From nobody Sun Oct 5 16:15:52 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4B2D28DF3C; Fri, 1 Aug 2025 21:26:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754083579; cv=none; b=lBdbFUgn+tUgUZ3/zAyvccwUlfVd8UTT54v/HZf2p8ru4GBGhAf28BvzSLcAXzERz7fyVzDej4L6yYEruU7nshPhELhO6awlJChYLjII7tfF3YbQAk443+NNkQu4nWG6/mE1ylVHdMF3yx8XEdhcUcS2IJgwpQAVtfSmfQfm3Qs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754083579; c=relaxed/simple; bh=FGVWbDM46/kQ8Qx86FzpGFJNytKs5fhu9qmULAUtmiQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W18jL0dSB63GQi3teQhnAHh0qZc++w3J9R0dtHq1gyOL/DjXRZej6cIRZPYnmoNnru9PTslNrgClwzojfFHSkfRb3Tqpiil6EcvoDMlRFl4qnAXOyeul0R7za/E0OY2BNYkMhM7cqSdl+djZJ9Vi+btQ5f2b6pK7KZ69g2vPpg8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aAA04uNB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aAA04uNB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D63FC4CEF4; Fri, 1 Aug 2025 21:26:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754083579; bh=FGVWbDM46/kQ8Qx86FzpGFJNytKs5fhu9qmULAUtmiQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aAA04uNBey7sQ0XVGfzni3JsLFmCU0J4cfoODJINtsNA3YWURaImVWIMY1e7CsUb8 UKZ/T5u1Y5RpvmPrXZiFnB8R0tt0G4phorQA1agypLhu5jgd8VguxCI0I1azwnHNaW REdG7WHhCiCxcjMEohqThx9bwi/q4+e8/y/kuRLgr79nzqyM+ONV7BqmLaFbv5OVm+ X8lAOAt967SAo19FDHsHvorKul1GFpz8FZJ8ROshDtJj/J1SkKgDJMtRU16jBiCfY4 OdhG70vKt6RH40DNYiA9+8h1N8JHR2cylp5omzzSnM87VKt4hxioRLfkhWrTxl6CUf ixM+4ODKVf5Rg== From: Eric Biggers To: Peter Huewe , Jarkko Sakkinen , linux-integrity@vger.kernel.org Cc: Jason Gunthorpe , James Bottomley , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Biggers Subject: [PATCH v2 2/2] tpm: Use HMAC-SHA256 library instead of open-coded HMAC Date: Fri, 1 Aug 2025 14:24:22 -0700 Message-ID: <20250801212422.9590-3-ebiggers@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250801212422.9590-1-ebiggers@kernel.org> References: <20250801212422.9590-1-ebiggers@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that there are easy-to-use HMAC-SHA256 library functions, use these in tpm2-sessions.c instead of open-coding the HMAC algorithm. Note that the new implementation correctly handles keys longer than 64 bytes (SHA256_BLOCK_SIZE), whereas the old implementation handled such keys incorrectly. But it doesn't appear that such keys were being used. Signed-off-by: Eric Biggers Reviewed-by: Jarkko Sakkinen --- drivers/char/tpm/tpm2-sessions.c | 98 +++++++++----------------------- 1 file changed, 27 insertions(+), 71 deletions(-) diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessi= ons.c index 5fbd62ee50903..6d03c224e6b21 100644 --- a/drivers/char/tpm/tpm2-sessions.c +++ b/drivers/char/tpm/tpm2-sessions.c @@ -67,12 +67,11 @@ #include #include #include #include #include -#include -#include +#include #include =20 /* maximum number of names the TPM must remember for authorization */ #define AUTH_MAX_NAMES 3 =20 @@ -383,55 +382,10 @@ EXPORT_SYMBOL_GPL(tpm_buf_append_hmac_session); #ifdef CONFIG_TCG_TPM2_HMAC =20 static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy, u32 *handle, u8 *name); =20 -/* - * It turns out the crypto hmac(sha256) is hard for us to consume - * because it assumes a fixed key and the TPM seems to change the key - * on every operation, so we weld the hmac init and final functions in - * here to give it the same usage characteristics as a regular hash - */ -static void tpm2_hmac_init(struct sha256_ctx *sctx, u8 *key, u32 key_len) -{ - u8 pad[SHA256_BLOCK_SIZE]; - int i; - - sha256_init(sctx); - for (i =3D 0; i < sizeof(pad); i++) { - if (i < key_len) - pad[i] =3D key[i]; - else - pad[i] =3D 0; - pad[i] ^=3D HMAC_IPAD_VALUE; - } - sha256_update(sctx, pad, sizeof(pad)); -} - -static void tpm2_hmac_final(struct sha256_ctx *sctx, u8 *key, u32 key_len, - u8 *out) -{ - u8 pad[SHA256_BLOCK_SIZE]; - int i; - - for (i =3D 0; i < sizeof(pad); i++) { - if (i < key_len) - pad[i] =3D key[i]; - else - pad[i] =3D 0; - pad[i] ^=3D HMAC_OPAD_VALUE; - } - - /* collect the final hash; use out as temporary storage */ - sha256_final(sctx, out); - - sha256_init(sctx); - sha256_update(sctx, pad, sizeof(pad)); - sha256_update(sctx, out, SHA256_DIGEST_SIZE); - sha256_final(sctx, out); -} - /* * assume hash sha256 and nonces u, v of size SHA256_DIGEST_SIZE but * otherwise standard tpm2_KDFa. Note output is in bytes not bits. */ static void tpm2_KDFa(u8 *key, u32 key_len, const char *label, u8 *u, @@ -439,20 +393,20 @@ static void tpm2_KDFa(u8 *key, u32 key_len, const cha= r *label, u8 *u, { u32 counter =3D 1; const __be32 bits =3D cpu_to_be32(bytes * 8); =20 while (bytes > 0) { - struct sha256_ctx sctx; + struct hmac_sha256_ctx hctx; __be32 c =3D cpu_to_be32(counter); =20 - tpm2_hmac_init(&sctx, key, key_len); - sha256_update(&sctx, (u8 *)&c, sizeof(c)); - sha256_update(&sctx, label, strlen(label)+1); - sha256_update(&sctx, u, SHA256_DIGEST_SIZE); - sha256_update(&sctx, v, SHA256_DIGEST_SIZE); - sha256_update(&sctx, (u8 *)&bits, sizeof(bits)); - tpm2_hmac_final(&sctx, key, key_len, out); + hmac_sha256_init_usingrawkey(&hctx, key, key_len); + hmac_sha256_update(&hctx, (u8 *)&c, sizeof(c)); + hmac_sha256_update(&hctx, label, strlen(label) + 1); + hmac_sha256_update(&hctx, u, SHA256_DIGEST_SIZE); + hmac_sha256_update(&hctx, v, SHA256_DIGEST_SIZE); + hmac_sha256_update(&hctx, (u8 *)&bits, sizeof(bits)); + hmac_sha256_final(&hctx, out); =20 bytes -=3D SHA256_DIGEST_SIZE; counter++; out +=3D SHA256_DIGEST_SIZE; } @@ -592,10 +546,11 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip,= struct tpm_buf *buf) off_t offset_s =3D TPM_HEADER_SIZE, offset_p; u8 *hmac =3D NULL; u32 attrs; u8 cphash[SHA256_DIGEST_SIZE]; struct sha256_ctx sctx; + struct hmac_sha256_ctx hctx; =20 if (!auth) return; =20 /* save the command code in BE format */ @@ -703,18 +658,18 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip,= struct tpm_buf *buf) sha256_update(&sctx, &buf->data[offset_s], tpm_buf_length(buf) - offset_s); sha256_final(&sctx, cphash); =20 /* now calculate the hmac */ - tpm2_hmac_init(&sctx, auth->session_key, sizeof(auth->session_key) - + auth->passphrase_len); - sha256_update(&sctx, cphash, sizeof(cphash)); - sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce)); - sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce)); - sha256_update(&sctx, &auth->attrs, 1); - tpm2_hmac_final(&sctx, auth->session_key, sizeof(auth->session_key) - + auth->passphrase_len, hmac); + hmac_sha256_init_usingrawkey(&hctx, auth->session_key, + sizeof(auth->session_key) + + auth->passphrase_len); + hmac_sha256_update(&hctx, cphash, sizeof(cphash)); + hmac_sha256_update(&hctx, auth->our_nonce, sizeof(auth->our_nonce)); + hmac_sha256_update(&hctx, auth->tpm_nonce, sizeof(auth->tpm_nonce)); + hmac_sha256_update(&hctx, &auth->attrs, 1); + hmac_sha256_final(&hctx, hmac); } EXPORT_SYMBOL(tpm_buf_fill_hmac_session); =20 /** * tpm_buf_check_hmac_response() - check the TPM return HMAC for correctne= ss @@ -750,10 +705,11 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip= , struct tpm_buf *buf, struct tpm2_auth *auth =3D chip->auth; off_t offset_s, offset_p; u8 rphash[SHA256_DIGEST_SIZE]; u32 attrs, cc; struct sha256_ctx sctx; + struct hmac_sha256_ctx hctx; u16 tag =3D be16_to_cpu(head->tag); int parm_len, len, i, handles; =20 if (!auth) return rc; @@ -819,19 +775,19 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip= , struct tpm_buf *buf, sha256_update(&sctx, (u8 *)&auth->ordinal, sizeof(auth->ordinal)); sha256_update(&sctx, &buf->data[offset_p], parm_len); sha256_final(&sctx, rphash); =20 /* now calculate the hmac */ - tpm2_hmac_init(&sctx, auth->session_key, sizeof(auth->session_key) - + auth->passphrase_len); - sha256_update(&sctx, rphash, sizeof(rphash)); - sha256_update(&sctx, auth->tpm_nonce, sizeof(auth->tpm_nonce)); - sha256_update(&sctx, auth->our_nonce, sizeof(auth->our_nonce)); - sha256_update(&sctx, &auth->attrs, 1); + hmac_sha256_init_usingrawkey(&hctx, auth->session_key, + sizeof(auth->session_key) + + auth->passphrase_len); + hmac_sha256_update(&hctx, rphash, sizeof(rphash)); + hmac_sha256_update(&hctx, auth->tpm_nonce, sizeof(auth->tpm_nonce)); + hmac_sha256_update(&hctx, auth->our_nonce, sizeof(auth->our_nonce)); + hmac_sha256_update(&hctx, &auth->attrs, 1); /* we're done with the rphash, so put our idea of the hmac there */ - tpm2_hmac_final(&sctx, auth->session_key, sizeof(auth->session_key) - + auth->passphrase_len, rphash); + hmac_sha256_final(&hctx, rphash); if (crypto_memneq(rphash, &buf->data[offset_s], SHA256_DIGEST_SIZE)) { dev_err(&chip->dev, "TPM: HMAC check failed\n"); goto out; } rc =3D 0; --=20 2.50.1