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>
This commit is contained in:
Mimi Zohar 2013-06-07 12:16:37 +02:00
parent 9b9d4ce592
commit e7a2ad7eb6
3 changed files with 64 additions and 3 deletions

View File

@ -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

View File

@ -71,6 +71,41 @@ config IMA_DEFAULT_TEMPLATE
default "ima" if IMA_TEMPLATE
default "ima-ng" if IMA_NG_TEMPLATE
choice
prompt "Default integrity hash algorithm"
default IMA_DEFAULT_HASH_SHA1
depends on IMA
help
Select the default hash algorithm used for the measurement
list, integrity appraisal and audit log. The compiled default
hash algorithm can be overwritten using the kernel command
line 'ima_hash=' option.
config IMA_DEFAULT_HASH_SHA1
bool "SHA1 (default)"
depends on CRYPTO_SHA1
config IMA_DEFAULT_HASH_SHA256
bool "SHA256"
depends on CRYPTO_SHA256 && !IMA_TEMPLATE
config IMA_DEFAULT_HASH_SHA512
bool "SHA512"
depends on CRYPTO_SHA512 && !IMA_TEMPLATE
config IMA_DEFAULT_HASH_WP512
bool "WP512"
depends on CRYPTO_WP512 && !IMA_TEMPLATE
endchoice
config IMA_DEFAULT_HASH
string
depends on IMA
default "sha1" if IMA_DEFAULT_HASH_SHA1
default "sha256" if IMA_DEFAULT_HASH_SHA256
default "sha512" if IMA_DEFAULT_HASH_SHA512
default "wp512" if IMA_DEFAULT_HASH_WP512
config IMA_APPRAISE
bool "Appraise integrity measurements"
depends on IMA

View File

@ -37,11 +37,32 @@ int ima_appraise;
#endif
int ima_hash_algo = HASH_ALGO_SHA1;
static int hash_setup_done;
static int __init hash_setup(char *str)
{
if (strncmp(str, "md5", 3) == 0)
ima_hash_algo = HASH_ALGO_MD5;
struct ima_template_desc *template_desc = ima_template_desc_current();
int i;
if (hash_setup_done)
return 1;
if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
if (strncmp(str, "sha1", 4) == 0)
ima_hash_algo = HASH_ALGO_SHA1;
else if (strncmp(str, "md5", 3) == 0)
ima_hash_algo = HASH_ALGO_MD5;
goto out;
}
for (i = 0; i < HASH_ALGO__LAST; i++) {
if (strcmp(str, hash_algo_name[i]) == 0) {
ima_hash_algo = i;
break;
}
}
out:
hash_setup_done = 1;
return 1;
}
__setup("ima_hash=", hash_setup);
@ -306,6 +327,7 @@ static int __init init_ima(void)
{
int error;
hash_setup(CONFIG_IMA_DEFAULT_HASH);
error = ima_init();
if (!error)
ima_initialized = 1;