Merge pull request #137601 from fzakaria/faridzakaria/glibc-netbase

glibc: allow environment variable for /etc/ files (i.e. /etc/protocols)

doc/builders/packages/etc-files.section.md

@@ -0,0 +1,17 @@
+# /etc files {#etc}
+
+Certain calls in glibc require access to runtime files found in /etc such as `/etc/protocols` or `/etc/services` -- [getprotobyname](https://linux.die.net/man/3/getprotobyname) is one such function.
+
+On non-NixOS distributions these files are typically provided by packages (i.e. [netbase](https://packages.debian.org/sid/netbase)) if not already pre-installed in your distribution. This can cause non-reproducibility for code if they rely on these files being present.
+
+If [iana-etc](https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.iana-etc.x86_64-linux) is part of your _buildInputs_ then it will set the environment varaibles `NIX_ETC_PROTOCOLS` and `NIX_ETC_SERVICES` to the corresponding files in the package through a _setup-hook_.
+
+```bash
+❯ nix-shell -p iana-etc
+
+[nix-shell:~]$ env | grep NIX_ETC
+NIX_ETC_SERVICES=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/services
+NIX_ETC_PROTOCOLS=/nix/store/aj866hr8fad8flnggwdhrldm0g799ccz-iana-etc-20210225/etc/protocols
+```
+
+Nixpkg's version of [glibc](https://hydra.nixos.org/job/nixos/trunk-combined/nixpkgs.glibc.x86_64-linux) has been patched to check for the existence of these environment variables. If the environment variable are *not set*, then it will attempt to find the files at the default location within _/etc_.

doc/builders/packages/index.xml

@@ -17,6 +17,7 @@
  <xi:include href="kakoune.section.xml" />
  <xi:include href="linux.section.xml" />
  <xi:include href="locales.section.xml" />
+ <xi:include href="etc-files.section.xml" />
  <xi:include href="nginx.section.xml" />
  <xi:include href="opengl.section.xml" />
  <xi:include href="shell-helpers.section.xml" />

pkgs/data/misc/iana-etc/default.nix

@@ -1,17 +1,23 @@
-{ lib, fetchzip }:
+{ lib, fetchzip, stdenvNoCC, writeText }:
 
 let
   version = "20210225";
-in fetchzip {
+in stdenvNoCC.mkDerivation {
   name = "iana-etc-${version}";
-  url = "https://github.com/Mic92/iana-etc/releases/download/${version}/iana-etc-${version}.tar.gz";
-  sha256 = "sha256-NVvZG3EJEYOXFDTBXD5m9sg/8msyMiBMkiZr+ZxWZ/g=";
+  src = fetchzip {
+    url = "https://github.com/Mic92/iana-etc/releases/download/${version}/iana-etc-${version}.tar.gz";
+    sha256 = "sha256:1bbbnj2ya0apyyhnw37521yl1hrz3zy3l8dw6sacmir0y6pmx9gi";
+  };
 
-  postFetch = ''
-    tar -xzvf $downloadedFile --strip-components=1
+  installPhase = ''
     install -D -m0644 -t $out/etc services protocols
   '';
 
+  setupHook = writeText "setup-hook" ''
+    export NIX_ETC_PROTOCOLS=@out@/etc/protocols
+    export NIX_ETC_SERVICES=@out@/etc/services
+  '';
+
   meta = with lib; {
     homepage = "https://github.com/Mic92/iana-etc";
     description = "IANA protocol and port number assignments (/etc/protocols and /etc/services)";

pkgs/development/libraries/glibc/common.nix

@@ -120,6 +120,9 @@ stdenv.mkDerivation ({
       })
 
       ./fix-x64-abi.patch
+
+      /* https://github.com/NixOS/nixpkgs/pull/137601 */
+      ./nix-nss-open-files.patch
     ]
     ++ lib.optional stdenv.hostPlatform.isMusl ./fix-rpc-types-musl-conflicts.patch
     ++ lib.optional stdenv.buildPlatform.isDarwin ./darwin-cross-build.patch;

pkgs/development/libraries/glibc/nix-nss-open-files.patch

@@ -0,0 +1,51 @@
+diff --git a/nss/nss_files/files-XXX.c b/nss/nss_files/files-XXX.c
+index 1db9e46127..3a567e0224 100644
+--- a/nss/nss_files/files-XXX.c
++++ b/nss/nss_files/files-XXX.c
+@@ -75,8 +75,20 @@ internal_setent (FILE **stream)
+ 
+   if (*stream == NULL)
+     {
+-      *stream = __nss_files_fopen (DATAFILE);
+-
++      const char *file = DATAFILE;
++
++      #ifdef NIX_DATAFILE
++      // use the Nix environment variable such as `NIX_ETC_PROTOCOLS`
++      char *path = secure_getenv (NIX_DATAFILE);
++
++      // if the environment variable is set, then read from the /nix/store entry instead
++      if (path && path[0]) {
++        file = path;
++      }
++      #endif
++      
++      *stream = __nss_files_fopen (file);
++    
+       if (*stream == NULL)
+ 	status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
+     }
+diff --git a/nss/nss_files/files-proto.c b/nss/nss_files/files-proto.c
+index c30bedc0aa..b321e68d3c 100644
+--- a/nss/nss_files/files-proto.c
++++ b/nss/nss_files/files-proto.c
+@@ -23,6 +23,7 @@ NSS_DECLARE_MODULE_FUNCTIONS (files)
+ 
+ #define ENTNAME		protoent
+ #define DATABASE	"protocols"
++#define NIX_DATAFILE "NIX_ETC_PROTOCOLS"
+ 
+ struct protoent_data {};
+ 
+diff --git a/nss/nss_files/files-service.c b/nss/nss_files/files-service.c
+index bfc2590699..0bff36aee5 100644
+--- a/nss/nss_files/files-service.c
++++ b/nss/nss_files/files-service.c
+@@ -24,6 +24,7 @@ NSS_DECLARE_MODULE_FUNCTIONS (files)
+ 
+ #define ENTNAME		servent
+ #define DATABASE	"services"
++#define NIX_DATAFILE "NIX_ETC_SERVICES"
+ 
+ struct servent_data {};
+