52 lines
1.8 KiB
C
52 lines
1.8 KiB
C
#include "asn1.h"
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size_t scan_asn1rawint(const char* src,const char* max,size_t len,long* l) {
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size_t i;
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long m;
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if (src>=max || max-src<len)
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return 0; // input buffer too small
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m=(*src>>7); // -1 if negative, 0 otherwise
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// if (*src<0) m=-1; else m=0; // negative number?
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if (len>1 && *src==m) {
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// we want to catch things like 00 01
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// but a leading 0 byte is needed for 00 a0 because otherwise it would be -96
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if ((src[1]>>7)==m)
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return 0; // non-minimal encoding
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if (len>sizeof(m)+1)
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return 0; // value too large, does not fit
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} else
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if (len>sizeof(m))
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return 0; // value too large, does not fit
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for (i=0; i<len; ++i) {
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m=(m<<8)|(unsigned char)src[i];
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}
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*l=m;
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return len;
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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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int main() {
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char buf[10];
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long l;
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assert(scan_asn1rawint(buf, buf, 0, &l) == 0); // no input
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assert(scan_asn1rawint(buf, buf+10, 0, &l) == 0); // no input
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strcpy(buf,"\x01");
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assert(scan_asn1rawint(buf, buf+10, 1, &l) == 1 && l == 1); // OK
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memcpy(buf,"\x00\x01",2);
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assert(scan_asn1rawint(buf, buf+10, 1, &l) == 1 && l == 0); // OK
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assert(scan_asn1rawint(buf, buf+10, 2, &l) == 0); // non-minimal
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memcpy(buf,"\xa0",1);
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assert(scan_asn1rawint(buf, buf+10, 1, &l) == 1 && l == -96); // OK
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memcpy(buf,"\x00\xa0",2);
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assert(scan_asn1rawint(buf, buf+10, 2, &l) == 2 && l == 160); // OK
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memcpy(buf,"\x01\x02\x03\x04\x05\x06\x07\x08\x09",9);
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assert(scan_asn1rawint(buf, buf+10, 9, &l) == 0); // value too large, not representable
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memcpy(buf,"\xff\x01\x02\x03\x04\x05\x06\x07\x08\x09",10);
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assert(scan_asn1rawint(buf, buf+10, 10, &l) == 0); // value too large, not representable
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assert(scan_asn1rawint(buf, buf+1, 3, &l) == 0); // buffer too small for length
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}
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#endif
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