@@ -2,6 +2,7 @@ package dockerignore

 import (

 	"bufio"

+	"bytes"

 	"fmt"

 	"io"

 	"path/filepath"

@@ -18,10 +19,18 @@ func ReadAll(reader io.ReadCloser) ([]string, error) {

 	defer reader.Close()

 	scanner := bufio.NewScanner(reader)

 	var excludes []string

+	currentLine := 0

+	utf8bom := []byte{0xEF, 0xBB, 0xBF}

 	for scanner.Scan() {

+		scannedBytes := scanner.Bytes()

+		// We trim UTF8 BOM

+		if currentLine == 0 {

+			scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)

+		}

+		pattern := string(scannedBytes)

+		currentLine++

 		// Lines starting with # (comments) are ignored before processing

-		pattern := scanner.Text()

 		if strings.HasPrefix(pattern, "#") {

 			continue

 		}

@@ -6805,3 +6805,27 @@ func (s *DockerSuite) TestBuildWithUTF8BOM(c *check.C) {

 	_, err = buildImageFromContext(name, ctx, true)

 	c.Assert(err, check.IsNil)

 }

+

+// Test case for UTF-8 BOM in .dockerignore, related to #23221

+func (s *DockerSuite) TestBuildWithUTF8BOMDockerignore(c *check.C) {

+	name := "test-with-utf8-bom-dockerignore"

+	dockerfile := `

+        FROM busybox

+		ADD . /tmp/

+		RUN ls -la /tmp

+		RUN sh -c "! ls /tmp/Dockerfile"

+		RUN ls /tmp/.dockerignore`

+	dockerignore := []byte("./Dockerfile\n")

+	bomDockerignore := append([]byte{0xEF, 0xBB, 0xBF}, dockerignore...)

+	ctx, err := fakeContext(dockerfile, map[string]string{

+		"Dockerfile": dockerfile,

+	})

+	c.Assert(err, check.IsNil)

+	defer ctx.Close()

+	err = ctx.addFile(".dockerignore", bomDockerignore)

+	c.Assert(err, check.IsNil)

+	_, err = buildImageFromContext(name, ctx, true)

+	if err != nil {

+		c.Fatal(err)

+	}

+}