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parse_cseq: reject overlarge CSeq numbers to avoid unsigned overflow #553

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parse_cseq: reject overlarge CSeq numbers to avoid unsigned overflow #553

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10 changes: 10 additions & 0 deletions core/sip/parse_cseq.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@

#include "log.h"

#include <limits.h>

int parse_cseq(sip_cseq* cseq, const char* beg, int len)
{
enum {
Expand Down Expand Up @@ -65,6 +67,14 @@ int parse_cseq(sip_cseq* cseq, const char* beg, int len)
if(!IS_DIGIT(*c)){
return MALFORMED_SIP_MSG;
}
// reject overlarge CSeq numbers: the RFC 3261 CSeq value is a
// 32-bit quantity and 'num' is unsigned int; without this guard
// the accumulation silently wraps, so distinct on-wire CSeq
// strings can collapse to the same value and corrupt
// transaction matching.
if(cseq->num > (UINT_MAX - (unsigned int)(*c - '0')) / 10){
return MALFORMED_SIP_MSG;
}
cseq->num = cseq->num*10 + *c - '0';
Comment on lines +70 to 78
break;
}
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