Merge branch 'tmp-fuzzers-update' into 'master'

fuzz: update ed448 fuzzer traces and other fuzz improvements

See merge request gnutls/gnutls!1177

11 files changed, 161 insertions, 41 deletions

diff --git a/fuzz/README-adding-traces.md b/fuzz/README-adding-traces.md
index 485c8bbb3d..20866f6ff3 100644
--- a/fuzz/README-adding-traces.md
+++ b/fuzz/README-adding-traces.md
@@ -1,10 +1,14 @@
 # Generate and add new protocol traces 
 
+## Step 1: compilation
+
 Compile GnuTLS as:
 ```
 ./configure --enable-fuzzer-target --disable-doc
 ```
 
+## Step 2: Get the traces
+
 Start the server with the necessary parameters (here TLS1.3 is assumed).
 ```
 ./gnutls-http-serv --priority NORMAL:-VERS-ALL:+VERS-TLS1.3
@@ -17,6 +21,19 @@ gnutls-cli localhost:5556 --priority NORMAL:-VERS-ALL:+VERS-TLS1.3:-KX-ALL:+PSK
 gnutls-cli localhost:5556 --priority NORMAL:-VERS-ALL:+VERS-TLS1.3:-KX-ALL:+DHE-PSK --insecure --save-server-trace /tmp/server-trace-psk2 --save-client-trace /tmp/client-trace-psk2 --pskusername test --pskkey 8a7759b3f26983c453e448060bde8981
 ```
 
+## Step 3: Ensure server can read them
+
+If there is a new key type tested, ensure that `gnutls_server_fuzzer` and
+`gnutls_client_fuzzer` enable it, and set the appropriate keys.
+
+To verify that connection proceeds past to reading the first packet use:
+$ make gnutls_server_fuzzer gnutls_client_fuzzer
+$ GNUTLS_DEBUG_LEVEL=6 gnutls_server_fuzzer /tmp/server-trace-x509
+$ GNUTLS_DEBUG_LEVEL=6 gnutls_client_fuzzer /tmp/client-trace-x509
+
+
+## Step 4: Copy the traces
+
 cp /tmp/server-trace-x509 fuzz/gnutls_client_fuzzer.in/$(sha1sum /tmp/server-trace-x509|cut -d ' ' -f 1)
 cp /tmp/server-trace-psk1 fuzz/gnutls_psk_client_fuzzer.in/$(sha1sum /tmp/server-trace-psk1|cut -d ' ' -f 1)
 cp /tmp/server-trace-psk2 fuzz/gnutls_psk_client_fuzzer.in/$(sha1sum /tmp/server-trace-psk2|cut -d ' ' -f 1)
diff --git a/fuzz/certs.h b/fuzz/certs.h
index c95f63b5dd..de57f9d4fe 100644
--- a/fuzz/certs.h
+++ b/fuzz/certs.h
@@ -300,6 +300,74 @@ static const uint8_t kEd25519PrivateKeyDER[] = {
 	0xe5, 0xb4, 0x5f, 0x9b, 0xd7, 0xa6, 0xf8, 0x36, 0x0c, 0x92, 0x59, 0x70
 };
 
+static const uint8_t kEd448PrivateKeyDER[] = {
+	0x30, 0x47, 0x02, 0x01, 0x00, 0x30, 0x05, 0x06, 0x03, 0x2b, 0x65, 0x71,
+	0x04, 0x3b, 0x04, 0x39, 0x0c, 0xf8, 0x7e, 0xb0, 0x94, 0xbf, 0x46, 0xd1,
+	0x61, 0xbd, 0xe3, 0xb9, 0x9d, 0x1d, 0x32, 0x85, 0x6f, 0xec, 0xfa, 0xe0,
+	0x14, 0x23, 0x92, 0xcd, 0x98, 0xc0, 0x91, 0xdb, 0x20, 0x6d, 0x17, 0x4b,
+	0xbf, 0x8e, 0xf4, 0x76, 0xa9, 0xcf, 0x74, 0x6d, 0x94, 0x30, 0x6c, 0x56,
+	0x5f, 0x97, 0xac, 0x50, 0x79, 0x6f, 0x02, 0x1e, 0xff, 0x8d, 0x77, 0x9c,
+	0xa5
+};
+
+static const uint8_t kEd448CertificateDER[] = {
+	0x30, 0x82, 0x02, 0x86, 0x30, 0x82, 0x01, 0x3e, 0xa0, 0x03, 0x02, 0x01,
+	0x02, 0x02, 0x14, 0x71, 0x76, 0x43, 0x3c, 0xd1, 0x31, 0x93, 0x61, 0xdd,
+	0xf7, 0x39, 0x0e, 0x77, 0xd7, 0x35, 0x41, 0x3b, 0x9d, 0xed, 0x8d, 0x30,
+	0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x0b,
+	0x05, 0x00, 0x30, 0x19, 0x31, 0x17, 0x30, 0x15, 0x06, 0x03, 0x55, 0x04,
+	0x03, 0x13, 0x0e, 0x47, 0x6e, 0x75, 0x54, 0x4c, 0x53, 0x20, 0x54, 0x65,
+	0x73, 0x74, 0x20, 0x43, 0x41, 0x30, 0x20, 0x17, 0x0d, 0x31, 0x39, 0x30,
+	0x34, 0x32, 0x34, 0x31, 0x34, 0x35, 0x36, 0x35, 0x38, 0x5a, 0x18, 0x0f,
+	0x39, 0x39, 0x39, 0x39, 0x31, 0x32, 0x33, 0x31, 0x32, 0x33, 0x35, 0x39,
+	0x35, 0x39, 0x5a, 0x30, 0x00, 0x30, 0x43, 0x30, 0x05, 0x06, 0x03, 0x2b,
+	0x65, 0x71, 0x03, 0x3a, 0x00, 0x9a, 0xdd, 0xde, 0x61, 0xf6, 0x68, 0xf2,
+	0xdb, 0xc0, 0xac, 0x24, 0x87, 0x4a, 0xdb, 0x47, 0xa2, 0xaa, 0x6a, 0xd5,
+	0x9f, 0xa8, 0x88, 0xbd, 0xc5, 0xd4, 0x30, 0x70, 0x5e, 0xd0, 0x79, 0x6a,
+	0x8c, 0x33, 0x07, 0x82, 0xb5, 0x18, 0x60, 0x78, 0x5b, 0xe6, 0x3f, 0xd7,
+	0x9b, 0x1c, 0x7c, 0xf5, 0x8f, 0xd7, 0x28, 0xb2, 0xbf, 0x3d, 0x77, 0x39,
+	0x51, 0x00, 0xa3, 0x81, 0x8d, 0x30, 0x81, 0x8a, 0x30, 0x0c, 0x06, 0x03,
+	0x55, 0x1d, 0x13, 0x01, 0x01, 0xff, 0x04, 0x02, 0x30, 0x00, 0x30, 0x14,
+	0x06, 0x03, 0x55, 0x1d, 0x11, 0x04, 0x0d, 0x30, 0x0b, 0x82, 0x09, 0x6c,
+	0x6f, 0x63, 0x61, 0x6c, 0x68, 0x6f, 0x73, 0x74, 0x30, 0x13, 0x06, 0x03,
+	0x55, 0x1d, 0x25, 0x04, 0x0c, 0x30, 0x0a, 0x06, 0x08, 0x2b, 0x06, 0x01,
+	0x05, 0x05, 0x07, 0x03, 0x01, 0x30, 0x0f, 0x06, 0x03, 0x55, 0x1d, 0x0f,
+	0x01, 0x01, 0xff, 0x04, 0x05, 0x03, 0x03, 0x07, 0x80, 0x00, 0x30, 0x1d,
+	0x06, 0x03, 0x55, 0x1d, 0x0e, 0x04, 0x16, 0x04, 0x14, 0x60, 0x1a, 0x34,
+	0x07, 0x71, 0x25, 0xec, 0x23, 0x5a, 0xe5, 0x71, 0xbc, 0x95, 0xec, 0x1b,
+	0x8b, 0x9a, 0x19, 0xdc, 0xfb, 0x30, 0x1f, 0x06, 0x03, 0x55, 0x1d, 0x23,
+	0x04, 0x18, 0x30, 0x16, 0x80, 0x14, 0x4d, 0x56, 0xb7, 0x6a, 0x00, 0x58,
+	0xf1, 0x67, 0x92, 0xf4, 0xa6, 0x75, 0x55, 0x1b, 0x8e, 0x53, 0x01, 0x03,
+	0xef, 0xcf, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
+	0x01, 0x01, 0x0b, 0x05, 0x00, 0x03, 0x82, 0x01, 0x31, 0x00, 0x2f, 0xec,
+	0xc8, 0x85, 0xde, 0x78, 0x08, 0xab, 0x6d, 0x2e, 0xd7, 0xc2, 0x9f, 0x04,
+	0xe1, 0xbb, 0x50, 0x73, 0xfc, 0xf5, 0x15, 0xb0, 0x48, 0xa5, 0x39, 0x0c,
+	0x9b, 0xe0, 0x6f, 0xf6, 0x7f, 0xfd, 0x4a, 0xb2, 0x08, 0xa2, 0x27, 0xe7,
+	0x68, 0x1b, 0x37, 0x28, 0xde, 0xd4, 0x19, 0xa4, 0xd2, 0x76, 0xff, 0x1d,
+	0xa6, 0x02, 0x06, 0x87, 0x3d, 0x1e, 0x07, 0xfc, 0x7c, 0x8b, 0xf7, 0xdc,
+	0x78, 0x10, 0xc9, 0xc6, 0x66, 0x93, 0xd3, 0x19, 0x3c, 0xa6, 0x77, 0xb7,
+	0xee, 0xe3, 0x1d, 0x15, 0xd5, 0x59, 0x28, 0xd9, 0xd9, 0x7f, 0x4c, 0xc2,
+	0x6e, 0x79, 0x00, 0xaf, 0xdd, 0xdc, 0x61, 0x68, 0xeb, 0x2e, 0x96, 0x39,
+	0xdd, 0xd6, 0x4c, 0x9b, 0x10, 0x69, 0x4d, 0x05, 0x84, 0xd7, 0x5c, 0x03,
+	0x63, 0xf1, 0xe3, 0x6d, 0x79, 0xd8, 0x2e, 0xb5, 0x40, 0x27, 0xb8, 0x3f,
+	0x97, 0xb5, 0xea, 0x97, 0x5b, 0x78, 0x5d, 0x9f, 0x73, 0x00, 0xf4, 0x93,
+	0x63, 0x99, 0x13, 0x36, 0xf9, 0x21, 0xef, 0x82, 0xdc, 0x16, 0xf4, 0x9a,
+	0x96, 0x5c, 0xe9, 0xce, 0x78, 0x85, 0x48, 0x7f, 0x5b, 0xff, 0x7d, 0x8e,
+	0xde, 0xb5, 0x70, 0x81, 0x24, 0x39, 0x8e, 0xd2, 0xaa, 0x61, 0xf3, 0x6b,
+	0x54, 0x61, 0xac, 0x27, 0xf6, 0x1f, 0xec, 0x35, 0xe6, 0x22, 0xd2, 0xb8,
+	0xef, 0x1d, 0x94, 0x47, 0x8e, 0x29, 0x70, 0x87, 0x2e, 0x9f, 0x36, 0x53,
+	0xba, 0xe8, 0x4f, 0x97, 0xa2, 0xcd, 0x7a, 0x52, 0x27, 0xb8, 0xfa, 0x2f,
+	0xa0, 0x9a, 0x7c, 0xce, 0xc1, 0xde, 0x70, 0x0f, 0x2c, 0x7b, 0x6a, 0x18,
+	0x3b, 0x72, 0x34, 0x7c, 0x11, 0x77, 0x0a, 0x9c, 0x1d, 0x2c, 0x18, 0xc4,
+	0x34, 0xa7, 0x58, 0x5a, 0xb7, 0x58, 0xff, 0x2f, 0x7c, 0xda, 0x70, 0xaa,
+	0x78, 0xa4, 0x89, 0x06, 0x55, 0xee, 0xbf, 0x52, 0x89, 0xbf, 0x18, 0x0a,
+	0x6f, 0x08, 0x51, 0xa2, 0x47, 0x59, 0x96, 0x06, 0xd9, 0x0e, 0x01, 0x72,
+	0x5b, 0x3f, 0x7e, 0x74, 0xe9, 0x6a, 0x2f, 0x54, 0x00, 0xa4, 0x1e, 0x38,
+	0x03, 0x6c, 0xa0, 0xb2, 0xb4, 0xf8, 0x33, 0x16, 0x4c, 0x1b, 0x0c, 0x00,
+	0xa7, 0x7d, 0x84, 0xa3, 0x33, 0x44, 0x31, 0x96, 0x50, 0x9a, 0x99, 0xf2,
+	0x4a, 0xdd
+};
+
 /* Raw public-key key material for testing */
 static char rawpk_public_key_pem1[] =
 	"-----BEGIN PUBLIC KEY-----\n"
@@ -365,4 +433,14 @@ const gnutls_datum_t rawpk_private_key1 = {
 	sizeof(rawpk_private_key_pem1) - 1
 };
 
+#define IGNORE_CERTS \
+	(void) kEd25519PrivateKeyDER; \
+	(void) kEd25519CertificateDER; \
+	(void) kEd448PrivateKeyDER; \
+	(void) kEd448CertificateDER; \
+	(void) kECDSAPrivateKeyDER; \
+	(void) kECDSACertificateDER; \
+	(void) kRSAPrivateKeyDER; \
+	(void) kRSACertificateDER
+
 #endif
diff --git a/fuzz/gnutls_client_fuzzer.c b/fuzz/gnutls_client_fuzzer.c
index f5c969d990..b68cdb6d7c 100644
--- a/fuzz/gnutls_client_fuzzer.c
+++ b/fuzz/gnutls_client_fuzzer.c
@@ -46,7 +46,7 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 	assert(res >= 0);
 
 	/*res = gnutls_set_default_priority(session);*/
-	res = gnutls_priority_set_direct(session, "NORMAL:"VERS_STR, NULL);
+	res = gnutls_priority_set_direct(session, "NORMAL:+SIGN-EDDSA-ED448:"VERS_STR, NULL);
 	assert(res >= 0);
 
 	memdata.data = data;
diff --git a/fuzz/gnutls_server_fuzzer.in/96c552adcacf4108c319533ea61c33f4240ad0fd b/fuzz/gnutls_client_fuzzer.in/96c552adcacf4108c319533ea61c33f4240ad0fd
index feceb0a220..feceb0a220 100644
--- a/fuzz/gnutls_server_fuzzer.in/96c552adcacf4108c319533ea61c33f4240ad0fd
+++ b/fuzz/gnutls_client_fuzzer.in/96c552adcacf4108c319533ea61c33f4240ad0fd
diff --git a/fuzz/gnutls_client_rawpk_fuzzer.c b/fuzz/gnutls_client_rawpk_fuzzer.c
index af4336363a..c20b885538 100644
--- a/fuzz/gnutls_client_rawpk_fuzzer.c
+++ b/fuzz/gnutls_client_rawpk_fuzzer.c
@@ -54,13 +54,7 @@
 
 int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 {
-	(void) kEd25519PrivateKeyDER;
-	(void) kEd25519CertificateDER;
-	(void) kECDSAPrivateKeyDER;
-	(void) kECDSACertificateDER;
-	(void) kRSAPrivateKeyDER;
-	(void) kRSACertificateDER;
-
+	IGNORE_CERTS;
 	int res;
 	gnutls_session_t session;
 	gnutls_certificate_credentials_t rawpk_cred;
diff --git a/fuzz/gnutls_psk_server_fuzzer.c b/fuzz/gnutls_psk_server_fuzzer.c
index 3c1f62df19..d07e2eef60 100644
--- a/fuzz/gnutls_psk_server_fuzzer.c
+++ b/fuzz/gnutls_psk_server_fuzzer.c
@@ -51,6 +51,7 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 	gnutls_datum_t rsa_cert, rsa_key;
 	gnutls_datum_t ecdsa_cert, ecdsa_key;
 	gnutls_datum_t ed25519_cert, ed25519_key;
+	gnutls_datum_t ed448_cert, ed448_key;
 	gnutls_session_t session;
 	gnutls_certificate_credentials_t xcred;
 	gnutls_psk_server_credentials_t pcred;
@@ -83,6 +84,11 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 	ed25519_key.data = (unsigned char *)kEd25519PrivateKeyDER;
 	ed25519_key.size = sizeof(kEd25519PrivateKeyDER);
 
+	ed448_cert.data = (unsigned char *)kEd448CertificateDER;
+	ed448_cert.size = sizeof(kEd448CertificateDER);
+	ed448_key.data = (unsigned char *)kEd448PrivateKeyDER;
+	ed448_key.size = sizeof(kEd448PrivateKeyDER);
+
 	res =
 		gnutls_certificate_set_x509_key_mem(xcred, &rsa_cert, &rsa_key,
 		GNUTLS_X509_FMT_DER);
@@ -98,6 +104,11 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 		GNUTLS_X509_FMT_DER);
 	assert(res >= 0);
 
+	res =
+		gnutls_certificate_set_x509_key_mem(xcred, &ed448_cert, &ed448_key,
+		GNUTLS_X509_FMT_DER);
+	assert(res >= 0);
+
 	gnutls_certificate_set_known_dh_params(xcred, GNUTLS_SEC_PARAM_MEDIUM);
 
 	res = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, xcred);
diff --git a/fuzz/gnutls_server_fuzzer.c b/fuzz/gnutls_server_fuzzer.c
index 3ef02aec3c..c42ff21efa 100644
--- a/fuzz/gnutls_server_fuzzer.c
+++ b/fuzz/gnutls_server_fuzzer.c
@@ -34,6 +34,7 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 	gnutls_datum_t rsa_cert, rsa_key;
 	gnutls_datum_t ecdsa_cert, ecdsa_key;
 	gnutls_datum_t ed25519_cert, ed25519_key;
+	gnutls_datum_t ed448_cert, ed448_key;
 	gnutls_session_t session;
 	gnutls_certificate_credentials_t xcred;
 	struct mem_st memdata;
@@ -59,6 +60,11 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 	ed25519_key.data = (unsigned char *)kEd25519PrivateKeyDER;
 	ed25519_key.size = sizeof(kEd25519PrivateKeyDER);
 
+	ed448_cert.data = (unsigned char *)kEd448CertificateDER;
+	ed448_cert.size = sizeof(kEd448CertificateDER);
+	ed448_key.data = (unsigned char *)kEd448PrivateKeyDER;
+	ed448_key.size = sizeof(kEd448PrivateKeyDER);
+
 	res =
 		gnutls_certificate_set_x509_key_mem(xcred, &rsa_cert, &rsa_key,
 		GNUTLS_X509_FMT_DER);
@@ -74,13 +80,18 @@ int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 		GNUTLS_X509_FMT_DER);
 	assert(res >= 0);
 
+	res =
+		gnutls_certificate_set_x509_key_mem(xcred, &ed448_cert, &ed448_key,
+		GNUTLS_X509_FMT_DER);
+	assert(res >= 0);
+
 	gnutls_certificate_set_known_dh_params(xcred, GNUTLS_SEC_PARAM_MEDIUM);
 
 	res = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, xcred);
 	assert(res >= 0);
 
 	/*res = gnutls_set_default_priority(session);*/
-	res = gnutls_priority_set_direct(session, "NORMAL:"VERS_STR, NULL);
+	res = gnutls_priority_set_direct(session, "NORMAL:+SIGN-EDDSA-ED448:"VERS_STR, NULL);
 	assert(res >= 0);
 
 	memdata.data = data;
diff --git a/fuzz/gnutls_client_fuzzer.in/5ef0df17445fb4098d15536a1195a47cb55b6845 b/fuzz/gnutls_server_fuzzer.in/5ef0df17445fb4098d15536a1195a47cb55b6845
index 45eede51d0..45eede51d0 100644
--- a/fuzz/gnutls_client_fuzzer.in/5ef0df17445fb4098d15536a1195a47cb55b6845
+++ b/fuzz/gnutls_server_fuzzer.in/5ef0df17445fb4098d15536a1195a47cb55b6845
diff --git a/fuzz/gnutls_server_rawpk_fuzzer.c b/fuzz/gnutls_server_rawpk_fuzzer.c
index 854f5872fe..a1a6713869 100644
--- a/fuzz/gnutls_server_rawpk_fuzzer.c
+++ b/fuzz/gnutls_server_rawpk_fuzzer.c
@@ -50,13 +50,7 @@
 
 int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 {
-	(void) kEd25519PrivateKeyDER;
-	(void) kEd25519CertificateDER;
-	(void) kECDSAPrivateKeyDER;
-	(void) kECDSACertificateDER;
-	(void) kRSAPrivateKeyDER;
-	(void) kRSACertificateDER;
-
+	IGNORE_CERTS;
 	int res;
 	gnutls_session_t session;
 	gnutls_certificate_credentials_t rawpk_cred;
diff --git a/fuzz/gnutls_srp_server_fuzzer.c b/fuzz/gnutls_srp_server_fuzzer.c
index 567b7d45c9..04301638e4 100644
--- a/fuzz/gnutls_srp_server_fuzzer.c
+++ b/fuzz/gnutls_srp_server_fuzzer.c
@@ -61,6 +61,7 @@ srp_cb(gnutls_session_t session, const char *username,
 
 int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size)
 {
+	IGNORE_CERTS;
 	int res;
 	gnutls_datum_t rsa_cert, rsa_key;
 	gnutls_datum_t ecdsa_cert, ecdsa_key;
diff --git a/fuzz/main.c b/fuzz/main.c
index cdeba17238..b2223d0fc7 100644
--- a/fuzz/main.c
+++ b/fuzz/main.c
@@ -43,6 +43,41 @@
 #  define SLASH '/'
 #endif
 
+static int test_single_file(const char *fname)
+{
+	int fd, ret;
+	struct stat st;
+	uint8_t *data;
+	ssize_t n;
+
+	if ((fd = open(fname, O_RDONLY)) == -1) {
+		fprintf(stderr, "Failed to open %s (%d)\n", fname, errno);
+		return -1;
+	}
+
+	if (fstat(fd, &st) != 0) {
+		fprintf(stderr, "Failed to stat %d (%d)\n", fd, errno);
+		close(fd);
+		return -1;
+	}
+
+	data = malloc(st.st_size);
+	if ((n = read(fd, data, st.st_size)) == st.st_size) {
+		printf("testing %llu bytes from '%s'\n", (unsigned long long) st.st_size, fname);
+		fflush(stdout);
+		LLVMFuzzerTestOneInput(data, st.st_size);
+		fflush(stderr);
+		ret = 0;
+	} else {
+		fprintf(stderr, "Failed to read %llu bytes from %s (%d), got %zd\n", (unsigned long long) st.st_size, fname, errno, n);
+		ret = -1;
+	}
+
+	free(data);
+	close(fd);
+	return ret;
+}
+
 static int test_all_from(const char *dirname)
 {
 	DIR *dirp;
@@ -55,31 +90,8 @@ static int test_all_from(const char *dirname)
 			char fname[strlen(dirname) + strlen(dp->d_name) + 2];
 			snprintf(fname, sizeof(fname), "%s/%s", dirname, dp->d_name);
 
-			int fd;
-			if ((fd = open(fname, O_RDONLY)) == -1) {
-				fprintf(stderr, "Failed to open %s (%d)\n", fname, errno);
-				continue;
-			}
-
-			struct stat st;
-			if (fstat(fd, &st) != 0) {
-				fprintf(stderr, "Failed to stat %d (%d)\n", fd, errno);
-				close(fd);
+			if (test_single_file(fname) < 0)
 				continue;
-			}
-
-			uint8_t *data = malloc(st.st_size);
-			ssize_t n;
-			if ((n = read(fd, data, st.st_size)) == st.st_size) {
-				printf("testing %llu bytes from '%s'\n", (unsigned long long) st.st_size, fname);
-				fflush(stdout);
-				LLVMFuzzerTestOneInput(data, st.st_size);
-				fflush(stderr);
-			} else
-				fprintf(stderr, "Failed to read %llu bytes from %s (%d), got %zd\n", (unsigned long long) st.st_size, fname, errno, n);
-
-			free(data);
-			close(fd);
 		}
 		closedir(dirp);
 		return 0;
@@ -108,7 +120,9 @@ int main(int argc, char **argv)
 	target_len -= 4; // ignore .exe
 #endif
 
-	{
+	if (argc > 1) { /* test a single file */
+		test_single_file(argv[1]);
+	} else { /* test the target directory */
 		int rc;
 		char corporadir[sizeof(SRCDIR) + 1 + target_len + 8];
 		snprintf(corporadir, sizeof(corporadir), SRCDIR "/%.*s.in", (int) target_len, target);