ima: enable support for larger default filedata hash algorithms

The IMA measurement list contains two hashes - a template data hash
and a filedata hash.  The template data hash is committed to the TPM,
which is limited, by the TPM v1.2 specification, to 20 bytes.  The
filedata hash is defined as 20 bytes as well.

Now that support for variable length measurement list templates was
added, the filedata hash is not limited to 20 bytes.  This patch adds
Kconfig support for defining larger default filedata hash algorithms
and replacing the builtin default with one specified on the kernel
command line.

<uapi/linux/hash_info.h> contains a list of hash algorithms.  The
Kconfig default hash algorithm is a subset of this list, but any hash
algorithm included in the list can be specified at boot, using the
'ima_hash=' kernel command line option.

Changelog v2:
- update Kconfig

Changelog:
- support hashes that are configured
- use generic HASH_ALGO_ definitions
- add Kconfig support
- hash_setup must be called only once (Dmitry)
- removed trailing whitespaces (Roberto Sassu)

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>

1 files changed, 5 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2b78cb55ac34..1e8761c89a2c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1181,9 +1181,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         owned by uid=0.
 
         ima_hash=       [IMA]
-                        Format: { "sha1" | "md5" }
+                        Format: { md5 | sha1 | rmd160 | sha256 | sha384
+                                   | sha512 | ... }
                         default: "sha1"
 
+                        The list of supported hash algorithms is defined
+                        in crypto/hash_info.h.
+
         ima_tcb         [IMA]
                         Load a policy which meets the needs of the Trusted
                         Computing Base.  This means IMA will measure all