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extend ima_measurement --pcrs option to support per-bank pcr files

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Extend the ima_measurement --pcrs option to support per-bank pcr files.
The extended syntax is "--pcrs algorithm,pathname".  If no algorithm
is specified, it defaults to sha1 as before.  Multiple --pcrs options
are now supported, one per bank of PCRs. The file format remains
unchanged.  If --pcrs is specified, only try to read PCRs from the
specified file(s); do not fall back to trying to read from sysfs
or the TPM itself in this case since the user requested use of
the files.

Create per-bank pcr files, depends on "tpm: add sysfs exports for all
banks of PCR registers" kernel patch:
$ cat tpm2pcrread.sh
for alg in sha1 sha256
do
  rm -f pcr-$alg
  pcr=0;
  while [ $pcr -lt 24 ];
  do
    printf "PCR-%02d: " $pcr >> pcr-$alg;
    cat /sys/class/tpm/tpm0/pcr-$alg/$pcr >> pcr-$alg;
    pcr=$[$pcr+1];
  done
done
$ sh ./tpm2pcrread.sh

Pass only the sha1 PCRs to evmctl defaulting to sha1:
$ sudo evmctl ima_measurement --pcrs pcr-sha1 /sys/kernel/security/integrity/ima/binary_runtime_measurements

Pass only the sha1 PCRs to evmctl with explicit selection of sha1:
$ sudo evmctl ima_measurement --pcrs sha1,pcr-sha1 /sys/kernel/security/integrity/ima/binary_runtime_measurements

Pass both sha1 and sha256 PCRs to evmctl:
$ sudo evmctl ima_measurement --pcrs sha1,pcr-sha1 --pcrs sha256,pcr-sha256 /sys/kernel/security/integrity/ima/binary_runtime_measurements

Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[zohar@linux.ibm.com: although support for exporting TPM 2.0 PCRs has
not yet been upstreamed, add support for the file format anyway.]
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Stephen Smalley
2020-07-27 09:21:10 -04:00
committed by Mimi Zohar
parent 79ab82f55f
commit 8e2738dd44
3 changed files with 114 additions and 64 deletions
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@@ -31,7 +31,7 @@ COMMANDS
ima_sign [--sigfile] [--key key] [--pass password] file
ima_verify file
ima_hash file
ima_measurement [--validate] [--verify] [--verify-sig [--key "key1, key2, ..."]] [--pcrs file] file
ima_measurement [--validate] [--verify] [--verify-sig [--key "key1, key2, ..."]] [--pcrs [hash-algorithm,]file [--pcrs hash-algorithm,file] ...] file
ima_fix [-t fdsxm] path
sign_hash [--key key] [--pass password]
hmac [--imahash | --imasig ] file
@@ -59,7 +59,7 @@ OPTIONS
--m32 force EVM hmac/signature for 32 bit target system
--m64 force EVM hmac/signature for 64 bit target system
--engine e preload OpenSSL engine e (such as: gost)
--pcrs file containing TPM 1.2 pcrs
--pcrs file containing TPM pcrs, one per hash-algorithm/bank
--validate ignore ToMToU measurement violations
--verify verify the template data digest
--verify-sig verify the file signature based on the file hash, both