Security notes / Unsorted: Difference between revisions
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===What is it?=== | ===What is it?=== | ||
It's a hardware module that assists a few security needs | |||
Part of its job is just to be ''separate'', because that allows it to do some things with more secrecy than is easy to guarantee otherwise -- if used well, that is. And with footnotes (separation is also potential [[attack surface]]) | |||
For some other needs it's more of a coprocessor thing, which doesn't always make much difference | |||
Physically, TPM started as a clearly separate extra chip/module, that might be built into laptops (fairly common in business laptops), and for PC motherboards started as a plug-in module that was originally very optional -- and now, years later, Microsoft is pushing very hard on the concept, in that they refuse to run Windows 11 if it's not there ''or'' it's an older version[https://support.microsoft.com/en-us/windows/enable-tpm-2-0-on-your-pc-1fd5a332-360d-4f46-a1e7-ae6b0c90645c]. | |||
'''Integrated?''' | |||
These days, you also find TPM is integrated into CPUs (Intel calls it PTT, AMD calls it fTPM). | |||
This is functionally similar to a separate TPM - it has its own storage, it can't be altered, only talked to via the same specific protocol. | |||
Upsides | Upsides | ||
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* it's possible that some attacks might be possible due to being integrated. | * it's possible that some attacks might be possible due to being integrated. | ||
:: Yes, it's isolated by a communication channel - that was part of the point - and TPM(1) communication is more easily sniffed if it's an exposed trace because that is ''itself'' unencrypted | :: Yes, it's isolated by a communication channel - that was part of the point - and TPM(1) communication is more easily sniffed if it's an exposed trace because that is ''itself'' unencrypted | ||
:: I wouldn't be surprised if there are side-channel attacks due to being on the same silicon. | :: yet I wouldn't be surprised if there are side-channel attacks due to being on the same silicon. | ||
Downsides: | Downsides: | ||
* it is now harder to upgrade the CPU ( | * it is now harder to upgrade the CPU (rarely a thing in laptops, but surely so in desktops) | ||
<!-- | <!-- | ||
It can be confusing that motherboards may allow ''either'' a physical module or such integrated TPM. | |||
{{comment|(You ''could'' implement the spec in code, but doing so means you lose the isolated environment, which defeats half the point)}} | {{comment|(You ''could'' implement the spec in code, but doing so means you lose the isolated environment, which defeats half the point)}} | ||
--> | --> | ||
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===What does it do?=== | ===What does it do?=== | ||
Being part of a [http://en.wikipedia.org/wiki/Trusted_Computing larger idea], | |||
the TPM is a different thing to different people/needs. | |||
It should also be note that it only makes attack surface smaller when used well. | |||
Used poorly it changes very little, | |||
Used poorly it changes little | and there is also the concept of blind trust leading to riskier behaviour. | ||
{{comment|(I'm still waiting for the day that more than a few percent of people start using GPG in an actually secure way, and that's twenty years old)}} | |||
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More technically, it e.g. | More technically, it e.g. | ||
* helps store some keys, | * helps store some keys, | ||
* can | * can create derived keys without revealing the original | ||
* can do certain encryption/decryption for you | * can do certain encryption/decryption for you | ||
* may let you mark keys as "never allow these keys to be copied out" - which effectively ties certain keys to specific TPM hardware ''permanently'' | |||
That | |||
: may makes it harder to steal certain keys, | |||
: may force us to use mechanisms that use derived keys rather than the master key, | |||
: | |||
: | : may mean there are some cases where you can ''use'' a key it stored without every transporting it out | ||
:: | :: you might e.g. [[message signing]] (to prove you have a key) without ever having that key in RAM | ||
: | : may let you tie certain uses to specific hardware (for better and worse) | ||
:: | :: great for a select few uses, and alleviates certain physical attacks, because now only a single piece of hardware can do a thing | ||
:: complete show stoppers for others | :: complete show stoppers for others | ||
:: and risky for some others yet | :: and a potentially risky tradeoff for some others yet - for example, you can force an encrypted drive to only work on the computer you encrypted it on. And if ever separated, you can basically never read that data again. | ||
: you can prevent running boot code that wasn't previously approved | : you can prevent running boot code that wasn't previously approved | ||
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<!-- | <!-- | ||
https://docs.microsoft.com/en-us/windows/security/information-protection/tpm/how-windows-uses-the-tpm | https://docs.microsoft.com/en-us/windows/security/information-protection/tpm/how-windows-uses-the-tpm | ||
'''Why is it useful at all?''' | '''Why is it useful at all?''' | ||
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'''Key storage''' is one good reason. | '''Key storage''' is one good reason. | ||
In practical terms, consider that all cryptography needs a key. | In practical terms, consider that practically all cryptography needs a key. | ||
While being used, that needs to sit somewhere as long as we ''might'' need it. | While being used, that needs to sit somewhere as long as we ''might'' need it. |
Revision as of 16:39, 26 September 2023
Security related stuff.
Securing services
Unsorted - · Anonymization notes · website security notes · integrated security hardware · Glossary · unsorted |
TPM
What is it?
It's a hardware module that assists a few security needs
Part of its job is just to be separate, because that allows it to do some things with more secrecy than is easy to guarantee otherwise -- if used well, that is. And with footnotes (separation is also potential attack surface)
For some other needs it's more of a coprocessor thing, which doesn't always make much difference
Physically, TPM started as a clearly separate extra chip/module, that might be built into laptops (fairly common in business laptops), and for PC motherboards started as a plug-in module that was originally very optional -- and now, years later, Microsoft is pushing very hard on the concept, in that they refuse to run Windows 11 if it's not there or it's an older version[1].
Integrated?
These days, you also find TPM is integrated into CPUs (Intel calls it PTT, AMD calls it fTPM).
This is functionally similar to a separate TPM - it has its own storage, it can't be altered, only talked to via the same specific protocol.
Upsides
- saves having to deal with one more component
- and helps against some physical attacks
Arguables:
- it's possible that some attacks might be possible due to being integrated.
- Yes, it's isolated by a communication channel - that was part of the point - and TPM(1) communication is more easily sniffed if it's an exposed trace because that is itself unencrypted
- yet I wouldn't be surprised if there are side-channel attacks due to being on the same silicon.
Downsides:
- it is now harder to upgrade the CPU (rarely a thing in laptops, but surely so in desktops)
What does it do?
Being part of a larger idea, the TPM is a different thing to different people/needs.
It should also be note that it only makes attack surface smaller when used well.
Used poorly it changes very little,
and there is also the concept of blind trust leading to riskier behaviour.
(I'm still waiting for the day that more than a few percent of people start using GPG in an actually secure way, and that's twenty years old)
More technically, it e.g.
- helps store some keys,
- can create derived keys without revealing the original
- can do certain encryption/decryption for you
- may let you mark keys as "never allow these keys to be copied out" - which effectively ties certain keys to specific TPM hardware permanently
That
- may makes it harder to steal certain keys,
- may force us to use mechanisms that use derived keys rather than the master key,
- may mean there are some cases where you can use a key it stored without every transporting it out
- you might e.g. message signing (to prove you have a key) without ever having that key in RAM
- may let you tie certain uses to specific hardware (for better and worse)
- great for a select few uses, and alleviates certain physical attacks, because now only a single piece of hardware can do a thing
- complete show stoppers for others
- and a potentially risky tradeoff for some others yet - for example, you can force an encrypted drive to only work on the computer you encrypted it on. And if ever separated, you can basically never read that data again.
- you can prevent running boot code that wasn't previously approved
- as protection against malware that alters the boot
- again, with footnotes. Like - who does the approving?
On secure boot
"Can't detect TPM device"
Means the BIOS knows that you can plug in a TPM module, and is looking for it (configured to do so, or always does), and doesn't find one.
So tell it not to look for one (if you can), plug one in, or ignore this message. It's often under a header named something like 'Trusted Computing'
Some BIOSes will always look for it(verify), in which case you can just ignore the message.
More acronyms
What does TPM not (necessarily) protect?
TPM versus TPM2
Use and criticism, strengths and weaknesses
See also
Nonce
Challenge/response
JSON Web Signature, Encryption, Tokens
GSSAPI notes
GSSAPI is a IETF standard to make it easier for various software to do various strong auth, e.g. Kerberos.
It also allows various other auth schemes to be plugged into it.
Which also makes it potentially interesting for SSO setups within an organisation.
(not unlike SASL, which can include GSSAPI)
It's used by things like OpenSSH,
NaCl
There are two security related things called NaCl - which are completely unrelated to each other.
(There are also other things called salt, like automation software Salt (a.k.a. Saltstack)