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apparmor: switch SECURITY_APPARMOR_HASH from sha1 to sha256 

sha1 is insecure and has colisions, thus it is not useful for even
lightweight policy hash checks. Switch to sha256, which on modern
hardware is fast enough.

Separately as per NIST Policy on Hash Functions, sha1 usage must be
withdrawn by 2030. This config option currently is one of many that
holds up sha1 usage.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
Dimitri John Ledkov 2023-10-22 20:40:26 +01:00 committed by John Johansen
parent b85ea95d08
commit e44a4dc4b3
3 changed files with 17 additions and 17 deletions
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12
security/apparmor/Kconfig
View File

@ -57,10 +57,10 @@ config SECURITY_APPARMOR_INTROSPECT_POLICY
cpu is paramount.
config SECURITY_APPARMOR_HASH
bool "Enable introspection of sha1 hashes for loaded profiles"
bool "Enable introspection of sha256 hashes for loaded profiles"
depends on SECURITY_APPARMOR_INTROSPECT_POLICY
select CRYPTO
select CRYPTO_SHA1
select CRYPTO_SHA256
default y
help
This option selects whether introspection of loaded policy
@ -74,10 +74,10 @@ config SECURITY_APPARMOR_HASH_DEFAULT
depends on SECURITY_APPARMOR_HASH
default y
help
This option selects whether sha1 hashing of loaded policy
is enabled by default. The generation of sha1 hashes for
loaded policy provide system administrators a quick way
to verify that policy in the kernel matches what is expected,
This option selects whether sha256 hashing of loaded policy
is enabled by default. The generation of sha256 hashes for
loaded policy provide system administrators a quick way to
verify that policy in the kernel matches what is expected,
however it can slow down policy load on some devices. In
these cases policy hashing can be disabled by default and
enabled only if needed.

16
security/apparmor/apparmorfs.c
View File

@ -1474,7 +1474,7 @@ int __aa_fs_create_rawdata(struct aa_ns *ns, struct aa_loaddata *rawdata)
rawdata->dents[AAFS_LOADDATA_REVISION] = dent;
if (aa_g_hash_policy) {
dent = aafs_create_file("sha1", S_IFREG | 0444, dir,
dent = aafs_create_file("sha256", S_IFREG | 0444, dir,
rawdata, &seq_rawdata_hash_fops);
if (IS_ERR(dent))
goto fail;
@ -1648,11 +1648,11 @@ static const char *rawdata_get_link_base(struct dentry *dentry,
return target;
}
static const char *rawdata_get_link_sha1(struct dentry *dentry,
static const char *rawdata_get_link_sha256(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
return rawdata_get_link_base(dentry, inode, done, "sha1");
return rawdata_get_link_base(dentry, inode, done, "sha256");
}
static const char *rawdata_get_link_abi(struct dentry *dentry,
@ -1669,8 +1669,8 @@ static const char *rawdata_get_link_data(struct dentry *dentry,
return rawdata_get_link_base(dentry, inode, done, "raw_data");
}
static const struct inode_operations rawdata_link_sha1_iops = {
.get_link = rawdata_get_link_sha1,
static const struct inode_operations rawdata_link_sha256_iops = {
.get_link = rawdata_get_link_sha256,
};
static const struct inode_operations rawdata_link_abi_iops = {
@ -1743,7 +1743,7 @@ int __aafs_profile_mkdir(struct aa_profile *profile, struct dentry *parent)
profile->dents[AAFS_PROF_ATTACH] = dent;
if (profile->hash) {
dent = create_profile_file(dir, "sha1", profile,
dent = create_profile_file(dir, "sha256", profile,
&seq_profile_hash_fops);
if (IS_ERR(dent))
goto fail;
@ -1753,9 +1753,9 @@ int __aafs_profile_mkdir(struct aa_profile *profile, struct dentry *parent)
#ifdef CONFIG_SECURITY_APPARMOR_EXPORT_BINARY
if (profile->rawdata) {
if (aa_g_hash_policy) {
dent = aafs_create("raw_sha1", S_IFLNK | 0444, dir,
dent = aafs_create("raw_sha256", S_IFLNK | 0444, dir,
profile->label.proxy, NULL, NULL,
&rawdata_link_sha1_iops);
&rawdata_link_sha256_iops);
if (IS_ERR(dent))
goto fail;
aa_get_proxy(profile->label.proxy);

6
security/apparmor/crypto.c
View File

@ -106,16 +106,16 @@ static int __init init_profile_hash(void)
if (!apparmor_initialized)
return 0;
tfm = crypto_alloc_shash("sha1", 0, 0);
tfm = crypto_alloc_shash("sha256", 0, 0);
if (IS_ERR(tfm)) {
int error = PTR_ERR(tfm);
AA_ERROR("failed to setup profile sha1 hashing: %d\n", error);
AA_ERROR("failed to setup profile sha256 hashing: %d\n", error);
return error;
}
apparmor_tfm = tfm;
apparmor_hash_size = crypto_shash_digestsize(apparmor_tfm);
aa_info_message("AppArmor sha1 policy hashing enabled");
aa_info_message("AppArmor sha256 policy hashing enabled");
return 0;
}