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Message-ID: <a0f4bdcb-dc21-4255-abbe-9f557046e7f7@schaufler-ca.com>
Date: Mon, 26 Aug 2024 11:45:22 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Georgia Garcia <georgia.garcia@...onical.com>, paul@...l-moore.com,
linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
mic@...ikod.net, Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH 03/13] LSM: Add lsmblob_to_secctx hook
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@...aufler-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.
>
>> + 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;
>> +}
>> +
>> 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),
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