decode/ppp: fix iplen check int handling

[victorjulien]

** CID 1596376:    (CONSTANT_EXPRESSION_RESULT)
/src/decode-ppp.c: 64 in DecodePPPCompressedProto()
/src/decode-ppp.c: 55 in DecodePPPCompressedProto()

________________________________________________________________________________________________________
*** CID 1596376:    (CONSTANT_EXPRESSION_RESULT)
/src/decode-ppp.c: 64 in DecodePPPCompressedProto()
58             case 0x57: { /* PPP_IPV6 */
59                 if (unlikely(len < (data_offset + IPV6_HEADER_LEN))) {
60                     ENGINE_SET_INVALID_EVENT(p, PPPIPV6_PKT_TOO_SMALL);
61                     return TM_ECODE_FAILED;
62                 }
63                 DEBUG_VALIDATE_BUG_ON(len < data_offset);
>>>     CID 1596376:    (CONSTANT_EXPRESSION_RESULT)
>>>     "65535 /* 32767 * 2 + 1 */ < (uint16_t)(len - data_offset)" is always false regardless of the values of its operands. This occurs as the logical first operand of "?:".
64                 uint16_t iplen = MIN(USHRT_MAX, (uint16_t)(len - data_offset));
65                 return DecodeIPV6(tv, dtv, p, pkt + data_offset, iplen);
66             }
67             case 0x2f: /* PPP_VJ_UCOMP */
68                 if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
69                     ENGINE_SET_INVALID_EVENT(p, PPPVJU_PKT_TOO_SMALL);
/src/decode-ppp.c: 55 in DecodePPPCompressedProto()
49             case 0x21: { /* PPP_IP */
50                 if (unlikely(len < (data_offset + IPV4_HEADER_LEN))) {
51                     ENGINE_SET_INVALID_EVENT(p, PPPVJU_PKT_TOO_SMALL);
52                     return TM_ECODE_FAILED;
53                 }
54                 DEBUG_VALIDATE_BUG_ON(len < data_offset);
>>>     CID 1596376:    (CONSTANT_EXPRESSION_RESULT)
>>>     "65535 /* 32767 * 2 + 1 */ < (uint16_t)(len - data_offset)" is always false regardless of the values of its operands. This occurs as the logical first operand of "?:".
55                 uint16_t iplen = MIN(USHRT_MAX, (uint16_t)(len - data_offset));
56                 return DecodeIPV4(tv, dtv, p, pkt + data_offset, iplen);
57             }
58             case 0x57: { /* PPP_IPV6 */
59                 if (unlikely(len < (data_offset + IPV6_HEADER_LEN))) {
60                     ENGINE_SET_INVALID_EVENT(p, PPPIPV6_PKT_TOO_SMALL);

[inashivb]

LGTM 🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.94%. Comparing base (c305ed1) to head (9e7d2ac).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10855      +/-   ##
==========================================
+ Coverage   82.88%   82.94%   +0.05%     
==========================================
  Files         914      914              
  Lines      246936   246936              
==========================================
+ Hits       204671   204816     +145     
+ Misses      42265    42120     -145     

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fuzzcorpus	64.50% <0.00%> (+0.13%)	⬆️
suricata-verify	62.16% <100.00%> (-0.03%)	⬇️
unittests	62.32% <0.00%> (+<0.01%)	⬆️

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[victorjulien]

Merged in #10865, thanks!