On 12/27/2013 05:37 PM, Ursa Major wrote:
Hi ,
I am new to openssl, and am very keen to learn how how the integrity
checking is performed.
In my understanding, the incore computes the integrity of the codes
and placed them in an .hmac file (I am not sure if my understanding
is correct). How is the text segment and data segment being loaded
for the integrity test (they should be the exact copy of the
'executables', but won't that be a circular proving as it embeds
itself within itself)? What are the contents of the segments? What
is the mechanism of the working?
IMHO this question would be more appropriate for the openssl-users list.
I presume you're asking about the OpenSSL FIPS Object Module integrity
test, which is part of the mandated POST (Power On Self Test) process.
The implementation of that integrity test is documented at a conceptual
level in the FIPS module User Guide:
http://www.openssl.org/docs/fips/UserGuide-2.0.pdf
Simply put, at build time an HMAC-SHA1 digest is calculated over the
TEXT and RODATA segments of object code, and stored in the FIPS module.
One or both of two different techniques can be used for determining that
digest. Typically the premain intermediate executable is used for
native compilation and an incore utility for cross-compilation.
At runtime the stored digest is calculated over the TEXT and RODATA
segments of live memory and compared with the previously stored value.
That mechanism is of course also fully exposed in the source code:
http://www.openssl.org/source/openssl-fips-2.0.5.tar.gz
In particular look at fips.c, fips_premain.c, fipsld, and incore (for ELF).
-Steve M.
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Steve Marquess
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