From patchwork Sun Jan 15 17:22:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 13102392 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0400C677F1 for ; Sun, 15 Jan 2023 17:23:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231213AbjAORXA (ORCPT ); Sun, 15 Jan 2023 12:23:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230401AbjAORW7 (ORCPT ); Sun, 15 Jan 2023 12:22:59 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B7FE76BB; Sun, 15 Jan 2023 09:22:58 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BDF5A60D45; Sun, 15 Jan 2023 17:22:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE14BC433D2; Sun, 15 Jan 2023 17:22:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673803377; bh=AjqV8+0VYKLv10L+gsZn40PnPiOYaT+0IncmJ1zhMoo=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=CbG//iwvNKcR4u5Mf9n9qKcllFnQnYZK1DHhYdw3H5WMy7MyHSWAiqzNqG0GiP/Oh h2UU520PPPjj8ZjiJFXtlCwwlf9H5mjuqfvu7HREhWwfU6lwiJeBH05ECWq1k2e5/h mBGo04QhWHCsWujYRkW4+spFjaQx8+lv7Dm1i+qQbmL88pqAC9s6pLHotBOFOgECgP vgTFWu41CSrCxfMcSUCwqMkLwWogyhjwqTDshKS+xXEYYcJFT5Jqy2NQm6qImzRui6 tZsPbCR/j7yo22FhFjZkD1ppEF6cXXSS2i9C1iLQ2uuXsOVXeC2RmYuPSoH5i9Q9S1 npscvHB7Albhw== Subject: [PATCH v2 25/41] SUNRPC: Add RFC 8009 encryption and decryption functions From: Chuck Lever To: linux-nfs@vger.kernel.org Cc: dhowells@redhat.com, simo@redhat.com, linux-kselftest@vger.kernel.org Date: Sun, 15 Jan 2023 12:22:56 -0500 Message-ID: <167380337603.10651.8246346264542438193.stgit@bazille.1015granger.net> In-Reply-To: <167380196429.10651.4103075913257868035.stgit@bazille.1015granger.net> References: <167380196429.10651.4103075913257868035.stgit@bazille.1015granger.net> User-Agent: StGit/1.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Chuck Lever RFC 8009 enctypes use different crypt formulae than previous Kerberos 5 encryption types. Section 1 of RFC 8009 explains the reason for this change: > The new types conform to the framework specified in [RFC3961], > but do not use the simplified profile, as the simplified profile > is not compliant with modern cryptographic best practices such as > calculating Message Authentication Codes (MACs) over ciphertext > rather than plaintext. Add new .encrypt and .decrypt functions to handle this variation. The new approach described above is referred to as Encrypt-then-MAC (or EtM). Hence the names of the new functions added here are prefixed with "krb5_etm_". A critical second difference with previous crypt formulae is that the cipher state is included in the computed HMAC. Note however that for RPCSEC, the initial cipher state is easy to compute on both initiator and acceptor because it is always all zeroes. Tested-by: Scott Mayhew Signed-off-by: Chuck Lever --- net/sunrpc/auth_gss/gss_krb5_crypto.c | 227 +++++++++++++++++++++++++++++++ net/sunrpc/auth_gss/gss_krb5_internal.h | 6 + net/sunrpc/auth_gss/gss_krb5_mech.c | 4 + 3 files changed, 237 insertions(+) diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c index 65c8b6982729..4f29216d414a 100644 --- a/net/sunrpc/auth_gss/gss_krb5_crypto.c +++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c @@ -867,3 +867,230 @@ gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len, ret = GSS_S_FAILURE; return ret; } + +static u32 +krb5_etm_checksum(struct crypto_sync_skcipher *cipher, + struct crypto_ahash *tfm, const struct xdr_buf *body, + int body_offset, struct xdr_netobj *cksumout) +{ + unsigned int ivsize = crypto_sync_skcipher_ivsize(cipher); + struct ahash_request *req; + struct scatterlist sg[1]; + u8 *iv, *checksumdata; + int err = -ENOMEM; + + checksumdata = kmalloc(crypto_ahash_digestsize(tfm), GFP_KERNEL); + if (!checksumdata) + return GSS_S_FAILURE; + /* For RPCSEC, the "initial cipher state" is always all zeroes. */ + iv = kzalloc(ivsize, GFP_KERNEL); + if (!iv) + goto out_free_mem; + + req = ahash_request_alloc(tfm, GFP_KERNEL); + if (!req) + goto out_free_mem; + ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL); + err = crypto_ahash_init(req); + if (err) + goto out_free_ahash; + + sg_init_one(sg, iv, ivsize); + ahash_request_set_crypt(req, sg, NULL, ivsize); + err = crypto_ahash_update(req); + if (err) + goto out_free_ahash; + err = xdr_process_buf(body, body_offset, body->len - body_offset, + checksummer, req); + if (err) + goto out_free_ahash; + + ahash_request_set_crypt(req, NULL, checksumdata, 0); + err = crypto_ahash_final(req); + if (err) + goto out_free_ahash; + memcpy(cksumout->data, checksumdata, cksumout->len); + +out_free_ahash: + ahash_request_free(req); +out_free_mem: + kfree(iv); + kfree_sensitive(checksumdata); + return err ? GSS_S_FAILURE : GSS_S_COMPLETE; +} + +/** + * krb5_etm_encrypt - Encrypt using the RFC 8009 rules + * @kctx: Kerberos context + * @offset: starting offset of the payload, in bytes + * @buf: OUT: send buffer to contain the encrypted payload + * @pages: plaintext payload + * + * The main difference with aes_encrypt is that "The HMAC is + * calculated over the cipher state concatenated with the AES + * output, instead of being calculated over the confounder and + * plaintext. This allows the message receiver to verify the + * integrity of the message before decrypting the message." + * + * RFC 8009 Section 5: + * + * encryption function: as follows, where E() is AES encryption in + * CBC-CS3 mode, and h is the size of truncated HMAC (128 bits or + * 192 bits as described above). + * + * N = random value of length 128 bits (the AES block size) + * IV = cipher state + * C = E(Ke, N | plaintext, IV) + * H = HMAC(Ki, IV | C) + * ciphertext = C | H[1..h] + * + * This encryption formula provides AEAD EtM with key separation. + * + * Return values: + * %GSS_S_COMPLETE: Encryption successful + * %GSS_S_FAILURE: Encryption failed + */ +u32 +krb5_etm_encrypt(struct krb5_ctx *kctx, u32 offset, + struct xdr_buf *buf, struct page **pages) +{ + struct crypto_sync_skcipher *cipher, *aux_cipher; + struct crypto_ahash *ahash; + struct xdr_netobj hmac; + unsigned int conflen; + u8 *ecptr; + u32 err; + + if (kctx->initiate) { + cipher = kctx->initiator_enc; + aux_cipher = kctx->initiator_enc_aux; + ahash = kctx->initiator_integ; + } else { + cipher = kctx->acceptor_enc; + aux_cipher = kctx->acceptor_enc_aux; + ahash = kctx->acceptor_integ; + } + conflen = crypto_sync_skcipher_blocksize(cipher); + + offset += GSS_KRB5_TOK_HDR_LEN; + if (xdr_extend_head(buf, offset, conflen)) + return GSS_S_FAILURE; + krb5_make_confounder(buf->head[0].iov_base + offset, conflen); + offset -= GSS_KRB5_TOK_HDR_LEN; + + if (buf->tail[0].iov_base) { + ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len; + } else { + buf->tail[0].iov_base = buf->head[0].iov_base + + buf->head[0].iov_len; + buf->tail[0].iov_len = 0; + ecptr = buf->tail[0].iov_base; + } + + memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN); + buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN; + buf->len += GSS_KRB5_TOK_HDR_LEN; + + err = krb5_cbc_cts_encrypt(cipher, aux_cipher, + offset + GSS_KRB5_TOK_HDR_LEN, + buf, pages); + if (err) + return GSS_S_FAILURE; + + hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len; + hmac.len = kctx->gk5e->cksumlength; + err = krb5_etm_checksum(cipher, ahash, + buf, offset + GSS_KRB5_TOK_HDR_LEN, &hmac); + if (err) + goto out_err; + buf->tail[0].iov_len += kctx->gk5e->cksumlength; + buf->len += kctx->gk5e->cksumlength; + + return GSS_S_COMPLETE; + +out_err: + return GSS_S_FAILURE; +} + +/** + * krb5_etm_decrypt - Decrypt using the RFC 8009 rules + * @kctx: Kerberos context + * @offset: starting offset of the ciphertext, in bytes + * @len: + * @buf: + * @headskip: OUT: the enctype's confounder length, in octets + * @tailskip: OUT: the enctype's HMAC length, in octets + * + * RFC 8009 Section 5: + * + * decryption function: as follows, where D() is AES decryption in + * CBC-CS3 mode, and h is the size of truncated HMAC. + * + * (C, H) = ciphertext + * (Note: H is the last h bits of the ciphertext.) + * IV = cipher state + * if H != HMAC(Ki, IV | C)[1..h] + * stop, report error + * (N, P) = D(Ke, C, IV) + * + * Return values: + * %GSS_S_COMPLETE: Decryption successful + * %GSS_S_BAD_SIG: computed HMAC != received HMAC + * %GSS_S_FAILURE: Decryption failed + */ +u32 +krb5_etm_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len, + struct xdr_buf *buf, u32 *headskip, u32 *tailskip) +{ + struct crypto_sync_skcipher *cipher, *aux_cipher; + u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN]; + u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN]; + struct xdr_netobj our_hmac_obj; + struct crypto_ahash *ahash; + struct xdr_buf subbuf; + u32 ret = 0; + + if (kctx->initiate) { + cipher = kctx->acceptor_enc; + aux_cipher = kctx->acceptor_enc_aux; + ahash = kctx->acceptor_integ; + } else { + cipher = kctx->initiator_enc; + aux_cipher = kctx->initiator_enc_aux; + ahash = kctx->initiator_integ; + } + + /* Extract the ciphertext into @subbuf. */ + xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN, + (len - offset - GSS_KRB5_TOK_HDR_LEN - + kctx->gk5e->cksumlength)); + + our_hmac_obj.data = our_hmac; + our_hmac_obj.len = kctx->gk5e->cksumlength; + ret = krb5_etm_checksum(cipher, ahash, &subbuf, 0, &our_hmac_obj); + if (ret) + goto out_err; + ret = read_bytes_from_xdr_buf(buf, len - kctx->gk5e->cksumlength, + pkt_hmac, kctx->gk5e->cksumlength); + if (ret) + goto out_err; + if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) { + ret = GSS_S_BAD_SIG; + goto out_err; + } + + ret = krb5_cbc_cts_decrypt(cipher, aux_cipher, 0, &subbuf); + if (ret) { + ret = GSS_S_FAILURE; + goto out_err; + } + + *headskip = crypto_sync_skcipher_blocksize(cipher); + *tailskip = kctx->gk5e->cksumlength; + return GSS_S_COMPLETE; + +out_err: + if (ret != GSS_S_BAD_SIG) + ret = GSS_S_FAILURE; + return ret; +} diff --git a/net/sunrpc/auth_gss/gss_krb5_internal.h b/net/sunrpc/auth_gss/gss_krb5_internal.h index 33abf9ee9508..fd2ae11c5067 100644 --- a/net/sunrpc/auth_gss/gss_krb5_internal.h +++ b/net/sunrpc/auth_gss/gss_krb5_internal.h @@ -108,4 +108,10 @@ u32 gss_krb5_aes_encrypt(struct krb5_ctx *kctx, u32 offset, u32 gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len, struct xdr_buf *buf, u32 *plainoffset, u32 *plainlen); +u32 krb5_etm_encrypt(struct krb5_ctx *kctx, u32 offset, struct xdr_buf *buf, + struct page **pages); + +u32 krb5_etm_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len, + struct xdr_buf *buf, u32 *headskip, u32 *tailskip); + #endif /* _NET_SUNRPC_AUTH_GSS_KRB5_INTERNAL_H */ diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c index b55897cac459..7fe39e47c84f 100644 --- a/net/sunrpc/auth_gss/gss_krb5_mech.c +++ b/net/sunrpc/auth_gss/gss_krb5_mech.c @@ -167,6 +167,8 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = { .import_ctx = gss_krb5_import_ctx_v2, .derive_key = krb5_kdf_hmac_sha2, + .encrypt = krb5_etm_encrypt, + .decrypt = krb5_etm_decrypt, .get_mic = gss_krb5_get_mic_v2, .verify_mic = gss_krb5_verify_mic_v2, @@ -192,6 +194,8 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = { .import_ctx = gss_krb5_import_ctx_v2, .derive_key = krb5_kdf_hmac_sha2, + .encrypt = krb5_etm_encrypt, + .decrypt = krb5_etm_decrypt, .get_mic = gss_krb5_get_mic_v2, .verify_mic = gss_krb5_verify_mic_v2,