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edit approved Apr 2, 2014 at 18:35
northox
edit approved Apr 2, 2014 at 18:35
northox
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As there are 24 PCR's in TPM 1.2 specification. Some of these PCRs are reserved and cannot be extended by user's code. Below are the PCR Index with their Usageusage:

0 - CRTM, BIOS and Platform Extensions 
Platform1 - Platform Configuration 
Option2 - Option ROM Code 
Option3 - Option ROM Configuration and Data 
IPL7Code4 - IPL Code (MBR Information and Bootloader Stage 1) 
IPL5 - IPL Code and Configuration Data (for use by IPL Code) 
State6 - State Transition and Wake Events 
Reserved7 - Reserved for future usage. Do not use. 
Bootloader8 - Bootloader Stage 2 Part 1 
Bootloader9 - Bootloader Stage 2 Part 2 
Not10 - Not in Use. 
Not11 - Not in Use. 
Bootloader12 - Bootloader Command line Arguments 
Files13 - Files checked via check-file routine 
Files14 - Files which are actually loaded (e.g. Linux kernel, initrd, modules..) 
Not15 - Not in Use. 
Not16 - Not in Use. 
DRTM17 - DRTM
18-23 to 23. Not in Use.

whatWhat I understood that a user can extend all the PCR's which are not in use? Is this correct? I asked this question Because I have written my own code to extend PCR's (by following https://www.cylab.cmu.edu/tiw/slides/challener-handout.pdf) and it turns out that i can extend all the PCR's except from PCR 17 to PCR 22. And my understanding was that I can only extend few and especially cannot play with the lower ones from PCR 0 to PCR 7.

Your help is highly appreciated! I can send the code as well if required!

As there are 24 PCR's in TPM 1.2 specification. Some of these PCRs are reserved and cannot be extended by user's code. Below are the PCR Index with their Usage

CRTM, BIOS and Platform Extensions Platform Configuration Option ROM Code Option ROM Configuration and Data IPL7Code (MBR Information and Bootloader Stage 1) IPL Code and Configuration Data (for use by IPL Code) State Transition and Wake Events Reserved for future usage. Do not use. Bootloader Stage 2 Part 1 Bootloader Stage 2 Part 2 Not in Use. Not in Use. Bootloader Command line Arguments Files checked via check-file routine Files which are actually loaded (e.g. Linux kernel, initrd, modules..) Not in Use. Not in Use. DRTM 18-23. Not in Use.

what I understood that a user can extend all the PCR's which are not in use? Is this correct? I asked this question Because I have written my own code to extend PCR's (by following https://www.cylab.cmu.edu/tiw/slides/challener-handout.pdf) and it turns out that i can extend all the PCR's except from PCR 17 to PCR 22. And my understanding was that I can only extend few and especially cannot play with the lower ones from PCR 0 to PCR 7.

Your help is highly appreciated! I can send the code as well if required!

As there are 24 PCR's in TPM 1.2 specification. Some of these PCRs are reserved and cannot be extended by user's code. Below are the PCR Index with their usage:

0 - CRTM, BIOS and Platform Extensions 
1 - Platform Configuration 
2 - Option ROM Code 
3 - Option ROM Configuration and Data 
4 - IPL Code (MBR Information and Bootloader Stage 1) 
5 - IPL Code and Configuration Data (for use by IPL Code) 
6 - State Transition and Wake Events 
7 - Reserved for future usage. Do not use. 
8 - Bootloader Stage 2 Part 1 
9 - Bootloader Stage 2 Part 2 
10 - Not in Use. 
11 - Not in Use. 
12 - Bootloader Command line Arguments 
13 - Files checked via check-file routine 
14 - Files which are actually loaded (e.g. Linux kernel, initrd, modules..) 
15 - Not in Use. 
16 - Not in Use. 
17 - DRTM
18 to 23. Not in Use.

What I understood that a user can extend all the PCR's which are not in use? Is this correct? I asked this question Because I have written my own code to extend PCR's (by following https://www.cylab.cmu.edu/tiw/slides/challener-handout.pdf) and it turns out that i can extend all the PCR's except from PCR 17 to PCR 22. And my understanding was that I can only extend few and especially cannot play with the lower ones from PCR 0 to PCR 7.

Your help is highly appreciated! I can send the code as well if required!

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Geek
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WhichAs there are 24 PCR's in TPM 1.2 specification. Some of these PCRs are reserved and cannot be extended by user's code. Below are the PCR Index with their Usage

CRTM, BIOS and Platform Extensions Platform Configuration registers Option ROM Code Option ROM Configuration and Data IPL7Code (PCRMBR Information and Bootloader Stage 1) we can write on IPL Code and Configuration Data (for use by using our own codeIPL Code) State Transition and Wake Events Reserved for future usage. Do not use. Bootloader Stage 2 Part 1 Bootloader Stage 2 Part 2 Not in Use. Not in Use. Bootloader Command line Arguments Files checked via check-file routine Files which are actually loaded (e.g. Linux kernel, initrd, modules..) Not in Use. Not in Use. DRTM 18-23. Not in Use.

what I understood that a user can extend all the PCR's which are not in use? Is this correct? I knowasked this question Because I have written my own code to extend PCR's (by following https://www.cylab.cmu.edu/tiw/slides/challener-handout.pdf) and it turns out that we cannot modifyi can extend all the PCR0-PCR7 but what aboutPCR's except from PCR 17 to PCR 22. And my understanding was that I can only extend few and especially cannot play with the restlower ones from PCR 0 to PCR 7.

Your help is highly appreciated! I can send the code as well if required!

Which Platform Configuration registers (PCR) we can write on by using our own code? I know that we cannot modify the PCR0-PCR7 but what about the rest.

As there are 24 PCR's in TPM 1.2 specification. Some of these PCRs are reserved and cannot be extended by user's code. Below are the PCR Index with their Usage

CRTM, BIOS and Platform Extensions Platform Configuration Option ROM Code Option ROM Configuration and Data IPL7Code (MBR Information and Bootloader Stage 1) IPL Code and Configuration Data (for use by IPL Code) State Transition and Wake Events Reserved for future usage. Do not use. Bootloader Stage 2 Part 1 Bootloader Stage 2 Part 2 Not in Use. Not in Use. Bootloader Command line Arguments Files checked via check-file routine Files which are actually loaded (e.g. Linux kernel, initrd, modules..) Not in Use. Not in Use. DRTM 18-23. Not in Use.

what I understood that a user can extend all the PCR's which are not in use? Is this correct? I asked this question Because I have written my own code to extend PCR's (by following https://www.cylab.cmu.edu/tiw/slides/challener-handout.pdf) and it turns out that i can extend all the PCR's except from PCR 17 to PCR 22. And my understanding was that I can only extend few and especially cannot play with the lower ones from PCR 0 to PCR 7.

Your help is highly appreciated! I can send the code as well if required!

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Geek
Geek
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Which PCR we can extend by using our own code?

Which Platform Configuration registers (PCR) we can write on by using our own code? I know that we cannot modify the PCR0-PCR7 but what about the rest.