[dhcp_relay] Check payload size to prevent buffer overflow in dhcpv6 option #9740
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yxieca
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Why I did it
When parsing through relay reply packets, parse_dhcpv6_option introduces vulnerability in buffer overflow, allowing up to 2 byte/65535 copied into a fixed buffer of size 4096.
How I did it
Add bound checks to before and after option parsing
How to verify it
Send a dummy packet with option length greater than 4096. dhcp6relay should not perform memcpy on invalid option length.
Which release branch to backport (provide reason below if selected)
Description for the changelog
A picture of a cute animal (not mandatory but encouraged)