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Bug 877003 - net-dns/c-ares uses hardcoded paths to /etc outside of prefix
Summary: net-dns/c-ares uses hardcoded paths to /etc outside of prefix
Status: UNCONFIRMED
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Gentoo's Team for Core System packages
URL:
Whiteboard:
Keywords: PATCH
Depends on:
Blocks:
 
Reported: 2022-10-13 17:42 UTC by Nick Bowler
Modified: 2023-05-10 07:38 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---


Attachments
proposed fix (c-ares-respect-sysconfdir.patch,2.50 KB, patch)
2022-10-13 17:43 UTC, Nick Bowler
Details | Diff

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Description Nick Bowler 2022-10-13 17:42:00 UTC
On prefix installations, the c-ares library does its own name resolution (not using libc resolver) using hardcoded paths to system files outside of the prefix.

In particular, it has hardcoded paths to /etc/nsswitch.conf, /etc/resolv.conf and /etc/hosts, ignoring the prefixed versions of these files like applications using the libc resolver do.

This problem specifically affects net-misc/curl, and applications which use curl (such as git), as recent versions of curl have the "adns" flag enabled by default.

Portage 3.0.38.1 (python 3.10.7-final-0, default/linux/amd64/17.0, gcc-12.2.0, glibc-2.36-r4, 3.10.0-1160.11.1.el7.x86_64 x86_64)
=================================================================
System uname: Linux-3.10.0-1160.11.1.el7.x86_64-x86_64-Intel-R-_Core-TM-_i7-4790_CPU_@_3.60GHz-with-glibc2.36
KiB Mem:    16204164 total,   5284896 free
KiB Swap:   32605180 total,  32595964 free
Timestamp of repository gentoo: Thu, 13 Oct 2022 00:45:01 +0000
sh bash 5.1_p16-r2
ld GNU ld (Gentoo 2.38 p4) 2.38
ccache version 4.6.1 [enabled]
app-misc/pax-utils:        1.3.5::gentoo
app-shells/bash:           5.1_p16-r2::gentoo
dev-lang/perl:             5.36.0::gentoo
dev-lang/python:           2.7.18_p13::gentoo, 3.6.15-r1::gentoo, 3.7.12_p1-r1::gentoo, 3.8.13_p8::gentoo, 3.9.13::gentoo, 3.10.7::gentoo, 3.11.0_rc2::gentoo
dev-lang/rust:             1.61.0-r1::gentoo
dev-lang/rust-bin:         1.61.0::gentoo
dev-util/ccache:           4.6.1::gentoo
dev-util/cmake:            3.23.2::gentoo
dev-util/meson:            0.63.2-r1::gentoo
sys-apps/baselayout:       2.8::gentoo
sys-apps/openrc:           0.45.2::gentoo
sys-apps/sandbox:          2.29::gentoo
sys-devel/autoconf:        2.13-r1::gentoo, 2.69-r5::gentoo, 2.71-r4::gentoo
sys-devel/automake:        1.16.5::gentoo
sys-devel/binutils:        2.38-r2::gentoo, 2.39-r3::gentoo
sys-devel/binutils-config: 5.4.1::gentoo
sys-devel/clang:           13.0.1::gentoo, 14.0.6::gentoo
sys-devel/gcc:             9.3.0-r2::gentoo, 11.3.0::gentoo, 12.2.0::gentoo
sys-devel/gcc-config:      2.8::gentoo
sys-devel/libtool:         2.4.7::gentoo
sys-devel/llvm:            11.1.0::gentoo, 13.0.1::gentoo, 14.0.6::gentoo
sys-devel/make:            4.3::gentoo
sys-kernel/linux-headers:  6.0::gentoo (virtual/os-headers)
sys-libs/glibc:            2.36-r4::gentoo
Repositories:

gentoo
    location: /SCRATCH/gentoo/srv/repos/gentoo
    sync-type: webrsync
    sync-uri: rsync://rsync.gentoo.org/gentoo-portage
    priority: -1000
    sync-webrsync-verify-signature: true

gentoo-draconx
    location: /SCRATCH/gentoo/srv/repos/gentoo-draconx
    masters: gentoo

gentoo-fixes
    location: /SCRATCH/gentoo/srv/repos/gentoo-fixes
    masters: gentoo

ACCEPT_KEYWORDS="amd64 ~amd64"
ACCEPT_LICENSE="@FREE"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-O2 -march=haswell -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/SCRATCH/gentoo/etc /etc /usr/share/gnupg/qualified.txt"
CONFIG_PROTECT_MASK="/SCRATCH/gentoo/etc/env.d /SCRATCH/gentoo/etc/gentoo-release /etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c"
CONFIG_SHELL="/SCRATCH/gentoo/bin/bash"
CXXFLAGS="-O2 -march=haswell -pipe"
DISTDIR="/SCRATCH/gentoo/var/cache/distfiles"
EMERGE_DEFAULT_OPTS="--quiet-build --keep-going --autounmask=n --autounmask-write=n --dynamic-deps=n --unordered-display --verbose-conflicts --with-bdeps-auto=n"
ENV_UNSET="CARGO_HOME DBUS_SESSION_BUS_ADDRESS DISPLAY GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR XDG_STATE_HOME"
FCFLAGS="-O2 -pipe"
FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs binpkg-multi-instance buildpkg-live ccache config-protect-if-modified distlocks ebuild-locks fixlafiles force-prefix ipc-sandbox merge-sync multilib-strict network-sandbox news parallel-fetch pid-sandbox preserve-libs protect-owned qa-unresolved-soname-deps sfperms strict unknown-features-warn unmerge-logs unmerge-orphans unprivileged xattr"
FFLAGS="-O2 -pipe"
GENTOO_MIRRORS="http://distfiles.gentoo.org"
LANG="en_CA.UTF-8"
LDFLAGS="-Wl,-O1 -Wl,--as-needed"
MAKEOPTS="-j5"
PKGDIR="/SCRATCH/gentoo/var/cache/binpkgs"
PORTAGE_CONFIGROOT="/SCRATCH/gentoo/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git"
PORTAGE_TMPDIR="/SCRATCH/gentoo/var/tmp"
SHELL="/SCRATCH/gentoo/bin/zsh"
USE="X acl amd64 bzip2 cli crypt cups dri exif fbcon fontconfig fortran gdbm iconv icu ipv6 jpeg lcms libglvnd libtirpc lzma multilib ncurses nls nptl openmp pcre perl png prefix python readline seccomp split-usr ssl svg truetype unicode xattr xft xinerama zlib" ABI_X86="64" ADA_TARGET="gnat_2020" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="libinput" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LUA_SINGLE_TARGET="lua5-1" LUA_TARGETS="lua5-1" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php7-4 php8-0" POSTGRES_TARGETS="postgres12 postgres13" PYTHON_SINGLE_TARGET="python3_10" PYTHON_TARGETS="python3_10" RUBY_TARGETS="ruby27" USERLAND="GNU" VIDEO_CARDS="amdgpu fbdev intel nouveau radeon radeonsi vesa dummy v4l" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq proto steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset:  ADDR2LINE, AR, ARFLAGS, AS, ASFLAGS, CC, CCLD, CPP, CPPFLAGS, CTARGET, CXX, CXXFILT, ELFEDIT, EXTRA_ECONF, F77FLAGS, FC, GCOV, GPROF, INSTALL_MASK, LC_ALL, LD, LEX, LFLAGS, LIBTOOL, LINGUAS, MAKE, MAKEFLAGS, NM, OBJCOPY, OBJDUMP, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, RANLIB, READELF, RUSTFLAGS, SIZE, STRINGS, STRIP, YACC, YFLAGS
Comment 1 Nick Bowler 2022-10-13 17:43:20 UTC
Created attachment 823947 [details, diff]
proposed fix

This patch adjusts c-ares to respect sysconfdir setting and resolves the problem.
Comment 2 Sam James archtester Gentoo Infrastructure gentoo-dev Security 2022-10-13 19:59:19 UTC
(In reply to Nick Bowler from comment #1)
> Created attachment 823947 [details, diff] [details, diff]
> proposed fix
> 
> This patch adjusts c-ares to respect sysconfdir setting and resolves the
> problem.

Could you send the patch upstream?
Comment 3 Fabian Groffen gentoo-dev 2023-05-10 06:53:59 UTC
Interestingly enough /etc/resolv.conf doesn't make much sense to grab from prefix.  I think in RAP you could have nsswitch but also there I doubt you want to use it.  Non-RAP certainly don't want these paths prefixed, else no resolving would be possible at all any more.
Comment 4 Nick Bowler 2023-05-10 07:26:45 UTC
All normal prefixed applications using the prefix libc resolver are performing name resolution using the settings from prefixed /etc/nsswitch.conf, prefixed /etc/hosts, and prefixed /etc/resolv.conf.

Only curl (via USE=adns / c-ares) is getting this different from every other application as it decides to bypass the libc resolver and use a completely different set of configuration files.

Using prefixed configuration files is expected and desired behaviour, as I see it.  I can easily symlink /prefix/etc/resolv.conf or whatever to the host system if this is needed (it is not).  I can't direct /etc/resolv.conf back to the prefix.
Comment 5 Fabian Groffen gentoo-dev 2023-05-10 07:38:48 UTC
You're describing RAP.

I think we could add those symlinks you talk about to a base-package or something, but at this point noone would have those symlinks, so all non-RAP prefixes would be broken.

The easiest is probably to apply this patch conditional for !prefix-guest.

Nicer solution probably is to pull in some virtual that sets up symlinks or something for hosts that lack these.