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Avoid UB when packing a domain name #1613

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Avoid UB when packing a domain name #1613

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jtstrs
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@jtstrs jtstrs commented Dec 5, 2023 •
edited by rousskov
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rfc1035NamePack() called rfc1035LabelPack() with a nil label buffer.
Feeding memcpy() a nil buffer is undefined behavior, even if size is 0.

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Can one of the admins verify this patch?

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jtstrs commented Dec 5, 2023

Using memcpy is undefined behiour according to
https://en.cppreference.com/w/cpp/string/byte/memcpy

If either dest or src is an [invalid or null pointer],
the behavior is undefined, even if count is zero.

rousskov
rousskov requested changes Dec 5, 2023
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Thank you for working on fixing this bug!

src/dns/rfc1035.cc Outdated Show resolved Hide resolved
@rousskov rousskov added the S-waiting-for-author author action is expected (and usually required) label Dec 12, 2023
jtstrs and others added 2 commits December 13, 2023 11:55
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2fddaed
@rousskov
fixup: AAA, diff reduction, and new comment polishing
fa8318d 
When I suggested the new comment text,
I did not know that RFC 1034 had the following text: 

    the null (i.e., zero length) label used for the root.
@rousskov rousskov changed the title Avoid UB when packing name Avoid UB when packing a domain name Dec 13, 2023
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Thank you for addressing my primary concern. I am approving this PR after polishing its code and PR metadata a little. @jtstrs, please double check my changes.

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yadij
yadij approved these changes Dec 17, 2023
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We still have the UB implied by potential memcpy() mistakes. But replacing the one in label packing with memove() can be done when the other ones are updated.

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@yadij yadij added M-cleared-for-merge https://github.com/measurement-factory/anubis#pull-request-labels S-could-use-an-approval An approval may speed this PR merger (but is not required) and removed S-waiting-for-author author action is expected (and usually required) labels Dec 17, 2023
@rousskov rousskov removed the S-could-use-an-approval An approval may speed this PR merger (but is not required) label Dec 18, 2023
@rousskov rousskov mentioned this pull request Dec 18, 2023
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OK to test

@squid-anubis squid-anubis added the M-waiting-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels label Dec 22, 2023
squid-anubis pushed a commit that referenced this pull request Dec 22, 2023
@jtstrs @squid-anubis
Avoid UB when packing a domain name (#1613)
2f204c4 
rfc1035NamePack() called rfc1035LabelPack() with a nil label buffer.
Feeding memcpy() a nil buffer is undefined behavior, even if size is 0.
@squid-anubis squid-anubis added M-failed-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels M-failed-staging-other https://github.com/measurement-factory/anubis#pull-request-labels and removed M-waiting-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels labels Dec 22, 2023
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kinkie commented Dec 22, 2023

OK to test

@kinkie kinkie removed M-failed-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels M-failed-staging-other https://github.com/measurement-factory/anubis#pull-request-labels labels Dec 24, 2023
squid-anubis pushed a commit that referenced this pull request Dec 24, 2023
@jtstrs @squid-anubis
Avoid UB when packing a domain name (#1613)
be4bca3 
rfc1035NamePack() called rfc1035LabelPack() with a nil label buffer.
Feeding memcpy() a nil buffer is undefined behavior, even if size is 0.
@squid-anubis squid-anubis added the M-waiting-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels label Dec 24, 2023
@squid-anubis squid-anubis removed the M-waiting-staging-checks https://github.com/measurement-factory/anubis#pull-request-labels label Dec 25, 2023
@squid-anubis squid-anubis added M-merged https://github.com/measurement-factory/anubis#pull-request-labels and removed M-cleared-for-merge https://github.com/measurement-factory/anubis#pull-request-labels labels Dec 25, 2023
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@kinkie kinkie kinkie approved these changes

@yadij yadij yadij approved these changes

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