObjectHeaders(w, objInfo, nil)
// Verify 'If-Modified-Since' and 'If-Unmodified-Since'.
lastModified := objInfo.ModTime
if checkLastModified(w, r, lastModified) {
@ -286,9 +301,6 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
return
}
// Set standard object headers.
setObjectHeaders(w, objInfo, nil)
// Successfull response.
w.WriteHeader(http.StatusOK)
}