Change default directory for storing the .rnd file on Windows

Previously we would try %RANDFILE%, then %HOME% and finally "C:".
Unfortunately this often ends up being "C:" which the user may not
have write permission for.

Now we try %RANDFILE% first, and then the same set of environment vars
as GetTempFile() uses, i.e. %TMP%, then %TEMP%, %USERPROFILE% and
%SYSTEMROOT%. If all else fails we fall back to %HOME% and only then "C:".

Reviewed-by: Rich Salz <rsalz@openssl.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/crypto/rand/randfile.c b/crypto/rand/randfile.c
index 49f5405dbc..19cce2c7a8 100644
--- a/crypto/rand/randfile.c
+++ b/crypto/rand/randfile.c
@@ -286,8 +286,22 @@ const char *RAND_file_name(char *buf, size_t size)
         if (OPENSSL_strlcpy(buf, s, size) >= size)
             return NULL;
     } else {
+#ifdef OPENSSL_SYS_WINDOWS
+        /*
+         * We use the same env variables as GetTempFile() - but that function
+         * uses TCHARs, but getenv() gives us chars so its easier to do it this
+         * way
+         */
+        if ((s = getenv("TMP")) == NULL
+            && (s = getenv("TEMP")) == NULL
+            && (s = getenv("USERPROFILE")) == NULL
+            && (s = getenv("SYSTEMROOT")) == NULL) {
+            s = getenv("HOME");
+        }
+#else
         if (OPENSSL_issetugid() == 0)
             s = getenv("HOME");
+#endif
 #ifdef DEFAULT_HOME
         if (s == NULL) {
             s = DEFAULT_HOME;