+/* Open a file with the desired permissions, minus the umask.
+ Also, if we want to create an executable file, we call fchmod()
+ to set the executable bits. */
+
+FILE *fopenmask(const char *filename, const char *mode, mode_t perms) {
+ mode_t mask = umask(0);
+ perms &= ~mask;
+ umask(~perms);
+ FILE *f = fopen(filename, mode);
+#ifdef HAVE_FCHMOD
+ if((perms & 0444) && f)
+ fchmod(fileno(f), perms);
+#endif
+ umask(mask);
+ return f;
+}
+
+static void disable_old_keys(const char *filename, const char *what) {
+ char tmpfile[PATH_MAX] = "";
+ char buf[1024];
+ bool disabled = false;
+ bool block = false;
+ bool error = false;
+ FILE *r, *w;
+
+ r = fopen(filename, "r");
+ if(!r)
+ return;
+
+ snprintf(tmpfile, sizeof tmpfile, "%s.tmp", filename);
+
+ struct stat st = {.st_mode = 0600};
+ fstat(fileno(r), &st);
+ w = fopenmask(tmpfile, "w", st.st_mode);
+
+ while(fgets(buf, sizeof buf, r)) {
+ if(!block && !strncmp(buf, "-----BEGIN ", 11)) {
+ if((strstr(buf, " EC ") && strstr(what, "ECDSA")) || (strstr(buf, " RSA ") && strstr(what, "RSA"))) {
+ disabled = true;
+ block = true;
+ }
+ }
+
+ bool ecdsapubkey = !strncasecmp(buf, "ECDSAPublicKey", 14) && strchr(" \t=", buf[14]) && strstr(what, "ECDSA");
+
+ if(ecdsapubkey)
+ disabled = true;
+
+ if(w) {
+ if(block || ecdsapubkey)
+ fputc('#', w);
+ if(fputs(buf, w) < 0) {
+ error = true;
+ break;
+ }
+ }
+
+ if(block && !strncmp(buf, "-----END ", 9))
+ block = false;
+ }
+
+ if(w)
+ if(fclose(w) < 0)
+ error = true;
+ if(ferror(r) || fclose(r) < 0)
+ error = true;
+
+ if(disabled) {
+ if(!w || error) {
+ fprintf(stderr, "Warning: old key(s) found, remove them by hand!\n");
+ if(w)
+ unlink(tmpfile);
+ return;
+ }
+
+#ifdef HAVE_MINGW
+ // We cannot atomically replace files on Windows.
+ char bakfile[PATH_MAX] = "";
+ snprintf(bakfile, sizeof bakfile, "%s.bak", filename);
+ if(rename(filename, bakfile) || rename(tmpfile, filename)) {
+ rename(bakfile, filename);
+#else
+ if(rename(tmpfile, filename)) {
+#endif
+ fprintf(stderr, "Warning: old key(s) found, remove them by hand!\n");
+ } else {
+#ifdef HAVE_MINGW
+ unlink(bakfile);
+#endif
+ fprintf(stderr, "Warning: old key(s) found and disabled.\n");
+ }
+ }
+
+ unlink(tmpfile);
+}
+
+static FILE *ask_and_open(const char *filename, const char *what, const char *mode, bool ask, mode_t perms) {