| Message ID | 20210407105252.30721-5-roberto.sassu@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | evm: Improve usability of portable signatures | expand |
On 4/7/2021 3:52 AM, Roberto Sassu wrote: > ima_inode_setxattr() and ima_inode_removexattr() hooks are called before an > operation is performed. Thus, ima_reset_appraise_flags() should not be > called there, as flags might be unnecessarily reset if the operation is > denied. > > This patch introduces the post hooks ima_inode_post_setxattr() and > ima_inode_post_removexattr(), and adds the call to > ima_reset_appraise_flags() in the new functions. > > Cc: Casey Schaufler <casey@schaufler-ca.com> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- > fs/xattr.c | 2 ++ > include/linux/ima.h | 18 ++++++++++++++++++ > security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++++++++--- > security/security.c | 1 + > 4 files changed, 43 insertions(+), 3 deletions(-) > > diff --git a/fs/xattr.c b/fs/xattr.c > index b3444e06cded..81847f132d26 100644 > --- a/fs/xattr.c > +++ b/fs/xattr.c > @@ -16,6 +16,7 @@ > #include <linux/namei.h> > #include <linux/security.h> > #include <linux/evm.h> > +#include <linux/ima.h> > #include <linux/syscalls.h> > #include <linux/export.h> > #include <linux/fsnotify.h> > @@ -502,6 +503,7 @@ __vfs_removexattr_locked(struct user_namespace *mnt_userns, > > if (!error) { > fsnotify_xattr(dentry); > + ima_inode_post_removexattr(dentry, name); > evm_inode_post_removexattr(dentry, name); > } > > diff --git a/include/linux/ima.h b/include/linux/ima.h > index 61d5723ec303..5e059da43857 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -171,7 +171,13 @@ extern void ima_inode_post_setattr(struct user_namespace *mnt_userns, > struct dentry *dentry); > extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, > const void *xattr_value, size_t xattr_value_len); > +extern void ima_inode_post_setxattr(struct dentry *dentry, > + const char *xattr_name, > + const void *xattr_value, > + size_t xattr_value_len); > extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name); > +extern void ima_inode_post_removexattr(struct dentry *dentry, > + const char *xattr_name); > #else > static inline bool is_ima_appraise_enabled(void) > { > @@ -192,11 +198,23 @@ static inline int ima_inode_setxattr(struct dentry *dentry, > return 0; > } > > +static inline void ima_inode_post_setxattr(struct dentry *dentry, > + const char *xattr_name, > + const void *xattr_value, > + size_t xattr_value_len) > +{ > +} > + > static inline int ima_inode_removexattr(struct dentry *dentry, > const char *xattr_name) > { > return 0; > } > + > +static inline void ima_inode_post_removexattr(struct dentry *dentry, > + const char *xattr_name) > +{ > +} > #endif /* CONFIG_IMA_APPRAISE */ > > #if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index 565e33ff19d0..1f029e4c8d7f 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, > if (result == 1) { > if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) > return -EINVAL; > - ima_reset_appraise_flags(d_backing_inode(dentry), > - xvalue->type == EVM_IMA_XATTR_DIGSIG); > result = 0; > } > return result; > } > > +void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, > + const void *xattr_value, size_t xattr_value_len) > +{ > + const struct evm_ima_xattr_data *xvalue = xattr_value; > + int result; > + > + result = ima_protect_xattr(dentry, xattr_name, xattr_value, > + xattr_value_len); > + if (result == 1) > + ima_reset_appraise_flags(d_backing_inode(dentry), > + xvalue->type == EVM_IMA_XATTR_DIGSIG); > +} > + Now you're calling ima_protect_xattr() twice for each setxattr. Is that safe? Is it performant? Does it matter? > int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) > { > int result; > > result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > if (result == 1) { > - ima_reset_appraise_flags(d_backing_inode(dentry), 0); > result = 0; > } > return result; > } > + > +void ima_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) > +{ > + int result; > + > + result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > + if (result == 1) > + ima_reset_appraise_flags(d_backing_inode(dentry), 0); > +} Now you're calling ima_protect_xattr() twice for each removexattr. Is that safe? Is it performant? Does it matter? > diff --git a/security/security.c b/security/security.c > index 5ac96b16f8fa..efb1f874dc41 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -1319,6 +1319,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name, > if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > return; > call_void_hook(inode_post_setxattr, dentry, name, value, size, flags); > + ima_inode_post_setxattr(dentry, name, value, size); > evm_inode_post_setxattr(dentry, name, value, size); > } >
> From: Casey Schaufler [mailto:casey@schaufler-ca.com] > Sent: Wednesday, April 7, 2021 6:18 PM > On 4/7/2021 3:52 AM, Roberto Sassu wrote: > > ima_inode_setxattr() and ima_inode_removexattr() hooks are called > before an > > operation is performed. Thus, ima_reset_appraise_flags() should not be > > called there, as flags might be unnecessarily reset if the operation is > > denied. > > > > This patch introduces the post hooks ima_inode_post_setxattr() and > > ima_inode_post_removexattr(), and adds the call to > > ima_reset_appraise_flags() in the new functions. > > > > Cc: Casey Schaufler <casey@schaufler-ca.com> > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > > --- > > fs/xattr.c | 2 ++ > > include/linux/ima.h | 18 ++++++++++++++++++ > > security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++++++++-- > - > > security/security.c | 1 + > > 4 files changed, 43 insertions(+), 3 deletions(-) > > > > diff --git a/fs/xattr.c b/fs/xattr.c > > index b3444e06cded..81847f132d26 100644 > > --- a/fs/xattr.c > > +++ b/fs/xattr.c > > @@ -16,6 +16,7 @@ > > #include <linux/namei.h> > > #include <linux/security.h> > > #include <linux/evm.h> > > +#include <linux/ima.h> > > #include <linux/syscalls.h> > > #include <linux/export.h> > > #include <linux/fsnotify.h> > > @@ -502,6 +503,7 @@ __vfs_removexattr_locked(struct > user_namespace *mnt_userns, > > > > if (!error) { > > fsnotify_xattr(dentry); > > + ima_inode_post_removexattr(dentry, name); > > evm_inode_post_removexattr(dentry, name); > > } > > > > diff --git a/include/linux/ima.h b/include/linux/ima.h > > index 61d5723ec303..5e059da43857 100644 > > --- a/include/linux/ima.h > > +++ b/include/linux/ima.h > > @@ -171,7 +171,13 @@ extern void ima_inode_post_setattr(struct > user_namespace *mnt_userns, > > struct dentry *dentry); > > extern int ima_inode_setxattr(struct dentry *dentry, const char > *xattr_name, > > const void *xattr_value, size_t xattr_value_len); > > +extern void ima_inode_post_setxattr(struct dentry *dentry, > > + const char *xattr_name, > > + const void *xattr_value, > > + size_t xattr_value_len); > > extern int ima_inode_removexattr(struct dentry *dentry, const char > *xattr_name); > > +extern void ima_inode_post_removexattr(struct dentry *dentry, > > + const char *xattr_name); > > #else > > static inline bool is_ima_appraise_enabled(void) > > { > > @@ -192,11 +198,23 @@ static inline int ima_inode_setxattr(struct dentry > *dentry, > > return 0; > > } > > > > +static inline void ima_inode_post_setxattr(struct dentry *dentry, > > + const char *xattr_name, > > + const void *xattr_value, > > + size_t xattr_value_len) > > +{ > > +} > > + > > static inline int ima_inode_removexattr(struct dentry *dentry, > > const char *xattr_name) > > { > > return 0; > > } > > + > > +static inline void ima_inode_post_removexattr(struct dentry *dentry, > > + const char *xattr_name) > > +{ > > +} > > #endif /* CONFIG_IMA_APPRAISE */ > > > > #if defined(CONFIG_IMA_APPRAISE) && > defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) > > diff --git a/security/integrity/ima/ima_appraise.c > b/security/integrity/ima/ima_appraise.c > > index 565e33ff19d0..1f029e4c8d7f 100644 > > --- a/security/integrity/ima/ima_appraise.c > > +++ b/security/integrity/ima/ima_appraise.c > > @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, > const char *xattr_name, > > if (result == 1) { > > if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) > > return -EINVAL; > > - ima_reset_appraise_flags(d_backing_inode(dentry), > > - xvalue->type == EVM_IMA_XATTR_DIGSIG); > > result = 0; > > } > > return result; > > } > > > > +void ima_inode_post_setxattr(struct dentry *dentry, const char > *xattr_name, > > + const void *xattr_value, size_t xattr_value_len) > > +{ > > + const struct evm_ima_xattr_data *xvalue = xattr_value; > > + int result; > > + > > + result = ima_protect_xattr(dentry, xattr_name, xattr_value, > > + xattr_value_len); > > + if (result == 1) > > + ima_reset_appraise_flags(d_backing_inode(dentry), > > + xvalue->type == EVM_IMA_XATTR_DIGSIG); > > +} > > + > > Now you're calling ima_protect_xattr() twice for each setxattr. > Is that safe? Is it performant? Does it matter? Hi Casey I would expect that this does not have a significant impact on the performance (it is just a strcmp on the xattr name). Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > > int ima_inode_removexattr(struct dentry *dentry, const char > *xattr_name) > > { > > int result; > > > > result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > > if (result == 1) { > > - ima_reset_appraise_flags(d_backing_inode(dentry), 0); > > result = 0; > > } > > return result; > > } > > + > > +void ima_inode_post_removexattr(struct dentry *dentry, const char > *xattr_name) > > +{ > > + int result; > > + > > + result = ima_protect_xattr(dentry, xattr_name, NULL, 0); > > + if (result == 1) > > + ima_reset_appraise_flags(d_backing_inode(dentry), 0); > > +} > > Now you're calling ima_protect_xattr() twice for each removexattr. > Is that safe? Is it performant? Does it matter? > > > diff --git a/security/security.c b/security/security.c > > index 5ac96b16f8fa..efb1f874dc41 100644 > > --- a/security/security.c > > +++ b/security/security.c > > @@ -1319,6 +1319,7 @@ void security_inode_post_setxattr(struct dentry > *dentry, const char *name, > > if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) > > return; > > call_void_hook(inode_post_setxattr, dentry, name, value, size, > flags); > > + ima_inode_post_setxattr(dentry, name, value, size); > > evm_inode_post_setxattr(dentry, name, value, size); > > } > >
On Wed, 2021-04-07 at 09:17 -0700, Casey Schaufler wrote: > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > > index 565e33ff19d0..1f029e4c8d7f 100644 > > --- a/security/integrity/ima/ima_appraise.c > > +++ b/security/integrity/ima/ima_appraise.c > > @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, > > if (result == 1) { > > if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) > > return -EINVAL; > > - ima_reset_appraise_flags(d_backing_inode(dentry), > > - xvalue->type == EVM_IMA_XATTR_DIGSIG); > > result = 0; > > } > > return result; > > } > > > > +void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, > > + const void *xattr_value, size_t xattr_value_len) > > +{ > > + const struct evm_ima_xattr_data *xvalue = xattr_value; > > + int result; > > + > > + result = ima_protect_xattr(dentry, xattr_name, xattr_value, > > + xattr_value_len); > > + if (result == 1) > > + ima_reset_appraise_flags(d_backing_inode(dentry), > > + xvalue->type == EVM_IMA_XATTR_DIGSIG); > > +} > > + > > Now you're calling ima_protect_xattr() twice for each setxattr. > Is that safe? Is it performant? Does it matter? The first time the call to ima_protect_xattr() prevents the security.ima from being inappropriately modified. The second time it resets the cached status flags. From a performance perspective, unnecessarily re-calcuating the file hash is worse than rechecking the security xattr string. Mimi
diff --git a/fs/xattr.c b/fs/xattr.c index b3444e06cded..81847f132d26 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -16,6 +16,7 @@ #include <linux/namei.h> #include <linux/security.h> #include <linux/evm.h> +#include <linux/ima.h> #include <linux/syscalls.h> #include <linux/export.h> #include <linux/fsnotify.h> @@ -502,6 +503,7 @@ __vfs_removexattr_locked(struct user_namespace *mnt_userns, if (!error) { fsnotify_xattr(dentry); + ima_inode_post_removexattr(dentry, name); evm_inode_post_removexattr(dentry, name); } diff --git a/include/linux/ima.h b/include/linux/ima.h index 61d5723ec303..5e059da43857 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -171,7 +171,13 @@ extern void ima_inode_post_setattr(struct user_namespace *mnt_userns, struct dentry *dentry); extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len); +extern void ima_inode_post_setxattr(struct dentry *dentry, + const char *xattr_name, + const void *xattr_value, + size_t xattr_value_len); extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name); +extern void ima_inode_post_removexattr(struct dentry *dentry, + const char *xattr_name); #else static inline bool is_ima_appraise_enabled(void) { @@ -192,11 +198,23 @@ static inline int ima_inode_setxattr(struct dentry *dentry, return 0; } +static inline void ima_inode_post_setxattr(struct dentry *dentry, + const char *xattr_name, + const void *xattr_value, + size_t xattr_value_len) +{ +} + static inline int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) { return 0; } + +static inline void ima_inode_post_removexattr(struct dentry *dentry, + const char *xattr_name) +{ +} #endif /* CONFIG_IMA_APPRAISE */ #if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 565e33ff19d0..1f029e4c8d7f 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, if (result == 1) { if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) return -EINVAL; - ima_reset_appraise_flags(d_backing_inode(dentry), - xvalue->type == EVM_IMA_XATTR_DIGSIG); result = 0; } return result; } +void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + const struct evm_ima_xattr_data *xvalue = xattr_value; + int result; + + result = ima_protect_xattr(dentry, xattr_name, xattr_value, + xattr_value_len); + if (result == 1) + ima_reset_appraise_flags(d_backing_inode(dentry), + xvalue->type == EVM_IMA_XATTR_DIGSIG); +} + int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) { int result; result = ima_protect_xattr(dentry, xattr_name, NULL, 0); if (result == 1) { - ima_reset_appraise_flags(d_backing_inode(dentry), 0); result = 0; } return result; } + +void ima_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) +{ + int result; + + result = ima_protect_xattr(dentry, xattr_name, NULL, 0); + if (result == 1) + ima_reset_appraise_flags(d_backing_inode(dentry), 0); +} diff --git a/security/security.c b/security/security.c index 5ac96b16f8fa..efb1f874dc41 100644 --- a/security/security.c +++ b/security/security.c @@ -1319,6 +1319,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name, if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) return; call_void_hook(inode_post_setxattr, dentry, name, value, size, flags); + ima_inode_post_setxattr(dentry, name, value, size); evm_inode_post_setxattr(dentry, name, value, size); }
ima_inode_setxattr() and ima_inode_removexattr() hooks are called before an operation is performed. Thus, ima_reset_appraise_flags() should not be called there, as flags might be unnecessarily reset if the operation is denied. This patch introduces the post hooks ima_inode_post_setxattr() and ima_inode_post_removexattr(), and adds the call to ima_reset_appraise_flags() in the new functions. Cc: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- fs/xattr.c | 2 ++ include/linux/ima.h | 18 ++++++++++++++++++ security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++++++++--- security/security.c | 1 + 4 files changed, 43 insertions(+), 3 deletions(-)