tpm2-sessions: Fix out of range indexing in name_size

'name_size' does not have any range checks, and it just directly indexes
with TPM_ALG_ID, which could lead into memory corruption at worst.

Address the issue by only processing known values and returning -EINVAL for
unrecognized values.

Make also 'tpm_buf_append_name' and 'tpm_buf_fill_hmac_session' fallible so
that errors are detected before causing any spurious TPM traffic.

End also the authorization session on failure in both of the functions, as
the session state would be then by definition corrupted.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 1085b8276bb4 ("tpm: Add the rest of the session HMAC API")
Reviewed-by: Jonathan McDowell <noodles@meta.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

2 files changed, 111 insertions, 44 deletions

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index dd502322f499..be4a9c7f2e1a 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -199,7 +199,11 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	}
 
 	if (!disable_pcr_integrity) {
-		tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
+		rc = tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
+		if (rc) {
+			tpm_buf_destroy(&buf);
+			return rc;
+		}
 		tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0);
 	} else {
 		tpm_buf_append_handle(chip, &buf, pcr_idx);
@@ -214,8 +218,14 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 			       chip->allocated_banks[i].digest_size);
 	}
 
-	if (!disable_pcr_integrity)
-		tpm_buf_fill_hmac_session(chip, &buf);
+	if (!disable_pcr_integrity) {
+		rc = tpm_buf_fill_hmac_session(chip, &buf);
+		if (rc) {
+			tpm_buf_destroy(&buf);
+			return rc;
+		}
+	}
+
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
 	if (!disable_pcr_integrity)
 		rc = tpm_buf_check_hmac_response(chip, &buf, rc);
@@ -273,7 +283,12 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 						| TPM2_SA_CONTINUE_SESSION,
 						NULL, 0);
 		tpm_buf_append_u16(&buf, num_bytes);
-		tpm_buf_fill_hmac_session(chip, &buf);
+		err = tpm_buf_fill_hmac_session(chip, &buf);
+		if (err) {
+			tpm_buf_destroy(&buf);
+			return err;
+		}
+
 		err = tpm_transmit_cmd(chip, &buf,
 				       offsetof(struct tpm2_get_random_out,
 						buffer),
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 6d03c224e6b2..385014dbca39 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -144,16 +144,23 @@ struct tpm2_auth {
 /*
  * Name Size based on TPM algorithm (assumes no hash bigger than 255)
  */
-static u8 name_size(const u8 *name)
+static int name_size(const u8 *name)
 {
-	static u8 size_map[] = {
-		[TPM_ALG_SHA1] = SHA1_DIGEST_SIZE,
-		[TPM_ALG_SHA256] = SHA256_DIGEST_SIZE,
-		[TPM_ALG_SHA384] = SHA384_DIGEST_SIZE,
-		[TPM_ALG_SHA512] = SHA512_DIGEST_SIZE,
-	};
-	u16 alg = get_unaligned_be16(name);
-	return size_map[alg] + 2;
+	u16 hash_alg = get_unaligned_be16(name);
+
+	switch (hash_alg) {
+	case TPM_ALG_SHA1:
+		return SHA1_DIGEST_SIZE + 2;
+	case TPM_ALG_SHA256:
+		return SHA256_DIGEST_SIZE + 2;
+	case TPM_ALG_SHA384:
+		return SHA384_DIGEST_SIZE + 2;
+	case TPM_ALG_SHA512:
+		return SHA512_DIGEST_SIZE + 2;
+	default:
+		pr_warn("tpm: unsupported name algorithm: 0x%04x\n", hash_alg);
+		return -EINVAL;
+	}
 }
 
 static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
@@ -161,6 +168,7 @@ static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
 	struct tpm_header *head = (struct tpm_header *)buf->data;
 	off_t offset = TPM_HEADER_SIZE;
 	u32 tot_len = be32_to_cpu(head->length);
+	int ret;
 	u32 val;
 
 	/* we're starting after the header so adjust the length */
@@ -173,8 +181,13 @@ static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
 	offset += val;
 	/* name */
 	val = tpm_buf_read_u16(buf, &offset);
-	if (val != name_size(&buf->data[offset]))
+	ret = name_size(&buf->data[offset]);
+	if (ret < 0)
+		return ret;
+
+	if (val != ret)
 		return -EINVAL;
+
 	memcpy(name, &buf->data[offset], val);
 	/* forget the rest */
 	return 0;
@@ -221,46 +234,72 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
  * As with most tpm_buf operations, success is assumed because failure
  * will be caused by an incorrect programming model and indicated by a
  * kernel message.
+ *
+ * Ends the authorization session on failure.
  */
-void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
-			 u32 handle, u8 *name)
+int tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
+			u32 handle, u8 *name)
 {
 #ifdef CONFIG_TCG_TPM2_HMAC
 	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
 	struct tpm2_auth *auth;
 	int slot;
+	int ret;
 #endif
 
 	if (!tpm2_chip_auth(chip)) {
 		tpm_buf_append_handle(chip, buf, handle);
-		return;
+		return 0;
 	}
 
 #ifdef CONFIG_TCG_TPM2_HMAC
 	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE) / 4;
 	if (slot >= AUTH_MAX_NAMES) {
-		dev_err(&chip->dev, "TPM: too many handles\n");
-		return;
+		dev_err(&chip->dev, "too many handles\n");
+		ret = -EIO;
+		goto err;
 	}
 	auth = chip->auth;
-	WARN(auth->session != tpm_buf_length(buf),
-	     "name added in wrong place\n");
+	if (auth->session != tpm_buf_length(buf)) {
+		dev_err(&chip->dev, "session state malformed");
+		ret = -EIO;
+		goto err;
+	}
 	tpm_buf_append_u32(buf, handle);
 	auth->session += 4;
 
 	if (mso == TPM2_MSO_PERSISTENT ||
 	    mso == TPM2_MSO_VOLATILE ||
 	    mso == TPM2_MSO_NVRAM) {
-		if (!name)
-			tpm2_read_public(chip, handle, auth->name[slot]);
+		if (!name) {
+			ret = tpm2_read_public(chip, handle, auth->name[slot]);
+			if (ret)
+				goto err;
+		}
 	} else {
-		if (name)
-			dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
+		if (name) {
+			dev_err(&chip->dev, "handle 0x%08x does not use a name\n",
+				handle);
+			ret = -EIO;
+			goto err;
+		}
 	}
 
 	auth->name_h[slot] = handle;
-	if (name)
-		memcpy(auth->name[slot], name, name_size(name));
+	if (name) {
+		ret = name_size(name);
+		if (ret < 0)
+			goto err;
+
+		memcpy(auth->name[slot], name, ret);
+	}
+#endif
+	return 0;
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+err:
+	tpm2_end_auth_session(chip);
+	return tpm_ret_to_err(ret);
 #endif
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_name);
@@ -533,11 +572,9 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
  * encryption key and encrypts the first parameter of the command
  * buffer with it.
  *
- * As with most tpm_buf operations, success is assumed because failure
- * will be caused by an incorrect programming model and indicated by a
- * kernel message.
+ * Ends the authorization session on failure.
  */
-void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
+int tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 {
 	u32 cc, handles, val;
 	struct tpm2_auth *auth = chip->auth;
@@ -549,9 +586,12 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	u8 cphash[SHA256_DIGEST_SIZE];
 	struct sha256_ctx sctx;
 	struct hmac_sha256_ctx hctx;
+	int ret;
 
-	if (!auth)
-		return;
+	if (!auth) {
+		ret = -EIO;
+		goto err;
+	}
 
 	/* save the command code in BE format */
 	auth->ordinal = head->ordinal;
@@ -560,9 +600,11 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 
 	i = tpm2_find_cc(chip, cc);
 	if (i < 0) {
-		dev_err(&chip->dev, "Command 0x%x not found in TPM\n", cc);
-		return;
+		dev_err(&chip->dev, "command 0x%08x not found\n", cc);
+		ret = -EIO;
+		goto err;
 	}
+
 	attrs = chip->cc_attrs_tbl[i];
 
 	handles = (attrs >> TPM2_CC_ATTR_CHANDLES) & GENMASK(2, 0);
@@ -576,9 +618,9 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 		u32 handle = tpm_buf_read_u32(buf, &offset_s);
 
 		if (auth->name_h[i] != handle) {
-			dev_err(&chip->dev, "TPM: handle %d wrong for name\n",
-				  i);
-			return;
+			dev_err(&chip->dev, "invalid handle 0x%08x\n", handle);
+			ret = -EIO;
+			goto err;
 		}
 	}
 	/* point offset_s to the start of the sessions */
@@ -609,12 +651,14 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 		offset_s += len;
 	}
 	if (offset_s != offset_p) {
-		dev_err(&chip->dev, "TPM session length is incorrect\n");
-		return;
+		dev_err(&chip->dev, "session length is incorrect\n");
+		ret = -EIO;
+		goto err;
 	}
 	if (!hmac) {
-		dev_err(&chip->dev, "TPM could not find HMAC session\n");
-		return;
+		dev_err(&chip->dev, "could not find HMAC session\n");
+		ret = -EIO;
+		goto err;
 	}
 
 	/* encrypt before HMAC */
@@ -646,8 +690,11 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 		if (mso == TPM2_MSO_PERSISTENT ||
 		    mso == TPM2_MSO_VOLATILE ||
 		    mso == TPM2_MSO_NVRAM) {
-			sha256_update(&sctx, auth->name[i],
-				      name_size(auth->name[i]));
+			ret = name_size(auth->name[i]);
+			if (ret < 0)
+				goto err;
+
+			sha256_update(&sctx, auth->name[i], ret);
 		} else {
 			__be32 h = cpu_to_be32(auth->name_h[i]);
 
@@ -668,6 +715,11 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	hmac_sha256_update(&hctx, auth->tpm_nonce, sizeof(auth->tpm_nonce));
 	hmac_sha256_update(&hctx, &auth->attrs, 1);
 	hmac_sha256_final(&hctx, hmac);
+	return 0;
+
+err:
+	tpm2_end_auth_session(chip);
+	return ret;
 }
 EXPORT_SYMBOL(tpm_buf_fill_hmac_session);