Re: [PATCH 03/13] LSM: Add lsmblob_to_secctx hook

[Georgia Garcia <georgia.garcia@canonical.com>]

On Mon, 2024-08-26 at 11:45 -0700, Casey Schaufler wrote:
> On 8/26/2024 10:43 AM, Georgia Garcia wrote:
> > Hi Casey
> > 
> > On Sun, 2024-08-25 at 12:00 -0700, Casey Schaufler wrote:
> > > Add a new hook security_lsmblob_to_secctx() and its LSM specific
> > > implementations. The LSM specific code will use the lsmblob element
> > > allocated for that module. This allows for the possibility that more
> > > than one module may be called upon to translate a secid to a string,
> > > as can occur in the audit code.
> > > 
> > > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> > > ---
> > >  include/linux/lsm_hook_defs.h     |  2 ++
> > >  include/linux/security.h          | 11 +++++++++-
> > >  security/apparmor/include/secid.h |  2 ++
> > >  security/apparmor/lsm.c           |  1 +
> > >  security/apparmor/secid.c         | 36 +++++++++++++++++++++++++++++++
> > >  security/security.c               | 30 ++++++++++++++++++++++++++
> > >  security/selinux/hooks.c          | 16 ++++++++++++--
> > >  security/smack/smack_lsm.c        | 31 +++++++++++++++++++++-----
> > >  8 files changed, 121 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> > > index 1d3bdf71109e..3e5f6baa7b9f 100644
> > > --- a/include/linux/lsm_hook_defs.h
> > > +++ b/include/linux/lsm_hook_defs.h
> > > @@ -291,6 +291,8 @@ LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
> > >  LSM_HOOK(int, 0, ismaclabel, const char *name)
> > >  LSM_HOOK(int, -EOPNOTSUPP, secid_to_secctx, u32 secid, char **secdata,
> > >  	 u32 *seclen)
> > > +LSM_HOOK(int, -EOPNOTSUPP, lsmblob_to_secctx, struct lsmblob *blob,
> > > +	 char **secdata, u32 *seclen)
> > >  LSM_HOOK(int, 0, secctx_to_secid, const char *secdata, u32 seclen, u32 *secid)
> > >  LSM_HOOK(void, LSM_RET_VOID, release_secctx, char *secdata, u32 seclen)
> > >  LSM_HOOK(void, LSM_RET_VOID, inode_invalidate_secctx, struct inode *inode)
> > > diff --git a/include/linux/security.h b/include/linux/security.h
> > > index c0ed2119a622..457fafc32fb0 100644
> > > --- a/include/linux/security.h
> > > +++ b/include/linux/security.h
> > > @@ -520,6 +520,8 @@ int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
> > >  int security_netlink_send(struct sock *sk, struct sk_buff *skb);
> > >  int security_ismaclabel(const char *name);
> > >  int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
> > > +int security_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +			       u32 *seclen);
> > >  int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
> > >  void security_release_secctx(char *secdata, u32 seclen);
> > >  void security_inode_invalidate_secctx(struct inode *inode);
> > > @@ -1461,7 +1463,14 @@ static inline int security_ismaclabel(const char *name)
> > >  	return 0;
> > >  }
> > >  
> > > -static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> > > +static inline int security_secid_to_secctx(u32 secid, char **secdata,
> > > +					   u32 *seclen)
> > > +{
> > > +	return -EOPNOTSUPP;
> > > +}
> > > +
> > > +static inline int security_lsmblob_to_secctx(struct lsmblob *blob,
> > > +					     char **secdata, u32 *seclen)
> > >  {
> > >  	return -EOPNOTSUPP;
> > >  }
> > > diff --git a/security/apparmor/include/secid.h b/security/apparmor/include/secid.h
> > > index a912a5d5d04f..816a425e2023 100644
> > > --- a/security/apparmor/include/secid.h
> > > +++ b/security/apparmor/include/secid.h
> > > @@ -26,6 +26,8 @@ extern int apparmor_display_secid_mode;
> > >  
> > >  struct aa_label *aa_secid_to_label(u32 secid);
> > >  int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
> > > +int apparmor_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +			       u32 *seclen);
> > >  int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
> > >  void apparmor_release_secctx(char *secdata, u32 seclen);
> > >  
> > > diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> > > index 808060f9effb..050d103f5ca5 100644
> > > --- a/security/apparmor/lsm.c
> > > +++ b/security/apparmor/lsm.c
> > > @@ -1532,6 +1532,7 @@ static struct security_hook_list apparmor_hooks[] __ro_after_init = {
> > >  #endif
> > >  
> > >  	LSM_HOOK_INIT(secid_to_secctx, apparmor_secid_to_secctx),
> > > +	LSM_HOOK_INIT(lsmblob_to_secctx, apparmor_lsmblob_to_secctx),
> > >  	LSM_HOOK_INIT(secctx_to_secid, apparmor_secctx_to_secid),
> > >  	LSM_HOOK_INIT(release_secctx, apparmor_release_secctx),
> > >  
> > > diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c
> > > index 83d3d1e6d9dc..3c389e5810cd 100644
> > > --- a/security/apparmor/secid.c
> > > +++ b/security/apparmor/secid.c
> > > @@ -90,6 +90,42 @@ int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> > >  	return 0;
> > >  }
> > >  
> > > +int apparmor_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +			       u32 *seclen)
> > > +{
> > > +	/* TODO: cache secctx and ref count so we don't have to recreate */
> > > +	struct aa_label *label;
> > > +	int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT;
> > > +	int len;
> > > +
> > > +	AA_BUG(!seclen);
> > > +
> > > +	/* scaffolding */
> > > +	if (!blob->apparmor.label && blob->scaffold.secid)
> > > +		label = aa_secid_to_label(blob->scaffold.secid);
> > > +	else
> > > +		label = blob->apparmor.label;
> > > +
> > It would improve maintainability if the rest of the function was
> > refactored into label_to_secctx(...), for example, so it could be
> > shared by apparmor_secid_to_secctx and apparmor_lsmblob_to_secctx.
> 
> All uses of scaffold.secid disappear by patch 13/13 of this set.
> This code, being temporary and short lived, would not benefit much
> from being maintainable.

I was referring to the rest of the function which does not include the
scaffolding and remains duplicated by the end of the patch set.
From this section:

> > 
> > > +	if (!label)
> > > +		return -EINVAL;
> > > +
> > > +	if (apparmor_display_secid_mode)
> > > +		flags |= FLAG_SHOW_MODE;
> > > +
> > > +	if (secdata)
> > > +		len = aa_label_asxprint(secdata, root_ns, label,
> > > +					flags, GFP_ATOMIC);
> > > +	else
> > > +		len = aa_label_snxprint(NULL, 0, root_ns, label, flags);
> > > +
> > > +	if (len < 0)
> > > +		return -ENOMEM;
> > > +
> > > +	*seclen = len;
> > > +
> > > +	return 0;
> > > +}

To here.

> > > +
> > >  int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
> > >  {
> > >  	struct aa_label *label;
> > > diff --git a/security/security.c b/security/security.c
> > > index 64a6d6bbd1f4..bb541a3be410 100644
> > > --- a/security/security.c
> > > +++ b/security/security.c
> > > @@ -4192,6 +4192,36 @@ int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> > >  }
> > >  EXPORT_SYMBOL(security_secid_to_secctx);
> > >  
> > > +/**
> > > + * security_lsmblob_to_secctx() - Convert a lsmblob to a secctx
> > > + * @blob: lsm specific information
> > > + * @secdata: secctx
> > > + * @seclen: secctx length
> > > + *
> > > + * Convert a @blob entry to security context.  If @secdata is NULL the
> > > + * length of the result will be returned in @seclen, but no @secdata
> > > + * will be returned.  This does mean that the length could change between
> > > + * calls to check the length and the next call which actually allocates
> > > + * and returns the @secdata.
> > > + *
> > > + * Return: Return 0 on success, error on failure.
> > > + */
> > > +int security_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +			       u32 *seclen)
> > > +{
> > > +	struct security_hook_list *hp;
> > > +	int rc;
> > > +
> > > +	hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) {
> > > +		rc = hp->hook.lsmblob_to_secctx(blob, secdata, seclen);
> > > +		if (rc != LSM_RET_DEFAULT(secid_to_secctx))
> > > +			return rc;
> > > +	}
> > > +
> > > +	return LSM_RET_DEFAULT(secid_to_secctx);
> > > +}
> > > +EXPORT_SYMBOL(security_lsmblob_to_secctx);
> > > +
> > >  /**
> > >   * security_secctx_to_secid() - Convert a secctx to a secid
> > >   * @secdata: secctx
> > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > > index 55c78c318ccd..102489e6d579 100644
> > > --- a/security/selinux/hooks.c
> > > +++ b/security/selinux/hooks.c
> > > @@ -6610,8 +6610,19 @@ static int selinux_ismaclabel(const char *name)
> > >  
> > >  static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> > >  {
> > > -	return security_sid_to_context(secid,
> > > -				       secdata, seclen);
> > > +	return security_sid_to_context(secid, secdata, seclen);
> > > +}
> > > +
> > > +static int selinux_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +				     u32 *seclen)
> > > +{
> > > +	u32 secid = blob->selinux.secid;
> > > +
> > > +	/* scaffolding */
> > > +	if (!secid)
> > > +		secid = blob->scaffold.secid;
> > > +
> > > +	return security_sid_to_context(secid, secdata, seclen);
> > >  }
> > >  
> > >  static int selinux_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
> > > @@ -7388,6 +7399,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
> > >  	LSM_HOOK_INIT(inode_alloc_security, selinux_inode_alloc_security),
> > >  	LSM_HOOK_INIT(sem_alloc_security, selinux_sem_alloc_security),
> > >  	LSM_HOOK_INIT(secid_to_secctx, selinux_secid_to_secctx),
> > > +	LSM_HOOK_INIT(lsmblob_to_secctx, selinux_lsmblob_to_secctx),
> > >  	LSM_HOOK_INIT(inode_getsecctx, selinux_inode_getsecctx),
> > >  	LSM_HOOK_INIT(sk_alloc_security, selinux_sk_alloc_security),
> > >  	LSM_HOOK_INIT(tun_dev_alloc_security, selinux_tun_dev_alloc_security),
> > > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> > > index 52d5ef986db8..5d74d8590862 100644
> > > --- a/security/smack/smack_lsm.c
> > > +++ b/security/smack/smack_lsm.c
> > > @@ -4787,7 +4787,7 @@ static int smack_audit_rule_known(struct audit_krule *krule)
> > >  static int smack_audit_rule_match(struct lsmblob *blob, u32 field, u32 op,
> > >  				  void *vrule)
> > >  {
> > > -	struct smack_known *skp;
> > > +	struct smack_known *skp = blob->smack.skp;
> > >  	char *rule = vrule;
> > >  
> > >  	if (unlikely(!rule)) {
> > > @@ -4799,10 +4799,8 @@ static int smack_audit_rule_match(struct lsmblob *blob, u32 field, u32 op,
> > >  		return 0;
> > >  
> > >  	/* scaffolding */
> > > -	if (!blob->smack.skp && blob->scaffold.secid)
> > > +	if (!skp && blob->scaffold.secid)
> > >  		skp = smack_from_secid(blob->scaffold.secid);
> > > -	else
> > > -		skp = blob->smack.skp;
> > >  
> > >  	/*
> > >  	 * No need to do string comparisons. If a match occurs,
> > > @@ -4833,7 +4831,6 @@ static int smack_ismaclabel(const char *name)
> > >  	return (strcmp(name, XATTR_SMACK_SUFFIX) == 0);
> > >  }
> > >  
> > > -
> > >  /**
> > >   * smack_secid_to_secctx - return the smack label for a secid
> > >   * @secid: incoming integer
> > > @@ -4852,6 +4849,29 @@ static int smack_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> > >  	return 0;
> > >  }
> > >  
> > > +/**
> > > + * smack_lsmblob_to_secctx - return the smack label
> > > + * @blob: includes incoming Smack data
> > > + * @secdata: destination
> > > + * @seclen: how long it is
> > > + *
> > > + * Exists for audit code.
> > > + */
> > > +static int smack_lsmblob_to_secctx(struct lsmblob *blob, char **secdata,
> > > +				   u32 *seclen)
> > > +{
> > > +	struct smack_known *skp = blob->smack.skp;
> > > +
> > > +	/* scaffolding */
> > > +	if (!skp && blob->scaffold.secid)
> > > +		skp = smack_from_secid(blob->scaffold.secid);
> > > +
> > > +	if (secdata)
> > > +		*secdata = skp->smk_known;
> > > +	*seclen = strlen(skp->smk_known);
> > > +	return 0;
> > > +}
> > > +
> > >  /**
> > >   * smack_secctx_to_secid - return the secid for a smack label
> > >   * @secdata: smack label
> > > @@ -5208,6 +5228,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
> > >  
> > >  	LSM_HOOK_INIT(ismaclabel, smack_ismaclabel),
> > >  	LSM_HOOK_INIT(secid_to_secctx, smack_secid_to_secctx),
> > > +	LSM_HOOK_INIT(lsmblob_to_secctx, smack_lsmblob_to_secctx),
> > >  	LSM_HOOK_INIT(secctx_to_secid, smack_secctx_to_secid),
> > >  	LSM_HOOK_INIT(inode_notifysecctx, smack_inode_notifysecctx),
> > >  	LSM_HOOK_INIT(inode_setsecctx, smack_inode_setsecctx),