tls: fix crash when opening priv key for writing

The open syscall will return a negative value if the call fails. Switch
the check to look for this instead of 0.

before:

[gmnisrv] generating certificate for localhost
gmnisrv: src/tls.c:68: tls_host_gencert: Assertion `pf' failed.
abort (core dumped)  ./gmnisrv -C config.ini

after:

[gmnisrv] generating certificate for localhost
[gmnisrv] opening private key for writing failed: No such file or directory
[gmnisrv] TLS initialization failed

Signed-off-by: William Casarin <jb55@jb55.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/tls.c b/src/tls.c
index ca8a307..f7ed344 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -58,7 +58,7 @@ tls_host_gencert(struct gmnisrv_tls *tlsconf, struct gmnisrv_host *host,
 	assert(r);
 
 	int pfd = open(keypath, O_CREAT | O_WRONLY, 0600);
-	if (!pfd) {
+	if (pfd < 0) {
 		server_error("opening private key for writing failed: %s",
 			strerror(errno));
 		return 1;