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 an 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. Signed-off-by: Srish Srinivasan <[email protected]> --- security/keys/trusted-keys/trusted_tpm2.c | 47 +++++++++++++++++++---- 1 file changed, 39 insertions(+), 8 deletions(-) diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 67225dd562a9..efb016a6d4b8 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -24,24 +24,54 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, u8 *src, u32 len) { 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; + u8 *work, *work1; + u8 *end_work; u8 *priv, *pub; - u16 priv_len, pub_len; + u32 priv_len, pub_len; int ret; - priv_len = get_unaligned_be16(src) + 2; + /* + * TPM2_Create Response Parameters: + * + * outPrivate + * outPublic + * creationData + * creationHash + * creationTicket + * + * Validate outPrivate and outPublic against the response parameter + * length before accessing them. + */ + if (len < sizeof(__be16)) + return -EFAULT; + + priv_len = get_unaligned_be16(src); + if (priv_len > len - sizeof(__be16)) + return -EFAULT; + + priv_len += sizeof(__be16); priv = src; + if (len - priv_len < sizeof(__be16)) + return -EFAULT; + src += priv_len; - pub_len = get_unaligned_be16(src) + 2; + pub_len = get_unaligned_be16(src); + if (pub_len > len - priv_len - sizeof(__be16)) + return -EFAULT; + + pub_len += sizeof(__be16); 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)); @@ -335,10 +365,11 @@ 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) { - rc = -E2BIG; + if (buf->flags & TPM_BUF_INVALID) { + rc = -EFAULT; goto out; } + if (buf->length - offset < blob_len) { rc = -EFAULT; goto out; -- 2.53.0
