25 lines
729 B
C
25 lines
729 B
C
#include "asn1.h"
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unsigned int scan_asn1length(const char* src,const char* max,unsigned long* length) {
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const char* orig=src;
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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 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)-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 (src+*length<src) return 0;
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return src-orig;
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}
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