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32 lines
1.1 KiB
C
32 lines
1.1 KiB
C
#include "scan.h"
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size_t scan_asn1derlengthvalue(const char* src,size_t len,unsigned long long* value) {
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if (len==0 || len>=-(uintptr_t)src) return 0;
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unsigned int i,c=*src;
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unsigned long long l;
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if ((c&0x80)==0) {
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*value=c;
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return 1;
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}
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/* Highest bit set: lower 7 bits is the length of the length value in bytes. */
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c&=0x7f;
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if (!c) return 0; /* length 0x80 means indefinite length encoding, not supported here */
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l=(unsigned char)src[1];
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if (l==0) return 0; /* not minimally encoded: 0x82 0x00 0xc2 instead of 0x81 0xc2 */
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if (c>sizeof(l)) return 0; /* too many bytes, does not fit into target integer type */
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if (c+1>len) return 0; /* not enough data in input buffer */
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for (i=2; i<=c; ++i)
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l=l*256+(unsigned char)src[i];
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if (l<0x7f) return 0; /* not minimally encoded: 0x81 0x70 instead of 0x70 */
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*value=l;
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return i;
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}
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size_t scan_asn1derlength(const char* src,size_t len,unsigned long long* value) {
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unsigned long long l;
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size_t i=scan_asn1derlengthvalue(src,len,&l);
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if (l > len-i) return 0; /* make sure data would fit into buffer */
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*value=l;
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return i;
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}
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