[Openvpn-devel,v3,2/3] Allow external EC key through --management-external-key

Message ID	1516909513-31683-1-git-send-email-selva.nair@gmail.com
State	Accepted
Headers	show Return-Path: <openvpn-devel-bounces@lists.sourceforge.net> From: selva.nair@gmail.com To: openvpn-devel@lists.sourceforge.net Date: Thu, 25 Jan 2018 14:45:13 -0500 Message-Id: <1516909513-31683-1-git-send-email-selva.nair@gmail.com> In-Reply-To: <1516301696-11308-1-git-send-email-selva.nair@gmail.com> References: <1516301696-11308-1-git-send-email-selva.nair@gmail.com> RBL: Sender listed at http://www.dnswl.org/, no trust [209.85.214.43 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.0 AWL AWL: Adjusted score from AWL reputation of From: address Subject: [Openvpn-devel] [PATCH v3 2/3] Allow external EC key through --management-external-key Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: openvpn-devel-bounces@lists.sourceforge.net X-getmail-retrieved-from-mailbox: Inbox
Series	None \| expand [Openvpn-devel,v3,2/3] Allow external EC key through --management-external-key

diff --git a/doc/management-notes.txt b/doc/management-notes.txt index 070c2d6..96470d0 100644 --- a/doc/management-notes.txt +++ b/doc/management-notes.txt @@ -779,14 +779,14 @@ COMMAND -- rsa-sig (OpenVPN 2.3 or higher, management version <= 1) Provides support for external storage of the private key. Requires the --management-external-key option. This option can be used instead of "key" in client mode, and allows the client to run without the need to load the -actual private key. When the SSL protocol needs to perform an RSA sign +actual private key. When the SSL protocol needs to perform a sign operation, the data to be signed will be sent to the management interface via a notification as follows: >PK_SIGN:[BASE64_DATA] (if client announces support for management version > 1) >RSA_SIGN:[BASE64_DATA] (only older clients will be prompted like this) -The management interface client should then create a PKCS#1 v1.5 signature of +The management interface client should then create an appropriate signature of the (decoded) BASE64_DATA using the private key and return the SSL signature as follows: @@ -797,8 +797,9 @@ pk-sig (or rsa-sig) . END -Base64 encoded output of RSA_private_encrypt() (OpenSSL) or mbedtls_pk_sign() -(mbed TLS) will provide a correct signature. +Base64 encoded output of RSA_private_encrypt for RSA or ECDSA_sign() for EC +using OpenSSL or mbedtls_pk_sign() using mbed TLS will provide a correct +signature. This capability is intended to allow the use of arbitrary cryptographic service providers with OpenVPN via the management interface. diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c index 242b464..74ce596 100644 --- a/src/openvpn/ssl_openssl.c +++ b/src/openvpn/ssl_openssl.c @@ -1043,58 +1043,51 @@ openvpn_extkey_rsa_finish(RSA *rsa) return 1; } -/* sign arbitrary data */ +/* Pass the input hash in 'dgst' to management and get the signature back. + * On input siglen contains the capacity of the buffer 'sig'. + * On return signature is in sig. + * Return value is signature length or -1 on error. + */ static int -rsa_priv_enc(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding) +get_sig_from_man(const unsigned char *dgst, unsigned int dgstlen, + unsigned char *sig, unsigned int siglen) { - /* optional app data in rsa->meth->app_data; */ char *in_b64 = NULL; char *out_b64 = NULL; - int ret = -1; - int len; + int len = -1; - if (padding != RSA_PKCS1_PADDING) - { - RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE); - goto done; - } - - /* convert 'from' to base64 */ - if (openvpn_base64_encode(from, flen, &in_b64) <= 0) - { - goto done; - } - - /* call MI for signature */ - if (management) + /* convert 'dgst' to base64 */ + if (management + && openvpn_base64_encode(dgst, dgstlen, &in_b64) > 0) { out_b64 = management_query_pk_sig(management, in_b64); } - if (!out_b64) + if (out_b64) { - goto done; + len = openvpn_base64_decode(out_b64, sig, siglen); } - /* decode base64 signature to binary */ - len = RSA_size(rsa); - ret = openvpn_base64_decode(out_b64, to, len); + free(in_b64); + free(out_b64); + return len; +} - /* verify length */ - if (ret != len) - { - ret = -1; - } +/* sign arbitrary data */ +static int +rsa_priv_enc(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding) +{ + unsigned int len = RSA_size(rsa); + int ret = -1; -done: - if (in_b64) - { - free(in_b64); - } - if (out_b64) + if (padding != RSA_PKCS1_PADDING) { - free(out_b64); + RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE); + return -1; } - return ret; + + ret = get_sig_from_man(from, flen, to, len); + + return (ret == len)? ret : -1; } static int @@ -1166,6 +1159,130 @@ err: return 0; } +#if OPENSSL_VERSION_NUMBER > 0x10100000L && !defined(OPENSSL_NO_EC) + +/* called when EC_KEY is destroyed */ +static void +openvpn_extkey_ec_finish(EC_KEY *ec) +{ + /* release the method structure */ + const EC_KEY_METHOD *ec_meth = EC_KEY_get_method(ec); + EC_KEY_METHOD_free((EC_KEY_METHOD *) ec_meth); +} + +/* EC_KEY_METHOD callback: sign(). + * Sign the hash using EC key and return DER encoded signature in sig, + * its length in siglen. Return value is 1 on success, 0 on error. + */ +static int +ecdsa_sign(int type, const unsigned char *dgst, int dgstlen, unsigned char *sig, + unsigned int *siglen, const BIGNUM *kinv, const BIGNUM *r, EC_KEY *ec) +{ + int capacity = ECDSA_size(ec); + int len = get_sig_from_man(dgst, dgstlen, sig, capacity); + + if (len > 0) + { + *siglen = len; + return 1; + } + return 0; +} + +/* EC_KEY_METHOD callback: sign_setup(). We do no precomputations */ +static int +ecdsa_sign_setup(EC_KEY *ec, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) +{ + return 1; +} + +/* EC_KEY_METHOD callback: sign_sig(). + * Sign the hash and return the result as a newly allocated ECDS_SIG + * struct or NULL on error. + */ +static ECDSA_SIG * +ecdsa_sign_sig(const unsigned char *dgst, int dgstlen, const BIGNUM *in_kinv, + const BIGNUM *in_r, EC_KEY *ec) +{ + ECDSA_SIG *ecsig = NULL; + unsigned int len = ECDSA_size(ec); + struct gc_arena gc = gc_new(); + + unsigned char *buf = gc_malloc(len, false, &gc); + if (ecdsa_sign(0, dgst, dgstlen, buf, &len, NULL, NULL, ec) != 1) + { + goto out; + } + /* const char ** should be avoided: not up to us, so we cast our way through */ + ecsig = d2i_ECDSA_SIG(NULL, (const unsigned char **)&buf, len); + +out: + gc_free(&gc); + return ecsig; +} + +static int +tls_ctx_use_external_ec_key(struct tls_root_ctx *ctx, EVP_PKEY *pkey) +{ + EC_KEY *ec = NULL; + EVP_PKEY *privkey = NULL; + EC_KEY_METHOD *ec_method; + + ASSERT(ctx); + + ec_method = EC_KEY_METHOD_new(EC_KEY_OpenSSL()); + if (!ec_method) + { + goto err; + } + + /* Among init methods, we only need the finish method */ + EC_KEY_METHOD_set_init(ec_method, NULL, openvpn_extkey_ec_finish, NULL, NULL, NULL, NULL); + EC_KEY_METHOD_set_sign(ec_method, ecdsa_sign, ecdsa_sign_setup, ecdsa_sign_sig); + + ec = EC_KEY_dup(EVP_PKEY_get0_EC_KEY(pkey)); + if (!ec) + { + EC_KEY_METHOD_free(ec_method); + goto err; + } + if (!EC_KEY_set_method(ec, ec_method)) + { + EC_KEY_METHOD_free(ec_method); + goto err; + } + /* from this point ec_method will get freed when ec is freed */ + + privkey = EVP_PKEY_new(); + if (!EVP_PKEY_assign_EC_KEY(privkey, ec)) + { + goto err; + } + /* from this point ec will get freed when privkey is freed */ + + if (!SSL_CTX_use_PrivateKey(ctx->ctx, privkey)) + { + ec = NULL; /* avoid double freeing it below */ + goto err; + } + + EVP_PKEY_free(privkey); /* this will down ref privkey and ec */ + return 1; + +err: + /* Reach here only when ec and privkey can be independenly freed */ + if (privkey) + { + EVP_PKEY_free(privkey); + } + if(ec) + { + EC_KEY_free(ec); + } + return 0; +} +#endif /* OPENSSL_VERSION_NUMBER > 1.1.0 dev */ + int tls_ctx_use_external_private_key(struct tls_root_ctx *ctx, const char *cert_file, const char *cert_file_inline) @@ -1183,18 +1300,33 @@ tls_ctx_use_external_private_key(struct tls_root_ctx *ctx, ASSERT(pkey); /* NULL before SSL_CTX_use_certificate() is called */ X509_free(cert); - if (EVP_PKEY_get0_RSA(pkey)) + if (EVP_PKEY_id(pkey) == EVP_PKEY_RSA) { if (!tls_ctx_use_external_rsa_key(ctx, pkey)) { goto err; } } +#if OPENSSL_VERSION_NUMBER > 0x10100000L && !defined(OPENSSL_NO_EC) + else if (EVP_PKEY_id(pkey) == EVP_PKEY_EC) + { + if (!tls_ctx_use_external_ec_key(ctx, pkey)) + { + goto err; + } + } + else + { + crypto_msg(M_WARN, "management-external-key requires an RSA or EC certificate"); + goto err; + } +#else else { - crypto_msg(M_WARN, "management-external-key requires a RSA certificate"); + crypto_msg(M_WARN, "management-external-key requires an RSA certificate"); goto err; } +#endif /* OPENSSL_VERSION_NUMBER > 1.1.0 dev */ return 1; err:

[Openvpn-devel,v3,2/3] Allow external EC key through --management-external-key

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