test(xcat-core): cover the here-document that embeds a postscript

The install-time post script embeds xcatdsklspost, xcatinstallpost and
xcatpostinit1 with "#INCLUDE:<path>#" inside a here-document. The template
copies each file verbatim, so a line in the postscript that equals the
here-document delimiter ends that here-document early, and the rest of the
postscript becomes shell code in the generated install script.

Nothing measured that. The new test assembles every such embedding the six
post.* install scripts declare, and asserts that bash parses the result and
that no line of the embedded file equals the delimiter.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

xCAT-test/unit/postscript_heredoc_embedding.t

@@ -0,0 +1,82 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use File::Temp qw(tempdir);
+use Test::More;
+
+# The install-time post script embeds whole postscripts with "#INCLUDE:<path>#" inside a
+# here-document. The template copies the file verbatim, so a line in the postscript that
+# equals the here-document delimiter ends that here-document early. The generated install
+# script then holds the rest of the postscript as shell code.
+#
+# That happened: a "cat >> ... <<EOF" added to xcatdsklspost put a line "EOF" in the file,
+# post.xcat embeds it with "cat >/opt/xcat/xcatdsklspost << 'EOF'", and every diskfull
+# install ran a post script that bash refused to parse. No postscript ran, so remoteshell
+# never installed the root key and the node answered "Permission denied (publickey)".
+
+my $root = "$FindBin::Bin/../..";
+my $scriptdir = "$root/xCAT-server/share/xcat/install/scripts";
+plan skip_all => "$scriptdir not found" unless -d $scriptdir;
+
+# Return every (post script, delimiter, embedded file) the install scripts declare.
+sub embeddings {
+    my @found;
+    opendir(my $dh, $scriptdir) or die "cannot read $scriptdir: $!";
+    my @posts = sort grep { /^post\./ and -f "$scriptdir/$_" } readdir($dh);
+    closedir $dh;
+
+    for my $post (@posts) {
+        open(my $fh, '<', "$scriptdir/$post") or die "cannot read $post: $!";
+        my @lines = <$fh>;
+        close $fh;
+        for my $i (0 .. $#lines - 1) {
+            # cat >file << 'EOF'   /   (cat  << 'EOF'
+            my ($delim) = $lines[$i] =~ /<<-?\s*'([A-Za-z_][A-Za-z0-9_]*)'\s*$/;
+            next unless defined $delim;
+            my ($include) = $lines[$i + 1] =~ /^#INCLUDE:(.+)#\s*$/;
+            next unless defined $include;
+            # The include path is a template expression; only its last element names the file.
+            next unless $include =~ m{/postscripts/([^/#]+)$};
+            my $file = "$root/xCAT/postscripts/$1";
+            next unless -f $file;
+            push @found, { post => $post, delim => $delim, file => $file, name => $1 };
+        }
+    }
+    return @found;
+}
+
+my @embeddings = embeddings();
+die 'no "#INCLUDE:" inside a here-document was found; the scan no longer matches the install scripts'
+    unless @embeddings;
+
+my $scratch = tempdir(CLEANUP => 1);
+
+for my $e (@embeddings) {
+    my $label = "$e->{post} embeds $e->{name} in a <<'$e->{delim}' here-document";
+
+    open(my $fh, '<', $e->{file}) or die "cannot read $e->{file}: $!";
+    my @body = <$fh>;
+    close $fh;
+
+    my @collisions = grep { $body[$_] =~ /^\Q$e->{delim}\E\s*$/ } 0 .. $#body;
+    is(scalar @collisions, 0,
+        "$label, and no line of $e->{name} is \"$e->{delim}\"")
+        or diag("$e->{name} line(s) " . join(', ', map { $_ + 1 } @collisions)
+              . " end the here-document early");
+
+    # Assemble the embedding the way the template does and let bash parse it. bash reads the
+    # here-document up to the first delimiter line, so an early end leaves the rest of the
+    # postscript as commands. -n parses and runs nothing.
+    my $script = "$scratch/$e->{post}.$e->{name}.sh";
+    open(my $out, '>', $script) or die "cannot write $script: $!";
+    print $out "cat >\"\$1\" <<'$e->{delim}'\n", @body, "$e->{delim}\n";
+    close $out;
+
+    my $errors = qx{bash -n \Q$script\E 2>&1};
+    is($?, 0, "$label, and bash parses the result")
+        or diag($errors);
+}
+
+done_testing();