curl: support XDG_CONFIG_HOME to find .curlrcbagder/XDG_CONFIG_HOME

Added test433 to verify. Updated documentation.

Reviewed-by: Jay Satiro
Suggested-by: Eli Schwartz
Fixes #5829
Closes #5837

7 files changed, 120 insertions, 12 deletions

diff --git a/docs/cmdline-opts/config.d b/docs/cmdline-opts/config.d
index df3d39220..be46f7598 100644
--- a/docs/cmdline-opts/config.d
+++ b/docs/cmdline-opts/config.d
@@ -34,13 +34,19 @@ When curl is invoked, it (unless --disable is used) checks for a default
 config file and uses it if found. The default config file is checked for in
 the following places in this order:
 
-1) curl tries to find the "home dir": It first checks for the CURL_HOME and
-then the HOME environment variables. Failing that, it uses getpwuid() on
-Unix-like systems (which returns the home dir given the current user in your
-system). On Windows, it then checks for the APPDATA variable, or as a last
-resort the '%USERPROFILE%\\Application Data'.
+1) Use the CURL_HOME environment variable if set
 
-2) On windows, if there is no .curlrc file in the home dir, it checks for one
+2) Use the XDG_CONFIG_HOME environment variable if set (Added in 7.73.0)
+
+3) Use the HOME environment variable if set
+
+4) Non-windows: use getpwuid to find the home directory
+
+5) Windows: use APPDATA if set
+
+6) Windows: use "USERPROFILE\Application Data" if set
+
+7) On windows, if there is no .curlrc file in the home dir, it checks for one
 in the same dir the curl executable is placed. On Unix-like systems, it will
 simply try to load .curlrc from the determined home dir.
 
diff --git a/src/tool_homedir.c b/src/tool_homedir.c
index 719ff6a55..3529672d6 100644
--- a/src/tool_homedir.c
+++ b/src/tool_homedir.c
@@ -25,6 +25,13 @@
 #  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_homedir.h"
@@ -45,7 +52,27 @@ static char *GetEnv(const char *variable)
 }
 
 /* return the home directory of the current user as an allocated string */
-char *homedir(void)
+
+/*
+ * The original logic found a home dir to use (by checking a range of
+ * environment variables and last using getpwuid) and returned that for the
+ * parent to use.
+ *
+ * With the XDG_CONFIG_HOME support (added much later than the other), this
+ * variable is treated differently in order to not ruin existing installations
+ * even if this environment variable is set. If this variable is set, and a
+ * file name is set to check, then only if that file name exists in that
+ * directory will it be returned as a "home directory".
+ *
+ * 1. use CURL_HOME if set
+ * 2. use XDG_CONFIG_HOME if set and fname is present
+ * 3. use HOME if set
+ * 4. Non-windows: use getpwuid
+ * 5. Windows: use APPDATA if set
+ * 6. Windows: use "USERPROFILE\Application Data" is set
+ */
+
+char *homedir(const char *fname)
 {
   char *home;
 
@@ -53,6 +80,22 @@ char *homedir(void)
   if(home)
     return home;
 
+  if(fname) {
+    home = GetEnv("XDG_CONFIG_HOME");
+    if(home) {
+      char *c = curl_maprintf("%s" DIR_CHAR "%s", home, fname);
+      if(c) {
+        int fd = open(c, O_RDONLY);
+        curl_free(c);
+        if(fd >= 0) {
+          close(fd);
+          return home;
+        }
+      }
+      free(home);
+    }
+  }
+
   home = GetEnv("HOME");
   if(home)
     return home;
diff --git a/src/tool_homedir.h b/src/tool_homedir.h
index 1f9d54a63..66defc200 100644
--- a/src/tool_homedir.h
+++ b/src/tool_homedir.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, 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
@@ -23,6 +23,6 @@
  ***************************************************************************/
 #include "tool_setup.h"
 
-char *homedir(void);
+char *homedir(const char *fname);
 
 #endif /* HEADER_CURL_TOOL_HOMEDIR_H */
diff --git a/src/tool_operate.c b/src/tool_operate.c
index ad4e85dd8..320b852e0 100644
--- a/src/tool_operate.c
+++ b/src/tool_operate.c
@@ -1696,7 +1696,7 @@ static CURLcode single_transfer(struct GlobalConfig *global,
             char *home;
             char *file;
             result = CURLE_FAILED_INIT;
-            home = homedir();
+            home = homedir(NULL);
             if(home) {
               file = aprintf("%s/.ssh/known_hosts", home);
               if(file) {
diff --git a/src/tool_parsecfg.c b/src/tool_parsecfg.c
index 5aeb2eebf..4e56492cb 100644
--- a/src/tool_parsecfg.c
+++ b/src/tool_parsecfg.c
@@ -82,7 +82,7 @@ int parseconfig(const char *filename, struct GlobalConfig *global)
   if(!filename || !*filename) {
     /* NULL or no file name attempts to load .curlrc from the homedir! */
 
-    char *home = homedir();    /* portable homedir finder */
+    char *home = homedir(".curlrc");
 #ifndef WIN32
     if(home) {
       pathalloc = curl_maprintf("%s%s.curlrc", home, DIR_CHAR);
diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc
index 3752502ef..01714238d 100644
--- a/tests/data/Makefile.inc
+++ b/tests/data/Makefile.inc
@@ -66,7 +66,7 @@ test393 test394 test395 test396 test397 \
 test400 test401 test402 test403 test404 test405 test406 test407 test408 \
 test409 \
 \
-test430 test431 test432 \
+test430 test431 test432 test433 \
 \
 test490 test491 test492 \
 \
diff --git a/tests/data/test433 b/tests/data/test433
new file mode 100644
index 000000000..90e54f05f
--- /dev/null
+++ b/tests/data/test433
@@ -0,0 +1,59 @@
+<testcase>
+<info>
+<keywords>
+--config
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Content-Length: 6
+Content-Type: text/1
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<file1 name="log/.curlrc">
+--next
+header = "a: a"
+data = "curlrc read"
+</file1>
+<server>
+http
+</server>
+<setenv>
+XDG_CONFIG_HOME=%PWD/log
+</setenv>
+<name>
+Verify XDG_CONFIG_HOME use to find .curlrc
+</name>
+<command>
+%HOSTIP:%HTTPPORT/433
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol nonewline="yes">
+POST /433 HTTP/1.1

+Host: %HOSTIP:%HTTPPORT

+Accept: */*

+a: a

+Content-Length: 11

+Content-Type: application/x-www-form-urlencoded

+

+curlrc read
+</protocol>
+</verify>
+</testcase>