Return error when a bit string indicates an invalid amount of bits left

Reviewed-by: Matt Caswell <matt@openssl.org>

Author: kroeckx

crypto/asn1/a_bitstr.c

@@ -136,11 +136,16 @@ ASN1_BIT_STRING *c2i_ASN1_BIT_STRING(ASN1_BIT_STRING **a,
 
 	p= *pp;
 	i= *(p++);
+	if (i > 7)
+		{
+		i=ASN1_R_INVALID_BIT_STRING_BITS_LEFT;
+		goto err;
+		}
 	/* We do this to preserve the settings.  If we modify
 	 * the settings, via the _set_bit function, we will recalculate
 	 * on output */
 	ret->flags&= ~(ASN1_STRING_FLAG_BITS_LEFT|0x07); /* clear */
-	ret->flags|=(ASN1_STRING_FLAG_BITS_LEFT|(i&0x07)); /* set */
+	ret->flags|=(ASN1_STRING_FLAG_BITS_LEFT|i); /* set */
 
 	if (len-- > 1) /* using one because of the bits left byte */
 		{

crypto/asn1/asn1.h

@@ -1329,6 +1329,7 @@ void ERR_load_ASN1_strings(void);
 #define ASN1_R_ILLEGAL_TIME_VALUE			 184
 #define ASN1_R_INTEGER_NOT_ASCII_FORMAT			 185
 #define ASN1_R_INTEGER_TOO_LARGE_FOR_LONG		 128
+#define ASN1_R_INVALID_BIT_STRING_BITS_LEFT		 220
 #define ASN1_R_INVALID_BMPSTRING_LENGTH			 129
 #define ASN1_R_INVALID_DIGIT				 130
 #define ASN1_R_INVALID_MIME_TYPE			 205

crypto/asn1/asn1_err.c

@@ -246,6 +246,7 @@ static ERR_STRING_DATA ASN1_str_reasons[]=
 {ERR_REASON(ASN1_R_ILLEGAL_TIME_VALUE)   ,"illegal time value"},
 {ERR_REASON(ASN1_R_INTEGER_NOT_ASCII_FORMAT),"integer not ascii format"},
 {ERR_REASON(ASN1_R_INTEGER_TOO_LARGE_FOR_LONG),"integer too large for long"},
+{ERR_REASON(ASN1_R_INVALID_BIT_STRING_BITS_LEFT),"invalid bit string bits left"},
 {ERR_REASON(ASN1_R_INVALID_BMPSTRING_LENGTH),"invalid bmpstring length"},
 {ERR_REASON(ASN1_R_INVALID_DIGIT)        ,"invalid digit"},
 {ERR_REASON(ASN1_R_INVALID_MIME_TYPE)    ,"invalid mime type"},