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# 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')

### 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::Cipher.new('aes-256-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_sha1` 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

You should never use ECB mode unless you are absolutely sure that you absolutely need it

Because of this, you will end up with a mode that explicitly requires an IV in any case. 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

Always create a secure random IV for every encryption of your Cipher

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

Although the key is generally a random value, too, it is a bad choice as an IV. There are elaborate ways how an attacker can take advantage of such an IV. As a general rule of thumb, exposing the key directly or indirectly should be avoided at all cost and exceptions only be made with good reason.

### Calling `Cipher#final`

ECB (which should not be used) and CBC are both block-based modes. This means that unlike for the other streaming-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 streaming-mode 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.new('aes-128-cbc')
    cipher.encrypt
    key = cipher.random_key
    iv = cipher.random_iv

    encrypted = cipher.update(data) + cipher.final
    ...
    decipher = OpenSSL::Cipher.new('aes-128-cbc')
    decipher.decrypt
    decipher.key = key
    decipher.iv = iv

    plain = decipher.update(encrypted) + decipher.final

    puts data == plain #=> true

### Authenticated Encryption and Associated `Data` (AEAD)

If the `OpenSSL` version used supports it, an Authenticated Encryption mode (such as GCM or CCM) should always be preferred over any unauthenticated mode. Currently, `OpenSSL` supports AE only in combination with Associated `Data` (AEAD) where additional associated data is included in the encryption process to compute a tag at the end of the encryption. This tag will also be used in the decryption process and by verifying its validity, the authenticity of a given ciphertext is established.

This is superior to unauthenticated modes in that it allows to detect if somebody effectively changed the ciphertext after it had been encrypted. This prevents malicious modifications of the ciphertext that could otherwise be exploited to modify ciphertexts in ways beneficial to potential attackers.

Associated data, also called additional authenticated data (AAD), is optionally used where there is additional information, such as headers or some metadata, that must be also authenticated but not necessarily need to be encrypted.

An example using the GCM (Galois/Counter Mode). You have 16 bytes key, 12 bytes (96 bits) nonce and the associated data auth_data. Be sure not to reuse the key and nonce pair. Reusing an nonce ruins the security guarantees of GCM mode.

    key = OpenSSL::Random.random_bytes(16)
    nonce = OpenSSL::Random.random_bytes(12)
    auth_data = "authenticated but unencrypted data"
    data = "encrypted data"

    cipher = OpenSSL::Cipher.new('aes-128-gcm').encrypt
    cipher.key = key
    cipher.iv = nonce
    cipher.auth_data = auth_data

    encrypted = cipher.update(data) + cipher.final
    tag = cipher.auth_tag(16)

Now you are the receiver. You know the key and have received nonce, auth_data, encrypted and tag through an untrusted network. Note that GCM accepts an arbitrary length tag between 1 and 16 bytes. You may additionally need to check that the received tag has the correct length, or you allow attackers to forge a valid single byte tag for the tampered ciphertext with a probability of 1/256.

    raise "tag is truncated!" unless tag.bytesize == 16
    decipher = OpenSSL::Cipher.new('aes-128-gcm').decrypt
    decipher.key = key
    decipher.iv = nonce
    decipher.auth_tag = tag # could be called at any time before #final
    decipher.auth_data = auth_data

    decrypted = decipher.update(encrypted) + decipher.final

    puts data == decrypted #=> true

Note that other AEAD ciphers may require additional steps, such as setting the expected tag length (`auth_tag_len=`) or the total data length (`ccm_data_len=`) in advance. Make sure to read the relevant man page for details.

### Public Class Methods

OpenSSL::Cipher.ciphers → array[string...]
Source

    static VALUE
    ossl_s_ciphers(VALUE self)
    {
        VALUE ary;

        ary = rb_ary_new();
        OBJ_NAME_do_all_sorted(OBJ_NAME_TYPE_CIPHER_METH,
                               add_cipher_name_to_ary,
                               (void*)ary);

        return ary;
    }

Returns the names of all available ciphers in an array.

new(string) → cipher
Source

    static VALUE
    ossl_cipher_initialize(VALUE self, VALUE str)
    {
        EVP_CIPHER_CTX *ctx;
        const EVP_CIPHER *cipher;
        VALUE cipher_holder;

        GetCipherInit(self, ctx);
        if (ctx) {
            ossl_raise(rb_eRuntimeError, "Cipher already initialized!");
        }
        cipher = ossl_evp_cipher_fetch(str, &cipher_holder);
        AllocCipher(self, ctx);
        if (EVP_CipherInit_ex(ctx, cipher, NULL, NULL, NULL, -1) != 1)
            ossl_raise(eCipherError, "EVP_CipherInit_ex");
        rb_ivar_set(self, id_cipher_holder, cipher_holder);

        return self;
    }

The string must contain a valid cipher name like “aes-256-cbc”.

A list of cipher names is available by calling `OpenSSL::Cipher.ciphers`.

### Public Instance Methods

auth_data = string
Source

    static VALUE
    ossl_cipher_set_auth_data(VALUE self, VALUE data)
    {
        EVP_CIPHER_CTX *ctx;
        unsigned char *in;
        long in_len, out_len;

        StringValue(data);

        in = (unsigned char *) RSTRING_PTR(data);
        in_len = RSTRING_LEN(data);

        GetCipher(self, ctx);
        if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
            ossl_raise(eCipherError, "AEAD not supported by this cipher");

        if (!ossl_cipher_update_long(ctx, NULL, &out_len, in, in_len))
            ossl_raise(eCipherError, "couldn't set additional authenticated data");

        return data;
    }

Sets additional authenticated data (AAD), also called associated data, for this `Cipher`. This method is available for AEAD ciphers.

The contents of this field should be non-sensitive data which will be added to the ciphertext to generate the authentication tag which validates the contents of the ciphertext.

This method must be called after `key=` and `iv=` have been set, but before starting actual encryption or decryption with `update`. In some cipher modes, `auth_tag_len=` and `ccm_data_len=` may also need to be called before this method.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3). This method internally calls EVP_CipherUpdate() with the output buffer set to NULL.

auth_tag(tag_len = 16) → String
Source

    static VALUE
    ossl_cipher_get_auth_tag(int argc, VALUE *argv, VALUE self)
    {
        VALUE vtag_len, ret;
        EVP_CIPHER_CTX *ctx;
        int tag_len = 16;

        rb_scan_args(argc, argv, "01", &vtag_len);
        if (NIL_P(vtag_len))
            vtag_len = rb_attr_get(self, id_auth_tag_len);
        if (!NIL_P(vtag_len))
            tag_len = NUM2INT(vtag_len);

        GetCipher(self, ctx);

        if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
            ossl_raise(eCipherError, "authentication tag not supported by this cipher");

        ret = rb_str_new(NULL, tag_len);
        if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, tag_len, RSTRING_PTR(ret)))
            ossl_raise(eCipherError, "retrieving the authentication tag failed");

        return ret;
    }

Gets the generated authentication tag. This method is available for AEAD ciphers, and should be called after encryption has been finalized by calling `final`.

The returned tag will be tag_len bytes long. Some cipher modes require the desired length in advance using a separate call to `auth_tag_len=`, before starting encryption.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3). This method internally calls EVP_CIPHER_CTX_ctrl() with EVP_CTRL_AEAD_GET_TAG.

auth_tag = string
Source

    static VALUE
    ossl_cipher_set_auth_tag(VALUE self, VALUE vtag)
    {
        EVP_CIPHER_CTX *ctx;
        unsigned char *tag;
        int tag_len;

        StringValue(vtag);
        tag = (unsigned char *) RSTRING_PTR(vtag);
        tag_len = RSTRING_LENINT(vtag);

        GetCipher(self, ctx);
        if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
            ossl_raise(eCipherError, "authentication tag not supported by this cipher");

        if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, tag_len, tag))
            ossl_raise(eCipherError, "unable to set AEAD tag");

        return vtag;
    }

Sets the authentication tag to verify the integrity of the ciphertext.

The authentication tag must be set before `final` is called. The tag is verified during the `final` call.

Note that, for CCM mode and OCB mode, the expected length of the tag must be set before starting decryption by a separate call to `auth_tag_len=`. The content of the tag can be provided at any time before `final` is called.

NOTE: The caller must ensure that the `String` passed to this method has the desired length. Some cipher modes support variable tag lengths, and this method may accept a truncated tag without raising an exception.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3). This method internally calls EVP_CIPHER_CTX_ctrl() with EVP_CTRL_AEAD_SET_TAG.

auth_tag_len = integer
Source

    static VALUE
    ossl_cipher_set_auth_tag_len(VALUE self, VALUE vlen)
    {
        int tag_len = NUM2INT(vlen);
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);
        if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
            ossl_raise(eCipherError, "AEAD not supported by this cipher");

        if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, tag_len, NULL))
            ossl_raise(eCipherError, "unable to set authentication tag length");

        /* for #auth_tag */
        rb_ivar_set(self, id_auth_tag_len, INT2NUM(tag_len));

        return vlen;
    }

Sets the length of the expected authentication tag for this `Cipher`. This method is available for some of AEAD ciphers that require the length to be set before starting encryption or decryption, such as CCM mode or OCB mode.

For CCM mode and OCB mode, the tag length must be set before `iv=` is set.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3). This method internally calls EVP_CIPHER_CTX_ctrl() with EVP_CTRL_AEAD_SET_TAG and a NULL buffer.

authenticated? → true | false
Source

    static VALUE
    ossl_cipher_is_authenticated(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);

        return (EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER) ? Qtrue : Qfalse;
    }

Indicates whether this `Cipher` instance uses an AEAD mode.

block_size → integer
Source

    static VALUE
    ossl_cipher_block_size(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);

        return INT2NUM(EVP_CIPHER_CTX_block_size(ctx));
    }

Returns the size in bytes of the blocks on which this `Cipher` operates on.

ccm_data_len = integer
Source

    static VALUE
    ossl_cipher_set_ccm_data_len(VALUE self, VALUE data_len)
    {
        int in_len, out_len;
        EVP_CIPHER_CTX *ctx;

        in_len = NUM2INT(data_len);

        GetCipher(self, ctx);
        if (EVP_CipherUpdate(ctx, NULL, &out_len, NULL, in_len) != 1)
            ossl_raise(eCipherError, NULL);

        return data_len;
    }

Sets the total length of the plaintext / ciphertext message that will be processed by `update` in CCM mode.

Make sure to call this method after `key=` and `iv=` have been set, and before `auth_data=` or `update` are called.

This method is only available for CCM mode ciphers.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3).

decrypt → self
Source

    static VALUE
    ossl_cipher_decrypt(VALUE self)
    {
        return ossl_cipher_init(self, 0);
    }

Initializes the `Cipher` for decryption.

Make sure to call either `encrypt` or `decrypt` before using the `Cipher` for any operation or setting any parameters.

Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, 0).

encrypt → self
Source

    static VALUE
    ossl_cipher_encrypt(VALUE self)
    {
        return ossl_cipher_init(self, 1);
    }

Initializes the `Cipher` for encryption.

Make sure to call either `encrypt` or `decrypt` before using the `Cipher` for any operation or setting any parameters.

Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, 1).

final → string
Source

    static VALUE
    ossl_cipher_final(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;
        int out_len;
        VALUE str;

        GetCipher(self, ctx);
        str = rb_str_new(0, EVP_CIPHER_CTX_block_size(ctx));
        if (!EVP_CipherFinal_ex(ctx, (unsigned char *)RSTRING_PTR(str), &out_len)) {
            /* For AEAD ciphers, this is likely an authentication failure */
            if (EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER) {
                /* For AEAD ciphers, EVP_CipherFinal_ex failures are authentication tag verification failures */
                ossl_raise(eAuthTagError, "AEAD authentication tag verification failed");
            }
            else {
                /* For non-AEAD ciphers */
                ossl_raise(eCipherError, "cipher final failed");
            }
        }
        rb_str_set_len(str, out_len);

        return str;
    }

Returns the remaining data held in the cipher object. Further calls to `Cipher#update` or `Cipher#final` are invalid. This call should always be made as the last call of an encryption or decryption operation, after having fed the entire plaintext or ciphertext to the `Cipher` instance.

When encrypting using an AEAD cipher, the authentication tag can be retrieved by `auth_tag` after `final` has been called.

When decrypting using an AEAD cipher, this method will verify the integrity of the ciphertext and the associated data with the authentication tag, which must be set by `auth_tag=` prior to calling this method. If the verification fails, `CipherError` will be raised.

iv = string
Source

    static VALUE
    ossl_cipher_set_iv(VALUE self, VALUE iv)
    {
        EVP_CIPHER_CTX *ctx;
        int iv_len = 0;

        StringValue(iv);
        GetCipher(self, ctx);

        if (EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER)
            iv_len = (int)(VALUE)EVP_CIPHER_CTX_get_app_data(ctx);
        if (!iv_len)
            iv_len = EVP_CIPHER_CTX_iv_length(ctx);
        if (RSTRING_LEN(iv) != iv_len)
            ossl_raise(rb_eArgError, "iv must be %d bytes", iv_len);

        if (EVP_CipherInit_ex(ctx, NULL, NULL, NULL, (unsigned char *)RSTRING_PTR(iv), -1) != 1)
            ossl_raise(eCipherError, NULL);

        return 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.

This method expects the `String` to have the length equal to `iv_len`. To use a different IV length with an AEAD cipher, `iv_len=` must be set prior to calling this method.

NOTE: In `OpenSSL` API conventions, the IV value may correspond to the “nonce” instead in some cipher modes. Refer to the `OpenSSL` man pages for details.

See also the man page EVP_CipherInit_ex(3).

iv_len → integer
Source

    static VALUE
    ossl_cipher_iv_length(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;
        int len = 0;

        GetCipher(self, ctx);
        if (EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER)
            len = (int)(VALUE)EVP_CIPHER_CTX_get_app_data(ctx);
        if (!len)
            len = EVP_CIPHER_CTX_iv_length(ctx);

        return INT2NUM(len);
    }

Returns the expected length in bytes for an IV for this `Cipher`.

iv_len = integer
Source

    static VALUE
    ossl_cipher_set_iv_length(VALUE self, VALUE iv_length)
    {
        int len = NUM2INT(iv_length);
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);
        if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
            ossl_raise(eCipherError, "cipher does not support AEAD");

        if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, len, NULL))
            ossl_raise(eCipherError, "unable to set IV length");

        /*
         * EVP_CIPHER_CTX_iv_length() returns the default length. So we need to save
         * the length somewhere. Luckily currently we aren't using app_data.
         */
        EVP_CIPHER_CTX_set_app_data(ctx, (void *)(VALUE)len);

        return iv_length;
    }

Sets the IV/nonce length for this `Cipher`. This method is available for AEAD ciphers that support variable IV lengths. This method can be called if a different IV length than OpenSSL’s default is desired, prior to calling `iv=`.

See also the “AEAD Interface” section of the man page EVP_EncryptInit(3). This method internally calls EVP_CIPHER_CTX_ctrl() with EVP_CTRL_AEAD_SET_IVLEN.

key = string
Source

    static VALUE
    ossl_cipher_set_key(VALUE self, VALUE key)
    {
        EVP_CIPHER_CTX *ctx;
        int key_len;

        StringValue(key);
        GetCipher(self, ctx);

        key_len = EVP_CIPHER_CTX_key_length(ctx);
        if (RSTRING_LEN(key) != key_len)
            ossl_raise(rb_eArgError, "key must be %d bytes", key_len);

        if (EVP_CipherInit_ex(ctx, NULL, NULL, (unsigned char *)RSTRING_PTR(key), NULL, -1) != 1)
            ossl_raise(eCipherError, NULL);

        rb_ivar_set(self, id_key_set, Qtrue);

        return 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`.

See also the man page EVP_CipherInit_ex(3).

key_len → integer
Source

    static VALUE
    ossl_cipher_key_length(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);

        return INT2NUM(EVP_CIPHER_CTX_key_length(ctx));
    }

Returns the key length in bytes of the `Cipher`.

key_len = integer
Source

    static VALUE
    ossl_cipher_set_key_length(VALUE self, VALUE key_length)
    {
        int len = NUM2INT(key_length);
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);
        if (EVP_CIPHER_CTX_set_key_length(ctx, len) != 1)
            ossl_raise(eCipherError, NULL);

        return key_length;
    }

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).

See EVP_CIPHER_CTX_set_key_length for further information.

name → string
Source

    static VALUE
    ossl_cipher_name(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);

        return rb_str_new2(EVP_CIPHER_name(EVP_CIPHER_CTX_cipher(ctx)));
    }

Returns the short name of the cipher which may differ slightly from the original name provided.

padding = 1 or 0
Source

    static VALUE
    ossl_cipher_set_padding(VALUE self, VALUE padding)
    {
        EVP_CIPHER_CTX *ctx;
        int pad = NUM2INT(padding);

        GetCipher(self, ctx);
        if (EVP_CIPHER_CTX_set_padding(ctx, pad) != 1)
            ossl_raise(eCipherError, NULL);
        return padding;
    }

Enables or disables padding. By default encryption operations are padded using standard block padding and the padding is checked and removed when decrypting. If the pad parameter is zero then no padding is performed, the total amount of data encrypted or decrypted must then be a multiple of the block size or an error will occur.

See EVP_CIPHER_CTX_set_padding for further information.

pkcs5_keyivgen(pass, salt = nil, iterations = 2048, digest = "MD5") → nil
Source

    static VALUE
    ossl_cipher_pkcs5_keyivgen(int argc, VALUE *argv, VALUE self)
    {
        EVP_CIPHER_CTX *ctx;
        const EVP_MD *digest;
        VALUE vpass, vsalt, viter, vdigest, md_holder;
        unsigned char key[EVP_MAX_KEY_LENGTH], iv[EVP_MAX_IV_LENGTH], *salt = NULL;
        int iter;

        rb_scan_args(argc, argv, "13", &vpass, &vsalt, &viter, &vdigest);
        StringValue(vpass);
        if(!NIL_P(vsalt)){
            StringValue(vsalt);
            if(RSTRING_LEN(vsalt) != PKCS5_SALT_LEN)
                ossl_raise(eCipherError, "salt must be an 8-octet string");
            salt = (unsigned char *)RSTRING_PTR(vsalt);
        }
        iter = NIL_P(viter) ? 2048 : NUM2INT(viter);
        if (iter <= 0)
            rb_raise(rb_eArgError, "iterations must be a positive integer");
        digest = NIL_P(vdigest) ? EVP_md5() : ossl_evp_md_fetch(vdigest, &md_holder);
        GetCipher(self, ctx);
        EVP_BytesToKey(EVP_CIPHER_CTX_cipher(ctx), digest, salt,
                       (unsigned char *)RSTRING_PTR(vpass), RSTRING_LENINT(vpass), iter, key, iv);
        if (EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, -1) != 1)
            ossl_raise(eCipherError, NULL);
        OPENSSL_cleanse(key, sizeof key);
        OPENSSL_cleanse(iv, sizeof iv);

        rb_ivar_set(self, id_key_set, Qtrue);

        return Qnil;
    }

Generates and sets the key/IV based on a password.

WARNING: This method is deprecated and should not be used. This method corresponds to EVP_BytesToKey(), a non-standard `OpenSSL` extension of the legacy PKCS #5 v1.5 key derivation function. See `OpenSSL::KDF` for other options to derive keys from passwords.

### Parameters

- salt must be an 8 byte string if provided.

- iterations is an integer with a default of 2048.

- digest is a `Digest` object that defaults to ‘MD5’

random_iv → iv
Source

    # File ext/openssl/lib/openssl/cipher.rb, line 55
    def random_iv
      str = OpenSSL::Random.random_bytes(self.iv_len)
      self.iv = str
    end

Generate a random IV with `OpenSSL::Random.random_bytes` and sets it to the cipher, and returns it.

You must call `encrypt` or `decrypt` before calling this method.

random_key → key
Source

    # File ext/openssl/lib/openssl/cipher.rb, line 43
    def random_key
      str = OpenSSL::Random.random_bytes(self.key_len)
      self.key = str
    end

Generate a random key with `OpenSSL::Random.random_bytes` and sets it to the cipher, and returns it.

You must call `encrypt` or `decrypt` before calling this method.

reset → self
Source

    static VALUE
    ossl_cipher_reset(VALUE self)
    {
        EVP_CIPHER_CTX *ctx;

        GetCipher(self, ctx);
        if (EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, -1) != 1)
            ossl_raise(eCipherError, NULL);

        return self;
    }

Fully resets the internal state of the `Cipher`. By using this, the same `Cipher` instance may be used several times for encryption or decryption tasks.

Internally calls EVP_CipherInit_ex(ctx, NULL, NULL, NULL, NULL, -1).

update(data [, buffer]) → string or buffer
Source

    static VALUE
    ossl_cipher_update(int argc, VALUE *argv, VALUE self)
    {
        EVP_CIPHER_CTX *ctx;
        unsigned char *in;
        long in_len, out_len;
        VALUE data, str;

        rb_scan_args(argc, argv, "11", &data, &str);

        if (!RTEST(rb_attr_get(self, id_key_set)))
            ossl_raise(eCipherError, "key not set");

        StringValue(data);
        in = (unsigned char *)RSTRING_PTR(data);
        in_len = RSTRING_LEN(data);
        GetCipher(self, ctx);

        /*
         * As of OpenSSL 3.2, there is no reliable way to determine the required
         * output buffer size for arbitrary cipher modes.
         * https://github.com/openssl/openssl/issues/22628
         *
         * in_len+block_size is usually sufficient, but AES key wrap with padding
         * ciphers require in_len+15 even though they have a block size of 8 bytes.
         *
         * Using EVP_MAX_BLOCK_LENGTH (32) as a safe upper bound for ciphers
         * currently implemented in OpenSSL, but this can change in the future.
         */
        if (in_len > LONG_MAX - EVP_MAX_BLOCK_LENGTH) {
            ossl_raise(rb_eRangeError,
                       "data too big to make output buffer: %ld bytes", in_len);
        }
        out_len = in_len + EVP_MAX_BLOCK_LENGTH;

        if (NIL_P(str))
            str = rb_str_buf_new(out_len);
        else {
            StringValue(str);
            if ((long)rb_str_capacity(str) >= out_len)
                rb_str_modify(str);
            else
                rb_str_modify_expand(str, out_len - RSTRING_LEN(str));
        }

        if (!ossl_cipher_update_long(ctx, (unsigned char *)RSTRING_PTR(str),
                                     &out_len, in, in_len))
            ossl_raise(eCipherError, "EVP_CipherUpdate");
        rb_str_set_len(str, out_len);

        return str;
    }

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.

If buffer is given, the encryption/decryption result will be written to it. buffer will be resized automatically.

NOTE: When decrypting using an AEAD cipher, the integrity of the output is not verified until `final` has been called.