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Fix TIFF color map index bounds #573

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Merged
treeform merged 1 commit into from
Apr 30, 2026
Merged

Fix TIFF color map index bounds #573

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2 changes: 1 addition & 1 deletion src/pixie/fileformats/tiff.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -234,7 +234,7 @@ proc decodeTiff*(data: string): Tiff =
failInvalid()
for i in 0 ..< result.data.len:
let colorMapIndex = decompressed[i].int
if colorMapIndex > colorMap.len:
if colorMapIndex >= colorMap.len:
failInvalid()
result.data[i] = colorMap[colorMapIndex]

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49 changes: 49 additions & 0 deletions tests/test_tiff.nim
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Expand Up @@ -4,3 +4,52 @@ let
t = decodeTiff(readFile("tests/fileformats/tiff/pc260001.tif"))
image = newImage(t)
# image.writeFile("tests/fileformats/tiff/pc260001.png")

block:
proc addLe16(data: var string, value: int) =
data.add(char(value and 0xff))
data.add(char((value shr 8) and 0xff))

proc addLe32(data: var string, value: int) =
data.add(char(value and 0xff))
data.add(char((value shr 8) and 0xff))
data.add(char((value shr 16) and 0xff))
data.add(char((value shr 24) and 0xff))

proc addIfdEntry(
data: var string,
tag, fieldType, numValues, valueOrOffset: int
) =
data.addLe16(tag)
data.addLe16(fieldType)
data.addLe32(numValues)
data.addLe32(valueOrOffset)

const
ifdOffset = 8
entryCount = 9
colorMapOffset = ifdOffset + 2 + entryCount * 12 + 4
pixelDataOffset = colorMapOffset + 6

var payload = ""
payload.add("II")
payload.addLe16(42)
payload.addLe32(ifdOffset)
payload.addLe16(entryCount)
payload.addIfdEntry(0x0100, 4, 1, 1) # ImageWidth
payload.addIfdEntry(0x0101, 4, 1, 1) # ImageLength
payload.addIfdEntry(0x0102, 3, 1, 8) # BitsPerSample
payload.addIfdEntry(0x0103, 3, 1, 1) # Compression = none
payload.addIfdEntry(0x0106, 3, 1, 3) # PhotometricInterpretation = palette
payload.addIfdEntry(0x0111, 4, 1, pixelDataOffset)
payload.addIfdEntry(0x0116, 4, 1, 1) # RowsPerStrip
payload.addIfdEntry(0x0117, 4, 1, 1) # StripByteCounts
payload.addIfdEntry(0x0140, 3, 3, colorMapOffset)
payload.addLe32(0)
payload.addLe16(0)
payload.addLe16(0)
payload.addLe16(0)
payload.add(char(0x01))

doAssertRaises PixieError:
discard decodeTiff(payload)