[tpm2] tss2_createkey - unable to set persistent handle
z4pu at pm.me
| Newsgroups | dev.linux.lists.tpm2 |
|---|---|
| Message-ID | <[email protected]> |
Hello everyone
I am having issues using the Feature_API to create a key under the `/P_ECCP256SHA256/HS/SRK/` path. This is using `tss2_createkey` as well as using the Feature API programmatically. The issue is that I am able to generate a key at the path, but I am never able to set a persistent handle for it.
I would like to set a persistent handle for my child key as I am looking to use https://github.com/tpm2-software/tpm2-tss-engine/ programmatically. When loading a key using the engine library, according to https://github.com/tpm2-software/tpm2-tss-engine/blob/89327fa8b51962348c46ddc659fb8c3636336a60/src/tpm2-tss-engine.c#L190-L191, I can load a key by:
- specifying the persistent handle or
- providing the path to the encrypted TSS key file.
I am using the following:
- Ubuntu 20.04
- swtpm --version: TPM emulator version 0.7.0, Copyright (c) 2014-2021 IBM Corp. This is running in a Docker container exposing ports 2322 and 2321 using `docker run --name swtpm -p 2322:2322 -p 2321:2321 --rm --detach swtpm:latest`
- https://github.com/tpm2-software/tpm2-tss: latest master branch, based on release 2.4.6
- https://github.com/tpm2-software/tpm2-tools: latest master branch, based on 5.2 2021-09-28
fapi-config.json :
```
{
"profile_name": "P_ECCP256SHA256",
"profile_dir": "/usr/local/etc/tpm2-tss/fapi-profiles/",
"user_dir": "~/.local/share/tpm2-tss/user/keystore",
"system_dir": "/usr/local/var/lib/tpm2-tss/system/keystore",
"tcti": "swtpm:port=2321",
"ek_cert_less":"YES",
"system_pcrs" : [],
"log_dir" : "/usr/local/var/run/tpm2-tss/eventlog/"
}
```
The profiles at /usr/local/etc/tpm2-tss/fapi-profiles are the defaults:
```
cat /usr/local/etc/tpm2-tss/fapi-profiles/P_ECCP256SHA256.json
{
"type": "TPM2_ALG_ECC",
"nameAlg":"TPM2_ALG_SHA256",
"srk_template": "system,restricted,decrypt,0x81000001",
"srk_description": "Storage root key SRK",
"srk_persistent": 0,
"ek_template": "system,restricted,decrypt",
"ek_description": "Endorsement key EK",
"ecc_signing_scheme": {
"scheme":"TPM2_ALG_ECDSA",
"details":{
"hashAlg":"TPM2_ALG_SHA256"
},
},
"sym_mode":"TPM2_ALG_CFB",
"sym_parameters": {
"algorithm":"TPM2_ALG_AES",
"keyBits":"128",
"mode":"TPM2_ALG_CFB"
},
"sym_block_size": 16,
"pcr_selection": [
{ "hash": "TPM2_ALG_SHA1",
"pcrSelect": [ ],
},
{ "hash": "TPM2_ALG_SHA256",
"pcrSelect": [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 ]
}
],
"curveID": "TPM2_ECC_NIST_P256",
"ek_policy": {
"description": "Endorsement hierarchy used for policy secret.",
"policy":[
{
"type":"POLICYSECRET",
"objectName": "4000000b",
}
]
}
}
```
I'm also making sure to remove the following folders in between my experiments:
- /usr/local/var/lib/tpm2-tss/system/keystore/P_ECCP256SHA256
- /root/.local/share/tpm2-tss/user/keystore/P_ECCP256SHA256 (as my Docker container is running as root)
- ~/.local/share/tpm2-tss/user/keystore/P_ECCP256SHA256
The handle I am choosing for the child key is `0x81020001`, based on my reading of Table 7 of and the surrounding text at https://www.trustedcomputinggroup.org/wp-content/uploads/131011-Registry-of-reserved-TPM2-handles-and-localities.pdf
The sequence of commands I am running as root is:
- tss2_provision to provision the TPM
- tpm2_getcap handles-persistent to list the used handles: Output is `- 0x81800000 - 0x81800001`
- tss2_list to confirm that the keys under the hierarchies have been created. Output is `/P_ECCP256SHA256/HN:/P_ECCP256SHA256/HE:/P_ECCP256SHA256/HE/EK:/P_ECCP256SHA256/LOCKOUT:/P_ECCP256SHA256/HS/SRK:/P_ECCP256SHA256/HS`
- tss2_createkey --path="/P_ECCP256SHA256/HS/SRK/device_key" --type="sign, decrypt, noDa, 0x81020001" --authValue=""
- tss2_list again, Output is `/P_ECCP256SHA256/HN:/P_ECCP256SHA256/HE:/P_ECCP256SHA256/HE/EK:/P_ECCP256SHA256/LOCKOUT:/P_ECCP256SHA256/HS/SRK:/P_ECCP256SHA256/HS:/P_ECCP256SHA256/HS/SRK/device_key`
- tpm2_getcap handles-persistent does not list the requested handle: Output is `- 0x81800000 - 0x81800001`
However, when I restart the TPM, and do not provision it, I can run the following commands as root to generate a child key and the parent key with a persistent handle:
- tpm2_getcap handles-persistent: Output is `- 0x81800000 - 0x81800001`
- tpm2_createprimary --hierarchy=o --key-algorithm=ecc256 --key-context=owner_primary.ctx --format=pem --output=owner_primary_public_key.pem
output is
```
name-alg:
value: sha256
raw: 0xb
attributes:
value: fixedtpm|fixedparent|sensitivedataorigin|userwithauth|restricted|decrypt
raw: 0x30072
type:
value: ecc
raw: 0x23
curve-id:
value: NIST p256
raw: 0x3
kdfa-alg:
value: null
raw: 0x10
kdfa-halg:
value: (null)
raw: 0x0
scheme:
value: null
raw: 0x10
scheme-halg:
value: (null)
raw: 0x0
sym-alg:
value: aes
raw: 0x6
sym-mode:
value: cfb
raw: 0x43
sym-keybits: 128
x: 9eecfa05a9a8ddadc8adabe4c9ce3d34b60afe0fd35cc799e28badc638cae6ad
y: 30dfc43266c2aa3480f31366ac5d189abf793dae100f30b50b344b7207f03994
```
- tpm2_create --parent-context=owner_primary.ctx --key-algorithm=ecc256 --public=child_public.key --private=child_private.key
Output is
```
name-alg:
value: sha256
raw: 0xb
attributes:
value: fixedtpm|fixedparent|sensitivedataorigin|userwithauth|decrypt|sign
raw: 0x60072
type:
value: ecc
raw: 0x23
curve-id:
value: NIST p256
raw: 0x3
kdfa-alg:
value: null
raw: 0x10
kdfa-halg:
value: (null)
raw: 0x0
scheme:
value: null
raw: 0x10
scheme-halg:
value: (null)
raw: 0x0
sym-alg:
value: null
raw: 0x10
sym-mode:
value: (null)
raw: 0x0
sym-keybits: 0
x: 801553461b62972e1e3894e1baa1d56196774f829285f714a163c63a57a219de
y: ebfd148f186f2560a0a6713b5f6f50bfaa39b7a320304f8620c36bdee4dfa379
```
- tpm2_load --parent-context=owner_primary.ctx --public=child_public.key --private=child_private.key --key-context=child_key.ctx
Output is `name: 000b18738b4a5366d3f863920c7b98db696c723fd88e030b7cad32e1d3ac33e6fb6c`
- tpm2_evictcontrol --hierarchy=o --object-context=child_key.ctx 0x81020001
Output is
```
persistent-handle: 0x81020001
action: persisted
```
- tpm2_evictcontrol --hierarchy=o --object-context=owner_primary.ctx 0x81010001
Output is
```
persistent-handle: 0x81010001
action: persisted
```
- tpm2_getcap handles-persistent
Output is
```
- 0x81010001
- 0x81020001
- 0x81800000
- 0x81800001
```
- tss2_list
Output is an error message
```
WARNING:fapi:src/tss2-fapi/api/Fapi_List.c:216:Fapi_List_Finish() Path not found:
ERROR:fapi:src/tss2-fapi/api/Fapi_List.c:81:Fapi_List() ErrorCode (0x00060034) Entities_List
Fapi_List(0x60034) - fapi:Provisioning was not executed.
```
There isn't anything in `/usr/local/var/run/tpm2-tss/eventlog/` for me to look at, possibly because of the Dockerised setup.
I can later delete these persistent handles using e.g. tpm2_evictcontrol --hierarchy=o --object-context=0x81020001
Thanks very much in advance
Cheers
z.