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openSUSE patch: https://build.opensuse.org/package/view_file/openSUSE:Factory/mp3gain/0001-fix-security-bugs.patch?expand=1
Gentoo bug: https://bugs.gentoo.org/717940
----
From: Jason Craig <os-dev@jacraig.com>
Date: Mon, 30 Mar 2020 12:43:20 -0600
Subject: [PATCH] Fix various security issues including CVE-2019-18359
References: boo#1154971
Upstream: dead

Multiple POCs at https://github.com/zjuchenyuan/fuzzpoc were fixed.
--- a/apetag.c
+++ b/apetag.c
@@ -16,6 +16,13 @@
 #define _stricmp strcasecmp
 #endif /* WIN32 */
 
+// Min and max values for gain and peak in order to fit in allotted space in the APE tags. For gain that is nine chars,
+// including a + or -. For peak that is eight chars, including a - but no +. Both will always have six precision digits.
+#define MIN_GAIN -9.999999
+#define MAX_GAIN 9.999999
+#define MIN_PEAK -9.99999
+#define MAX_PEAK 9.999999
+
 int ReadMP3ID3v1Tag(FILE *fi, unsigned char **tagbuff, long *tag_offset) {
     char tmp[128];
 
@@ -102,9 +109,9 @@ static int ReadMP3Lyrics3v2Tag ( FILE *fp, unsigned char **tagbuff, unsigned lon
 	if ( fseek (fp, *tag_offset - 128 - (long)sizeof (T) - len, SEEK_SET) ) return 0;
     if ( fread  (tmp, 1, 11, fp) != 11 ) return 0;
     if ( memcmp (tmp, "LYRICSBEGIN", 11) ) return 0;
-    
+
     taglen = 128 + Lyrics3GetNumber6(T.Length) + sizeof(T);
-    
+
     *tag_offset -= taglen;
     if (*tagbuff != NULL) {
         free(*tagbuff);
@@ -142,7 +149,7 @@ enum {
 
 unsigned long strlen_max(const char * ptr, unsigned long max) {
 	unsigned long n = 0;
-	while (ptr[n] && n < max) n++;
+	while (n < max && ptr[n]) n++;
 	return n;
 }
 
@@ -234,6 +241,14 @@ int ReadMP3APETag ( FILE *fp,  struct MP3GainTagInfo *info, struct APETagStruct
                 info->albumPeak = atof(value);
             } else if (!_stricmp(name,"MP3GAIN_UNDO")) {
 				/* value should be something like "+003,+003,W" */
+				/* If the file didn't specify enough bytes for the value (at least 11...see above), skip the tag. */
+				if(vsize < 11)
+				{
+					free(value);
+					free(name);
+					p += isize + 1 + vsize;
+					continue;
+				}
                 info->haveUndo = !0;
                 vp = value;
 				memcpy(tmpString,vp,4);
@@ -251,6 +266,14 @@ int ReadMP3APETag ( FILE *fp,  struct MP3GainTagInfo *info, struct APETagStruct
                 }
             } else if (!_stricmp(name,"MP3GAIN_MINMAX")) {
 				/* value should be something like "001,153" */
+				/* If the file didn't specify enough bytes for the value (at least 7...see above), skip the tag. */
+				if(vsize < 7)
+				{
+					free(value);
+					free(name);
+					p += isize + 1 + vsize;
+					continue;
+				}
                 info->haveMinMaxGain = !0;
                 vp = value;
 				memcpy(tmpString,vp,3);
@@ -289,7 +312,7 @@ int ReadMP3APETag ( FILE *fp,  struct MP3GainTagInfo *info, struct APETagStruct
     }
 
     free (buff);
-    
+
 	*tag_offset -= TagLen;
 	(*apeTag)->originalTagSize = TagLen;
 
@@ -318,7 +341,7 @@ int ReadMP3APETag ( FILE *fp,  struct MP3GainTagInfo *info, struct APETagStruct
 int truncate_file (char *filename, long truncLength) {
 
 #ifdef WIN32
-    
+
    int fh, result;
 
    /* Open a file */
@@ -370,10 +393,10 @@ int ReadMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct FileT
     fi = fopen(filename, "rb");
     if (fi == NULL)
 		return 0;
-	
+
 	fseek(fi, 0, SEEK_END);
     tag_offset = file_size = ftell(fi);
-	
+
 	fileTags->lyrics3TagSize = 0;
 
     do {
@@ -515,7 +538,7 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
 		Write_LE_Uint32(newFooter.Flags,1<<31); /* tag has header */
 		memset(newFooter.Reserved,0,sizeof(newFooter.Reserved));
 	}
-	
+
 	if (info->haveMinMaxGain) {
 		/* 8 bytes + "MP3GAIN_MINMAX" + '/0' + "123,123" = 30 bytes */
 		Write_LE_Uint32(mp3gainTagData,7);
@@ -575,7 +598,10 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
 		mp3gainTagData += 4;
 		strcpy(mp3gainTagData, "REPLAYGAIN_TRACK_GAIN");
 		mp3gainTagData += 22;
-		sprintf(valueString,"%-+9.6f", info->trackGain);
+		// Clamp the gain value to ensure that sprintf won't put more than 9 chars in valueString. In cases of very
+		// large trackGain value, valueString could overflow.
+		sprintf(valueString, "%-+9.6f", info->trackGain < MIN_GAIN ? MIN_GAIN
+			: (info->trackGain > MAX_GAIN ? MAX_GAIN : info->trackGain));
 		memcpy(mp3gainTagData, valueString, 9);
 		mp3gainTagData += 9;
 		memcpy(mp3gainTagData, " dB", 3);
@@ -589,7 +615,10 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
 		mp3gainTagData += 4;
 		strcpy(mp3gainTagData, "REPLAYGAIN_TRACK_PEAK");
 		mp3gainTagData += 22;
-		sprintf(valueString,"%-8.6f", info->trackPeak);
+		// Clamp the peak value to ensure that sprintf won't put more than 8 chars in valueString. In cases of very
+		// large trackPeak value, valueString could overflow.
+		sprintf(valueString,"%-8.6f", info->trackPeak < MIN_PEAK ? MIN_PEAK
+			: (info->trackPeak > MAX_PEAK ? MAX_PEAK : info->trackPeak));
 		memcpy(mp3gainTagData, valueString, 8);
 		mp3gainTagData += 8;
 	}
@@ -601,7 +630,9 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
 		mp3gainTagData += 4;
 		strcpy(mp3gainTagData, "REPLAYGAIN_ALBUM_GAIN");
 		mp3gainTagData += 22;
-		sprintf(valueString,"%-+9.6f", info->albumGain);
+		// Clamp the gain value, see haveTrackGain if above.
+		sprintf(valueString,"%-+9.6f", info->albumGain < MIN_GAIN ? MIN_GAIN
+			: (info->albumGain > MAX_GAIN ? MAX_GAIN : info->albumGain));
 		memcpy(mp3gainTagData, valueString, 9);
 		mp3gainTagData += 9;
 		memcpy(mp3gainTagData, " dB", 3);
@@ -615,7 +646,9 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
 		mp3gainTagData += 4;
 		strcpy(mp3gainTagData, "REPLAYGAIN_ALBUM_PEAK");
 		mp3gainTagData += 22;
-		sprintf(valueString,"%-8.6f", info->albumPeak);
+		// Clamp the peak value, see haveTrackPeak if above.
+		sprintf(valueString,"%-8.6f", info->albumPeak < MIN_PEAK ? MIN_PEAK
+			: (info->albumPeak > MAX_PEAK ? MAX_PEAK : info->albumPeak));
 		memcpy(mp3gainTagData, valueString, 8);
 		mp3gainTagData += 8;
 	}
@@ -641,7 +674,7 @@ int WriteMP3GainAPETag (char *filename, struct MP3GainTagInfo *info, struct File
     }                                                  //no Lyrics3 tag
 
 	fclose(outputFile);
-	
+
 	if (saveTimeStamp)
 		fileTime(filename,setStoredTime);
 
@@ -666,7 +699,7 @@ int RemoveMP3GainAPETag (char *filename, int saveTimeStamp) {
 	info.haveMinMaxGain = 0;
 	info.haveAlbumMinMaxGain = 0;
 	info.haveUndo = 0;
-    
+
     fileTags.apeTag = NULL;
     fileTags.id31tag = NULL;
     fileTags.lyrics3tag = NULL;