TPM2_Create returns outPrivate, outPublic, creationData, creationHash and creationTicket in its response parameter area. However, only outPrivate and outPublic are included in the trusted key blob. The size of the blob is therefore not determined by the size of the complete response parameter area.
tpm2_seal_trusted() currently compares the size of the complete response parameter area against MAX_BLOB_SIZE. This can reject a valid response when the remaining response outputs cause the entire response parameter area to exceed MAX_BLOB_SIZE, even though the outPrivate and outPublic TPM2B structures consumed by tpm2_key_encode() remain small enough to be encoded in the key blob. This is observed when creating larger trusted keys using the swtpm TPM 2.0 emulator backed by libtpms. For example, requesting a 113-byte key succeeds, 114 fails. ~$ keyctl add trusted trusted_key1 "new 113 keyhandle=0x81000001" @u 520504613 ~$ keyctl add trusted trusted_key2 "new 114 keyhandle=0x81000001" @u add_key: Argument list too long ~$ Remove the MAX_BLOB_SIZE check on the complete response parameter area. Instead, use the response length passed to tpm2_key_encode() to validate that the outPrivate and outPublic TPM2B structures are fully contained in the response before accessing them. Previously, a response parameter area larger than MAX_BLOB_SIZE was rejected with -E2BIG before ASN.1 encoding. With this change, if the resulting encoded blob does not fit in payload->blob, the error returned by asn1_encode_sequence() is propagated instead. Also, use scope-based cleanup to simplify resource management. Signed-off-by: Srish Srinivasan <[email protected]> --- Changelog: v3: - Simplify the TPM2B_PRIVATE and TPM2B_PUBLIC bounds checks - Use appropriate error codes for failure returns - Use scope-based cleanup to simplify resource management v2: - Exclude a comment pointed out by Jarkko security/keys/trusted-keys/trusted_tpm2.c | 42 +++++++++++++---------- 1 file changed, 24 insertions(+), 18 deletions(-) diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 906700c3d7f0..920f45c7864b 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -25,24 +25,36 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, { struct trusted_key_tpm *private = options->private; const int SCRATCH_SIZE = PAGE_SIZE; - u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL); - u8 *work = scratch, *work1; - u8 *end_work = scratch + SCRATCH_SIZE; + u8 *scratch __free(kfree) = NULL; + u8 *work, *work1; + u8 *end_work; u8 *priv, *pub; - u16 priv_len, pub_len; + u32 priv_len, pub_len; int ret; + if (len < 4) + return -EINVAL; + priv_len = get_unaligned_be16(src) + 2; - priv = src; + if (priv_len + 2 > len) + return -EIO; + priv = src; src += priv_len; pub_len = get_unaligned_be16(src) + 2; + if (pub_len + priv_len > len) + return -EIO; + pub = src; + scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL); if (!scratch) return -ENOMEM; + work = scratch; + end_work = scratch + SCRATCH_SIZE; + work = asn1_encode_oid(work, end_work, tpm2key_oid, asn1_oid_len(tpm2key_oid)); @@ -50,10 +62,9 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, unsigned char bool[3], *w = bool; /* tag 0 is emptyAuth */ w = asn1_encode_boolean(w, w + sizeof(bool), true); - if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) { - ret = PTR_ERR(w); - goto err; - } + if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) + return PTR_ERR(w); + work = asn1_encode_tag(work, end_work, 0, bool, w - bool); } @@ -65,8 +76,7 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, */ if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE, "BUG: scratch buffer is too small")) { - ret = -EINVAL; - goto err; + return -EINVAL; } work = asn1_encode_integer(work, end_work, private->keyhandle); @@ -79,15 +89,10 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, if (IS_ERR(work1)) { ret = PTR_ERR(work1); pr_err("BUG: ASN.1 encoder failed with %d\n", ret); - goto err; + return ret; } - kfree(scratch); return work1 - payload->blob; - -err: - kfree(scratch); - return ret; } struct tpm2_key_context { @@ -340,10 +345,11 @@ int tpm2_seal_trusted(struct tpm_chip *chip, goto out; blob_len = tpm_buf_read_u32(buf, &offset); - if (blob_len > MAX_BLOB_SIZE || buf->flags & TPM_BUF_INVALID) { + if (buf->flags & TPM_BUF_INVALID) { rc = -E2BIG; goto out; } + if (buf->length - offset < blob_len) { rc = -EFAULT; goto out; -- 2.53.0
