Skip to content

image: require BMP file header, not just BM #160

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
team-humaki wants to merge 1 commit into
base: master
Choose a base branch
from
Open

image: require BMP file header, not just BM #160

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
35 changes: 35 additions & 0 deletions match_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,16 @@ func TestMatch(t *testing.T) {
{[]byte{0xFF, 0xD8, 0xFF}, "jpg"},
{[]byte{0xFF, 0xD8, 0x00}, "unknown"},
{[]byte{0x89, 0x50, 0x4E, 0x47}, "png"},
{[]byte("BMW"), "unknown"},
{
[]byte{
'B', 'M',
0x3A, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x36, 0x00, 0x00, 0x00,
},
"bmp",
},
}

for _, test := range cases {
Expand All @@ -32,6 +42,30 @@ func TestMatch(t *testing.T) {
}
}

func TestBmpNotAsciiPrefix(t *testing.T) {
// Issue #117: "BMW" starts with BM but is not a BMP file.
kind, err := Match([]byte("BMW"))
if err != nil {
t.Fatalf("Match: %v", err)
}
if kind.Extension == "bmp" {
t.Fatalf("ASCII BMW matched as bmp")
}
if matchers.Bmp([]byte("BMW")) {
t.Fatalf("Bmp matcher accepted ASCII BMW")
}

header := make([]byte, 14)
header[0], header[1] = 'B', 'M'
if !matchers.Bmp(header) {
t.Fatalf("14-byte BM header with reserved=0 should match")
}
header[6] = 1
if matchers.Bmp(header) {
t.Fatalf("non-zero reserved field should not match")
}
}

func TestMatchFile(t *testing.T) {
cases := []struct {
ext string
Expand Down Expand Up @@ -100,6 +134,7 @@ func TestMatches(t *testing.T) {
{[]byte{0xFF, 0xD8, 0xFF}, true},
{[]byte{0xFF, 0x0, 0x0}, false},
{[]byte{0x89, 0x50, 0x4E, 0x47}, true},
{[]byte("BMW"), false},
}

for _, test := range cases {
Expand Down
12 changes: 9 additions & 3 deletions matchers/image.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -95,9 +95,15 @@ func Tiff(buf []byte) bool {
}

func Bmp(buf []byte) bool {
return len(buf) > 1 &&
buf[0] == 0x42 &&
buf[1] == 0x4D
// BITMAPFILEHEADER is 14 bytes: "BM" + size + reserved (must be 0) + pixel offset.
// Matching only "BM" treats short ASCII like "BMW" as image/bmp (issue #117).
if len(buf) < 14 {
return false
}
if buf[0] != 0x42 || buf[1] != 0x4D {
return false
}
return buf[6] == 0 && buf[7] == 0 && buf[8] == 0 && buf[9] == 0
}

func Jxr(buf []byte) bool {
Expand Down