| Message ID | 20230904133415.1799503-13-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | security: Move IMA and EVM to the LSM infrastructure | expand |
On 9/4/23 09:34, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > the inode_post_setattr hook. > > It is useful for EVM to recalculate the HMAC on modified file attributes > and other file metadata, after it verified the HMAC of current file > metadata with the inode_setattr hook. > > LSMs should use the new hook instead of inode_setattr, when they need to > know that the operation was done successfully (not known in inode_setattr). > The new hook cannot return an error and cannot cause the operation to be > reverted. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > fs/attr.c | 1 + > include/linux/lsm_hook_defs.h | 2 ++ > include/linux/security.h | 7 +++++++ > security/security.c | 16 ++++++++++++++++ > 4 files changed, 26 insertions(+) > > diff --git a/fs/attr.c b/fs/attr.c > index 431f667726c7..3c309eb456c6 100644 > --- a/fs/attr.c > +++ b/fs/attr.c > @@ -486,6 +486,7 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry, > > if (!error) { > fsnotify_change(dentry, ia_valid); > + security_inode_post_setattr(idmap, dentry, ia_valid); > ima_inode_post_setattr(idmap, dentry, ia_valid); > evm_inode_post_setattr(idmap, dentry, ia_valid); > } > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index fdf075a6b1bb..995d30336cfa 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -136,6 +136,8 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode, > LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask) > LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry, > struct iattr *attr) > +LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap, > + struct dentry *dentry, int ia_valid) > LSM_HOOK(int, 0, inode_getattr, const struct path *path) > LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap, > struct dentry *dentry, const char *name, const void *value, > diff --git a/include/linux/security.h b/include/linux/security.h > index dcb3604ffab8..820899db5276 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -355,6 +355,8 @@ int security_inode_follow_link(struct dentry *dentry, struct inode *inode, > int security_inode_permission(struct inode *inode, int mask); > int security_inode_setattr(struct mnt_idmap *idmap, > struct dentry *dentry, struct iattr *attr); > +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid); > int security_inode_getattr(const struct path *path); > int security_inode_setxattr(struct mnt_idmap *idmap, > struct dentry *dentry, const char *name, > @@ -856,6 +858,11 @@ static inline int security_inode_setattr(struct mnt_idmap *idmap, > return 0; > } > > +static inline void > +security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid) > +{ } Existing security_sem_free() and others are also formatted like it, so it should be ok. > + > static inline int security_inode_getattr(const struct path *path) > { > return 0; > diff --git a/security/security.c b/security/security.c > index 2b24d01cf181..764a6f28b3b9 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -2124,6 +2124,22 @@ int security_inode_setattr(struct mnt_idmap *idmap, > } > EXPORT_SYMBOL_GPL(security_inode_setattr); > > +/** > + * security_inode_post_setattr() - Update the inode after a setattr operation > + * @idmap: idmap of the mount > + * @dentry: file > + * @ia_valid: file attributes set > + * > + * Update inode security field after successful setting file attributes. > + */ > +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid) > +{ > + if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > + return; > + call_void_hook(inode_post_setattr, idmap, dentry, ia_valid); > +} > + > /** > * security_inode_getattr() - Check if getting file attributes is allowed > * @path: file Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
On Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > the inode_post_setattr hook. > > It is useful for EVM to recalculate the HMAC on modified file attributes > and other file metadata, after it verified the HMAC of current file > metadata with the inode_setattr hook. > > LSMs should use the new hook instead of inode_setattr, when they need to > know that the operation was done successfully (not known in inode_setattr). > The new hook cannot return an error and cannot cause the operation to be > reverted. > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > fs/attr.c | 1 + Hi Christian, Al could you please review and ack patches 12-19, which touch the VFS? Thanks a lot! Roberto > include/linux/lsm_hook_defs.h | 2 ++ > include/linux/security.h | 7 +++++++ > security/security.c | 16 ++++++++++++++++ > 4 files changed, 26 insertions(+) > > diff --git a/fs/attr.c b/fs/attr.c > index 431f667726c7..3c309eb456c6 100644 > --- a/fs/attr.c > +++ b/fs/attr.c > @@ -486,6 +486,7 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry, > > if (!error) { > fsnotify_change(dentry, ia_valid); > + security_inode_post_setattr(idmap, dentry, ia_valid); > ima_inode_post_setattr(idmap, dentry, ia_valid); > evm_inode_post_setattr(idmap, dentry, ia_valid); > } > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > index fdf075a6b1bb..995d30336cfa 100644 > --- a/include/linux/lsm_hook_defs.h > +++ b/include/linux/lsm_hook_defs.h > @@ -136,6 +136,8 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode, > LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask) > LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry, > struct iattr *attr) > +LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap, > + struct dentry *dentry, int ia_valid) > LSM_HOOK(int, 0, inode_getattr, const struct path *path) > LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap, > struct dentry *dentry, const char *name, const void *value, > diff --git a/include/linux/security.h b/include/linux/security.h > index dcb3604ffab8..820899db5276 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -355,6 +355,8 @@ int security_inode_follow_link(struct dentry *dentry, struct inode *inode, > int security_inode_permission(struct inode *inode, int mask); > int security_inode_setattr(struct mnt_idmap *idmap, > struct dentry *dentry, struct iattr *attr); > +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid); > int security_inode_getattr(const struct path *path); > int security_inode_setxattr(struct mnt_idmap *idmap, > struct dentry *dentry, const char *name, > @@ -856,6 +858,11 @@ static inline int security_inode_setattr(struct mnt_idmap *idmap, > return 0; > } > > +static inline void > +security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid) > +{ } > + > static inline int security_inode_getattr(const struct path *path) > { > return 0; > diff --git a/security/security.c b/security/security.c > index 2b24d01cf181..764a6f28b3b9 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -2124,6 +2124,22 @@ int security_inode_setattr(struct mnt_idmap *idmap, > } > EXPORT_SYMBOL_GPL(security_inode_setattr); > > +/** > + * security_inode_post_setattr() - Update the inode after a setattr operation > + * @idmap: idmap of the mount > + * @dentry: file > + * @ia_valid: file attributes set > + * > + * Update inode security field after successful setting file attributes. > + */ > +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, > + int ia_valid) > +{ > + if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > + return; > + call_void_hook(inode_post_setattr, idmap, dentry, ia_valid); > +} > + > /** > * security_inode_getattr() - Check if getting file attributes is allowed > * @path: file
gOn Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote: > From: Roberto Sassu <roberto.sassu@huawei.com> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > the inode_post_setattr hook. > > It is useful for EVM to recalculate the HMAC on modified file attributes > and other file metadata, after it verified the HMAC of current file > metadata with the inode_setattr hook. "useful"? At inode_setattr hook, EVM verifies the file's existing HMAC value. At inode_post_setattr, EVM re-calculates the file's HMAC based on the modified file attributes and other file metadata. > > LSMs should use the new hook instead of inode_setattr, when they need to > know that the operation was done successfully (not known in inode_setattr). > The new hook cannot return an error and cannot cause the operation to be > reverted. Other LSMs could similarly update security xattrs or ... > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
On Wed, 2023-10-11 at 20:08 -0400, Mimi Zohar wrote: > gOn Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote: > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > > the inode_post_setattr hook. > > > > It is useful for EVM to recalculate the HMAC on modified file attributes > > and other file metadata, after it verified the HMAC of current file > > metadata with the inode_setattr hook. > > "useful"? > > At inode_setattr hook, EVM verifies the file's existing HMAC value. At > inode_post_setattr, EVM re-calculates the file's HMAC based on the > modified file attributes and other file metadata. > > > > > LSMs should use the new hook instead of inode_setattr, when they need to > > know that the operation was done successfully (not known in inode_setattr). > > The new hook cannot return an error and cannot cause the operation to be > > reverted. > > Other LSMs could similarly update security xattrs or ... I added your sentence. The one above is to satisfy Casey's request to justify the addition of the new hook, and to explain why inode_setattr is not sufficient. Thanks Roberto > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
On Thu, 2023-10-12 at 09:42 +0200, Roberto Sassu wrote: > On Wed, 2023-10-11 at 20:08 -0400, Mimi Zohar wrote: > > gOn Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote: > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > > > the inode_post_setattr hook. > > > > > > It is useful for EVM to recalculate the HMAC on modified file attributes > > > and other file metadata, after it verified the HMAC of current file > > > metadata with the inode_setattr hook. > > > > "useful"? > > > > At inode_setattr hook, EVM verifies the file's existing HMAC value. At > > inode_post_setattr, EVM re-calculates the file's HMAC based on the > > modified file attributes and other file metadata. > > > > > > > > LSMs should use the new hook instead of inode_setattr, when they need to > > > know that the operation was done successfully (not known in inode_setattr). > > > The new hook cannot return an error and cannot cause the operation to be > > > reverted. > > > > Other LSMs could similarly update security xattrs or ... > > I added your sentence. The one above is to satisfy Casey's request to > justify the addition of the new hook, and to explain why inode_setattr > is not sufficient. I was suggesting simplifying the wording. Perhaps something like: Other LSMs could similarly take some action after successful file attri bute change.
On Thu, 2023-10-12 at 07:43 -0400, Mimi Zohar wrote: > On Thu, 2023-10-12 at 09:42 +0200, Roberto Sassu wrote: > > On Wed, 2023-10-11 at 20:08 -0400, Mimi Zohar wrote: > > > gOn Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote: > > > > From: Roberto Sassu <roberto.sassu@huawei.com> > > > > > > > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce > > > > the inode_post_setattr hook. > > > > > > > > It is useful for EVM to recalculate the HMAC on modified file attributes > > > > and other file metadata, after it verified the HMAC of current file > > > > metadata with the inode_setattr hook. > > > > > > "useful"? > > > > > > At inode_setattr hook, EVM verifies the file's existing HMAC value. At > > > inode_post_setattr, EVM re-calculates the file's HMAC based on the > > > modified file attributes and other file metadata. > > > > > > > > > > > LSMs should use the new hook instead of inode_setattr, when they need to > > > > know that the operation was done successfully (not known in inode_setattr). > > > > The new hook cannot return an error and cannot cause the operation to be > > > > reverted. > > > > > > Other LSMs could similarly update security xattrs or ... > > > > I added your sentence. The one above is to satisfy Casey's request to > > justify the addition of the new hook, and to explain why inode_setattr > > is not sufficient. > > I was suggesting simplifying the wording. Perhaps something like: > > Other LSMs could similarly take some action after successful file attri > bute change. Ok, will use that. Thanks Roberto
diff --git a/fs/attr.c b/fs/attr.c index 431f667726c7..3c309eb456c6 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -486,6 +486,7 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry, if (!error) { fsnotify_change(dentry, ia_valid); + security_inode_post_setattr(idmap, dentry, ia_valid); ima_inode_post_setattr(idmap, dentry, ia_valid); evm_inode_post_setattr(idmap, dentry, ia_valid); } diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index fdf075a6b1bb..995d30336cfa 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -136,6 +136,8 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode, LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask) LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr) +LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap, + struct dentry *dentry, int ia_valid) LSM_HOOK(int, 0, inode_getattr, const struct path *path) LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap, struct dentry *dentry, const char *name, const void *value, diff --git a/include/linux/security.h b/include/linux/security.h index dcb3604ffab8..820899db5276 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -355,6 +355,8 @@ int security_inode_follow_link(struct dentry *dentry, struct inode *inode, int security_inode_permission(struct inode *inode, int mask); int security_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr); +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, + int ia_valid); int security_inode_getattr(const struct path *path); int security_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, const char *name, @@ -856,6 +858,11 @@ static inline int security_inode_setattr(struct mnt_idmap *idmap, return 0; } +static inline void +security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, + int ia_valid) +{ } + static inline int security_inode_getattr(const struct path *path) { return 0; diff --git a/security/security.c b/security/security.c index 2b24d01cf181..764a6f28b3b9 100644 --- a/security/security.c +++ b/security/security.c @@ -2124,6 +2124,22 @@ int security_inode_setattr(struct mnt_idmap *idmap, } EXPORT_SYMBOL_GPL(security_inode_setattr); +/** + * security_inode_post_setattr() - Update the inode after a setattr operation + * @idmap: idmap of the mount + * @dentry: file + * @ia_valid: file attributes set + * + * Update inode security field after successful setting file attributes. + */ +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry, + int ia_valid) +{ + if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) + return; + call_void_hook(inode_post_setattr, idmap, dentry, ia_valid); +} + /** * security_inode_getattr() - Check if getting file attributes is allowed * @path: file