Added emblem blank pixels check

- Made possible thanks to (and using base code by) Ai4rei - eAthena
  r15263 and add-on patch
  http://hercules.ws/board/topic/2974-add-on-patch-for-ea-r15263-commit/
- Modified to allow checking for a percentage of transparent pixels
  rather than full image transparency.
- Tweaked to accept some other bmp formats that are currently allowed
  by the client.
- The performance hit from enabling this check is negligible (benchmarks
  show that scanning an emblem requires about half the time required to
  decompress it after it's received), but it does exist, as noted in the
  configuration file.
- Special thanks to Ind.

Signed-off-by: Haru <haru@dotalux.com>

1 files changed, 112 insertions, 10 deletions

diff --git a/src/map/clif.c b/src/map/clif.c
index 6740c7a74..c509da7dd 100644
--- a/src/map/clif.c
+++ b/src/map/clif.c
@@ -12967,20 +12967,122 @@ void clif_parse_GuildRequestEmblem(int fd,struct map_session_data *sd)
 		clif->guild_emblem(sd,g);
 }
 
-
 /// Validates data of a guild emblem (compressed bitmap)
-bool clif_validate_emblem(const uint8* emblem, unsigned long emblem_len) {
-	bool success;
-	uint8 buf[1800];  // no well-formed emblem bitmap is larger than 1782 (24 bit) / 1654 (8 bit) bytes
+bool clif_validate_emblem(const uint8 *emblem, unsigned long emblem_len) {
+	enum e_bitmapconst {
+		RGBTRIPLE_SIZE = 3,         // sizeof(RGBTRIPLE)
+		RGBQUAD_SIZE = 4,           // sizeof(RGBQUAD)
+		BITMAPFILEHEADER_SIZE = 14, // sizeof(BITMAPFILEHEADER)
+		BITMAPINFOHEADER_SIZE = 40, // sizeof(BITMAPINFOHEADER)
+		BITMAP_WIDTH = 24,
+		BITMAP_HEIGHT = 24,
+	};
+#pragma pack(push, 1)
+	struct s_bitmaptripple {
+		//uint8 b;
+		//uint8 g;
+		//uint8 r;
+		unsigned int rgb:24;
+	} __attribute__((packed));
+#pragma pack(pop)
+	uint8 buf[1800]; // no well-formed emblem bitmap is larger than 1782 (24 bit) / 1654 (8 bit) bytes
 	unsigned long buf_len = sizeof(buf);
+	int header = 0, bitmap = 0, offbits = 0, palettesize = 0, i = 0;
+
+	if( decode_zip(buf, &buf_len, emblem, emblem_len) != 0 || buf_len < BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE
+	 || RBUFW(buf,0) != 0x4d42 // BITMAPFILEHEADER.bfType (signature)
+	 || RBUFL(buf,2) != buf_len // BITMAPFILEHEADER.bfSize (file size)
+	 || RBUFL(buf,14) != BITMAPINFOHEADER_SIZE // BITMAPINFOHEADER.biSize (other headers are not supported)
+	 || RBUFL(buf,18) != BITMAP_WIDTH // BITMAPINFOHEADER.biWidth
+	 || RBUFL(buf,22) != BITMAP_HEIGHT // BITMAPINFOHEADER.biHeight (top-down bitmaps (-24) are not supported)
+	 || RBUFL(buf,30) != 0 // BITMAPINFOHEADER.biCompression == BI_RGB (compression not supported)
+	 ) {
+		// Invalid data
+		return false;
+	}
 
-	success = ( decode_zip(buf, &buf_len, emblem, emblem_len) == 0 && buf_len >= 18 )  // sizeof(BITMAPFILEHEADER) + sizeof(biSize) of the following info header struct
-			&& RBUFW(buf,0) == 0x4d42   // BITMAPFILEHEADER.bfType (signature)
-			&& RBUFL(buf,2) == buf_len  // BITMAPFILEHEADER.bfSize (file size)
-			&& RBUFL(buf,10) < buf_len  // BITMAPFILEHEADER.bfOffBits (offset to bitmap bits)
-			;
+	offbits = RBUFL(buf,10); // BITMAPFILEHEADER.bfOffBits (offset to bitmap bits)
+
+	switch( RBUFW(buf,28) ) { // BITMAPINFOHEADER.biBitCount
+		case 8:
+			palettesize = RBUFL(buf,46); // BITMAPINFOHEADER.biClrUsed (number of colors in the palette)
+			if( palettesize == 0 )
+				palettesize = 256; // Defaults to 2^n if set to zero
+			else if( palettesize > 256 )
+				return false;
+			header = BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE + RGBQUAD_SIZE * palettesize; // headers + palette
+			bitmap = BITMAP_WIDTH * BITMAP_HEIGHT;
+			break;
+		case 24:
+			header = BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE;
+			bitmap = BITMAP_WIDTH * BITMAP_HEIGHT * RGBTRIPLE_SIZE;
+			break;
+		default:
+			return false;
+	}
+
+	// NOTE: This check gives a little freedom for bitmap-producing implementations,
+	// that align the start of bitmap data, which is harmless but unnecessary.
+	// If you want it paranoidly strict, change the first condition from < to !=.
+	// This also allows files with trailing garbage at the end of the file.
+	// If you want to avoid that, change the last condition to !=.
+	if( offbits < header || buf_len <= bitmap || offbits > buf_len - bitmap ) {
+		return false;
+	}
 
-	return success;
+	if( battle_config.client_emblem_max_blank_percent < 100 ) {
+		int required_pixels = BITMAP_WIDTH * BITMAP_HEIGHT * (100 - battle_config.client_emblem_max_blank_percent) / 100;
+		int found_pixels = 0;
+		/// Checks what percentage of a guild emblem is blank. A blank emblem
+		/// consists solely of magenta pixels. Since the client uses 16-bit
+		/// colors, any magenta shade that reduces to #ff00ff passes off as
+		/// transparent color as well (down to #f807f8).
+		///
+		/// Unlike real magenta, reduced magenta causes the guild window to
+		/// become see-through in the transparent parts of the emblem
+		/// background (glitch).
+		switch( RBUFW(buf,28) ) {
+			case 8: // palette indexes
+			{
+				const uint8 *indexes = (const uint8 *)RBUFP(buf,offbits);
+				const uint32 *palette = (const uint32 *)RBUFP(buf,BITMAPFILEHEADER_SIZE + BITMAPINFOHEADER_SIZE);
+
+				for( i = 0; i < BITMAP_WIDTH * BITMAP_HEIGHT; i++ ) {
+					if( indexes[i] >= palettesize ) // Invalid color
+						return false;
+
+					// if( color->r < 0xF8 || color->g > 0x07 || color->b < 0xF8 )
+					if( ( palette[indexes[i]]&0x00F8F8F8 ) != 0x00F800F8 ) {
+						if( ++found_pixels >= required_pixels ) {
+							// Enough valid pixels were found
+							return true;
+						}
+					}
+				}
+				break;
+			}
+			case 24: // full colors
+			{
+				const struct s_bitmaptripple *pixels = (const struct s_bitmaptripple*)RBUFP(buf,offbits);
+
+				for( i = 0; i < BITMAP_WIDTH * BITMAP_HEIGHT; i++ ) {
+					// if( pixels[i].r < 0xF8 || pixels[i].g > 0x07 || pixels[i].b < 0xF8 )
+					if( ( pixels[i].rgb&0xF8F8F8 ) != 0xF800F8 ) {
+						if( ++found_pixels >= required_pixels ) {
+							// Enough valid pixels were found
+							return true;
+						}
+					}
+				}
+				break;
+			}
+		}
+
+		// Not enough non-blank pixels found
+		return false;
+	}
+
+	return true;
 }