| Message ID | 20210114151909.2344974-5-mic@digikod.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Enable root to update the blacklist keyring | expand |
On Thu, Jan 14, 2021 at 04:19:03PM +0100, Mickaël Salaün wrote: > From: David Howells <dhowells@redhat.com> > > KEY_FLAG_KEEP is not meant to be passed to keyring_alloc() or key_alloc(), > as these only take KEY_ALLOC_* flags. KEY_FLAG_KEEP has the same value as > KEY_ALLOC_BYPASS_RESTRICTION, but fortunately only key_create_or_update() > uses it. LSMs using the key_alloc hook don't check that flag. > > KEY_FLAG_KEEP is then ignored but fortunately (again) the root user cannot > write to the blacklist keyring, so it is not possible to remove a key/hash > from it. > > Fix this by adding a KEY_ALLOC_SET_KEEP flag that tells key_alloc() to set > KEY_FLAG_KEEP on the new key. blacklist_init() can then, correctly, pass > this to keyring_alloc(). OK, so thing work by luck now, but given the new patches which allow to append new keys they would break, right? > We can also use this in ima_mok_init() rather than setting the flag > manually. What does ima_mok_init() do? > Note that this doesn't fix an observable bug with the current > implementation but it is required to allow addition of new hashes to the > blacklist in the future without making it possible for them to be removed. > > Fixes: 734114f8782f ("KEYS: Add a system blacklist keyring") > cc: Mimi Zohar <zohar@linux.vnet.ibm.com> Nit: Cc > Cc: David Woodhouse <dwmw2@infradead.org> > Reported-by: Mickaël Salaün <mic@linux.microsoft.com> > Signed-off-by: David Howells <dhowells@redhat.com> > [mic@linux.microsoft.com: fix ima_mok_init()] > Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> > --- > > Changes since v2: > * Cherry-pick rewritten v1 patch from > https://lore.kernel.org/lkml/2659836.1607940186@warthog.procyon.org.uk/ > to rebase on v5.11-rc3 and fix ima_mok_init(). > --- > certs/blacklist.c | 2 +- > include/linux/key.h | 1 + > security/integrity/ima/ima_mok.c | 4 +--- > security/keys/key.c | 2 ++ > 4 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/certs/blacklist.c b/certs/blacklist.c > index a888b934a1cd..029471947838 100644 > --- a/certs/blacklist.c > +++ b/certs/blacklist.c > @@ -162,7 +162,7 @@ static int __init blacklist_init(void) > KEY_USR_VIEW | KEY_USR_READ | > KEY_USR_SEARCH, > KEY_ALLOC_NOT_IN_QUOTA | > - KEY_FLAG_KEEP, > + KEY_ALLOC_SET_KEEP, > NULL, NULL); > if (IS_ERR(blacklist_keyring)) > panic("Can't allocate system blacklist keyring\n"); > diff --git a/include/linux/key.h b/include/linux/key.h > index 0f2e24f13c2b..eed3ce139a32 100644 > --- a/include/linux/key.h > +++ b/include/linux/key.h > @@ -289,6 +289,7 @@ extern struct key *key_alloc(struct key_type *type, > #define KEY_ALLOC_BUILT_IN 0x0004 /* Key is built into kernel */ > #define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */ > #define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */ > +#define KEY_ALLOC_SET_KEEP 0x0020 /* Set the KEEP flag on the key/keyring */ > > extern void key_revoke(struct key *key); > extern void key_invalidate(struct key *key); > diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c > index 36cadadbfba4..5594dd38ab04 100644 > --- a/security/integrity/ima/ima_mok.c > +++ b/security/integrity/ima/ima_mok.c > @@ -38,13 +38,11 @@ __init int ima_mok_init(void) > (KEY_POS_ALL & ~KEY_POS_SETATTR) | > KEY_USR_VIEW | KEY_USR_READ | > KEY_USR_WRITE | KEY_USR_SEARCH, > - KEY_ALLOC_NOT_IN_QUOTA, > + KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_SET_KEEP, > restriction, NULL); > > if (IS_ERR(ima_blacklist_keyring)) > panic("Can't allocate IMA blacklist keyring."); > - > - set_bit(KEY_FLAG_KEEP, &ima_blacklist_keyring->flags); > return 0; > } > device_initcall(ima_mok_init); > diff --git a/security/keys/key.c b/security/keys/key.c > index ebe752b137aa..c45afdd1dfbb 100644 > --- a/security/keys/key.c > +++ b/security/keys/key.c > @@ -303,6 +303,8 @@ struct key *key_alloc(struct key_type *type, const char *desc, > key->flags |= 1 << KEY_FLAG_BUILTIN; > if (flags & KEY_ALLOC_UID_KEYRING) > key->flags |= 1 << KEY_FLAG_UID_KEYRING; > + if (flags & KEY_ALLOC_SET_KEEP) > + key->flags |= 1 << KEY_FLAG_KEEP; > > #ifdef KEY_DEBUGGING > key->magic = KEY_DEBUG_MAGIC; > -- > 2.30.0 > Acked-by: Jarkko Sakkinen <jarkko@kernel.org> /Jarkko
On 20/01/2021 04:55, Jarkko Sakkinen wrote: > On Thu, Jan 14, 2021 at 04:19:03PM +0100, Mickaël Salaün wrote: >> From: David Howells <dhowells@redhat.com> >> >> KEY_FLAG_KEEP is not meant to be passed to keyring_alloc() or key_alloc(), >> as these only take KEY_ALLOC_* flags. KEY_FLAG_KEEP has the same value as >> KEY_ALLOC_BYPASS_RESTRICTION, but fortunately only key_create_or_update() >> uses it. LSMs using the key_alloc hook don't check that flag. >> >> KEY_FLAG_KEEP is then ignored but fortunately (again) the root user cannot >> write to the blacklist keyring, so it is not possible to remove a key/hash >> from it. >> >> Fix this by adding a KEY_ALLOC_SET_KEEP flag that tells key_alloc() to set >> KEY_FLAG_KEEP on the new key. blacklist_init() can then, correctly, pass >> this to keyring_alloc(). > > OK, so thing work by luck now, but given the new patches which allow > to append new keys they would break, right? Without this fix, patch 9/10 would allow to remove and modify keys from the blacklist keyring. > >> We can also use this in ima_mok_init() rather than setting the flag >> manually. > > What does ima_mok_init() do? This was initially an addition from David Howells, I only fixed the argument bit-ORing. ima_mok_init() allocates a blacklist keyring (with different properties) dedicated to IMA. >> Note that this doesn't fix an observable bug with the current >> implementation but it is required to allow addition of new hashes to the >> blacklist in the future without making it possible for them to be removed. >> >> Fixes: 734114f8782f ("KEYS: Add a system blacklist keyring") >> cc: Mimi Zohar <zohar@linux.vnet.ibm.com> > > Nit: Cc OK > >> Cc: David Woodhouse <dwmw2@infradead.org> >> Reported-by: Mickaël Salaün <mic@linux.microsoft.com> >> Signed-off-by: David Howells <dhowells@redhat.com> >> [mic@linux.microsoft.com: fix ima_mok_init()] >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> >> --- >> >> Changes since v2: >> * Cherry-pick rewritten v1 patch from >> https://lore.kernel.org/lkml/2659836.1607940186@warthog.procyon.org.uk/ >> to rebase on v5.11-rc3 and fix ima_mok_init(). >> --- >> certs/blacklist.c | 2 +- >> include/linux/key.h | 1 + >> security/integrity/ima/ima_mok.c | 4 +--- >> security/keys/key.c | 2 ++ >> 4 files changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/certs/blacklist.c b/certs/blacklist.c >> index a888b934a1cd..029471947838 100644 >> --- a/certs/blacklist.c >> +++ b/certs/blacklist.c >> @@ -162,7 +162,7 @@ static int __init blacklist_init(void) >> KEY_USR_VIEW | KEY_USR_READ | >> KEY_USR_SEARCH, >> KEY_ALLOC_NOT_IN_QUOTA | >> - KEY_FLAG_KEEP, >> + KEY_ALLOC_SET_KEEP, >> NULL, NULL); >> if (IS_ERR(blacklist_keyring)) >> panic("Can't allocate system blacklist keyring\n"); >> diff --git a/include/linux/key.h b/include/linux/key.h >> index 0f2e24f13c2b..eed3ce139a32 100644 >> --- a/include/linux/key.h >> +++ b/include/linux/key.h >> @@ -289,6 +289,7 @@ extern struct key *key_alloc(struct key_type *type, >> #define KEY_ALLOC_BUILT_IN 0x0004 /* Key is built into kernel */ >> #define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */ >> #define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */ >> +#define KEY_ALLOC_SET_KEEP 0x0020 /* Set the KEEP flag on the key/keyring */ >> >> extern void key_revoke(struct key *key); >> extern void key_invalidate(struct key *key); >> diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c >> index 36cadadbfba4..5594dd38ab04 100644 >> --- a/security/integrity/ima/ima_mok.c >> +++ b/security/integrity/ima/ima_mok.c >> @@ -38,13 +38,11 @@ __init int ima_mok_init(void) >> (KEY_POS_ALL & ~KEY_POS_SETATTR) | >> KEY_USR_VIEW | KEY_USR_READ | >> KEY_USR_WRITE | KEY_USR_SEARCH, >> - KEY_ALLOC_NOT_IN_QUOTA, >> + KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_SET_KEEP, >> restriction, NULL); >> >> if (IS_ERR(ima_blacklist_keyring)) >> panic("Can't allocate IMA blacklist keyring."); >> - >> - set_bit(KEY_FLAG_KEEP, &ima_blacklist_keyring->flags); >> return 0; >> } >> device_initcall(ima_mok_init); >> diff --git a/security/keys/key.c b/security/keys/key.c >> index ebe752b137aa..c45afdd1dfbb 100644 >> --- a/security/keys/key.c >> +++ b/security/keys/key.c >> @@ -303,6 +303,8 @@ struct key *key_alloc(struct key_type *type, const char *desc, >> key->flags |= 1 << KEY_FLAG_BUILTIN; >> if (flags & KEY_ALLOC_UID_KEYRING) >> key->flags |= 1 << KEY_FLAG_UID_KEYRING; >> + if (flags & KEY_ALLOC_SET_KEEP) >> + key->flags |= 1 << KEY_FLAG_KEEP; >> >> #ifdef KEY_DEBUGGING >> key->magic = KEY_DEBUG_MAGIC; >> -- >> 2.30.0 >> > > Acked-by: Jarkko Sakkinen <jarkko@kernel.org> > > /Jarkko >
On Wed, Jan 20, 2021 at 12:15:10PM +0100, Mickaël Salaün wrote: > > On 20/01/2021 04:55, Jarkko Sakkinen wrote: > > On Thu, Jan 14, 2021 at 04:19:03PM +0100, Mickaël Salaün wrote: > >> From: David Howells <dhowells@redhat.com> > >> > >> KEY_FLAG_KEEP is not meant to be passed to keyring_alloc() or key_alloc(), > >> as these only take KEY_ALLOC_* flags. KEY_FLAG_KEEP has the same value as > >> KEY_ALLOC_BYPASS_RESTRICTION, but fortunately only key_create_or_update() > >> uses it. LSMs using the key_alloc hook don't check that flag. > >> > >> KEY_FLAG_KEEP is then ignored but fortunately (again) the root user cannot > >> write to the blacklist keyring, so it is not possible to remove a key/hash > >> from it. > >> > >> Fix this by adding a KEY_ALLOC_SET_KEEP flag that tells key_alloc() to set > >> KEY_FLAG_KEEP on the new key. blacklist_init() can then, correctly, pass > >> this to keyring_alloc(). > > > > OK, so thing work by luck now, but given the new patches which allow > > to append new keys they would break, right? > > Without this fix, patch 9/10 would allow to remove and modify keys from > the blacklist keyring. > > > > >> We can also use this in ima_mok_init() rather than setting the flag > >> manually. > > > > What does ima_mok_init() do? > > This was initially an addition from David Howells, I only fixed the > argument bit-ORing. ima_mok_init() allocates a blacklist keyring (with > different properties) dedicated to IMA. Please add this to the commit message. /Jarkko
diff --git a/certs/blacklist.c b/certs/blacklist.c index a888b934a1cd..029471947838 100644 --- a/certs/blacklist.c +++ b/certs/blacklist.c @@ -162,7 +162,7 @@ static int __init blacklist_init(void) KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH, KEY_ALLOC_NOT_IN_QUOTA | - KEY_FLAG_KEEP, + KEY_ALLOC_SET_KEEP, NULL, NULL); if (IS_ERR(blacklist_keyring)) panic("Can't allocate system blacklist keyring\n"); diff --git a/include/linux/key.h b/include/linux/key.h index 0f2e24f13c2b..eed3ce139a32 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -289,6 +289,7 @@ extern struct key *key_alloc(struct key_type *type, #define KEY_ALLOC_BUILT_IN 0x0004 /* Key is built into kernel */ #define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */ #define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */ +#define KEY_ALLOC_SET_KEEP 0x0020 /* Set the KEEP flag on the key/keyring */ extern void key_revoke(struct key *key); extern void key_invalidate(struct key *key); diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c index 36cadadbfba4..5594dd38ab04 100644 --- a/security/integrity/ima/ima_mok.c +++ b/security/integrity/ima/ima_mok.c @@ -38,13 +38,11 @@ __init int ima_mok_init(void) (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_WRITE | KEY_USR_SEARCH, - KEY_ALLOC_NOT_IN_QUOTA, + KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_SET_KEEP, restriction, NULL); if (IS_ERR(ima_blacklist_keyring)) panic("Can't allocate IMA blacklist keyring."); - - set_bit(KEY_FLAG_KEEP, &ima_blacklist_keyring->flags); return 0; } device_initcall(ima_mok_init); diff --git a/security/keys/key.c b/security/keys/key.c index ebe752b137aa..c45afdd1dfbb 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -303,6 +303,8 @@ struct key *key_alloc(struct key_type *type, const char *desc, key->flags |= 1 << KEY_FLAG_BUILTIN; if (flags & KEY_ALLOC_UID_KEYRING) key->flags |= 1 << KEY_FLAG_UID_KEYRING; + if (flags & KEY_ALLOC_SET_KEEP) + key->flags |= 1 << KEY_FLAG_KEEP; #ifdef KEY_DEBUGGING key->magic = KEY_DEBUG_MAGIC;