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Diffstat (limited to 'ext/openssl/ossl_kdf.c')
| -rw-r--r-- | ext/openssl/ossl_kdf.c | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/ext/openssl/ossl_kdf.c b/ext/openssl/ossl_kdf.c new file mode 100644 index 0000000000..9fa42e174a --- /dev/null +++ b/ext/openssl/ossl_kdf.c @@ -0,0 +1,221 @@ +/* + * Ruby/OpenSSL Project + * Copyright (C) 2007, 2017 Ruby/OpenSSL Project Authors + */ +#include "ossl.h" + +static VALUE mKDF, eKDF; + +/* + * call-seq: + * KDF.pbkdf2_hmac(pass, salt:, iterations:, length:, hash:) -> aString + * + * PKCS #5 PBKDF2 (Password-Based Key Derivation Function 2) in combination + * with HMAC. Takes _pass_, _salt_ and _iterations_, and then derives a key + * of _length_ bytes. + * + * For more information about PBKDF2, see RFC 2898 Section 5.2 + * (https://tools.ietf.org/html/rfc2898#section-5.2). + * + * === Parameters + * pass :: The passphrase. + * salt :: The salt. Salts prevent attacks based on dictionaries of common + * passwords and attacks based on rainbow tables. It is a public + * value that can be safely stored along with the password (e.g. + * if the derived value is used for password storage). + * iterations :: The iteration count. This provides the ability to tune the + * algorithm. It is better to use the highest count possible for + * the maximum resistance to brute-force attacks. + * length :: The desired length of the derived key in octets. + * hash :: The hash algorithm used with HMAC for the PRF. May be a String + * representing the algorithm name, or an instance of + * OpenSSL::Digest. + */ +static VALUE +kdf_pbkdf2_hmac(int argc, VALUE *argv, VALUE self) +{ + VALUE pass, salt, opts, kwargs[4], str; + static ID kwargs_ids[4]; + int iters, len; + const EVP_MD *md; + + if (!kwargs_ids[0]) { + kwargs_ids[0] = rb_intern_const("salt"); + kwargs_ids[1] = rb_intern_const("iterations"); + kwargs_ids[2] = rb_intern_const("length"); + kwargs_ids[3] = rb_intern_const("hash"); + } + rb_scan_args(argc, argv, "1:", &pass, &opts); + rb_get_kwargs(opts, kwargs_ids, 4, 0, kwargs); + + StringValue(pass); + salt = StringValue(kwargs[0]); + iters = NUM2INT(kwargs[1]); + len = NUM2INT(kwargs[2]); + md = ossl_evp_get_digestbyname(kwargs[3]); + + str = rb_str_new(0, len); + if (!PKCS5_PBKDF2_HMAC(RSTRING_PTR(pass), RSTRING_LENINT(pass), + (unsigned char *)RSTRING_PTR(salt), + RSTRING_LENINT(salt), iters, md, len, + (unsigned char *)RSTRING_PTR(str))) + ossl_raise(eKDF, "PKCS5_PBKDF2_HMAC"); + + return str; +} + +#if defined(HAVE_EVP_PBE_SCRYPT) +/* + * call-seq: + * KDF.scrypt(pass, salt:, N:, r:, p:, length:) -> aString + * + * Derives a key from _pass_ using given parameters with the scrypt + * password-based key derivation function. The result can be used for password + * storage. + * + * scrypt is designed to be memory-hard and more secure against brute-force + * attacks using custom hardwares than alternative KDFs such as PBKDF2 or + * bcrypt. + * + * The keyword arguments _N_, _r_ and _p_ can be used to tune scrypt. RFC 7914 + * (published on 2016-08, https://tools.ietf.org/html/rfc7914#section-2) states + * that using values r=8 and p=1 appears to yield good results. + * + * See RFC 7914 (https://tools.ietf.org/html/rfc7914) for more information. + * + * === Parameters + * pass :: Passphrase. + * salt :: Salt. + * N :: CPU/memory cost parameter. This must be a power of 2. + * r :: Block size parameter. + * p :: Parallelization parameter. + * length :: Length in octets of the derived key. + * + * === Example + * pass = "password" + * salt = SecureRandom.random_bytes(16) + * dk = OpenSSL::KDF.scrypt(pass, salt: salt, N: 2**14, r: 8, p: 1, length: 32) + * p dk #=> "\xDA\xE4\xE2...\x7F\xA1\x01T" + */ +static VALUE +kdf_scrypt(int argc, VALUE *argv, VALUE self) +{ + VALUE pass, salt, opts, kwargs[5], str; + static ID kwargs_ids[5]; + size_t len; + uint64_t N, r, p, maxmem; + + if (!kwargs_ids[0]) { + kwargs_ids[0] = rb_intern_const("salt"); + kwargs_ids[1] = rb_intern_const("N"); + kwargs_ids[2] = rb_intern_const("r"); + kwargs_ids[3] = rb_intern_const("p"); + kwargs_ids[4] = rb_intern_const("length"); + } + rb_scan_args(argc, argv, "1:", &pass, &opts); + rb_get_kwargs(opts, kwargs_ids, 5, 0, kwargs); + + StringValue(pass); + salt = StringValue(kwargs[0]); + N = NUM2UINT64T(kwargs[1]); + r = NUM2UINT64T(kwargs[2]); + p = NUM2UINT64T(kwargs[3]); + len = NUM2LONG(kwargs[4]); + /* + * OpenSSL uses 32MB by default (if zero is specified), which is too small. + * Let's not limit memory consumption but just let malloc() fail inside + * OpenSSL. The amount is controllable by other parameters. + */ + maxmem = SIZE_MAX; + + str = rb_str_new(0, len); + if (!EVP_PBE_scrypt(RSTRING_PTR(pass), RSTRING_LEN(pass), + (unsigned char *)RSTRING_PTR(salt), RSTRING_LEN(salt), + N, r, p, maxmem, (unsigned char *)RSTRING_PTR(str), len)) + ossl_raise(eKDF, "EVP_PBE_scrypt"); + + return str; +} +#endif + +void +Init_ossl_kdf(void) +{ +#if 0 + mOSSL = rb_define_module("OpenSSL"); + eOSSLError = rb_define_class_under(mOSSL, "OpenSSLError", rb_eStandardError); +#endif + + /* + * Document-module: OpenSSL::KDF + * + * Provides functionality of various KDFs (key derivation function). + * + * KDF is typically used for securely deriving arbitrary length symmetric + * keys to be used with an OpenSSL::Cipher from passwords. Another use case + * is for storing passwords: Due to the ability to tweak the effort of + * computation by increasing the iteration count, computation can be slowed + * down artificially in order to render possible attacks infeasible. + * + * Currently, OpenSSL::KDF provides implementations for the following KDF: + * + * * PKCS #5 PBKDF2 (Password-Based Key Derivation Function 2) in + * combination with HMAC + * * scrypt + * + * == Examples + * === Generating a 128 bit key for a Cipher (e.g. AES) + * pass = "secret" + * salt = OpenSSL::Random.random_bytes(16) + * iter = 20_000 + * key_len = 16 + * key = OpenSSL::KDF.pbkdf2_hmac(pass, salt: salt, iterations: iter, + * length: key_len, hash: "sha1") + * + * === Storing Passwords + * pass = "secret" + * # store this with the generated value + * salt = OpenSSL::Random.random_bytes(16) + * iter = 20_000 + * hash = OpenSSL::Digest::SHA256.new + * len = hash.digest_length + * # the final value to be stored + * value = OpenSSL::KDF.pbkdf2_hmac(pass, salt: salt, iterations: iter, + * length: len, hash: hash) + * + * == Important Note on Checking Passwords + * When comparing passwords provided by the user with previously stored + * values, a common mistake made is comparing the two values using "==". + * Typically, "==" short-circuits on evaluation, and is therefore + * vulnerable to timing attacks. The proper way is to use a method that + * always takes the same amount of time when comparing two values, thus + * not leaking any information to potential attackers. To compare two + * values, the following could be used: + * + * def eql_time_cmp(a, b) + * unless a.length == b.length + * return false + * end + * cmp = b.bytes + * result = 0 + * a.bytes.each_with_index {|c,i| + * result |= c ^ cmp[i] + * } + * result == 0 + * end + * + * Please note that the premature return in case of differing lengths + * typically does not leak valuable information - when using PBKDF2, the + * length of the values to be compared is of fixed size. + */ + mKDF = rb_define_module_under(mOSSL, "KDF"); + /* + * Generic exception class raised if an error occurs in OpenSSL::KDF module. + */ + eKDF = rb_define_class_under(mKDF, "KDFError", eOSSLError); + + rb_define_module_function(mKDF, "pbkdf2_hmac", kdf_pbkdf2_hmac, -1); +#if defined(HAVE_EVP_PBE_SCRYPT) + rb_define_module_function(mKDF, "scrypt", kdf_scrypt, -1); +#endif +} |