diff options
Diffstat (limited to 'ext/openssl')
-rw-r--r-- | ext/openssl/ossl_cipher.c | 227 |
1 files changed, 204 insertions, 23 deletions
diff --git a/ext/openssl/ossl_cipher.c b/ext/openssl/ossl_cipher.c index 7a30641153..147ba6b872 100644 --- a/ext/openssl/ossl_cipher.c +++ b/ext/openssl/ossl_cipher.c @@ -126,6 +126,7 @@ ossl_cipher_initialize(VALUE self, VALUE str) return self; } + static VALUE ossl_cipher_copy(VALUE self, VALUE other) { @@ -181,6 +182,9 @@ ossl_s_ciphers(VALUE self) * call-seq: * cipher.reset -> self * + * Fully resets the internal state of the Cipher. By using this, the same + * Cipher instance may be used several times for en- or decryption tasks. + * * Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, -1). */ static VALUE @@ -243,7 +247,10 @@ ossl_cipher_init(int argc, VALUE *argv, VALUE self, int mode) * call-seq: * cipher.encrypt -> self * - * Make sure to call .encrypt or .decrypt before using any of the following methods: + * Initializes the Cipher for encryption. + * + * Make sure to call Cipher#encrypt or Cipher#decrypt before using any of the + * following methods: * * [key=, iv=, random_key, random_iv, pkcs5_keyivgen] * * Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, 1). @@ -258,7 +265,10 @@ ossl_cipher_encrypt(int argc, VALUE *argv, VALUE self) * call-seq: * cipher.decrypt -> self * - * Make sure to call .encrypt or .decrypt before using any of the following methods: + * Initializes the Cipher for decryption. + * + * Make sure to call Cipher#encrypt or Cipher#decrypt before using any of the + * following methods: * * [key=, iv=, random_key, random_iv, pkcs5_keyivgen] * * Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, 0). @@ -273,11 +283,13 @@ ossl_cipher_decrypt(int argc, VALUE *argv, VALUE self) * call-seq: * cipher.pkcs5_keyivgen(pass [, salt [, iterations [, digest]]] ) -> nil * - * Generates and sets the key/iv based on a password. + * Generates and sets the key/IV based on a password. * - * WARNING: This method is only PKCS5 v1.5 compliant when using RC2, RC4-40, or DES - * with MD5 or SHA1. Using anything else (like AES) will generate the key/iv using an - * OpenSSL specific method. Use a PKCS5 v2 key generation method instead. + * WARNING: This method is only PKCS5 v1.5 compliant when using RC2, RC4-40, + * or DES with MD5 or SHA1. Using anything else (like AES) will generate the + * key/iv using an OpenSSL specific method. This method is deprecated and + * should no longer be used. Use a PKCS5 v2 key generation method from + * OpenSSL::PKCS5 instead. * * === Parameters * +salt+ must be an 8 byte string if provided. @@ -322,6 +334,11 @@ ossl_cipher_pkcs5_keyivgen(int argc, VALUE *argv, VALUE self) * call-seq: * cipher.update(data [, buffer]) -> string or buffer * + * Encrypts data in a streaming fashion. Hand consecutive blocks of data + * to the +update+ method in order to encrypt it. Returns the encrypted + * data chunk. When done, the output of Cipher#final should be additionally + * added to the result. + * * === Parameters * +data+ is a nonempty string. * +buffer+ is an optional string to store the result. @@ -360,9 +377,10 @@ ossl_cipher_update(int argc, VALUE *argv, VALUE self) /* * call-seq: - * cipher.final -> aString + * cipher.final -> string * - * Returns the remaining data held in the cipher object. Further calls to update() or final() will return garbage. + * Returns the remaining data held in the cipher object. Further calls to + * Cipher#update or Cipher#final will return garbage. * * See EVP_CipherFinal_ex for further information. */ @@ -387,7 +405,8 @@ ossl_cipher_final(VALUE self) * call-seq: * cipher.name -> string * - * Returns the name of the cipher which may differ slightly from the original name provided. + * Returns the name of the cipher which may differ slightly from the original + * name provided. */ static VALUE ossl_cipher_name(VALUE self) @@ -403,9 +422,12 @@ ossl_cipher_name(VALUE self) * call-seq: * cipher.key = string -> string * - * Sets the cipher key. + * Sets the cipher key. To generate a key, you should either use a secure + * random byte string or, if the key is to be derived from a password, you + * should rely on PBKDF2 functionality provided by OpenSSL::PKCS5. To + * generate a secure random-based key, Cipher#random_key may be used. * - * Only call this method after calling cipher.encrypt or cipher.decrypt. + * Only call this method after calling Cipher#encrypt or Cipher#decrypt. */ static VALUE ossl_cipher_set_key(VALUE self, VALUE key) @@ -428,9 +450,16 @@ ossl_cipher_set_key(VALUE self, VALUE key) * call-seq: * cipher.iv = string -> string * - * Sets the cipher iv. + * Sets the cipher IV. Please note that since you should never be using ECB + * mode, an IV is always explicitly required and should be set prior to + * encryption. The IV itself can be safely transmitted in public, but it + * should be unpredictable to prevent certain kinds of attacks. You may use + * Cipher#random_iv to create a secure random IV. + * + * Only call this method after calling Cipher#encrypt or Cipher#decrypt. * - * Only call this method after calling cipher.encrypt or cipher.decrypt. + * If not explicitly set, the OpenSSL default of an all-zeroes ("\\0") IV is + * used. */ static VALUE ossl_cipher_set_iv(VALUE self, VALUE iv) @@ -454,8 +483,9 @@ ossl_cipher_set_iv(VALUE self, VALUE iv) * call-seq: * cipher.key_len = integer -> integer * - * Sets the key length of the cipher. If the cipher is a fixed length cipher then attempting to set the key - * length to any value other than the fixed value is an error. + * Sets the key length of the cipher. If the cipher is a fixed length cipher + * then attempting to set the key length to any value other than the fixed + * value is an error. * * Under normal circumstances you do not need to call this method (and probably shouldn't). * @@ -508,30 +538,28 @@ ossl_cipher_set_padding(VALUE self, VALUE padding) GetCipher(self, ctx); \ return INT2NUM(EVP_CIPHER_##func(EVP_CIPHER_CTX_cipher(ctx))); \ } -CIPHER_0ARG_INT(key_length) -CIPHER_0ARG_INT(iv_length) -CIPHER_0ARG_INT(block_size) -#if 0 /* * call-seq: * cipher.key_len -> integer * + * Returns the key length in bytes of the Cipher. */ -static VALUE ossl_cipher_key_length() { } +CIPHER_0ARG_INT(key_length) /* * call-seq: * cipher.iv_len -> integer * + * Returns the expected length in bytes for an IV for this Cipher. */ -static VALUE ossl_cipher_iv_length() { } +CIPHER_0ARG_INT(iv_length) /* * call-seq: * cipher.block_size -> integer * + * Returns the size in bytes of the blocks on which this Cipher operates on. */ -static VALUE ossl_cipher_block_size() { } -#endif +CIPHER_0ARG_INT(block_size) /* * INIT @@ -542,6 +570,159 @@ Init_ossl_cipher(void) #if 0 mOSSL = rb_define_module("OpenSSL"); /* let rdoc know about mOSSL */ #endif + + /* Document-class: OpenSSL::Cipher + * + * Provides symmetric algorithms for encryption and decryption. The + * algorithms that are available depend on the particular version + * of OpenSSL that is installed. + * + * === Listing all supported algorithms + * + * A list of supported algorithms can be obtained by + * + * puts OpenSSL::Cipher.ciphers + * + * === Instantiating a Cipher + * + * There are several ways to create a Cipher instance. Generally, a + * Cipher algorithm is categorized by its name, the key length in bits + * and the cipher mode to be used. The most generic way to create a + * Cipher is the following + * + * cipher = OpenSSL::Cipher.new('<name>-<key length>-<mode>') + * + * That is, a string consisting of the hyphenated concatenation of the + * individual components name, key length and mode. Either all-uppercase + * or all lowercase strings may be used, for example: + * + * cipher = OpenSSL::Cipher.new('AES-128-CBC') + * + * For each algorithm supported, there is a class defined under the + * Cipher class that goes by the name of the cipher, e.g. to obtain an + * instance of AES, you could also use + * + * # these are equivalent + * cipher = OpenSSL::Cipher::AES.new(128, :CBC) + * cipher = OpenSSL::Cipher::AES.new(128, 'CBC') + * cipher = OpenSSL::Cipher::AES.new('128-CBC') + * + * Finally, due to its wide-spread use, there are also extra classes + * defined for the different key sizes of AES + * + * cipher = OpenSSL::Cipher::AES128.new(:CBC) + * cipher = OpenSSL::Cipher::AES192.new(:CBC) + * cipher = OpenSSL::Cipher::AES256.new(:CBC) + * + * === Choosing either encryption or decryption mode + * + * Encryption and decryption are often very similar operations for + * symmetric algorithms, this is reflected by not having to choose + * different classes for either operation, both can be done using the + * same class. Still, after obtaining a Cipher instance, we need to + * tell the instance what it is that we intend to do with it, so we + * need to call either + * + * cipher.encrypt + * + * or + * + * cipher.decrypt + * + * on the Cipher instance. This should be the first call after creating + * the instance, otherwise configuration that has already been set could + * get lost in the process. + * + * === Choosing a key + * + * Symmetric encryption requires a key that is the same for the encrypting + * and for the decrypting party and after initial key establishment should + * be kept as private information. There are a lot of ways to create + * insecure keys, the most notable is to simply take a password as the key + * without processing the password further. A simple and secure way to + * create a key for a particular Cipher is + * + * cipher = OpenSSL::AES256.new(:CFB) + * cipher.encrypt + * key = cipher.random_key # also sets the generated key on the Cipher + * + * If you absolutely need to use passwords as encryption keys, you + * should use Password-Based Key Derivation Function 2 (PBKDF2) by + * generating the key with the help of the functionality provided by + * OpenSSL::PKCS5.pbkdf2_hmac or OpenSSL::PKCS5.pbkdf2_hmac. + * + * Although there is Cipher#pkcs5_keyivgen, its use is deprecated and + * it should only be used in legacy applications because it does not use + * the newer PKCS#5 v2 algorithms. + * + * === Choosing an IV + * + * The cipher modes CBC, CFB, OFB and CTR all need an "initialization + * vector", or short, IV. ECB mode is the only mode that does not require + * an IV, but there is almost no legitimate use case for this mode + * because of the fact that it does not sufficiently hide plaintext + * patterns. Therefore + * + * <b>You should never use ECB mode unless you are absolutely sure that + * you absolutely need it</b> + * + * Because of this, you will end up with a mode that explicitly requires + * an IV in any case. Note that for backwards compatibility reasons, + * setting an IV is not explicitly mandated by the Cipher API. If not + * set, OpenSSL itself defaults to an all-zeroes IV ("\\0", not the + * character). Although the IV can be seen as public information, i.e. + * it may be transmitted in public once generated, it should still stay + * unpredictable to prevent certain kinds of attacks. Therefore, ideally + * + * <b>Always create a secure random IV for every encryption of your + * Cipher</b> + * + * A new, random IV should be created for every encryption of data. Think + * of the IV as a nonce (number used once) - it's public but random and + * unpredictable. A secure random IV can be created as follows + * + * cipher = ... + * cipher.encrypt + * key = cipher.random_key + * iv = cipher.random_iv # also sets the generated IV on the Cipher + * + * === Calling Cipher#final + * + * ECB (which should not be used) and CBC are both block-based modes. + * This means that unlike for the other stream-based modes, they operate + * on fixed-size blocks of data, and therefore they require a + * "finalization" step to produce or correctly decrypt the last block of + * data by appropriately handling some form of padding. Therefore it is + * essential to add the output of OpenSSL::Cipher#final to your + * encryption/decryption buffer or you will end up with decryption errors + * or truncated data. + * + * Although this is not really necessary for stream-based ciphers, it is + * still recommended to apply the same pattern of adding the output of + * Cipher#final there as well - it also enables you to switch between + * modes more easily in the future. + * + * === Encrypting and decrypting some data + * + * data = "Very, very confidential data" + * + * cipher = OpenSSL::Cipher::AES.new(128, :CBC) + * cipher.encrypt + * key = cipher.random_key + * iv = cipher.random_iv + * + * encrypted = cipher.update(data) + cipher.final + * ... + * decipher = OpenSSL::Cipher::AES.new(128, :CBC) + * decipher.decrypt + * decipher.key = key + * decipher.iv = iv + * + * plain = decipher.update(encrypted) + decipher.final + * + * puts data == plain #=> true + * + */ cCipher = rb_define_class_under(mOSSL, "Cipher", rb_cObject); eCipherError = rb_define_class_under(cCipher, "CipherError", eOSSLError); |