Re: [PATCH 01/10] Security: Add hook to calculate context based on a negative dentry.

Casey Schaufler
2010-06-11T02:31:39Z

David P. Quigley wrote:
> There is a time where we need to calculate a context without the
> inode having been created yet. To do this we take the negative dentry and
> calculate a context based on the process and the parent directory contexts.
>
> Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
> Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
> ---
> include/linux/security.h | 22 ++++++++++++++++++++++
> security/capability.c | 6 ++++++
> security/security.c | 7 +++++++
> security/selinux/hooks.c | 32 ++++++++++++++++++++++++++++++++
> 4 files changed, 67 insertions(+), 0 deletions(-)
>

You should be able to figure out the Smack hook as well.
Hint: it's current->security.

> diff --git a/include/linux/security.h b/include/linux/security.h
> index 3158dd9..4d01784 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -322,6 +322,14 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
> * Parse a string of security data filling in the opts structure
> * @options string containing all mount options known by the LSM
> * @opts binary data structure usable by the LSM
> + * @dentry_init_security:
> + * Compute a context for a dentry as the inode is not yet available
> + * since NFSv4 has no label backed by an EA anyway.
> + * @dentry dentry to use in calculating the context.
> + * @mode mode used to determine resource type.
> + * @ctx pointer to place the pointer to the resulting context in.
> + * @ctxlen point to place the length of the resulting context.
> + *
> *
> * Security hooks for inode operations.
> *
> @@ -1501,6 +1509,9 @@ struct security_operations {
> void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
> struct super_block *newsb);
> int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
> + int (*dentry_init_security) (struct dentry *dentry, int mode,
> + void **ctx, u32 *ctxlen);
> +
>
> #ifdef CONFIG_SECURITY_PATH
> int (*path_unlink) (struct path *dir, struct dentry *dentry);
> @@ -1795,6 +1806,8 @@ int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *o
> void security_sb_clone_mnt_opts(const struct super_block *oldsb,
> struct super_block *newsb);
> int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
> +int security_dentry_init_security (struct dentry *dentry, int mode,
> + void **ctx, u32 *ctxlen);
>
> int security_inode_alloc(struct inode *inode);
> void security_inode_free(struct inode *inode);
> @@ -2157,6 +2170,15 @@ static inline int security_inode_alloc(struct inode *inode)
> static inline void security_inode_free(struct inode *inode)
> { }
>
> +static inline int security_dentry_init_security (struct dentry *dentry,
> + int mode,
> + void **ctx,
> + u32 *ctxlen)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +
> static inline int security_inode_init_security(struct inode *inode,
> struct inode *dir,
> char **name,
> diff --git a/security/capability.c b/security/capability.c
> index 4875142..9ce1c2f 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -134,6 +134,11 @@ static int cap_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
> return 0;
> }
>
> +static int cap_dentry_init_security(struct dentry *dentry, int mode, void **ctx, u32 *ctxlen)
> +{
> + return 0;
> +}
> +
> static int cap_inode_alloc_security(struct inode *inode)
> {
> return 0;
> @@ -952,6 +957,7 @@ void security_fixup_ops(struct security_operations *ops)
> set_to_cap_if_null(ops, sb_set_mnt_opts);
> set_to_cap_if_null(ops, sb_clone_mnt_opts);
> set_to_cap_if_null(ops, sb_parse_opts_str);
> + set_to_cap_if_null(ops, dentry_init_security);
> set_to_cap_if_null(ops, inode_alloc_security);
> set_to_cap_if_null(ops, inode_free_security);
> set_to_cap_if_null(ops, inode_init_security);
> diff --git a/security/security.c b/security/security.c
> index 687c6fd..c1b6847 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -386,6 +386,13 @@ void security_inode_free(struct inode *inode)
> security_ops->inode_free_security(inode);
> }
>
> +int security_dentry_init_security (struct dentry *dentry, int mode,
> + void **ctx, u32 *ctxlen)
> +{
> + return security_ops->dentry_init_security (dentry, mode, ctx, ctxlen);
> +}
> +EXPORT_SYMBOL(security_dentry_init_security);
> +
> int security_inode_init_security(struct inode *inode, struct inode *dir,
> char **name, void **value, size_t *len)
> {
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 5feecb4..435c51f 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2577,6 +2577,37 @@ static void selinux_inode_free_security(struct inode *inode)
> inode_free_security(inode);
> }
>
> +static int selinux_dentry_init_security(struct dentry *dentry, int mode, void **ctx, u32 *ctxlen)
> +{
> + struct cred *cred = current_cred();
> + struct task_security_struct *tsec;
> + struct inode_security_struct *dsec;
> + struct superblock_security_struct *sbsec;
> + struct inode *dir = dentry->d_parent->d_inode;
> + u32 newsid;
> + int rc;
> +
> + tsec = cred->security;
> + dsec = dir->i_security;
> + sbsec = dir->i_sb->s_security;
> +
> + if (tsec->create_sid && sbsec->behavior != SECURITY_FS_USE_MNTPOINT) {
> + newsid = tsec->create_sid;
> + } else {
> + rc = security_transition_sid(tsec->sid, dsec->sid,
> + inode_mode_to_security_class(mode),
> + &newsid);
> + if (rc) {
> + printk(KERN_WARNING "%s: "
> + "security_transition_sid failed, rc=%d\n",
> + __FUNCTION__, -rc);
> + return rc;
> + }
> + }
> +
> + return security_sid_to_context(newsid, (char **)ctx, ctxlen);
> +}
> +
> static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
> char **name, void **value,
> size_t *len)
> @@ -5484,6 +5515,7 @@ static struct security_operations selinux_ops = {
> .sb_clone_mnt_opts = selinux_sb_clone_mnt_opts,
> .sb_parse_opts_str = selinux_parse_opts_str,
>
> + .dentry_init_security = selinux_dentry_init_security,
>
> .inode_alloc_security = selinux_inode_alloc_security,
> .inode_free_security = selinux_inode_free_security,
>