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26 lines
850 B
C
26 lines
850 B
C
#include "scan.h"
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size_t scan_asn1derlength(const char* src,size_t len,unsigned long long* length) {
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const char* orig=src;
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const char* max=orig+len;
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if (src>=max) return 0;
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/* If the highest bit of the first byte is clear, the byte is the length.
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* Otherwise the next n bytes are the length (n being the lower 7 bits) */
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if (*src&0x80) {
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int chars=*src&0x7f;
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unsigned long long l=0;
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while (chars>0) {
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if (++src>=max) return 0;
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if (l>(((unsigned long long)-1)>>8)) return 0; /* catch integer overflow */
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l=l*256+(unsigned char)*src;
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--chars;
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}
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*length=l;
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} else
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*length=*src&0x7f;
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src++;
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if (src+*length>max) return 0; /* catch integer overflow */
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if ((uintptr_t)src+*length<(uintptr_t)src) return 0; /* gcc 4.1 removes this check without the cast to uintptr_t */
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return src-orig;
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}
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