fix(s3api): accept HTTP-date conditionals (#9863)

* fix(s3api): accept HTTP-date conditionals

Problem: Object conditional headers rejected valid HTTP-date values in RFC850 or ANSIC format for If-Modified-Since and If-Unmodified-Since.

Root cause: parseConditionalHeaders used time.Parse(time.RFC1123), accepting only one HTTP-date representation instead of the standard formats accepted by net/http.ParseTime.

Fix: Parse conditional date headers with http.ParseTime so RFC1123, RFC850, and ANSIC HTTP-date forms are accepted.

Reproduction: go test ./weed/s3api -run TestParseConditionalHeadersAcceptsHTTPDateFormats -count=1 failed before the fix with ErrInvalidRequest for RFC850 and ANSIC date values.

Validation: env GOCACHE=/private/tmp/seaweedfs-go-cache go test ./weed/s3api -run TestParseConditionalHeadersAcceptsHTTPDateFormats -count=1; env GOCACHE=/private/tmp/seaweedfs-go-cache go test ./weed/s3api -count=1; git diff --check; git diff --cached --check

* fix(s3api): accept HTTP-date copy-source conditionals

Mirror the put-path http.ParseTime switch onto the copy-source If-Modified-Since / If-Unmodified-Since headers, which still rejected valid RFC850 and ANSIC dates.

* fix(s3api): keep RFC1123 UTC-zone dates working alongside http.ParseTime

http.ParseTime rejects the "UTC" zone that Go clients emit via t.UTC().Format(time.RFC1123), which the old RFC1123 parser accepted. Add a parseHTTPDate helper that tries http.ParseTime first and falls back to RFC1123, so the put and copy-source conditional date headers accept the union of HTTP-date formats plus the UTC zone.

---------

Co-authored-by: Chris Lu <chris.lu@gmail.com>

weed/s3api/s3api_object_routed_write_test.go

@@ -3,9 +3,11 @@ package s3api
 import (
 	"net/http"
 	"testing"
+	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
+	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
 )
 
 func reqWith(headers map[string]string) *http.Request {
@@ -101,6 +103,92 @@ func TestBuildWriteCondition(t *testing.T) {
 	})
 }
 
+func TestParseConditionalHeadersAcceptsHTTPDateFormats(t *testing.T) {
+	testCases := []struct {
+		name     string
+		header   string
+		value    string
+		expected time.Time
+	}{
+		{
+			name:     "If-Modified-Since RFC850",
+			header:   s3_constants.IfModifiedSince,
+			value:    "Sunday, 06-Nov-94 08:49:37 GMT",
+			expected: time.Date(1994, time.November, 6, 8, 49, 37, 0, time.UTC),
+		},
+		{
+			name:     "If-Unmodified-Since ANSIC",
+			header:   s3_constants.IfUnmodifiedSince,
+			value:    "Sun Nov  6 08:49:37 1994",
+			expected: time.Date(1994, time.November, 6, 8, 49, 37, 0, time.UTC),
+		},
+		{
+			// Go clients build this with t.UTC().Format(time.RFC1123); the "UTC"
+			// zone is rejected by http.ParseTime but was accepted before, so the
+			// RFC1123 fallback must keep it working.
+			name:     "If-Modified-Since RFC1123 UTC zone",
+			header:   s3_constants.IfModifiedSince,
+			value:    "Wed, 21 Oct 2015 07:28:00 UTC",
+			expected: time.Date(2015, time.October, 21, 7, 28, 0, 0, time.UTC),
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			r := reqWith(map[string]string{testCase.header: testCase.value})
+
+			headers, errCode := parseConditionalHeaders(r)
+			if errCode != s3err.ErrNone {
+				t.Fatalf("expected %s to be accepted, got %v", testCase.header, errCode)
+			}
+			if !headers.isSet {
+				t.Fatal("expected conditional headers to be marked set")
+			}
+			parsed := headers.ifModifiedSince
+			if testCase.header == s3_constants.IfUnmodifiedSince {
+				parsed = headers.ifUnmodifiedSince
+			}
+			if !parsed.Equal(testCase.expected) {
+				t.Fatalf("expected parsed time %v, got %v", testCase.expected, parsed)
+			}
+		})
+	}
+}
+
+func TestValidateConditionalCopyHeadersAcceptsHTTPDateFormats(t *testing.T) {
+	testCases := []struct {
+		name   string
+		header string
+		value  string
+		mtime  int64 // source mtime chosen so the condition passes
+	}{
+		{
+			name:   "X-Amz-Copy-Source-If-Modified-Since RFC850",
+			header: s3_constants.AmzCopySourceIfModifiedSince,
+			value:  "Sunday, 06-Nov-94 08:49:37 GMT",
+			mtime:  1577836800, // 2020-01-01, modified after the 1994 header
+		},
+		{
+			name:   "X-Amz-Copy-Source-If-Unmodified-Since ANSIC",
+			header: s3_constants.AmzCopySourceIfUnmodifiedSince,
+			value:  "Sun Nov  6 08:49:37 1994",
+			mtime:  631152000, // 1990-01-01, not modified after the 1994 header
+		},
+	}
+
+	var s3a *S3ApiServer // method does not use the receiver
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			r := reqWith(map[string]string{testCase.header: testCase.value})
+			entry := &filer_pb.Entry{Attributes: &filer_pb.FuseAttributes{Mtime: testCase.mtime}}
+
+			if errCode := s3a.validateConditionalCopyHeaders(r, entry); errCode != s3err.ErrNone {
+				t.Fatalf("expected %s to be accepted, got %v", testCase.header, errCode)
+			}
+		})
+	}
+}
+
 func TestBuildDeleteCondition(t *testing.T) {
 	t.Run("no If-Match is unconditional", func(t *testing.T) {
 		cond, ok := buildDeleteCondition(reqWith(nil))