diff --git a/src/invitation.c b/src/invitation.c
index 415c2377..3102e416 100644
--- a/src/invitation.c
+++ b/src/invitation.c
@@ -335,7 +335,11 @@ int cmd_invite(int argc, char *argv[]) {
 			return 1;
 		}
 		chmod(filename, 0600);
-		ecdsa_write_pem_private_key(key, f);
+		if(!ecdsa_write_pem_private_key(key, f)) {
+			fprintf(stderr, "Could not write ECDSA private key\n");
+			fclose(f);
+			return 1;
+		}
 		fclose(f);
 
 		if(connect_tincd(false))
@@ -704,6 +708,8 @@ make_names:
 
 	snprintf(filename, sizeof filename, "%s" SLASH "ed25519_key.priv", confbase);
 	f = fopenmask(filename, "w", 0600);
+	if(!f)
+		return false;
 
 	if(!ecdsa_write_pem_private_key(key, f)) {
 		fprintf(stderr, "Error writing private key!\n");
@@ -725,10 +731,14 @@ make_names:
 	snprintf(filename, sizeof filename, "%s" SLASH "rsa_key.priv", confbase);
 	f = fopenmask(filename, "w", 0600);
 
-	rsa_write_pem_private_key(rsa, f);
+	if(!f || !rsa_write_pem_private_key(rsa, f)) {
+		fprintf(stderr, "Could not write private RSA key\n");
+	} else if(!rsa_write_pem_public_key(rsa, fh)) {
+		fprintf(stderr, "Could not write public RSA key\n");
+	}
+
 	fclose(f);
 
-	rsa_write_pem_public_key(rsa, fh);
 	fclose(fh);
 
 	rsa_free(rsa);
diff --git a/src/sptps_keypair.c b/src/sptps_keypair.c
index 399404e1..fde86227 100644
--- a/src/sptps_keypair.c
+++ b/src/sptps_keypair.c
@@ -88,7 +88,10 @@ int main(int argc, char *argv[]) {
 	
 	FILE *fp = fopen(argv[1], "w");
 	if(fp) {
-		ecdsa_write_pem_private_key(key, fp);
+		if(!ecdsa_write_pem_private_key(key, fp)) {
+			fprintf(stderr, "Could not write ECDSA private key\n");
+			return 1;
+		}
 		fclose(fp);
 	} else {
 		fprintf(stderr, "Could not open '%s' for writing: %s\n", argv[1], strerror(errno));
@@ -97,7 +100,8 @@ int main(int argc, char *argv[]) {
 
 	fp = fopen(argv[2], "w");
 	if(fp) {
-		ecdsa_write_pem_public_key(key, fp);
+		if(!ecdsa_write_pem_public_key(key, fp))
+			fprintf(stderr, "Could not write ECDSA public key\n");
 		fclose(fp);
 	} else {
 		fprintf(stderr, "Could not open '%s' for writing: %s\n", argv[2], strerror(errno));
diff --git a/src/sptps_speed.c b/src/sptps_speed.c
index d03246c5..4cb1221b 100644
--- a/src/sptps_speed.c
+++ b/src/sptps_speed.c
@@ -102,19 +102,26 @@ int main(int argc, char *argv[]) {
 
 	fprintf(stderr, "Ed25519 sign for %lg seconds: ", duration);
 	for(clock_start(); clock_countto(duration);)
-		ecdsa_sign(key1, buf1, 256, buf2);
+		if(!ecdsa_sign(key1, buf1, 256, buf2))
+			return 1;
 	fprintf(stderr, "%22.2lf op/s\n", rate);
 
 	fprintf(stderr, "Ed25519 verify for %lg seconds: ", duration);
 	for(clock_start(); clock_countto(duration);)
-		ecdsa_verify(key1, buf1, 256, buf2);
+		if(!ecdsa_verify(key1, buf1, 256, buf2)) {
+			fprintf(stderr, "Signature verification failed\n");
+			return 1;
+		}
 	fprintf(stderr, "%20.2lf op/s\n", rate);
 
 	ecdh1 = ecdh_generate_public(buf1);
 	fprintf(stderr, "ECDH for %lg seconds: ", duration);
 	for(clock_start(); clock_countto(duration);) {
 		ecdh2 = ecdh_generate_public(buf2);
-		ecdh_compute_shared(ecdh2, buf1, buf3);
+		if(!ecdh2)
+			return 1;
+		if(!ecdh_compute_shared(ecdh2, buf1, buf3))
+			return 1;
 	}
 	fprintf(stderr, "%28.2lf op/s\n", rate);
 	ecdh_free(ecdh1);
diff --git a/src/tincctl.c b/src/tincctl.c
index c9d8c67c..00757c47 100644
--- a/src/tincctl.c
+++ b/src/tincctl.c
@@ -233,6 +233,12 @@ FILE *fopenmask(const char *filename, const char *mode, mode_t perms) {
 	perms &= ~mask;
 	umask(~perms);
 	FILE *f = fopen(filename, mode);
+
+	if(!f) {
+		fprintf(stderr, "Could not open %s: %s\n", filename, strerror(errno));
+		return NULL;
+	}
+
 #ifdef HAVE_FCHMOD
 	if((perms & 0444) && f)
 		fchmod(fileno(f), perms);