core: Add gpgrt_fnameconcat and gpgrt_absfnameconcat.

* src/gpg-error.h.in (gpgrt_fnameconcat): New.
(gpgrt_absfnameconcat): New.
* src/visibility.c (gpgrt_fnameconcat, gpgrt_absfnameconcat): New.
* src/stringutils.c: New file.
(_gpgrt_vfnameconcat): New.
(_gpgrt_fnameconcat, _gpgrt_absfnameconcat): New.
* src/gpg-error.def.in: Add new functions.
* src/gpg-error.vers: Ditto.
* src/sysutils.c: Include pwd.h.
(_gpgrt_getpwdir): New.
* configure.ac: Test for pwd.h, getpwnam, getpwuid, and their _r
variants.
* src/Makefile.am (libgpg_error_la_SOURCES): Add new file.

* tests/t-stringutils.c: New.
* tests/t-common.h (xmalloc, xstrdup, xfree): New.
(die): Kludge to avoid compiler warnings.
--

The new functions are based on the code of make_filename from GnuPG.
They have been written by me ages ago with only minor modifications by
David Shaw.  I re-license them from LGPL-3.0+ OR GPL-2.0+ to
LGPL-2.1-or-later.

Signed-off-by: Werner Koch <[email protected]>

9 files changed, 318 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index e9c057f..336fe2a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -198,6 +198,7 @@ libgpg_error_la_SOURCES = gettext.h $(arch_sources) \
 	strsource.c strerror.c code-to-errno.c code-from-errno.c \
 	visibility.c visibility.h \
 	sysutils.c \
+	stringutils.c \
 	syscall-clamp.c \
 	logging.c \
 	b64dec.c b64enc.c \
diff --git a/src/gpg-error.def.in b/src/gpg-error.def.in
index 0a584c4..4e3b5d7 100644
--- a/src/gpg-error.def.in
+++ b/src/gpg-error.def.in
@@ -229,4 +229,7 @@ EXPORTS
  gpgrt_add_emergency_cleanup  @174
  gpgrt_abort                  @175
 
+ gpgrt_fnameconcat            @178
+ gpgrt_absfnameconcat         @179
+
 ;; end of file with public symbols for Windows.
diff --git a/src/gpg-error.h.in b/src/gpg-error.h.in
index d118e90..470021d 100644
--- a/src/gpg-error.h.in
+++ b/src/gpg-error.h.in
@@ -1309,6 +1309,12 @@ void gpgrt_set_fixed_string_mapper (const char *(*f)(const char*));
  * numbering scheme a LEVEL of 3 is suitable; see the manual.  */
 int gpgrt_cmp_version (const char *a, const char *b, int level);
 
+/* Construct a filename from the NULL terminated list of parts.  Tilde
+ * expansion is done for the first argument.  The caller must release
+ * the result using gpgrt_free; on error ERRNO is set and NULL
+ * returned.  The second function returns an absolute filename.  */
+char *gpgrt_fnameconcat (const char *first, ...) GPGRT_ATTR_SENTINEL(0);
+char *gpgrt_absfnameconcat (const char *first, ...) GPGRT_ATTR_SENTINEL(0);
 
 
 #ifdef __cplusplus
diff --git a/src/gpg-error.vers b/src/gpg-error.vers
index eef4cbc..594342b 100644
--- a/src/gpg-error.vers
+++ b/src/gpg-error.vers
@@ -199,6 +199,9 @@ GPG_ERROR_1.0 {
     gpgrt_add_emergency_cleanup;
     gpgrt_abort;
 
+    gpgrt_fnameconcat;
+    gpgrt_absfnameconcat;
+
   local:
     *;
 };
diff --git a/src/gpgrt-int.h b/src/gpgrt-int.h
index 718b62c..97f0533 100644
--- a/src/gpgrt-int.h
+++ b/src/gpgrt-int.h
@@ -787,6 +787,17 @@ gpg_err_code_t _gpgrt_chdir (const char *name);
 /* Return the current WD as a malloced string.  */
 char *_gpgrt_getcwd (void);
 
+/* Return the home directory of user NAME.  */
+char *_gpgrt_getpwdir (const char *name);
+
+/* Expand and concat file name parts.  */
+char *_gpgrt_vfnameconcat (int want_abs, const char *first_part,
+                           va_list arg_ptr);
+char *_gpgrt_fnameconcat (const char *first_part,
+                          ... ) GPGRT_ATTR_SENTINEL(0);
+char *_gpgrt_absfnameconcat (const char *first_part,
+                             ... ) GPGRT_ATTR_SENTINEL(0);
+
 
 /*
  * Platform specific functions (Windows)
diff --git a/src/stringutils.c b/src/stringutils.c
new file mode 100644
index 0000000..d92398d
--- /dev/null
+++ b/src/stringutils.c
@@ -0,0 +1,224 @@
+/* stringutils.c - String helper functions.
+ * Copyright (C) 1997, 2014 Werner Koch
+ * Copyright (C) 2020 g10 Code GmbH
+ *
+ * This file is part of libgpg-error.
+ *
+ * libgpg-error is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * libgpg-error 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdarg.h>
+#include <errno.h>
+#ifdef HAVE_STAT
+# include <sys/stat.h>
+#endif
+#include <sys/types.h>
+#ifdef HAVE_PWD_H
+# include <pwd.h>
+#endif
+
+#include "gpgrt-int.h"
+
+
+/* Helper for _gpgrt_fnameconcat.  The additional flag WANT_ABS tells
+ * whether an absolute file name is requested.  */
+char *
+_gpgrt_vfnameconcat (int want_abs, const char *first_part, va_list arg_ptr)
+{
+  const char *argv[32];
+  int argc;
+  size_t n;
+  int skip = 1;  /* Characters to skip from FIRST_PART.  */
+  char *home_buffer = NULL;
+  char *name, *home, *p;
+
+  /* Put all args into an array becuase we need to scan them twice.  */
+  n = strlen (first_part) + 1;
+  argc = 0;
+  while ((argv[argc] = va_arg (arg_ptr, const char *)))
+    {
+      n += strlen (argv[argc]) + 1;
+      if (argc >= DIM (argv)-1)
+        {
+          _gpg_err_set_errno (EINVAL);
+          return NULL;
+        }
+      argc++;
+    }
+  n++;
+
+  home = NULL;
+  if (*first_part == '~')
+    {
+      if (first_part[1] == '/' || !first_part[1])
+        {
+          /* This is the "~/" or "~" case.  */
+          home_buffer = _gpgrt_getenv ("HOME");
+          if (!home_buffer)
+            home_buffer = _gpgrt_getpwdir (NULL);
+          home = home_buffer;
+          if (home && *home)
+            n += strlen (home);
+        }
+      else
+        {
+          /* This is the "~username/" or "~username" case.  */
+          char *user;
+
+          user = _gpgrt_strdup (first_part+1);
+          if (!user)
+            return NULL;
+
+          p = strchr (user, '/');
+          if (p)
+            *p = 0;
+          skip = 1 + strlen (user);
+
+          home = home_buffer = _gpgrt_getpwdir (user);
+          xfree (user);
+          if (home)
+            n += strlen (home);
+          else
+            skip = 1;
+        }
+    }
+
+  name = xtrymalloc (n);
+  if (!name)
+    {
+      _gpgrt_free (home_buffer);
+      return NULL;
+    }
+
+  if (home)
+    p = stpcpy (stpcpy (name, home), first_part + skip);
+  else
+    p = stpcpy (name, first_part);
+
+  xfree (home_buffer);
+  home_buffer = NULL;
+
+  for (argc=0; argv[argc]; argc++)
+    {
+      /* Avoid a leading double slash if the first part was "/".  */
+      if (!argc && name[0] == '/' && !name[1])
+        p = stpcpy (p, argv[argc]);
+      else
+        p = stpcpy (stpcpy (p, "/"), argv[argc]);
+    }
+
+  if (want_abs)
+    {
+#ifdef HAVE_W32_SYSTEM
+      p = strchr (name, ':');
+      if (p)
+        p++;
+      else
+        p = name;
+#else
+      p = name;
+#endif
+      if (*p != '/'
+#ifdef HAVE_W32_SYSTEM
+          && *p != '\\'
+#endif
+          )
+        {
+          home = _gpgrt_getcwd ();
+          if (!home)
+            {
+              xfree (name);
+              return NULL;
+            }
+
+          n = strlen (home) + 1 + strlen (name) + 1;
+          home_buffer = xtrymalloc (n);
+          if (!home_buffer)
+            {
+              xfree (home);
+              xfree (name);
+              return NULL;
+            }
+
+          if (p == name)
+            p = home_buffer;
+          else /* Windows case.  */
+            {
+              memcpy (home_buffer, p, p - name + 1);
+              p = home_buffer + (p - name + 1);
+            }
+
+          /* Avoid a leading double slash if the cwd is "/".  */
+          if (home[0] == '/' && !home[1])
+            strcpy (stpcpy (p, "/"), name);
+          else
+            strcpy (stpcpy (stpcpy (p, home), "/"), name);
+
+          xfree (home);
+          xfree (name);
+          name = home_buffer;
+          /* Let's do a simple compression to catch the common case of
+           * a trailing "/.".  */
+          n = strlen (name);
+          if (n > 2 && name[n-2] == '/' && name[n-1] == '.')
+            name[n-2] = 0;
+        }
+    }
+
+#ifdef HAVE_W32_SYSTEM
+  for (p=name; *p; p++)
+    if (*p == '\\')
+      *p = '/';
+#endif
+  return name;
+}
+
+
+/* Construct a filename from the NULL terminated list of parts.  Tilde
+ * expansion is done for the first argument.  The caller must release
+ * the result using gpgrt_free; on error ERRNO is set and NULL
+ * returned.  */
+char *
+_gpgrt_fnameconcat (const char *first_part, ... )
+{
+  va_list arg_ptr;
+  char *result;
+
+  va_start (arg_ptr, first_part);
+  result = _gpgrt_vfnameconcat (0, first_part, arg_ptr);
+  va_end (arg_ptr);
+  return result;
+}
+
+
+/* Construct a filename from the NULL terminated list of parts.  Tilde
+ * expansion is done for the first argument.  The caller must release
+ * the result using gpgrt_free; on error ERRNO is set and NULL
+ * returned.  This version returns an absolute filename. */
+char *
+_gpgrt_absfnameconcat (const char *first_part, ... )
+{
+  va_list arg_ptr;
+  char *result;
+
+  va_start (arg_ptr, first_part);
+  result = _gpgrt_vfnameconcat (1, first_part, arg_ptr);
+  va_end (arg_ptr);
+  return result;
+}
diff --git a/src/sysutils.c b/src/sysutils.c
index bc31d92..6bdd76f 100644
--- a/src/sysutils.c
+++ b/src/sysutils.c
@@ -32,6 +32,9 @@
 #endif
 #include <sys/types.h>
 #include <fcntl.h>
+#ifdef HAVE_PWD_H
+# include <pwd.h>
+#endif
 
 #include "gpgrt-int.h"
 
@@ -337,3 +340,39 @@ _gpgrt_getcwd (void)
 #endif
     }
 }
+
+
+/* Get the standard home directory for user NAME. If NAME is NULL the
+ * directory for the current user is retruned.  Caller must release
+ * the returned string.  */
+char *
+_gpgrt_getpwdir (const char *name)
+{
+  char *result = NULL;
+#ifdef HAVE_PWD_H
+  struct passwd *pwd = NULL;
+
+  if (name)
+    {
+#ifdef HAVE_GETPWNAM
+      /* Fixme: We should use getpwnam_r if available.  */
+      pwd = getpwnam (name);
+#endif
+    }
+  else
+    {
+#ifdef HAVE_GETPWUID
+      /* Fixme: We should use getpwuid_r if available.  */
+      pwd = getpwuid (getuid());
+#endif
+    }
+  if (pwd)
+    {
+      result = _gpgrt_strdup (pwd->pw_dir);
+    }
+#else /*!HAVE_PWD_H*/
+  /* No support at all.  */
+  (void)name;
+#endif /*HAVE_PWD_H*/
+  return result;
+}
diff --git a/src/visibility.c b/src/visibility.c
index d754032..5f88aad 100644
--- a/src/visibility.c
+++ b/src/visibility.c
@@ -1180,6 +1180,33 @@ gpgrt_cmp_version (const char *a, const char *b, int level)
 
 
 
+/* String utilities.  */
+char *
+gpgrt_fnameconcat (const char *first, ... )
+{
+  va_list arg_ptr;
+  char *result;
+
+  va_start (arg_ptr, first);
+  result = _gpgrt_vfnameconcat (0, first, arg_ptr);
+  va_end (arg_ptr);
+  return result;
+}
+
+char *
+gpgrt_absfnameconcat (const char *first, ... )
+{
+  va_list arg_ptr;
+  char *result;
+
+  va_start (arg_ptr, first);
+  result = _gpgrt_vfnameconcat (1, first, arg_ptr);
+  va_end (arg_ptr);
+  return result;
+}
+
+
+
 /* For consistency reasons we use function wrappers also for Windows
  * specific function despite that they are technically not needed.  */
 #ifdef HAVE_W32_SYSTEM
diff --git a/src/visibility.h b/src/visibility.h
index 28038d0..192f733 100644
--- a/src/visibility.h
+++ b/src/visibility.h
@@ -216,6 +216,10 @@ MARK_VISIBLE (gpgrt_set_usage_outfnc);
 
 MARK_VISIBLE (gpgrt_cmp_version);
 
+MARK_VISIBLE (gpgrt_fnameconcat);
+MARK_VISIBLE (gpgrt_absfnameconcat);
+
+
 #undef MARK_VISIBLE
 
 #else /*!_GPGRT_INCL_BY_VISIBILITY_C*/