1 #include "asn1.h"
2
scan_asn1BITSTRING(const char * src,const char * max,const char ** s,size_t * l)3 size_t scan_asn1BITSTRING(const char* src,const char* max,const char** s,size_t* l) {
4 size_t tmp;
5 unsigned long tag;
6 enum asn1_tagclass tc;
7 enum asn1_tagtype tt;
8 if ((tmp=scan_asn1string(src,max,&tc,&tt,&tag,s,l)))
9 if (tc==UNIVERSAL && tt==PRIMITIVE && tag==BIT_STRING) {
10 unsigned char lastbyte;
11 if (*l==0 || /* length must be at least 1 because for bit strings, the first octet contains the number of unused bits in the last octet */
12 (unsigned char)(**s)>7) /* the number of unused bits in the last octet must not be negative and can be at most 7 */
13 return 0;
14 /* these are DER checks */
15 /* can't have unused bits if the length is 0 */
16 if (*l==1 && **s)
17 return 0;
18 /* now check if the unused bits are 0 */
19 lastbyte=(*s)[*l+1];
20 if (lastbyte & (0xff >> (8-**s)))
21 return 0;
22 *l=(*l-1)*8-(unsigned char)(**s);
23 ++*s;
24 return tmp;
25 }
26 return 0;
27 }
28