[PATCH v2 2/4] tpm2-sessions: Fix tpm2_read_public range checks

[Jarkko Sakkinen]

'tpm2_read_public' has some rudimentary range checks but the function
does not ensure that the response buffer has enough bytes for the full
TPMT_HA payload.

Re-implement the function with necessary checks and validation.

Cc: sta...@vger.kernel.org # v6.10+
Fixes: d0a25bb961e6 ("tpm: Add HMAC session name/handle append")
Signed-off-by: Jarkko Sakkinen <jar...@kernel.org>
---
 drivers/char/tpm/tpm2-cmd.c      |  3 ++
 drivers/char/tpm/tpm2-sessions.c | 77 +++++++++++++++++---------------
 2 files changed, 44 insertions(+), 36 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 4473b81122e8..58a8477cda85 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -11,8 +11,11 @@
  * used by the kernel internally.
  */
 
+#include "linux/dev_printk.h"
+#include "linux/tpm.h"
 #include "tpm.h"
 #include <crypto/hash_info.h>
+#include <linux/unaligned.h>
 
 static bool disable_pcr_integrity;
 module_param(disable_pcr_integrity, bool, 0444);
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index dc6bee7e1ef6..964f44c2255d 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -163,54 +163,59 @@ static int name_size(const u8 *name)
        }
 }
 
-static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
+static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
 {
-       struct tpm_header *head = (struct tpm_header *)buf->data;
+       u32 mso = tpm2_handle_mso(handle);
        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 */
-       tot_len -= TPM_HEADER_SIZE;
-
-       /* skip public */
-       val = tpm_buf_read_u16(buf, &offset);
-       if (val > tot_len)
-               return -EINVAL;
-       offset += val;
-       /* name */
-
-       val = tpm_buf_read_u16(buf, &offset);
-       ret = name_size(&buf->data[offset]);
-       if (ret < 0)
-               return ret;
+       struct tpm_buf buf;
+       int rc, rc2;
 
-       if (val != ret)
+       if (mso != TPM2_MSO_PERSISTENT && mso != TPM2_MSO_VOLATILE &&
+           mso != TPM2_MSO_NVRAM)
                return -EINVAL;
 
-       memcpy(name, &buf->data[offset], val);
-       /* forget the rest */
-       return 0;
-}
-
-static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
-{
-       struct tpm_buf buf;
-       int rc;
-
        rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
        if (rc)
                return rc;
 
        tpm_buf_append_u32(&buf, handle);
-       rc = tpm_transmit_cmd(chip, &buf, 0, "read public");
-       if (rc == TPM2_RC_SUCCESS)
-               rc = tpm2_parse_read_public(name, &buf);
 
-       tpm_buf_destroy(&buf);
+       rc = tpm_transmit_cmd(chip, &buf, 0, "TPM2_ReadPublic");
+       if (rc) {
+               tpm_buf_destroy(&buf);
+               return tpm_ret_to_err(rc);
+       }
 
-       return rc;
+       /* Skip TPMT_PUBLIC: */
+       offset += tpm_buf_read_u16(&buf, &offset);
+
+       /*
+        * Ensure space for the length field of TPM2B_NAME and hashAlg field of
+        * TPMT_HA (the extra four bytes).
+        */
+       if (offset + 4 > tpm_buf_length(&buf)) {
+               tpm_buf_destroy(&buf);
+               return -EIO;
+       }
+
+       rc = tpm_buf_read_u16(&buf, &offset);
+       rc2 = name_size(&buf.data[offset]);
+
+       if (rc2 < 0)
+               return rc2;
+
+       if (rc != rc2) {
+               tpm_buf_destroy(&buf);
+               return -EIO;
+       }
+
+       if (offset + rc > tpm_buf_length(&buf)) {
+               tpm_buf_destroy(&buf);
+               return -EIO;
+       }
+
+       memcpy(name, &buf.data[offset], rc);
+       return 0;
 }
 #endif /* CONFIG_TCG_TPM2_HMAC */
 
-- 
2.52.0