2017-06-12 11:56:38 +00:00
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="ssec-relnotes-1.11.10">
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<title>Release 1.11.10 (2017-06-12)</title>
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<para>This release fixes a security bug in Nix’s “build user” build
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isolation mechanism. Previously, Nix builders had the ability to
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create setuid binaries owned by a <literal>nixbld</literal>
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user. Such a binary could then be used by an attacker to assume a
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<literal>nixbld</literal> identity and interfere with subsequent
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builds running under the same UID.</para>
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<para>To prevent this issue, Nix now disallows builders to create
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setuid and setgid binaries. On Linux, this is done using a seccomp BPF
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filter. Note that this imposes a small performance penalty (e.g. 1%
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when building GNU Hello). Using seccomp, we now also prevent the
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creation of extended attributes and POSIX ACLs since these cannot be
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represented in the NAR format and (in the case of POSIX ACLs) allow
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2017-06-12 12:04:52 +00:00
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bypassing regular Nix store permissions. On macOS, the restriction is
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2017-06-12 11:56:38 +00:00
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implemented using the existing sandbox mechanism, which now uses a
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minimal “allow all except the creation of setuid/setgid binaries”
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profile when regular sandboxing is disabled. On other platforms, the
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“build user” mechanism is now disabled.</para>
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<para>Thanks go to Linus Heckemann for discovering and reporting this
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bug.</para>
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</section>
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