Make absolutely sure we can write config files before accepting an invitation.

diff --git a/src/invitation.c b/src/invitation.c
index a5454bf449af45b14dd518a138c501fce8ac8c97..95478a7f431822afb2ebd5fd86e3b271d4d18763 100644 (file)
--- a/src/invitation.c
+++ b/src/invitation.c
@@ -749,9 +749,20 @@ int cmd_join(int argc, char *argv[]) {
                return 1;
        }
 
-       // Make sure confdir exists.
-       if(mkdir(confdir, 0755) && errno != EEXIST) {
-               fprintf(stderr, "Could not create directory %s: %s\n", CONFDIR, strerror(errno));
+       // Make sure confbase exists and is accessible.
+       if(mkdir(confbase, 0755) && errno != EEXIST) {
+               fprintf(stderr, "Could not create directory %s: %s\n", confbase, strerror(errno));
+               return 1;
+       }
+
+       if(access(confbase, R_OK | W_OK | X_OK)) {
+               fprintf(stderr, "No permission to write in directory %s: %s\n", confbase, strerror(errno));
+               return 1;
+       }
+
+       // If a netname or explicit configuration directory is specified, check for an existing tinc.conf.
+       if((netname || confbasegiven) && !access(tinc_conf, F_OK)) {
+               fprintf(stderr, "Configuration file %s already exists!\n", tinc_conf);
                return 1;
        }