tool_findfile: search for a file in the homedir

The homedir() function is now renamed into findfile() and iterates over
all the environment variables trying to access the file in question
until it finds it. Last resort is then getpwuid() if
available. Previously it would first try to find a home directory and if
that was set, insist on checking only that directory for the file. This
now returns the full file name it finds.

The Windows specific checks are now done differently too and in this
order:

1 - %USERPROFILE%
2 - %APPDATA%
3 - %USERPROFILE%\\Application Data

The windows order is modified to match how the Windows 10 ssh tool works
when it searches for .ssh/known_hosts.

Reported-by: jeffrson on github
Co-authored-by: Jay Satiro
Fixes #8033
Closes #8035

1 files changed, 134 insertions, 0 deletions

diff --git a/src/tool_findfile.c b/src/tool_findfile.c
new file mode 100644
index 000000000..cda8c8ed8
--- /dev/null
+++ b/src/tool_findfile.c
@@ -0,0 +1,134 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "tool_setup.h"
+
+#ifdef HAVE_PWD_H
+#  undef __NO_NET_API /* required for building for AmigaOS */
+#  include <pwd.h>
+#endif
+
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+
+#include <curl/mprintf.h>
+
+#include "tool_findfile.h"
+
+#include "memdebug.h" /* keep this as LAST include */
+
+struct finder {
+  const char *env;
+  const char *append;
+};
+
+static const struct finder list[] = {
+  { "CURL_HOME", NULL },
+  { "XDG_CONFIG_HOME", NULL },
+  { "HOME", NULL },
+#ifdef WIN32
+  { "USERPROFILE", NULL },
+  { "APPDATA", NULL },
+  { "USERPROFILE", "\\Application Data"},
+#endif
+  { NULL, NULL }
+};
+
+static char *checkhome(const char *home, const char *fname, bool dotscore)
+{
+  const char pref[2] = { '.', '_' };
+  int i;
+  for(i = 0; i < (dotscore ? 2 : 1); i++) {
+    char *c;
+    if(dotscore)
+      c = curl_maprintf("%s" DIR_CHAR "%c%s", home, pref[i], &fname[1]);
+    else
+      c = curl_maprintf("%s" DIR_CHAR "%s", home, fname);
+    if(c) {
+      int fd = open(c, O_RDONLY);
+      if(fd >= 0) {
+        char *path = strdup(c);
+        close(fd);
+        curl_free(c);
+        return path;
+      }
+      curl_free(c);
+    }
+  }
+  return NULL;
+}
+
+/*
+ * findfile() - return the full path name of the file.
+ *
+ * If 'dotscore' is TRUE, then check for the file first with a leading dot
+ * and then with a leading underscore.
+ *
+ * 1. Iterate over the environment variables in order, and if set, check for
+ *    the given file to be accessed there, then it is a match.
+ * 2. Non-windows: try getpwuid
+ */
+char *findfile(const char *fname, bool dotscore)
+{
+  int i;
+  DEBUGASSERT(fname && fname[0]);
+  DEBUGASSERT(!dotscore || (fname[0] == '.'));
+
+  if(!fname[0])
+    return NULL;
+
+  for(i = 0; list[i].env; i++) {
+    char *home = curl_getenv(list[i].env);
+    if(home) {
+      char *path;
+      if(!home[0]) {
+        curl_free(home);
+        continue;
+      }
+      if(list[i].append) {
+        char *c = curl_maprintf("%s%s", home, list[i].append);
+        curl_free(home);
+        if(!c)
+          return NULL;
+        home = c;
+      }
+      path = checkhome(home, fname, dotscore);
+      curl_free(home);
+      if(path)
+        return path;
+    }
+  }
+#if defined(HAVE_GETPWUID) && defined(HAVE_GETEUID)
+  {
+    struct passwd *pw = getpwuid(geteuid());
+    if(pw) {
+      char *home = pw->pw_dir;
+      if(home && home[0])
+        return checkhome(home, fname, FALSE);
+    }
+  }
+#endif /* PWD-stuff */
+  return NULL;
+}