Fix EC_KEY initialization race.

Submitted by: Adam Langley
openssl · Oct 5, 2012 · 75f0bc4 · 75f0bc4
1 parent 71a2440
commit 75f0bc4
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Showing 4 changed files with 38 additions and 7 deletions.
diff --git a/crypto/ec/ec.h b/crypto/ec/ec.h
@@ -321,7 +321,15 @@ void EC_KEY_set_conv_form(EC_KEY *, point_conversion_form_t);
 /* functions to set/get method specific data  */
 void *EC_KEY_get_key_method_data(EC_KEY *, 
 	void *(*dup_func)(void *), void (*free_func)(void *), void (*clear_free_func)(void *));
-void EC_KEY_insert_key_method_data(EC_KEY *, void *data,
+/** Sets the key method data of an EC_KEY object, if none has yet been set.
+ *  \param  key              EC_KEY object
+ *  \param  data             opaque data to install.
+ *  \param  dup_func         a function that duplicates |data|.
+ *  \param  free_func        a function that frees |data|.
+ *  \param  clear_free_func  a function that wipes and frees |data|.
+ *  \return the previously set data pointer, or NULL if |data| was inserted.
+ */
+void *EC_KEY_insert_key_method_data(EC_KEY *key, void *data,
 	void *(*dup_func)(void *), void (*free_func)(void *), void (*clear_free_func)(void *));
 /* wrapper functions for the underlying EC_GROUP object */
 void EC_KEY_set_asn1_flag(EC_KEY *, int);

diff --git a/crypto/ec/ec_key.c b/crypto/ec/ec_key.c
@@ -435,18 +435,27 @@ void EC_KEY_set_conv_form(EC_KEY *key, point_conversion_form_t cform)
 void *EC_KEY_get_key_method_data(EC_KEY *key,
 	void *(*dup_func)(void *), void (*free_func)(void *), void (*clear_free_func)(void *))
 	{
-	return EC_EX_DATA_get_data(key->method_data, dup_func, free_func, clear_free_func);
+	void *ret;
+
+	CRYPTO_r_lock(CRYPTO_LOCK_EC);
+	ret = EC_EX_DATA_get_data(key->method_data, dup_func, free_func, clear_free_func);
+	CRYPTO_r_unlock(CRYPTO_LOCK_EC);
+
+	return ret;
 	}
 
-void EC_KEY_insert_key_method_data(EC_KEY *key, void *data,
+void *EC_KEY_insert_key_method_data(EC_KEY *key, void *data,
 	void *(*dup_func)(void *), void (*free_func)(void *), void (*clear_free_func)(void *))
 	{
 	EC_EXTRA_DATA *ex_data;
+
 	CRYPTO_w_lock(CRYPTO_LOCK_EC);
 	ex_data = EC_EX_DATA_get_data(key->method_data, dup_func, free_func, clear_free_func);
 	if (ex_data == NULL)
 		EC_EX_DATA_set_data(&key->method_data, data, dup_func, free_func, clear_free_func);
 	CRYPTO_w_unlock(CRYPTO_LOCK_EC);
+
+	return ex_data;
 	}
 
 void EC_KEY_set_asn1_flag(EC_KEY *key, int flag)

diff --git a/crypto/ecdh/ech_lib.c b/crypto/ecdh/ech_lib.c
@@ -205,8 +205,15 @@ ECDH_DATA *ecdh_check(EC_KEY *key)
 		ecdh_data = (ECDH_DATA *)ecdh_data_new();
 		if (ecdh_data == NULL)
 			return NULL;
-		EC_KEY_insert_key_method_data(key, (void *)ecdh_data,
-			ecdh_data_dup, ecdh_data_free, ecdh_data_free);
+		data = EC_KEY_insert_key_method_data(key, (void *)ecdh_data,
+			   ecdh_data_dup, ecdh_data_free, ecdh_data_free);
+		if (data != NULL)
+			{
+			/* Another thread raced us to install the key_method
+			 * data and won. */
+			ecdh_data_free(ecdh_data);
+			ecdh_data = (ECDH_DATA *)data;
+			}
 	}
 	else
 		ecdh_data = (ECDH_DATA *)data;

diff --git a/crypto/ecdsa/ecs_lib.c b/crypto/ecdsa/ecs_lib.c
@@ -188,8 +188,15 @@ ECDSA_DATA *ecdsa_check(EC_KEY *key)
 		ecdsa_data = (ECDSA_DATA *)ecdsa_data_new();
 		if (ecdsa_data == NULL)
 			return NULL;
-		EC_KEY_insert_key_method_data(key, (void *)ecdsa_data,
-			ecdsa_data_dup, ecdsa_data_free, ecdsa_data_free);
+		data = EC_KEY_insert_key_method_data(key, (void *)ecdsa_data,
+			   ecdsa_data_dup, ecdsa_data_free, ecdsa_data_free);
+		if (data != NULL)
+			{
+			/* Another thread raced us to install the key_method
+			 * data and won. */
+			ecdsa_data_free(ecdsa_data);
+			ecdsa_data = (ECDSA_DATA *)data;
+			}
 	}
 	else
 		ecdsa_data = (ECDSA_DATA *)data;