tpm2_policycommandcode(1)

📦
version 5.8 · 10 versions
, in arch rolling

💅 tpm2_policycommandcode — the glow-up edition 🎀

okay so bestie, welcome to tpm2_policycommandcode(1) from the General Commands Manual section, and trust me when I say this one is lowkey iconic — it lets you lock down a TPM object so it'll only spill the tea to the specific commands you pick. it's giving bouncer-at-the-club energy. 🔥

✨ NAME ✨

tpm2_policycommandcode(1) — Restrict TPM object authorization to specific TPM commands. literally that's it, that's the vibe. 🌸

🦋 SYNOPSIS 🦋

tpm2_policycommandcode [OPTIONS] [ARGUMENT]

💜 DESCRIPTION 💜

tpm2_policycommandcode(1) — okay so it restricts TPM object authorization to specific TPM commands. super useful when you're in your "only these commands get to interact with my TPM object" era. protect your peace, bestie 🫶

as an argument it takes the command as an integer or a friendly string value. the friendly string → COMMAND CODE mapping lives in section COMMAND CODE MAPPINGS (scroll down, it's a whole mood). ✨

🎀 OPTIONS 🎀

  • -S, --session=FILE — a session file, and by that I mean the file that came out of tpm2_startauthsession(1)'s -S option. that's her. 💅
  • -L, --policy=FILE — the file where you save the policy digest. that's where the magic gets stored. ✨
  • ARGUMENT — the command line argument specifies TPM2 command code. no cap, that's what it does. 🌈
  • --cphash=FILE — file path to record the hash of the command parameters. this is commonly termed as cpHash. ⚠️ NOTE: when this option is selected, the tool will not actually execute the command — it simply returns a cpHash. so like, it's just vibing and reporting back, not doing the thing. 💀

🌸 References 🌸

(that's literally the section, bestie — it's just sitting there. heads up so you don't think I skipped it. 🎀)

💖 COMMON OPTIONS 💖

this collection of options are common to many programs and provide info that many users may expect. the whole squad basically. 👑

  • -h, --help=[man|no-man] — display the tool's manpage. by default it attempts to invoke the manpager for the tool, however, on failure will output a short tool summary. this is the same behavior if the man option argument is specified — however, if explicit man is requested, the tool will provide errors from man on stderr. if the no-man option is specified, or the manpager fails, the short options will be output to stdout.

to successfully use the manpages feature requires the manpages to be installed or on MANPATH, see man(1) for more details. iykyk. 📖

  • -v, --version — display version information for this tool, supported tctis, and exit. cute & informative. 💅
  • -V, --verbose — increase the information that the tool prints to the console during its execution. when using this option the file and line number are printed. literally so helpful for debugging, periodt. 🔍
  • -Q, --quiet — silence normal tool output to stdout. shhh 🤫
  • -Z, --enable-errata — enable the application of errata fixups. useful if an errata fixup needs to be applied to commands sent to the TPM. defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. ✨
  • -z, --pwd-session — use password session instead of a HMAC session for authentication. a clear text password is passed to the TPM to authorize the action. this option can be used to avoid problems when unsalted sessions are used in OpenSSL FIPS mode. if auth values are used, a salted session should be used for authentication. 🔐
  • -R, --autoflush — enable autoflush for transient objects created by the command. if a parent object is loaded from a context file, also the transient parent object will be flushed. autoflush can also be activated if the environment variable TPM2TOOLS_AUTOFLUSH is set to yes or true. 🚽✨
(yes, the original literally says "is is". we don't touch the source, bestie — that's a historical artifact now. 💀)

🔌 TCTI Configuration 🔌

the TCTI, or "Transmission Interface", is the communication mechanism with the TPM. TCTIs can be changed for communication with TPMs across different mediums. it's giving long-distance relationship with your hardware. 😭

to control the TCTI, the tools respect:

  1. the command line option -T or --tcti
  2. the environment variable: TPM2TOOLS_TCTI.

Note: the command line option always overrides the environment variable. no exceptions, that's the law. ⚖️

the current known TCTIs are:

  • tabrmd — the resource manager, called tabrmd. note that tabrmd and abrmd as a tcti name are synonymous. 👯
  • mssim — typically used for communicating to the TPM software simulator. 🖥️
  • device — used when talking directly to a TPM device file. 📁
  • none — do not initialize a connection with the TPM. some tools allow for off-tpm options and thus support not using a TCTI. tools that do not support it will error when attempted to be used without a TCTI connection. does not support ANY options and MUST BE presented as the exact text of "none". no cap, exact text. 💀

the arguments to either the command line option or the environment variable are in the form:

<tcti-name>:<tcti-option-config>

specifying an empty string for either the <tcti-name> or <tcti-option-config> results in the default being used for that portion respectively. so like, leave it blank, get the default. 🎀

🦋 TCTI Defaults 🦋

when a TCTI is not specified, the default TCTI is searched for using dlopen(3) semantics. the tools will search for tabrmd, device, and mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. so priorities, basically. 👑

you can query what TCTI will be chosen as the default by using the -v option to print the version information. the "default-tcti" key-value pair will indicate which of the aforementioned TCTIs is the default. ✨

🧚 Custom TCTIs 🧚

any TCTI that implements the dynamic TCTI interface can be loaded. the tools internally use dlopen(3), and the raw tcti-name value is used for the lookup. thus, this could be a path to the shared library, or a library name as understood by dlopen(3) semantics. build your own, bestie. 💅

🌈 TCTI OPTIONS 🌈

this collection of options are used to configure the various known TCTI modules available:

  • device — for the device TCTI, the TPM character device file for use by the device TCTI can be specified. the default is /dev/tpm0.

Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="device:/dev/tpm0"

  • mssim — for the mssim TCTI, the domain name or IP address and port number used by the simulator can be specified. the defaults are 127.0.0.1 and 2321.

Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TCTI="mssim:host=localhost,port=2321"

  • abrmd — for the abrmd TCTI, the configuration string format is a series of simple key value pairs separated by a , character. each key and value string are separated by a = character.
    • TCTI abrmd supports two keys:
      1. bus_name : the name of the tabrmd service on the bus (a string).
      2. bus_type : the type of the dbus instance (a string) limited to session and system.

specify the tabrmd tcti name and a config string of bus_name=com.example.FooBar:

\--tcti=tabrmd:bus_name=com.example.FooBar

specify the default (abrmd) tcti and a config string of bus_type=session:

\--tcti:bus_type=session
⚠️ NOTE: abrmd and tabrmd are synonymous. 🫶

👑 COMMAND CODE MAPPINGS 👑

the friendly strings below can be used en lieu of the raw integer values. so like, use the cute name OR the hex code. both slay. ✨

  • -TPM2_CC_AC_GetCapability: 0x194
  • -TPM2_CC_AC_Send: 0x195
  • -TPM2_CC_ActivateCredential: 0x147
  • -TPM2_CC_Certify: 0x148
  • -TPM2_CC_CertifyCreation: 0x14a
  • -TPM2_CC_ChangeEPS: 0x124
  • -TPM2_CC_ChangePPS: 0x125
  • -TPM2_CC_Clear: 0x126
  • -TPM2_CC_ClearControl: 0x127
  • -TPM2_CC_ClockRateAdjust: 0x130
  • -TPM2_CC_ClockSet: 0x128
  • -TPM2_CC_Commit: 0x18b
  • -TPM2_CC_ContextLoad: 0x161
  • -TPM2_CC_ContextSave: 0x162
  • -TPM2_CC_Create: 0x153
  • -TPM2_CC_CreateLoaded: 0x191
  • -TPM2_CC_CreatePrimary: 0x131
  • -TPM2_CC_DictionaryAttackLockReset: 0x139
  • -TPM2_CC_DictionaryAttackParameters: 0x13a
  • -TPM2_CC_Duplicate: 0x14b
  • -TPM2_CC_ECC_Parameters: 0x178
  • -TPM2_CC_ECDH_KeyGen: 0x163
  • -TPM2_CC_ECDH_ZGen: 0x154
  • -TPM2_CC_EC_Ephemeral: 0x18e
  • -TPM2_CC_EncryptDecrypt: 0x164
  • -TPM2_CC_EncryptDecrypt2: 0x193
  • -TPM2_CC_EventSequenceComplete: 0x185
  • -TPM2_CC_EvictControl: 0x120
  • -TPM2_CC_FieldUpgradeData: 0x141
  • -TPM2_CC_FieldUpgradeStart: 0x12f
  • -TPM2_CC_FirmwareRead: 0x179
  • -TPM2_CC_FlushContext: 0x165
  • -TPM2_CC_GetCapability: 0x17a
  • -TPM2_CC_GetCommandAuditDigest: 0x133
  • -TPM2_CC_GetRandom: 0x17b
  • -TPM2_CC_GetSessionAuditDigest: 0x14d
  • -TPM2_CC_GetTestResult: 0x17c
  • -TPM2_CC_GetTime: 0x14c
  • -TPM2_CC_Hash: 0x17d
  • -TPM2_CC_HashSequenceStart: 0x186
  • -TPM2_CC_HierarchyChangeAuth: 0x129
  • -TPM2_CC_HierarchyControl: 0x121
  • -TPM2_CC_HMAC: 0x155
  • -TPM2_CC_HMAC_Start: 0x15b
  • -TPM2_CC_Import: 0x156
  • -TPM2_CC_IncrementalSelfTest: 0x142
  • -TPM2_CC_Load: 0x157
  • -TPM2_CC_LoadExternal: 0x167
  • -TPM2_CC_MakeCredential: 0x168
  • -TPM2_CC_NV_Certify: 0x184
  • -TPM2_CC_NV_ChangeAuth: 0x13b
  • -TPM2_CC_NV_DefineSpace: 0x12a
  • -TPM2_CC_NV_Extend: 0x136
  • -TPM2_CC_NV_GlobalWriteLock: 0x132
  • -TPM2_CC_NV_Increment: 0x134
  • -TPM2_CC_NV_Read: 0x14e
  • -TPM2_CC_NV_ReadLock: 0x14f
  • -TPM2_CC_NV_ReadPublic: 0x169
  • -TPM2_CC_NV_SetBits: 0x135
  • -TPM2_CC_NV_UndefineSpace: 0x122
  • -TPM2_CC_NV_UndefineSpaceSpecial: 0x11f
  • -TPM2_CC_NV_Write: 0x137
  • -TPM2_CC_NV_WriteLock: 0x138
  • -TPM2_CC_ObjectChangeAuth: 0x150
  • -TPM2_CC_PCR_Allocate: 0x12b
  • -TPM2_CC_PCR_Event: 0x13c
  • -TPM2_CC_PCR_Extend: 0x182
  • -TPM2_CC_PCR_Read: 0x17e
  • -TPM2_CC_PCR_Reset: 0x13d
  • -TPM2_CC_PCR_SetAuthPolicy: 0x12c
  • -TPM2_CC_PCR_SetAuthValue: 0x183
  • -TPM2_CC_Policy_AC_SendSelect: 0x196
  • -TPM2_CC_PolicyAuthorize: 0x16a
  • -TPM2_CC_PolicyAuthorizeNV: 0x192
  • -TPM2_CC_PolicyAuthValue: 0x16b
  • -TPM2_CC_PolicyCommandCode: 0x16c
  • -TPM2_CC_PolicyCounterTimer: 0x16d
  • -TPM2_CC_PolicyCpHash: 0x16e
  • -TPM2_CC_PolicyDuplicationSelect: 0x188
  • -TPM2_CC_PolicyGetDigest: 0x189
  • -TPM2_CC_PolicyLocality: 0x16f
  • -TPM2_CC_PolicyNameHash: 0x170
  • -TPM2_CC_PolicyNV: 0x149
  • -TPM2_CC_PolicyNvWritten: 0x18f
  • -TPM2_CC_PolicyOR: 0x171
  • -TPM2_CC_PolicyPassword: 0x18c
  • -TPM2_CC_PolicyPCR: 0x17f
  • -TPM2_CC_PolicyPhysicalPresence: 0x187
  • -TPM2_CC_PolicyRestart: 0x180
  • -TPM2_CC_PolicySecret: 0x151
  • -TPM2_CC_PolicySigned: 0x160
  • -TPM2_CC_PolicyTemplate: 0x190
  • -TPM2_CC_PolicyTicket: 0x172
  • -TPM2_CC_PP_Commands: 0x12d
  • -TPM2_CC_Quote: 0x158
  • -TPM2_CC_ReadClock: 0x181
  • -TPM2_CC_ReadPublic: 0x173
  • -TPM2_CC_Rewrap: 0x152
  • -TPM2_CC_RSA_Decrypt: 0x159
  • -TPM2_CC_RSA_Encrypt: 0x174
  • -TPM2_CC_SelfTest: 0x143
  • -TPM2_CC_SequenceComplete: 0x13e
  • -TPM2_CC_SequenceUpdate: 0x15c
  • -TPM2_CC_SetAlgorithmSet: 0x13f
  • -TPM2_CC_SetCommandCodeAuditStatus: 0x140
  • -TPM2_CC_SetPrimaryPolicy: 0x12e
  • -TPM2_CC_Shutdown: 0x145
  • -TPM2_CC_Sign: 0x15d
  • -TPM2_CC_StartAuthSession: 0x176
  • -TPM2_CC_Startup: 0x144
  • -TPM2_CC_StirRandom: 0x146
  • -TPM2_CC_TestParms: 0x18a
  • -TPM2_CC_Unseal: 0x15e
  • -TPM2_CC_Vendor_TCG_Test: 0x20000000
  • -TPM2_CC_VerifySignature: 0x177
  • -TPM2_CC_ZGen_2Phase: 0x18d

to be continued, bestie — part 2 is coming and it's gonna eat 💅✨

✨ EXAMPLES ✨

Okay so picture this, bestie: you start a policy session and extend it with a specific command, like unseal. If you try to do any other operation, it would fail. That's literally the whole point, and it's iconic.

🧚 Create an unseal-only policy

tpm2_startauthsession -S session.dat

tpm2_policycommandcode -S session.dat -L policy.dat TPM2_CC_Unseal

tpm2_flushcontext session.dat

This is the “lock it to unseal and nothing else” starter pack ✨. No cap.

🎀 Create the object with unseal-only auth policy

tpm2_createprimary -C o -c prim.ctx

tpm2_create -C prim.ctx -u sealkey.pub -r sealkey.priv -L policy.dat \
  -i- <<< "SEALED-SECRET"

Now the object is built with that unseal-only auth policy. Obsessed.

🌸 Try unseal operation

tpm2_load -C prim.ctx -u sealkey.pub -r sealkey.priv -n sealkey.name \
  -c sealkey.ctx

tpm2_startauthsession --policy-session -S session.dat

tpm2_policycommandcode -S session.dat -L policy.dat TPM2_CC_Unseal

tpm2_unseal -p session:session.dat -c sealkey.ctx
SEALED-SECRET

tpm2_flushcontext session.dat

The unseal goes through and drops SEALED-SECRET right there. Slay 💅.

💀 Try any other operation

echo "Encrypt Me" > plain.txt

tpm2_encryptdecrypt plain.txt -o enc.txt -c sealkey.ctx plain.txt
ERROR: Esys_EncryptDecrypt2(0x12F) - tpm:error(2.0): authValue or authPolicy is
not available for selected entity

And that's the fail we expected: the policy says unseal-only, so this other operation gets the error treatment. The error text is right there, bestie — no cap.

💖 Returns 💖

Tools can return any of the following codes:

  • 0 — Success. 💅
  • 1 — General non-specific error.
  • 2 — Options handling error.
  • 3 — Authentication error.
  • 4 — TCTI related error.
  • 5 — Non supported scheme. Applicable to tpm2_testparams.

🚧 Limitations 🚧

It expects a session to be already established via tpm2_startauthsession(1) and requires one of the following:

  • direct device access
  • extended session support with tpm2-abrmd.
⚠️ Without it, most resource managers will not save session state between command invocations.

🐛 BUGS 🐛

Github Issues — that's where the bugs go, bestie.

🆘 HELP 🆘

See the Mailing List.

📜 License 📜

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0).

Okay, that's the whole page, bestie 🫶 — the footer's source/version is tpm2-tools, and the manual page is tpm2_policycommandcode(1). The date didn't show up in the footer, so that's the only garnish missing. Periodt. 💅

📦 where this page comes from