92 lines
2.9 KiB
C
92 lines
2.9 KiB
C
#include "asn1.h"
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#ifdef UNITTEST
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#undef UNITTEST
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#include "scan_asn1tagint.c"
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#define UNITTEST
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#endif
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size_t scan_asn1tag(const char* src,const char* max,enum asn1_tagclass* tc,enum asn1_tagtype* tt,unsigned long* tag) {
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if (max<=src)
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return 0;
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*tc=(*src&0xC0);
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*tt=(*src&0x20);
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/* The lower 5 bits are the tag, unless it's 0x1f, in which case the
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* next bytes are the tag: always take the lower 7 bits; the last byte
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* in the sequence is marked by a cleared high bit */
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if ((*src & 0x1f) == 0x1f) {
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size_t res=scan_asn1tagint(src+1,max,tag);
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if (res && *tag < 0x1f) // non-minimal encoding
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return 0;
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return res+!!res; /* add 1 unless it's 0, then leave 0 */
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} else {
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*tag=*src&0x1f;
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return 1;
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}
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}
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#ifdef UNITTEST
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#include <assert.h>
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#include <string.h>
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#ifdef __linux__
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#include <sys/types.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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// This wrapper maps a 64k buffer of memory and makes sure the page
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// after it will cause a segfault when accessed. Then we copy the input
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// data at the end of the 64k. This is to catch out of bounds reads.
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size_t wrapper(const char* src,const char* max,enum asn1_tagclass* tc,enum asn1_tagtype* tt,unsigned long* tag) {
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static char* base;
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if (!base) {
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base=mmap(0,64*1024+4*1024,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0);
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assert(base!=MAP_FAILED);
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mprotect(base+64*1024,4*1024,PROT_NONE);
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}
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assert(src<=max && max-src<64*1024);
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{
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size_t l = max-src;
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char* dest=base+64*1024-l;
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memcpy(dest, src, l);
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return scan_asn1tag(dest, dest+l, tc, tt, tag);
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}
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}
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#define scan_asn1tag wrapper
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#endif
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int main() {
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enum asn1_tagclass tc;
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enum asn1_tagtype tt;
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unsigned long tag;
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char buf[15];
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memset(buf,0,sizeof buf);
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assert(scan_asn1tag(buf,buf,&tc,&tt,&tag)==0); // empty input
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strcpy(buf,"\x01"); assert(scan_asn1tag(buf,buf+1,&tc,&tt,&tag)==1 && tc==UNIVERSAL && tt==PRIMITIVE && tag==BOOLEAN);
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/* incomplete input */
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strcpy(buf,"\x1f"); assert(scan_asn1tag(buf,buf+1,&tc,&tt,&tag)==0);
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/* long-form encoding when short-form would have sufficed */
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strcpy(buf,"\x1f\x1e");
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assert(scan_asn1tag(buf,buf+2,&tc,&tt,&tag)==0);
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/* OK */
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strcpy(buf,"\x1f\x1f");
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assert(scan_asn1tag(buf,buf+2,&tc,&tt,&tag)==2 && tc==UNIVERSAL && tt==PRIMITIVE && tag==0x1f);
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/* non-minimal encoding */
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strcpy(buf,"\x1f\x80\x01");
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assert(scan_asn1tag(buf,buf+3,&tc,&tt,&tag)==0);
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/* incomplete encoding */
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assert(scan_asn1tag(buf,buf+2,&tc,&tt,&tag)==0);
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strcpy(buf,"\x1f\x81\x00");
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assert(scan_asn1tag(buf,buf+3,&tc,&tt,&tag)==3 && tc==UNIVERSAL && tt==PRIMITIVE && tag==0x80);
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/* value not representable */
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memcpy(buf,"\x1f\xff\xff\xff\xff\xff\xff\xff\xff\xff\x7f",11);
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assert(scan_asn1tag(buf,buf+11,&tc,&tt,&tag)==0);
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memcpy(buf,"\x1f\x8f\xff\xff\xff\x7f",7);
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assert(scan_asn1tag(buf,buf+7,&tc,&tt,&tag)==6 && tc==UNIVERSAL && tt==PRIMITIVE && tag==0xffffffff);
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return 0;
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}
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#endif
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