[RFC/PATCH 1/5] gettext: fix bug in git-sh-i18n's eval_gettext() by using envsubst(1)

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change eval_gettext(1) in git-sh-i18n.sh to use a modified version of
gettext's envsubst(1) program, instead of using a clever (but broken)
printf + eval + printf trick.

Our previous fallback would incorrectly handle cases where the
variable being interpolated contained spaces. E.g.:

    cmd="git foo"; eval_gettext "command: \$cmd"

Would emit "command: gitfoo", instead of the correct "command: git
foo". This happened with a message in git-am.sh that used the $cmdline
variable.

To work around this, and to improve our variable expansion behavior
(eval has security issues) I've imported a stripped-down version of
gettext's envsubst(1) program.

Using it we pass the latter of the two tests added along with this
patch (the first one was just added for completeness).

Since we want to test both our fallback eval_gettext() and the one
we'll end up using (i.e. on Solaris) the new tests are executed in
both t0200-gettext-basic.sh and t0201-gettext-fallbacks.sh.

These are the modifications I made to envsubst.c as I turned it into
sh-i18n--envsubst.c:

 * Added our git-compat-util.h header for xrealloc() and friends.

 * Removed inclusion of gettext-specific headers.

 * Removed most of main() and replaced it with my own. The modified
   version doesn't do option parsing at all, because it doesn't need
   to.

 * Modified error() invocations to use our error() instead of
   error(3).

 * Replaced the gettext XNMALLOC(n, size) macro with just
   xmalloc(n). Since XNMALLOC() only allocated char's.

 * Removed functions made redundant since I deleted some code paths
   from main(). These were:

    * print_variables
    * note_variables
    * print_variable
    * string_list_init
    * cmp_string
    * string_list_sort
    * string_list_destroy
    * find_variables
    * note_variable
    * note_variables

 * Replaced the use of stdbool.h (a C99 header) by doing the following
   replacements on the code:

    * s/bool/unsigned short int/g
    * s/true/1/g
    * s/false/0/g

Reported-by: Johannes Sixt <j.sixt@viscovery.net>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 .gitignore                   |    1 +
 Makefile                     |    1 +
 git-sh-i18n.sh               |    7 +-
 sh-i18n--envsubst.c          |  303 ++++++++++++++++++++++++++++++++++++++++++
 t/lib-gettext.sh             |   25 ++++
 t/t0200-gettext-basic.sh     |    3 +
 t/t0201-gettext-fallbacks.sh |    3 +
 7 files changed, 338 insertions(+), 5 deletions(-)
 create mode 100644 sh-i18n--envsubst.c

diff --git a/.gitignore b/.gitignore
index 80ca718..d2d9ec2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -126,6 +126,7 @@
 /git-send-email
 /git-send-pack
 /git-sh-i18n
+/git-sh-i18n--envsubst
 /git-sh-setup
 /git-shell
 /git-shortlog
diff --git a/Makefile b/Makefile
index e1650ba..c55baa6 100644
--- a/Makefile
+++ b/Makefile
@@ -435,6 +435,7 @@ PROGRAM_OBJS += shell.o
 PROGRAM_OBJS += show-index.o
 PROGRAM_OBJS += upload-pack.o
 PROGRAM_OBJS += http-backend.o
+PROGRAM_OBJS += sh-i18n--envsubst.o
 
 PROGRAMS += $(patsubst %.o,git-%$X,$(PROGRAM_OBJS))
 
diff --git a/git-sh-i18n.sh b/git-sh-i18n.sh
index f8dd43a..41580a8 100644
--- a/git-sh-i18n.sh
+++ b/git-sh-i18n.sh
@@ -38,9 +38,7 @@ then
 
 		# Solaris has a gettext(1) but no eval_gettext(1)
 		eval_gettext () {
-			gettext_out=$(gettext "$1")
-			gettext_eval="printf '%s' \"$gettext_out\""
-			printf "%s" "`eval \"$gettext_eval\"`"
+			gettext "$1" | git sh-i18n--envsubst
 		}
 	else
 		# Since gettext.sh isn't available we'll have to define our own
@@ -55,8 +53,7 @@ then
 		}
 
 		eval_gettext () {
-			gettext_eval="printf '%s' \"$1\""
-			printf "%s" "`eval \"$gettext_eval\"`"
+			printf "%s" "$1" | git sh-i18n--envsubst
 		}
 	fi
 else
diff --git a/sh-i18n--envsubst.c b/sh-i18n--envsubst.c
new file mode 100644
index 0000000..d0e0cc9
--- /dev/null
+++ b/sh-i18n--envsubst.c
@@ -0,0 +1,303 @@
+/*
+ * sh-i18n--envsubst.c - a stripped-down version of gettext's envsubst(1)
+ *
+ * Copyright (C) 2010 Ævar Arnfjörð Bjarmason
+ *
+ * This is a modified version of
+ * 67d0871a8c:gettext-runtime/src/envsubst.c from the gettext.git
+ * repository. It has been stripped down to only implement the
+ * envsubst(1) features that we need in the git-sh-i18n fallbacks.
+ *
+ * The "Close standard error" part in main() is from
+ * 8dac033df0:gnulib-local/lib/closeout.c. The copyright notices for
+ * both files are reproduced immediately below.
+ */
+
+#include "git-compat-util.h"
+
+/* Substitution of environment variables in shell format strings.
+   Copyright (C) 2003-2007 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2003.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* closeout.c - close standard output and standard error
+   Copyright (C) 1998-2007 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#include <errno.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* If true, substitution shall be performed on all variables.  */
+static unsigned short int all_variables;
+
+static void subst_from_stdin (void);
+
+int
+main (int argc, char *argv[])
+{
+  all_variables = 1;
+
+  if (argc > 1)
+	{
+	  error ("too many arguments");
+	  exit (EXIT_FAILURE);
+	}
+
+  subst_from_stdin ();
+
+  /* Close standard error.  This is simpler than fwriteerror_no_ebadf, because
+     upon failure we don't need an errno - all we can do at this point is to
+     set an exit status.  */
+  errno = 0;
+  if (ferror (stderr) || fflush (stderr))
+    { 
+      fclose (stderr);
+      exit (EXIT_FAILURE);
+    }
+  if (fclose (stderr) && errno != EBADF)
+    exit (EXIT_FAILURE);
+
+  exit (EXIT_SUCCESS);
+}
+
+/* Type describing list of immutable strings,
+   implemented using a dynamic array.  */
+typedef struct string_list_ty string_list_ty;
+struct string_list_ty
+{
+  const char **item;
+  size_t nitems;
+  size_t nitems_max;
+};
+
+/* Append a single string to the end of a list of strings.  */
+static inline void
+string_list_append (string_list_ty *slp, const char *s)
+{
+  /* Grow the list.  */
+  if (slp->nitems >= slp->nitems_max)
+    {
+      size_t nbytes;
+
+      slp->nitems_max = slp->nitems_max * 2 + 4;
+      nbytes = slp->nitems_max * sizeof (slp->item[0]);
+      slp->item = (const char **) xrealloc (slp->item, nbytes);
+    }
+
+  /* Add the string to the end of the list.  */
+  slp->item[slp->nitems++] = s;
+}
+
+/* Test whether a string list contains a given string.  */
+static inline int
+string_list_member (const string_list_ty *slp, const char *s)
+{
+  size_t j;
+
+  for (j = 0; j < slp->nitems; ++j)
+    if (strcmp (slp->item[j], s) == 0)
+      return 1;
+  return 0;
+}
+
+/* Test whether a sorted string list contains a given string.  */
+static int
+sorted_string_list_member (const string_list_ty *slp, const char *s)
+{
+  size_t j1, j2;
+
+  j1 = 0;
+  j2 = slp->nitems;
+  if (j2 > 0)
+    {
+      /* Binary search.  */
+      while (j2 - j1 > 1)
+	{
+	  /* Here we know that if s is in the list, it is at an index j
+	     with j1 <= j < j2.  */
+	  size_t j = (j1 + j2) >> 1;
+	  int result = strcmp (slp->item[j], s);
+
+	  if (result > 0)
+	    j2 = j;
+	  else if (result == 0)
+	    return 1;
+	  else
+	    j1 = j + 1;
+	}
+      if (j2 > j1)
+	if (strcmp (slp->item[j1], s) == 0)
+	  return 1;
+    }
+  return 0;
+}
+
+
+/* Set of variables on which to perform substitution.
+   Used only if !all_variables.  */
+static string_list_ty variables_set;
+
+static int
+do_getc ()
+{
+  int c = getc (stdin);
+
+  if (c == EOF)
+    {
+      if (ferror (stdin))
+	error ("error while reading standard input");
+    }
+
+  return c;
+}
+
+static inline void
+do_ungetc (int c)
+{
+  if (c != EOF)
+    ungetc (c, stdin);
+}
+
+/* Copies stdin to stdout, performing substitutions.  */
+static void
+subst_from_stdin ()
+{
+  static char *buffer;
+  static size_t bufmax;
+  static size_t buflen;
+  int c;
+
+  for (;;)
+    {
+      c = do_getc ();
+      if (c == EOF)
+	break;
+      /* Look for $VARIABLE or ${VARIABLE}.  */
+      if (c == '$')
+	{
+	  unsigned short int opening_brace = 0;
+	  unsigned short int closing_brace = 0;
+
+	  c = do_getc ();
+	  if (c == '{')
+	    {
+	      opening_brace = 1;
+	      c = do_getc ();
+	    }
+	  if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_')
+	    {
+	      unsigned short int valid;
+
+	      /* Accumulate the VARIABLE in buffer.  */
+	      buflen = 0;
+	      do
+		{
+		  if (buflen >= bufmax)
+		    {
+		      bufmax = 2 * bufmax + 10;
+		      buffer = xrealloc (buffer, bufmax);
+		    }
+		  buffer[buflen++] = c;
+
+		  c = do_getc ();
+		}
+	      while ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')
+		     || (c >= '0' && c <= '9') || c == '_');
+
+	      if (opening_brace)
+		{
+		  if (c == '}')
+		    {
+		      closing_brace = 1;
+		      valid = 1;
+		    }
+		  else
+		    {
+		      valid = 0;
+		      do_ungetc (c);
+		    }
+		}
+	      else
+		{
+		  valid = 1;
+		  do_ungetc (c);
+		}
+
+	      if (valid)
+		{
+		  /* Terminate the variable in the buffer.  */
+		  if (buflen >= bufmax)
+		    {
+		      bufmax = 2 * bufmax + 10;
+		      buffer = xrealloc (buffer, bufmax);
+		    }
+		  buffer[buflen] = '\0';
+
+		  /* Test whether the variable shall be substituted.  */
+		  if (!all_variables
+		      && !sorted_string_list_member (&variables_set, buffer))
+		    valid = 0;
+		}
+
+	      if (valid)
+		{
+		  /* Substitute the variable's value from the environment.  */
+		  const char *env_value = getenv (buffer);
+
+		  if (env_value != NULL)
+		    fputs (env_value, stdout);
+		}
+	      else
+		{
+		  /* Perform no substitution at all.  Since the buffered input
+		     contains no other '$' than at the start, we can just
+		     output all the buffered contents.  */
+		  putchar ('$');
+		  if (opening_brace)
+		    putchar ('{');
+		  fwrite (buffer, buflen, 1, stdout);
+		  if (closing_brace)
+		    putchar ('}');
+		}
+	    }
+	  else
+	    {
+	      do_ungetc (c);
+	      putchar ('$');
+	      if (opening_brace)
+		putchar ('{');
+	    }
+	}
+      else
+	putchar (c);
+    }
+}
diff --git a/t/lib-gettext.sh b/t/lib-gettext.sh
index c9a079e..436192a 100644
--- a/t/lib-gettext.sh
+++ b/t/lib-gettext.sh
@@ -66,3 +66,28 @@ else
 		say "# lib-gettext: No GETTEXT support available"
 	fi
 fi
+
+test_eval_gettext_interpolation() {
+	test_expect_success NO_GETTEXT_POISON 'eval_gettext: our eval_gettext() fallback can interpolate whitespace variables' '
+	    git_am_cmdline="git am" &&
+	    export git_am_cmdline &&
+	    printf "test git am" >expect &&
+	    eval_gettext "test \$git_am_cmdline" >actual &&
+	    test_cmp expect actual
+	'
+
+	test_expect_success NO_GETTEXT_POISON 'eval_gettext: git am $cmdline bug' '
+	    cmdline="git am -3" &&
+	    export cmdline &&
+	    cat >expect <<EOF &&
+When you have resolved this problem run "git am -3 --resolved".
+If you would prefer to skip this patch, instead run "git am -3 --skip".
+To restore the original branch and stop patching run "git am -3 --abort".
+EOF
+	    eval_gettext "When you have resolved this problem run \"\$cmdline --resolved\".
+If you would prefer to skip this patch, instead run \"\$cmdline --skip\".
+To restore the original branch and stop patching run \"\$cmdline --abort\"." >actual &&
+	    echo >>actual &&
+	    test_cmp expect actual
+	'
+}
diff --git a/t/t0200-gettext-basic.sh b/t/t0200-gettext-basic.sh
index 8853d8a..58948fa 100755
--- a/t/t0200-gettext-basic.sh
+++ b/t/t0200-gettext-basic.sh
@@ -105,4 +105,7 @@ test_expect_success GETTEXT_LOCALE 'sanity: Some gettext("") data for real local
     test -s real-locale
 '
 
+# Test eval_gettext() interpolation with the actual eval_gettext function
+test_eval_gettext_interpolation
+
 test_done
diff --git a/t/t0201-gettext-fallbacks.sh b/t/t0201-gettext-fallbacks.sh
index 7a85d9b..6d18e21 100755
--- a/t/t0201-gettext-fallbacks.sh
+++ b/t/t0201-gettext-fallbacks.sh
@@ -46,4 +46,7 @@ test_expect_success NO_GETTEXT_POISON 'eval_gettext: our eval_gettext() fallback
     test_cmp expect actual
 '
 
+# Test eval_gettext() interpolation with the fallback eval_gettext function
+test_eval_gettext_interpolation
+
 test_done
-- 
1.7.3.2.312.ge13a7