s3api: allow unsigned SSE-C customer key headers on presigned requests (#11578)

* s3api: allow unsigned SSE-C customer key headers on presigned requests

AWS requires only x-amz-server-side-encryption-customer-algorithm to be signed on presigned URLs; the key and key-MD5 headers are supplied at request time. Since #9121 rejected any x-amz-* header outside SignedHeaders, SDK-generated presigned SSE-C requests (e.g. .NET GetPreSignedUrlRequest) fail with SignatureDoesNotMatch. Exempt the customer key and copy-source key headers for presigned requests only.

* s3api: test presigned SSE-C requests carrying unsigned key headers

weed/s3api/auth_signature_v4.go

@@ -848,6 +848,16 @@ var presignedSigV4ProtocolHeaders = map[string]struct{}{
 	"x-amz-signature":     {},
 }
 
+// presignedUnsignedSSECHeaders exempts SSE-C key material that AWS requires to
+// be sent but not signed on presigned requests: only the algorithm header is
+// part of the signature calculation.
+var presignedUnsignedSSECHeaders = map[string]struct{}{
+	strings.ToLower(s3_constants.AmzServerSideEncryptionCustomerKey):              {},
+	strings.ToLower(s3_constants.AmzServerSideEncryptionCustomerKeyMD5):           {},
+	strings.ToLower(s3_constants.AmzCopySourceServerSideEncryptionCustomerKey):    {},
+	strings.ToLower(s3_constants.AmzCopySourceServerSideEncryptionCustomerKeyMD5): {},
+}
+
 // verifySignedHeadersCoverage rejects requests that carry x-amz-* headers
 // outside of the SignedHeaders list. AWS SigV4 requires every x-amz-* header
 // present in the request to be covered by the signature; without this check a
@@ -874,6 +884,9 @@ func verifySignedHeadersCoverage(r *http.Request, signedHeaders []string, isPres
 			if _, exempt := presignedSigV4ProtocolHeaders[lower]; exempt {
 				continue
 			}
+			if _, exempt := presignedUnsignedSSECHeaders[lower]; exempt {
+				continue
+			}
 		}
 		glog.V(2).Infof("reject %s %s: unsigned header %q not in SignedHeaders", r.Method, r.URL.Path, name)
 		return s3err.ErrSignatureDoesNotMatch

weed/s3api/auth_signature_v4_unsigned_headers_test.go

@@ -142,6 +142,50 @@ func TestVerifySignedHeadersCoverage_Unit(t *testing.T) {
 			signedHeaders: []string{"HOST", "X-Amz-Tagging"},
 			want:          s3err.ErrNone,
 		},
+		{
+			name: "presigned exempts unsigned SSE-C key headers",
+			headers: map[string]string{
+				"X-Amz-Server-Side-Encryption-Customer-Algorithm": "AES256",
+				"X-Amz-Server-Side-Encryption-Customer-Key":       "key",
+				"X-Amz-Server-Side-Encryption-Customer-Key-MD5":   "md5",
+			},
+			signedHeaders: []string{"host", "x-amz-server-side-encryption-customer-algorithm"},
+			isPresigned:   true,
+			want:          s3err.ErrNone,
+		},
+		{
+			name: "presigned exempts unsigned SSE-C copy-source key headers",
+			headers: map[string]string{
+				"X-Amz-Copy-Source-Server-Side-Encryption-Customer-Algorithm": "AES256",
+				"X-Amz-Copy-Source-Server-Side-Encryption-Customer-Key":       "key",
+				"X-Amz-Copy-Source-Server-Side-Encryption-Customer-Key-MD5":   "md5",
+			},
+			signedHeaders: []string{"host", "x-amz-copy-source-server-side-encryption-customer-algorithm"},
+			isPresigned:   true,
+			want:          s3err.ErrNone,
+		},
+		{
+			name: "presigned still requires SSE-C algorithm to be signed",
+			headers: map[string]string{
+				"X-Amz-Server-Side-Encryption-Customer-Algorithm": "AES256",
+				"X-Amz-Server-Side-Encryption-Customer-Key":       "key",
+				"X-Amz-Server-Side-Encryption-Customer-Key-MD5":   "md5",
+			},
+			signedHeaders: []string{"host"},
+			isPresigned:   true,
+			want:          s3err.ErrSignatureDoesNotMatch,
+		},
+		{
+			name: "header-based does NOT exempt unsigned SSE-C key headers",
+			headers: map[string]string{
+				"X-Amz-Server-Side-Encryption-Customer-Algorithm": "AES256",
+				"X-Amz-Server-Side-Encryption-Customer-Key":       "key",
+				"X-Amz-Server-Side-Encryption-Customer-Key-MD5":   "md5",
+			},
+			signedHeaders: []string{"host", "x-amz-server-side-encryption-customer-algorithm"},
+			isPresigned:   false,
+			want:          s3err.ErrSignatureDoesNotMatch,
+		},
 	}
 
 	for _, tt := range tests {
@@ -203,6 +247,29 @@ func TestPresignedPutAcceptsSignedTagging(t *testing.T) {
 	}
 }
 
+// TestPresignedGetAcceptsUnsignedSSECKeyHeaders mirrors the AWS SDK presign
+// flow for SSE-C objects: only the algorithm header is signed while the key
+// and key-MD5 headers are attached to the request unsigned.
+func TestPresignedGetAcceptsUnsignedSSECKeyHeaders(t *testing.T) {
+	iam := newTestIAM()
+
+	req, err := newTestRequest(http.MethodGet, "http://127.0.0.1:9000/bucket/key", 0, nil)
+	if err != nil {
+		t.Fatalf("newTestRequest: %v", err)
+	}
+	req.Header.Set("X-Amz-Server-Side-Encryption-Customer-Algorithm", "AES256")
+	if err := preSignV4WithHeaders(iam, req, "AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY", 600, []string{"host", "x-amz-server-side-encryption-customer-algorithm"}); err != nil {
+		t.Fatalf("preSignV4WithHeaders: %v", err)
+	}
+	req.Header.Set("X-Amz-Server-Side-Encryption-Customer-Key", "MDEyMzQ1Njc4OTAxMjM0NTY3ODkwMTIzNDU2Nzg5MDE=")
+	req.Header.Set("X-Amz-Server-Side-Encryption-Customer-Key-MD5", "md5")
+
+	_, errCode := iam.reqSignatureV4Verify(req)
+	if errCode != s3err.ErrNone {
+		t.Fatalf("expected ErrNone for presigned SSE-C with unsigned key headers, got %v", errCode)
+	}
+}
+
 // preSignV4WithHeaders is a test helper that builds a presigned URL whose
 // SignedHeaders list covers the specified headers (which must already be set
 // on the request), then computes the signature over those headers and