* It turns out that the people who told me that removing a conffile in the

  preinst was sufficient to have dpkg replace it without prompting when
  moving a conffile between packages were very much mistaken. As far as I
  can tell, the only way to do this reliably is to write out the desired
  new text of the conffile in the preinst. This is gross, and requires
  shipping the text of all conffiles in the preinst too, but there's
  nothing for it. Fortunately this nonsense is only required for smooth
  upgrades from sarge.

5 files changed, 84 insertions, 5 deletions

diff --git a/debian/changelog b/debian/changelog
index 6a30e56f0..1a684c7fa 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -12,6 +12,14 @@ openssh (1:4.3p2-8) UNRELEASED; urgency=medium
     GSSAPICleanupCredentials. Mark GSSUseSessionCCache and
     GSSAPIUseSessionCredCache as known-but-unsupported options, and migrate
     away from them on upgrade.
+  * It turns out that the people who told me that removing a conffile in the
+    preinst was sufficient to have dpkg replace it without prompting when
+    moving a conffile between packages were very much mistaken. As far as I
+    can tell, the only way to do this reliably is to write out the desired
+    new text of the conffile in the preinst. This is gross, and requires
+    shipping the text of all conffiles in the preinst too, but there's
+    nothing for it. Fortunately this nonsense is only required for smooth
+    upgrades from sarge.
   * debconf template translations:
     - Add Romanian (thanks, Stan Ioan-Eugen; closes: #403528).
 
diff --git a/debian/openssh-client.preinst b/debian/openssh-client.preinst
index 0e200712e..9cf29dfba 100644
--- a/debian/openssh-client.preinst
+++ b/debian/openssh-client.preinst
@@ -1,17 +1,34 @@
 #! /bin/sh -e
 
+ETC_SSH_MODULI=@ETC_SSH_MODULI@
+
+ETC_SSH_SSH_CONFIG=@ETC_SSH_SSH_CONFIG@
+
 action="$1"
 version="$2"
 
 prepare_transfer_conffile () {
         CONFFILE="$1"
+        TEXT="$2"
+        MODE="$3"
         [ -e "$CONFFILE" ] || return 0
 
         md5sum="$(md5sum "$CONFFILE" |sed -e 's/ .*//')"
         old_md5sum="$(sed -n -e "/^Conffiles:/,/^[^ ]/{\\' $CONFFILE'{s/^ [^ ]* //;s/ .*//;p}}" /var/lib/dpkg/status)"
         if [ "$md5sum" = "$old_md5sum" ]; then
                 echo >&2 "Transferring ownership of conffile $CONFFILE ..."
+                # We have to write out the desired new text of the conffile,
+                # which is tricky in the preinst, hence the nasty way we
+                # have to hardcode the text here. Fortunately, this is only
+                # necessary with sarge's dpkg and older.
+                if echo "$TEXT" | head -n1 | grep -q '^@.*@$'; then
+                        echo >&2 'Unsubstituted conffile text! Please report this bug.'
+                        exit 1
+                fi
+                printf '%s' "$TEXT" >"$CONFFILE.dpkg-new"
+                chmod "$MODE" "$CONFFILE.dpkg-new"
                 mv -f "$CONFFILE" "$CONFFILE.moved-by-preinst"
+                mv -f "$CONFFILE.dpkg-new" "$CONFFILE"
                 return 0
         fi
 }
@@ -19,8 +36,8 @@ prepare_transfer_conffile () {
 case $action in
         install|upgrade)
                 if dpkg --compare-versions "$version" lt 0; then
-                        prepare_transfer_conffile /etc/ssh/moduli
-                        prepare_transfer_conffile /etc/ssh/ssh_config
+                        prepare_transfer_conffile /etc/ssh/moduli "$ETC_SSH_MODULI" 0644
+                        prepare_transfer_conffile /etc/ssh/ssh_config "$ETC_SSH_SSH_CONFIG" 0644
                 fi
                 ;;
 esac
diff --git a/debian/openssh-server.preinst b/debian/openssh-server.preinst
index a5c507bd4..2c2e2687c 100644
--- a/debian/openssh-server.preinst
+++ b/debian/openssh-server.preinst
@@ -1,17 +1,36 @@
 #!/bin/sh -e
 
+ETC_DEFAULT_SSH=@ETC_DEFAULT_SSH@
+
+ETC_INIT_D_SSH=@ETC_INIT_D_SSH@
+
+ETC_PAM_D_SSH=@ETC_PAM_D_SSH@
+
 action=$1
 version=$2
 
 prepare_transfer_conffile () {
         CONFFILE="$1"
+        TEXT="$2"
+        MODE="$3"
         [ -e "$CONFFILE" ] || return 0
 
         md5sum="$(md5sum "$CONFFILE" |sed -e 's/ .*//')"
         old_md5sum="$(sed -n -e "/^Conffiles:/,/^[^ ]/{\\' $CONFFILE'{s/^ [^ ]* //;s/ .*//;p}}" /var/lib/dpkg/status)"
         if [ "$md5sum" = "$old_md5sum" ]; then
                 echo >&2 "Transferring ownership of conffile $CONFFILE ..."
+                # We have to write out the desired new text of the conffile,
+                # which is tricky in the preinst, hence the nasty way we
+                # have to hardcode the text here. Fortunately, this is only
+                # necessary with sarge's dpkg and older.
+                if echo "$TEXT" | head -n1 | grep -q '^@.*@$'; then
+                        echo >&2 'Unsubstituted conffile text! Please report this bug.'
+                        exit 1
+                fi
+                printf '%s' "$TEXT" >"$CONFFILE.dpkg-new"
+                chmod "$MODE" "$CONFFILE.dpkg-new"
                 mv -f "$CONFFILE" "$CONFFILE.moved-by-preinst"
+                mv -f "$CONFFILE.dpkg-new" "$CONFFILE"
                 return 0
         fi
 }
@@ -92,9 +111,9 @@ EOF
   fi
 
   if dpkg --compare-versions "$version" lt 0; then
-    prepare_transfer_conffile /etc/default/ssh
-    prepare_transfer_conffile /etc/init.d/ssh
-    prepare_transfer_conffile /etc/pam.d/ssh
+    prepare_transfer_conffile /etc/default/ssh "$ETC_DEFAULT_SSH" 0644
+    prepare_transfer_conffile /etc/init.d/ssh "$ETC_INIT_D_SSH" 0755
+    prepare_transfer_conffile /etc/pam.d/ssh "$ETC_PAM_D_SSH" 0644
   fi
 fi
 
diff --git a/debian/rules b/debian/rules
index 4d9269666..fdef12dcf 100755
--- a/debian/rules
+++ b/debian/rules
@@ -195,6 +195,10 @@ binary-openssh-client: build install
         dh_installdeb
         test ! -e debian/ssh/etc/ssh/ssh_prng_cmds \
           || echo "/etc/ssh/ssh_prng_cmds" >> debian/openssh-client/DEBIAN/conffiles
+        perl -i debian/substitute-conffile.pl \
+                ETC_SSH_MODULI debian/openssh-client/etc/ssh/moduli \
+                ETC_SSH_SSH_CONFIG debian/openssh-client/etc/ssh/ssh_config \
+                debian/openssh-client/DEBIAN/preinst
         dh_shlibdeps
         dh_gencontrol -- -V'debconf-depends=debconf (>= $(MINDEBCONFVER)) | debconf-2.0'
         dh_md5sums
@@ -229,6 +233,11 @@ endif
         dh_compress
         dh_fixperms
         dh_installdeb
+        perl -i debian/substitute-conffile.pl \
+                ETC_DEFAULT_SSH debian/openssh-server/etc/default/ssh \
+                ETC_INIT_D_SSH debian/openssh-server/etc/init.d/ssh \
+                ETC_PAM_D_SSH debian/openssh-server/etc/pam.d/ssh \
+                debian/openssh-server/DEBIAN/preinst
         dh_shlibdeps
         dh_gencontrol -- -V'debconf-depends=debconf (>= $(MINDEBCONFVER)) | debconf-2.0' \
                          -V'pam-depends=$(PAMDEP)'
diff --git a/debian/substitute-conffile.pl b/debian/substitute-conffile.pl
new file mode 100644
index 000000000..7dd23363e
--- /dev/null
+++ b/debian/substitute-conffile.pl
@@ -0,0 +1,26 @@
+#! /usr/bin/perl -p
+
+# This is needed for a nasty preinst hack to work around a bug in sarge's
+# version of dpkg. It substitutes the literal text of conffiles into preinst
+# scripts so that they can be used when moving conffiles between packages.
+
+BEGIN {
+    %texts = ();
+    while (@ARGV > 1) {
+        my $name = $ARGV[0];
+        shift;
+        local *FILE;
+        open FILE, '<', $ARGV[0];
+        local $/ = undef;
+        my $text = <FILE>;
+        close FILE;
+        # Quote for the shell.
+        $text =~ s/'/'\\''/g;
+        shift;
+        $texts{$name} = $text;
+    }
+}
+
+for my $name (keys %texts) {
+    s/\@$name\@/'$texts{$name}'/g;
+}