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fix(apiv1): support comma-separated ETag lists in conditionals #336

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Merged
alecthomas merged 1 commit into from
Jun 22, 2026
Merged

fix(apiv1): support comma-separated ETag lists in conditionals #336

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19 changes: 17 additions & 2 deletions internal/strategy/apiv1.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ import (
"maps"
"net/http"
"os"
"strings"
"time"

"github.com/alecthomas/errors"
Expand Down Expand Up @@ -223,14 +224,28 @@ func (d *APIV1) httpError(w http.ResponseWriter, code int, err error, message st
// preconditions pass, otherwise the HTTP status code to send (304 or 412).
func checkConditionals(r *http.Request, etag string) int {
if ifMatch := r.Header.Get("If-Match"); ifMatch != "" {
if etag == "" || (ifMatch != "*" && ifMatch != etag) {
if etag == "" || !etagListMatches(ifMatch, etag) {
return http.StatusPreconditionFailed
}
}
if ifNoneMatch := r.Header.Get("If-None-Match"); ifNoneMatch != "" {
if (ifNoneMatch == "*" && etag != "") || ifNoneMatch == etag {
if etag != "" && etagListMatches(ifNoneMatch, etag) {
return http.StatusNotModified
}
}
return 0
}

// etagListMatches reports whether etag matches an RFC 7232 If-Match /
// If-None-Match header value, which may be a comma-separated list of ETags or
// the "*" wildcard. Stored ETags are always strong, so weak comparison is not
// required.
func etagListMatches(headerValue, etag string) bool {
for candidate := range strings.SplitSeq(headerValue, ",") {
candidate = strings.TrimSpace(candidate)
if candidate == "*" || candidate == etag {
return true
}
}
return false
}
4 changes: 4 additions & 0 deletions internal/strategy/apiv1_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,8 @@ func TestConditionalGetIfNoneMatch(t *testing.T) {
{name: "Matching", ifNoneMatch: etag, expectedStatus: http.StatusNotModified},
{name: "NonMatching", ifNoneMatch: `"wrong"`, expectedStatus: http.StatusOK},
{name: "Wildcard", ifNoneMatch: "*", expectedStatus: http.StatusNotModified},
{name: "ListMatching", ifNoneMatch: `"a", ` + etag + `, "b"`, expectedStatus: http.StatusNotModified},
{name: "ListNonMatching", ifNoneMatch: `"a", "b"`, expectedStatus: http.StatusOK},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down Expand Up @@ -134,6 +136,8 @@ func TestConditionalGetIfMatch(t *testing.T) {
{name: "Matching", ifMatch: etag, expectedStatus: http.StatusOK},
{name: "NonMatching", ifMatch: `"wrong"`, expectedStatus: http.StatusPreconditionFailed},
{name: "Wildcard", ifMatch: "*", expectedStatus: http.StatusOK},
{name: "ListMatching", ifMatch: `"a", ` + etag + `, "b"`, expectedStatus: http.StatusOK},
{name: "ListNonMatching", ifMatch: `"a", "b"`, expectedStatus: http.StatusPreconditionFailed},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
Expand Down