CVE-2019-17113: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') (CWE-120)
value: In libopenmpt before 0.3.19 and 0.4.x before 0.4.9, ModPlug_InstrumentName and ModPlug_SampleName in libopenmpt_modplug.c do not restrict the lengths of libmodplug output-buffer strings in the C API, leading to a buffer overflow.
CWE description: The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.
CVSS v3 base score: 9.8
Published: 2019-10-04T00:15Z
Repository: https://github.com/OpenMPT/openmpt
Language: C
Files changed: libopenmpt/libopenmpt_modplug.c
Commit date: 2019-10-02 13:37:46 +0000
Commit message: [Fix] libmodplug: C API: Limit the length of strings copied to the output buffer of ModPlug_InstrumentName() and ModPlug_SampleName() to 32 bytes (including terminating null) as is done by original libmodplug. This avoids potential buffer overflows in software relying on this limit instead of querying the required buffer size beforehand. libopenmpt can return strings longer than 32 bytes here beacuse the internal limit of 32 bytes applies to strings encoded in arbitrary character encodings but the API returns them converted to UTF-8, which can be longer. (reported by Antonio Morales Maldonado of Semmle Security Research Team)

git-svn-id: https://source.openmpt.org/svn/openmpt/trunk/OpenMPT@12127 56274372-70c3-4bfc-bfc3-4c3a0b034d27

Diff: diff --git a/libopenmpt/libopenmpt_modplug.c b/libopenmpt/libopenmpt_modplug.c
index d5b469552..da13edc3f 100644
--- a/libopenmpt/libopenmpt_modplug.c
+++ b/libopenmpt/libopenmpt_modplug.c
@@ -476,57 +476,39 @@ LIBOPENMPT_MODPLUG_API unsigned int ModPlug_NumChannels(ModPlugFile* file)
 }
 
 LIBOPENMPT_MODPLUG_API unsigned int ModPlug_SampleName(ModPlugFile* file, unsigned int qual, char* buff)
 {
 	const char* str;
-	unsigned int retval;
-	size_t tmpretval;
+	char buf[32];
 	if(!file) return 0;
 	str = openmpt_module_get_sample_name(file->mod,qual-1);
-	if(!str){
-		if(buff){
-			*buff = '\0';
-		}
-		return 0;
-	}
-	tmpretval = strlen(str);
-	if(tmpretval>=INT_MAX){
-		tmpretval = INT_MAX-1;
+	memset(buf,0,32);
+	if(str){
+		strncpy(buf,str,31);
+		openmpt_free_string(str);
 	}
-	retval = (int)tmpretval;
 	if(buff){
-		memcpy(buff,str,retval+1);
-		buff[retval] = '\0';
+		strncpy(buff,buf,32);
 	}
-	openmpt_free_string(str);
-	return retval;
+	return (unsigned int)strlen(buf);
 }
 
 LIBOPENMPT_MODPLUG_API unsigned int ModPlug_InstrumentName(ModPlugFile* file, unsigned int qual, char* buff)
 {
 	const char* str;
-	unsigned int retval;
-	size_t tmpretval;
+	char buf[32];
 	if(!file) return 0;
 	str = openmpt_module_get_instrument_name(file->mod,qual-1);
-	if(!str){
-		if(buff){
-			*buff = '\0';
-		}
-		return 0;
-	}
-	tmpretval = strlen(str);
-	if(tmpretval>=INT_MAX){
-		tmpretval = INT_MAX-1;
+	memset(buf,0,32);
+	if(str){
+		strncpy(buf,str,31);
+		openmpt_free_string(str);
 	}
-	retval = (int)tmpretval;
 	if(buff){
-		memcpy(buff,str,retval+1);
-		buff[retval] = '\0';
+		strncpy(buff,buf,32);
 	}
-	openmpt_free_string(str);
-	return retval;
+	return (unsigned int)strlen(buf);
 }
 
 LIBOPENMPT_MODPLUG_API ModPlugNote* ModPlug_GetPattern(ModPlugFile* file, int pattern, unsigned int* numrows)
 {
 	int c;

Vulnerable code: 	unsigned int retval;
	size_t tmpretval;
	if(!str){
		if(buff){
			*buff = '\0';
		}
		return 0;
	}
	tmpretval = strlen(str);
	if(tmpretval>=INT_MAX){
		tmpretval = INT_MAX-1;
	retval = (int)tmpretval;
		memcpy(buff,str,retval+1);
		buff[retval] = '\0';
	openmpt_free_string(str);
	return retval;
	unsigned int retval;
	size_t tmpretval;
	if(!str){
		if(buff){
			*buff = '\0';
		}
		return 0;
	}
	tmpretval = strlen(str);
	if(tmpretval>=INT_MAX){
		tmpretval = INT_MAX-1;
	retval = (int)tmpretval;
		memcpy(buff,str,retval+1);
		buff[retval] = '\0';
	openmpt_free_string(str);
	return retval;
Fixed code: 	char buf[32];
	memset(buf,0,32);
	if(str){
		strncpy(buf,str,31);
		openmpt_free_string(str);
		strncpy(buff,buf,32);
	return (unsigned int)strlen(buf);
	char buf[32];
	memset(buf,0,32);
	if(str){
		strncpy(buf,str,31);
		openmpt_free_string(str);
		strncpy(buff,buf,32);
	return (unsigned int)strlen(buf);