[v4,3/3] LSM: Add context interface for proc attrs
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Message ID 5767eed4-78ec-cc4c-2ece-c1fec4d752af@schaufler-ca.com
State New
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Commit Message

Casey Schaufler June 23, 2016, 9:11 p.m. UTC
Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs

The /proc/.../attr/current interface is used by all three
Linux security modules (SELinux, Smack and AppArmor) to
report and modify the process security attribute. This is
all fine when there is exactly one of these modules active
and the userspace code knows which it module it is.
It would require a major change to the "current" interface
to provide information about more than one set of process
security attributes. Instead, a "context" attribute is
added, which identifies the security module that the
information applies to. The format is:

        lsmname='context-value'
 
When multiple concurrent modules are supported the
/proc/.../attr/context interface will include the data
for all of the active modules.

        lsmname1='context-value1'lsmname2='context-value2'

The module specific subdirectories under attr contain context
entries that report the information for that specific module
in the same format.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

---
 fs/proc/base.c             |   4 ++
 security/apparmor/lsm.c    |  34 +++++++++++++--
 security/security.c        | 100 +++++++++++++++++++++++++++++++++++++++++++++
 security/selinux/hooks.c   |  22 +++++++++-
 security/smack/smack_lsm.c |  21 ++++++----
 5 files changed, 167 insertions(+), 14 deletions(-)


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Comments

Kees Cook June 23, 2016, 9:49 p.m. UTC | #1
On Thu, Jun 23, 2016 at 2:11 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
> Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs
>
> The /proc/.../attr/current interface is used by all three
> Linux security modules (SELinux, Smack and AppArmor) to
> report and modify the process security attribute. This is
> all fine when there is exactly one of these modules active
> and the userspace code knows which it module it is.
> It would require a major change to the "current" interface
> to provide information about more than one set of process
> security attributes. Instead, a "context" attribute is
> added, which identifies the security module that the
> information applies to. The format is:
>
>         lsmname='context-value'
>
> When multiple concurrent modules are supported the
> /proc/.../attr/context interface will include the data
> for all of the active modules.
>
>         lsmname1='context-value1'lsmname2='context-value2'
>
> The module specific subdirectories under attr contain context
> entries that report the information for that specific module
> in the same format.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>
> ---
>  fs/proc/base.c             |   4 ++
>  security/apparmor/lsm.c    |  34 +++++++++++++--
>  security/security.c        | 100 +++++++++++++++++++++++++++++++++++++++++++++
>  security/selinux/hooks.c   |  22 +++++++++-
>  security/smack/smack_lsm.c |  21 ++++++----
>  5 files changed, 167 insertions(+), 14 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 182bc28..df94f26 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2532,6 +2532,7 @@ static const struct pid_entry selinux_attr_dir_stuff[] = {
>         ATTR("selinux", "fscreate",     S_IRUGO|S_IWUGO),
>         ATTR("selinux", "keycreate",    S_IRUGO|S_IWUGO),
>         ATTR("selinux", "sockcreate",   S_IRUGO|S_IWUGO),
> +       ATTR("selinux", "context",      S_IRUGO|S_IWUGO),
>  };
>  LSM_DIR_OPS(selinux);
>  #endif
> @@ -2539,6 +2540,7 @@ LSM_DIR_OPS(selinux);
>  #ifdef CONFIG_SECURITY_SMACK
>  static const struct pid_entry smack_attr_dir_stuff[] = {
>         ATTR("smack", "current",        S_IRUGO|S_IWUGO),
> +       ATTR("smack", "context",        S_IRUGO|S_IWUGO),
>  };
>  LSM_DIR_OPS(smack);
>  #endif
> @@ -2548,6 +2550,7 @@ static const struct pid_entry apparmor_attr_dir_stuff[] = {
>         ATTR("apparmor", "current",     S_IRUGO|S_IWUGO),
>         ATTR("apparmor", "prev",        S_IRUGO),
>         ATTR("apparmor", "exec",        S_IRUGO|S_IWUGO),
> +       ATTR("apparmor", "context",     S_IRUGO|S_IWUGO),
>  };
>  LSM_DIR_OPS(apparmor);
>  #endif
> @@ -2559,6 +2562,7 @@ static const struct pid_entry attr_dir_stuff[] = {
>         ATTR(NULL, "fscreate",          S_IRUGO|S_IWUGO),
>         ATTR(NULL, "keycreate",         S_IRUGO|S_IWUGO),
>         ATTR(NULL, "sockcreate",        S_IRUGO|S_IWUGO),
> +       ATTR(NULL, "context",           S_IRUGO|S_IWUGO),
>  #ifdef CONFIG_SECURITY_SELINUX
>         DIR("selinux",                  S_IRUGO|S_IXUGO,
>             proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops),
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index fb0fb03..3790a7d 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -479,6 +479,8 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
>
>         if (strcmp(name, "current") == 0)
>                 profile = aa_get_newest_profile(cxt->profile);
> +       else if (strcmp(name, "context") == 0)
> +               profile = aa_get_newest_profile(cxt->profile);
>         else if (strcmp(name, "prev") == 0  && cxt->previous)
>                 profile = aa_get_newest_profile(cxt->previous);
>         else if (strcmp(name, "exec") == 0 && cxt->onexec)
> @@ -486,8 +488,29 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
>         else
>                 error = -EINVAL;
>
> -       if (profile)
> -               error = aa_getprocattr(profile, value);
> +       if (profile) {
> +               if (strcmp(name, "context") == 0) {
> +                       char *vp;
> +                       char *np;
> +
> +                       error = aa_getprocattr(profile, &vp);
> +                       if (error > 0) {
> +                               error += 12;
> +                               *value = kzalloc(error, GFP_KERNEL);
> +                               if (*value == NULL)
> +                                       error = -ENOMEM;
> +                               else {
> +                                       sprintf(*value, "apparmor='%s'", vp);

This and the others seem to still not be using kasprintf()?

-Kees

> +                                       np = strchr(*value, '\n');
> +                                       if (np != NULL) {
> +                                               np[0] = '\'';
> +                                               np[1] = '\0';
> +                                       }
> +                               }
> +                       }
> +               } else
> +                       error = aa_getprocattr(profile, value);
> +       }
>
>         aa_put_profile(profile);
>         put_cred(cred);
> @@ -530,7 +553,7 @@ static int apparmor_setprocattr(struct task_struct *task, char *name,
>                 return -EINVAL;
>
>         arg_size = size - (args - (char *) value);
> -       if (strcmp(name, "current") == 0) {
> +       if (strcmp(name, "current") == 0 || strcmp(name, "context") == 0) {
>                 if (strcmp(command, "changehat") == 0) {
>                         error = aa_setprocattr_changehat(args, arg_size,
>                                                          !AA_DO_TEST);
> @@ -552,7 +575,10 @@ static int apparmor_setprocattr(struct task_struct *task, char *name,
>                 else
>                         goto fail;
>         } else
> -               /* only support the "current" and "exec" process attributes */
> +               /*
> +                * only support the "current", context and "exec"
> +                * process attributes
> +                */
>                 return -EINVAL;
>
>         if (!error)
> diff --git a/security/security.c b/security/security.c
> index 1e9cb55..fec70b4 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1186,8 +1186,47 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>                                 char **value)
>  {
>         struct security_hook_list *hp;
> +       char *vp;
> +       char *cp = NULL;
>         int rc = -EINVAL;
> +       int trc;
>
> +       /*
> +        * "context" requires work here in addition to what
> +        * the modules provide.
> +        */
> +       if (strcmp(name, "context") == 0) {
> +               *value = NULL;
> +               list_for_each_entry(hp,
> +                               &security_hook_heads.getprocattr, list) {
> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
> +                               continue;
> +                       trc = hp->hook.getprocattr(p, "context", &vp);
> +                       if (trc == -ENOENT)
> +                               continue;
> +                       if (trc <= 0) {
> +                               kfree(*value);
> +                               return trc;
> +                       }
> +                       rc = trc;
> +                       if (*value == NULL) {
> +                               *value = vp;
> +                       } else {
> +                               cp = kasprintf(GFP_KERNEL, "%s%s", *value, vp);
> +                               if (cp == NULL) {
> +                                       kfree(*value);
> +                                       kfree(vp);
> +                                       return -ENOMEM;
> +                               }
> +                               kfree(*value);
> +                               kfree(vp);
> +                               *value = cp;
> +                       }
> +               }
> +               if (rc > 0)
> +                       return strlen(*value);
> +               return rc;
> +       }
>
>         list_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
>                 if (lsm != NULL && strcmp(lsm, hp->lsm))
> @@ -1204,7 +1243,68 @@ int security_setprocattr(struct task_struct *p, const char *lsm, char *name,
>  {
>         struct security_hook_list *hp;
>         int rc = -EINVAL;
> +       char *local;
> +       char *cp;
> +       int slen;
> +       int failed = 0;
>
> +       /*
> +        * If lsm is NULL look at all the modules to find one
> +        * that processes name. If lsm is not NULL only look at
> +        * that module.
> +        *
> +        * "context" is handled directly here.
> +        */
> +       if (strcmp(name, "context") == 0) {
> +               /*
> +                * First verify that the input is acceptable.
> +                * lsm1='v1'lsm2='v2'lsm3='v3'
> +                *
> +                * A note on the use of strncmp() below.
> +                * The check is for the substring at the beginning of cp.
> +                * The kzalloc of size + 1 ensures a terminated string.
> +                */
> +               local = kzalloc(size + 1, GFP_KERNEL);
> +               memcpy(local, value, size);
> +               cp = local;
> +               list_for_each_entry(hp, &security_hook_heads.setprocattr,
> +                                       list) {
> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
> +                               continue;
> +                       slen = strlen(hp->lsm);
> +                       if (strncmp(cp, hp->lsm, slen))
> +                               goto free_out;
> +                       cp += slen;
> +                       if (cp[0] != '=' || cp[1] != '\'' || cp[2] == '\'')
> +                               goto free_out;
> +                       for (cp += 2; cp[0] != '\''; cp++)
> +                               if (cp[0] == '\0')
> +                                       goto free_out;
> +                       cp++;
> +               }
> +               cp = local;
> +               list_for_each_entry(hp, &security_hook_heads.setprocattr,
> +                                       list) {
> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
> +                               continue;
> +                       cp += strlen(hp->lsm) + 2;
> +                       for (slen = 0; cp[slen] != '\''; slen++)
> +                               ;
> +                       cp[slen] = '\0';
> +
> +                       rc = hp->hook.setprocattr(p, "context", cp, slen);
> +                       if (rc < 0)
> +                               failed = rc;
> +                       cp += slen + 1;
> +               }
> +               if (failed != 0)
> +                       rc = failed;
> +               else
> +                       rc = size;
> +free_out:
> +               kfree(local);
> +               return rc;
> +       }
>         list_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
>                 if (lsm != NULL && strcmp(lsm, hp->lsm))
>                         continue;
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index ed3a757..3a21c2b 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5711,6 +5711,8 @@ static int selinux_getprocattr(struct task_struct *p,
>
>         if (!strcmp(name, "current"))
>                 sid = __tsec->sid;
> +       else if (!strcmp(name, "context"))
> +               sid = __tsec->sid;
>         else if (!strcmp(name, "prev"))
>                 sid = __tsec->osid;
>         else if (!strcmp(name, "exec"))
> @@ -5728,7 +5730,21 @@ static int selinux_getprocattr(struct task_struct *p,
>         if (!sid)
>                 return 0;
>
> -       error = security_sid_to_context(sid, value, &len);
> +       if (strcmp(name, "context")) {
> +               error = security_sid_to_context(sid, value, &len);
> +       } else {
> +               char *vp;
> +
> +               error = security_sid_to_context(sid, &vp, &len);
> +               if (!error) {
> +                       *value = kzalloc(len + 10, GFP_KERNEL);
> +                       if (*value == NULL)
> +                               error = -ENOMEM;
> +                       else
> +                               sprintf(*value, "selinux='%s'", vp);
> +               }
> +       }
> +
>         if (error)
>                 return error;
>         return len;
> @@ -5768,6 +5784,8 @@ static int selinux_setprocattr(struct task_struct *p,
>                 error = current_has_perm(p, PROCESS__SETSOCKCREATE);
>         else if (!strcmp(name, "current"))
>                 error = current_has_perm(p, PROCESS__SETCURRENT);
> +       else if (!strcmp(name, "context"))
> +               error = current_has_perm(p, PROCESS__SETCURRENT);
>         else
>                 error = -EINVAL;
>         if (error)
> @@ -5827,7 +5845,7 @@ static int selinux_setprocattr(struct task_struct *p,
>                 tsec->keycreate_sid = sid;
>         } else if (!strcmp(name, "sockcreate")) {
>                 tsec->sockcreate_sid = sid;
> -       } else if (!strcmp(name, "current")) {
> +       } else if (!strcmp(name, "current") || !strcmp(name, "context")) {
>                 error = -EINVAL;
>                 if (sid == 0)
>                         goto abort_change;
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 3577009..d2d8624 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -3576,16 +3576,21 @@ static int smack_getprocattr(struct task_struct *p, char *name, char **value)
>         char *cp;
>         int slen;
>
> -       if (strcmp(name, "current") != 0)
> +       if (strcmp(name, "current") == 0) {
> +               cp = kstrdup(skp->smk_known, GFP_KERNEL);
> +               if (cp == NULL)
> +                       return -ENOMEM;
> +       } else if (strcmp(name, "context") == 0) {
> +               slen = strlen(skp->smk_known) + 9;
> +               cp = kzalloc(slen, GFP_KERNEL);
> +               if (cp == NULL)
> +                       return -ENOMEM;
> +               sprintf(cp, "smack='%s'", skp->smk_known);
> +       } else
>                 return -EINVAL;
>
> -       cp = kstrdup(skp->smk_known, GFP_KERNEL);
> -       if (cp == NULL)
> -               return -ENOMEM;
> -
> -       slen = strlen(cp);
>         *value = cp;
> -       return slen;
> +       return strlen(cp);
>  }
>
>  /**
> @@ -3622,7 +3627,7 @@ static int smack_setprocattr(struct task_struct *p, char *name,
>         if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
>                 return -EINVAL;
>
> -       if (strcmp(name, "current") != 0)
> +       if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0)
>                 return -EINVAL;
>
>         skp = smk_import_entry(value, size);
>
Casey Schaufler June 23, 2016, 10:10 p.m. UTC | #2
On 6/23/2016 2:49 PM, Kees Cook wrote:
> On Thu, Jun 23, 2016 at 2:11 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs
>>
>> The /proc/.../attr/current interface is used by all three
>> Linux security modules (SELinux, Smack and AppArmor) to
>> report and modify the process security attribute. This is
>> all fine when there is exactly one of these modules active
>> and the userspace code knows which it module it is.
>> It would require a major change to the "current" interface
>> to provide information about more than one set of process
>> security attributes. Instead, a "context" attribute is
>> added, which identifies the security module that the
>> information applies to. The format is:
>>
>>         lsmname='context-value'
>>
>> When multiple concurrent modules are supported the
>> /proc/.../attr/context interface will include the data
>> for all of the active modules.
>>
>>         lsmname1='context-value1'lsmname2='context-value2'
>>
>> The module specific subdirectories under attr contain context
>> entries that report the information for that specific module
>> in the same format.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>
>> ---
>>  fs/proc/base.c             |   4 ++
>>  security/apparmor/lsm.c    |  34 +++++++++++++--
>>  security/security.c        | 100 +++++++++++++++++++++++++++++++++++++++++++++
>>  security/selinux/hooks.c   |  22 +++++++++-
>>  security/smack/smack_lsm.c |  21 ++++++----
>>  5 files changed, 167 insertions(+), 14 deletions(-)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 182bc28..df94f26 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -2532,6 +2532,7 @@ static const struct pid_entry selinux_attr_dir_stuff[] = {
>>         ATTR("selinux", "fscreate",     S_IRUGO|S_IWUGO),
>>         ATTR("selinux", "keycreate",    S_IRUGO|S_IWUGO),
>>         ATTR("selinux", "sockcreate",   S_IRUGO|S_IWUGO),
>> +       ATTR("selinux", "context",      S_IRUGO|S_IWUGO),
>>  };
>>  LSM_DIR_OPS(selinux);
>>  #endif
>> @@ -2539,6 +2540,7 @@ LSM_DIR_OPS(selinux);
>>  #ifdef CONFIG_SECURITY_SMACK
>>  static const struct pid_entry smack_attr_dir_stuff[] = {
>>         ATTR("smack", "current",        S_IRUGO|S_IWUGO),
>> +       ATTR("smack", "context",        S_IRUGO|S_IWUGO),
>>  };
>>  LSM_DIR_OPS(smack);
>>  #endif
>> @@ -2548,6 +2550,7 @@ static const struct pid_entry apparmor_attr_dir_stuff[] = {
>>         ATTR("apparmor", "current",     S_IRUGO|S_IWUGO),
>>         ATTR("apparmor", "prev",        S_IRUGO),
>>         ATTR("apparmor", "exec",        S_IRUGO|S_IWUGO),
>> +       ATTR("apparmor", "context",     S_IRUGO|S_IWUGO),
>>  };
>>  LSM_DIR_OPS(apparmor);
>>  #endif
>> @@ -2559,6 +2562,7 @@ static const struct pid_entry attr_dir_stuff[] = {
>>         ATTR(NULL, "fscreate",          S_IRUGO|S_IWUGO),
>>         ATTR(NULL, "keycreate",         S_IRUGO|S_IWUGO),
>>         ATTR(NULL, "sockcreate",        S_IRUGO|S_IWUGO),
>> +       ATTR(NULL, "context",           S_IRUGO|S_IWUGO),
>>  #ifdef CONFIG_SECURITY_SELINUX
>>         DIR("selinux",                  S_IRUGO|S_IXUGO,
>>             proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops),
>> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
>> index fb0fb03..3790a7d 100644
>> --- a/security/apparmor/lsm.c
>> +++ b/security/apparmor/lsm.c
>> @@ -479,6 +479,8 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
>>
>>         if (strcmp(name, "current") == 0)
>>                 profile = aa_get_newest_profile(cxt->profile);
>> +       else if (strcmp(name, "context") == 0)
>> +               profile = aa_get_newest_profile(cxt->profile);
>>         else if (strcmp(name, "prev") == 0  && cxt->previous)
>>                 profile = aa_get_newest_profile(cxt->previous);
>>         else if (strcmp(name, "exec") == 0 && cxt->onexec)
>> @@ -486,8 +488,29 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
>>         else
>>                 error = -EINVAL;
>>
>> -       if (profile)
>> -               error = aa_getprocattr(profile, value);
>> +       if (profile) {
>> +               if (strcmp(name, "context") == 0) {
>> +                       char *vp;
>> +                       char *np;
>> +
>> +                       error = aa_getprocattr(profile, &vp);
>> +                       if (error > 0) {
>> +                               error += 12;
>> +                               *value = kzalloc(error, GFP_KERNEL);
>> +                               if (*value == NULL)
>> +                                       error = -ENOMEM;
>> +                               else {
>> +                                       sprintf(*value, "apparmor='%s'", vp);
> This and the others seem to still not be using kasprintf()?

I got the one in security.c but missed the ones in the modules.
Sigh. It'll be in v4. Thank you.

>
> -Kees
>
>> +                                       np = strchr(*value, '\n');
>> +                                       if (np != NULL) {
>> +                                               np[0] = '\'';
>> +                                               np[1] = '\0';
>> +                                       }
>> +                               }
>> +                       }
>> +               } else
>> +                       error = aa_getprocattr(profile, value);
>> +       }
>>
>>         aa_put_profile(profile);
>>         put_cred(cred);
>> @@ -530,7 +553,7 @@ static int apparmor_setprocattr(struct task_struct *task, char *name,
>>                 return -EINVAL;
>>
>>         arg_size = size - (args - (char *) value);
>> -       if (strcmp(name, "current") == 0) {
>> +       if (strcmp(name, "current") == 0 || strcmp(name, "context") == 0) {
>>                 if (strcmp(command, "changehat") == 0) {
>>                         error = aa_setprocattr_changehat(args, arg_size,
>>                                                          !AA_DO_TEST);
>> @@ -552,7 +575,10 @@ static int apparmor_setprocattr(struct task_struct *task, char *name,
>>                 else
>>                         goto fail;
>>         } else
>> -               /* only support the "current" and "exec" process attributes */
>> +               /*
>> +                * only support the "current", context and "exec"
>> +                * process attributes
>> +                */
>>                 return -EINVAL;
>>
>>         if (!error)
>> diff --git a/security/security.c b/security/security.c
>> index 1e9cb55..fec70b4 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -1186,8 +1186,47 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>>                                 char **value)
>>  {
>>         struct security_hook_list *hp;
>> +       char *vp;
>> +       char *cp = NULL;
>>         int rc = -EINVAL;
>> +       int trc;
>>
>> +       /*
>> +        * "context" requires work here in addition to what
>> +        * the modules provide.
>> +        */
>> +       if (strcmp(name, "context") == 0) {
>> +               *value = NULL;
>> +               list_for_each_entry(hp,
>> +                               &security_hook_heads.getprocattr, list) {
>> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
>> +                               continue;
>> +                       trc = hp->hook.getprocattr(p, "context", &vp);
>> +                       if (trc == -ENOENT)
>> +                               continue;
>> +                       if (trc <= 0) {
>> +                               kfree(*value);
>> +                               return trc;
>> +                       }
>> +                       rc = trc;
>> +                       if (*value == NULL) {
>> +                               *value = vp;
>> +                       } else {
>> +                               cp = kasprintf(GFP_KERNEL, "%s%s", *value, vp);
>> +                               if (cp == NULL) {
>> +                                       kfree(*value);
>> +                                       kfree(vp);
>> +                                       return -ENOMEM;
>> +                               }
>> +                               kfree(*value);
>> +                               kfree(vp);
>> +                               *value = cp;
>> +                       }
>> +               }
>> +               if (rc > 0)
>> +                       return strlen(*value);
>> +               return rc;
>> +       }
>>
>>         list_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
>>                 if (lsm != NULL && strcmp(lsm, hp->lsm))
>> @@ -1204,7 +1243,68 @@ int security_setprocattr(struct task_struct *p, const char *lsm, char *name,
>>  {
>>         struct security_hook_list *hp;
>>         int rc = -EINVAL;
>> +       char *local;
>> +       char *cp;
>> +       int slen;
>> +       int failed = 0;
>>
>> +       /*
>> +        * If lsm is NULL look at all the modules to find one
>> +        * that processes name. If lsm is not NULL only look at
>> +        * that module.
>> +        *
>> +        * "context" is handled directly here.
>> +        */
>> +       if (strcmp(name, "context") == 0) {
>> +               /*
>> +                * First verify that the input is acceptable.
>> +                * lsm1='v1'lsm2='v2'lsm3='v3'
>> +                *
>> +                * A note on the use of strncmp() below.
>> +                * The check is for the substring at the beginning of cp.
>> +                * The kzalloc of size + 1 ensures a terminated string.
>> +                */
>> +               local = kzalloc(size + 1, GFP_KERNEL);
>> +               memcpy(local, value, size);
>> +               cp = local;
>> +               list_for_each_entry(hp, &security_hook_heads.setprocattr,
>> +                                       list) {
>> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
>> +                               continue;
>> +                       slen = strlen(hp->lsm);
>> +                       if (strncmp(cp, hp->lsm, slen))
>> +                               goto free_out;
>> +                       cp += slen;
>> +                       if (cp[0] != '=' || cp[1] != '\'' || cp[2] == '\'')
>> +                               goto free_out;
>> +                       for (cp += 2; cp[0] != '\''; cp++)
>> +                               if (cp[0] == '\0')
>> +                                       goto free_out;
>> +                       cp++;
>> +               }
>> +               cp = local;
>> +               list_for_each_entry(hp, &security_hook_heads.setprocattr,
>> +                                       list) {
>> +                       if (lsm != NULL && strcmp(lsm, hp->lsm))
>> +                               continue;
>> +                       cp += strlen(hp->lsm) + 2;
>> +                       for (slen = 0; cp[slen] != '\''; slen++)
>> +                               ;
>> +                       cp[slen] = '\0';
>> +
>> +                       rc = hp->hook.setprocattr(p, "context", cp, slen);
>> +                       if (rc < 0)
>> +                               failed = rc;
>> +                       cp += slen + 1;
>> +               }
>> +               if (failed != 0)
>> +                       rc = failed;
>> +               else
>> +                       rc = size;
>> +free_out:
>> +               kfree(local);
>> +               return rc;
>> +       }
>>         list_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
>>                 if (lsm != NULL && strcmp(lsm, hp->lsm))
>>                         continue;
>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
>> index ed3a757..3a21c2b 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -5711,6 +5711,8 @@ static int selinux_getprocattr(struct task_struct *p,
>>
>>         if (!strcmp(name, "current"))
>>                 sid = __tsec->sid;
>> +       else if (!strcmp(name, "context"))
>> +               sid = __tsec->sid;
>>         else if (!strcmp(name, "prev"))
>>                 sid = __tsec->osid;
>>         else if (!strcmp(name, "exec"))
>> @@ -5728,7 +5730,21 @@ static int selinux_getprocattr(struct task_struct *p,
>>         if (!sid)
>>                 return 0;
>>
>> -       error = security_sid_to_context(sid, value, &len);
>> +       if (strcmp(name, "context")) {
>> +               error = security_sid_to_context(sid, value, &len);
>> +       } else {
>> +               char *vp;
>> +
>> +               error = security_sid_to_context(sid, &vp, &len);
>> +               if (!error) {
>> +                       *value = kzalloc(len + 10, GFP_KERNEL);
>> +                       if (*value == NULL)
>> +                               error = -ENOMEM;
>> +                       else
>> +                               sprintf(*value, "selinux='%s'", vp);
>> +               }
>> +       }
>> +
>>         if (error)
>>                 return error;
>>         return len;
>> @@ -5768,6 +5784,8 @@ static int selinux_setprocattr(struct task_struct *p,
>>                 error = current_has_perm(p, PROCESS__SETSOCKCREATE);
>>         else if (!strcmp(name, "current"))
>>                 error = current_has_perm(p, PROCESS__SETCURRENT);
>> +       else if (!strcmp(name, "context"))
>> +               error = current_has_perm(p, PROCESS__SETCURRENT);
>>         else
>>                 error = -EINVAL;
>>         if (error)
>> @@ -5827,7 +5845,7 @@ static int selinux_setprocattr(struct task_struct *p,
>>                 tsec->keycreate_sid = sid;
>>         } else if (!strcmp(name, "sockcreate")) {
>>                 tsec->sockcreate_sid = sid;
>> -       } else if (!strcmp(name, "current")) {
>> +       } else if (!strcmp(name, "current") || !strcmp(name, "context")) {
>>                 error = -EINVAL;
>>                 if (sid == 0)
>>                         goto abort_change;
>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
>> index 3577009..d2d8624 100644
>> --- a/security/smack/smack_lsm.c
>> +++ b/security/smack/smack_lsm.c
>> @@ -3576,16 +3576,21 @@ static int smack_getprocattr(struct task_struct *p, char *name, char **value)
>>         char *cp;
>>         int slen;
>>
>> -       if (strcmp(name, "current") != 0)
>> +       if (strcmp(name, "current") == 0) {
>> +               cp = kstrdup(skp->smk_known, GFP_KERNEL);
>> +               if (cp == NULL)
>> +                       return -ENOMEM;
>> +       } else if (strcmp(name, "context") == 0) {
>> +               slen = strlen(skp->smk_known) + 9;
>> +               cp = kzalloc(slen, GFP_KERNEL);
>> +               if (cp == NULL)
>> +                       return -ENOMEM;
>> +               sprintf(cp, "smack='%s'", skp->smk_known);
>> +       } else
>>                 return -EINVAL;
>>
>> -       cp = kstrdup(skp->smk_known, GFP_KERNEL);
>> -       if (cp == NULL)
>> -               return -ENOMEM;
>> -
>> -       slen = strlen(cp);
>>         *value = cp;
>> -       return slen;
>> +       return strlen(cp);
>>  }
>>
>>  /**
>> @@ -3622,7 +3627,7 @@ static int smack_setprocattr(struct task_struct *p, char *name,
>>         if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
>>                 return -EINVAL;
>>
>> -       if (strcmp(name, "current") != 0)
>> +       if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0)
>>                 return -EINVAL;
>>
>>         skp = smk_import_entry(value, size);
>>
>
>

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Paul Moore June 24, 2016, 7:15 p.m. UTC | #3
On Thu, Jun 23, 2016 at 5:11 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
> Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs
>
> The /proc/.../attr/current interface is used by all three
> Linux security modules (SELinux, Smack and AppArmor) to
> report and modify the process security attribute. This is
> all fine when there is exactly one of these modules active
> and the userspace code knows which it module it is.
> It would require a major change to the "current" interface
> to provide information about more than one set of process
> security attributes. Instead, a "context" attribute is
> added, which identifies the security module that the
> information applies to. The format is:
>
>         lsmname='context-value'
>
> When multiple concurrent modules are supported the
> /proc/.../attr/context interface will include the data
> for all of the active modules.
>
>         lsmname1='context-value1'lsmname2='context-value2'
>
> The module specific subdirectories under attr contain context
> entries that report the information for that specific module
> in the same format.

I think a delimiter between the different LSMs would be a good idea.
A comma seems like a safe choice at the moment.
Casey Schaufler June 24, 2016, 7:56 p.m. UTC | #4
On 6/24/2016 12:15 PM, Paul Moore wrote:
> On Thu, Jun 23, 2016 at 5:11 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Subject: [PATCH v4 3/3] LSM: Add context interface for proc attrs
>>
>> The /proc/.../attr/current interface is used by all three
>> Linux security modules (SELinux, Smack and AppArmor) to
>> report and modify the process security attribute. This is
>> all fine when there is exactly one of these modules active
>> and the userspace code knows which it module it is.
>> It would require a major change to the "current" interface
>> to provide information about more than one set of process
>> security attributes. Instead, a "context" attribute is
>> added, which identifies the security module that the
>> information applies to. The format is:
>>
>>         lsmname='context-value'
>>
>> When multiple concurrent modules are supported the
>> /proc/.../attr/context interface will include the data
>> for all of the active modules.
>>
>>         lsmname1='context-value1'lsmname2='context-value2'
>>
>> The module specific subdirectories under attr contain context
>> entries that report the information for that specific module
>> in the same format.
> I think a delimiter between the different LSMs would be a good idea.
> A comma seems like a safe choice at the moment.

It's unnecessary and makes for more complicated code in
both directions, but everyone seems wedded to a delimiter.
I'll propose a v5 with a delimiter.

>

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Patch
diff mbox

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 182bc28..df94f26 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2532,6 +2532,7 @@  static const struct pid_entry selinux_attr_dir_stuff[] = {
 	ATTR("selinux", "fscreate",	S_IRUGO|S_IWUGO),
 	ATTR("selinux", "keycreate",	S_IRUGO|S_IWUGO),
 	ATTR("selinux", "sockcreate",	S_IRUGO|S_IWUGO),
+	ATTR("selinux", "context",	S_IRUGO|S_IWUGO),
 };
 LSM_DIR_OPS(selinux);
 #endif
@@ -2539,6 +2540,7 @@  LSM_DIR_OPS(selinux);
 #ifdef CONFIG_SECURITY_SMACK
 static const struct pid_entry smack_attr_dir_stuff[] = {
 	ATTR("smack", "current",	S_IRUGO|S_IWUGO),
+	ATTR("smack", "context",	S_IRUGO|S_IWUGO),
 };
 LSM_DIR_OPS(smack);
 #endif
@@ -2548,6 +2550,7 @@  static const struct pid_entry apparmor_attr_dir_stuff[] = {
 	ATTR("apparmor", "current",	S_IRUGO|S_IWUGO),
 	ATTR("apparmor", "prev",	S_IRUGO),
 	ATTR("apparmor", "exec",	S_IRUGO|S_IWUGO),
+	ATTR("apparmor", "context",	S_IRUGO|S_IWUGO),
 };
 LSM_DIR_OPS(apparmor);
 #endif
@@ -2559,6 +2562,7 @@  static const struct pid_entry attr_dir_stuff[] = {
 	ATTR(NULL, "fscreate",		S_IRUGO|S_IWUGO),
 	ATTR(NULL, "keycreate",		S_IRUGO|S_IWUGO),
 	ATTR(NULL, "sockcreate",	S_IRUGO|S_IWUGO),
+	ATTR(NULL, "context",		S_IRUGO|S_IWUGO),
 #ifdef CONFIG_SECURITY_SELINUX
 	DIR("selinux",			S_IRUGO|S_IXUGO,
 	    proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops),
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index fb0fb03..3790a7d 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -479,6 +479,8 @@  static int apparmor_getprocattr(struct task_struct *task, char *name,
 
 	if (strcmp(name, "current") == 0)
 		profile = aa_get_newest_profile(cxt->profile);
+	else if (strcmp(name, "context") == 0)
+		profile = aa_get_newest_profile(cxt->profile);
 	else if (strcmp(name, "prev") == 0  && cxt->previous)
 		profile = aa_get_newest_profile(cxt->previous);
 	else if (strcmp(name, "exec") == 0 && cxt->onexec)
@@ -486,8 +488,29 @@  static int apparmor_getprocattr(struct task_struct *task, char *name,
 	else
 		error = -EINVAL;
 
-	if (profile)
-		error = aa_getprocattr(profile, value);
+	if (profile) {
+		if (strcmp(name, "context") == 0) {
+			char *vp;
+			char *np;
+
+			error = aa_getprocattr(profile, &vp);
+			if (error > 0) {
+				error += 12;
+				*value = kzalloc(error, GFP_KERNEL);
+				if (*value == NULL)
+					error = -ENOMEM;
+				else {
+					sprintf(*value, "apparmor='%s'", vp);
+					np = strchr(*value, '\n');
+					if (np != NULL) {
+						np[0] = '\'';
+						np[1] = '\0';
+					}
+				}
+			}
+		} else
+			error = aa_getprocattr(profile, value);
+	}
 
 	aa_put_profile(profile);
 	put_cred(cred);
@@ -530,7 +553,7 @@  static int apparmor_setprocattr(struct task_struct *task, char *name,
 		return -EINVAL;
 
 	arg_size = size - (args - (char *) value);
-	if (strcmp(name, "current") == 0) {
+	if (strcmp(name, "current") == 0 || strcmp(name, "context") == 0) {
 		if (strcmp(command, "changehat") == 0) {
 			error = aa_setprocattr_changehat(args, arg_size,
 							 !AA_DO_TEST);
@@ -552,7 +575,10 @@  static int apparmor_setprocattr(struct task_struct *task, char *name,
 		else
 			goto fail;
 	} else
-		/* only support the "current" and "exec" process attributes */
+		/*
+		 * only support the "current", context and "exec"
+		 * process attributes
+		 */
 		return -EINVAL;
 
 	if (!error)
diff --git a/security/security.c b/security/security.c
index 1e9cb55..fec70b4 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1186,8 +1186,47 @@  int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
 				char **value)
 {
 	struct security_hook_list *hp;
+	char *vp;
+	char *cp = NULL;
 	int rc = -EINVAL;
+	int trc;
 
+	/*
+	 * "context" requires work here in addition to what
+	 * the modules provide.
+	 */
+	if (strcmp(name, "context") == 0) {
+		*value = NULL;
+		list_for_each_entry(hp,
+				&security_hook_heads.getprocattr, list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			trc = hp->hook.getprocattr(p, "context", &vp);
+			if (trc == -ENOENT)
+				continue;
+			if (trc <= 0) {
+				kfree(*value);
+				return trc;
+			}
+			rc = trc;
+			if (*value == NULL) {
+				*value = vp;
+			} else {
+				cp = kasprintf(GFP_KERNEL, "%s%s", *value, vp);
+				if (cp == NULL) {
+					kfree(*value);
+					kfree(vp);
+					return -ENOMEM;
+				}
+				kfree(*value);
+				kfree(vp);
+				*value = cp;
+			}
+		}
+		if (rc > 0)
+			return strlen(*value);
+		return rc;
+	}
 
 	list_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
 		if (lsm != NULL && strcmp(lsm, hp->lsm))
@@ -1204,7 +1243,68 @@  int security_setprocattr(struct task_struct *p, const char *lsm, char *name,
 {
 	struct security_hook_list *hp;
 	int rc = -EINVAL;
+	char *local;
+	char *cp;
+	int slen;
+	int failed = 0;
 
+	/*
+	 * If lsm is NULL look at all the modules to find one
+	 * that processes name. If lsm is not NULL only look at
+	 * that module.
+	 *
+	 * "context" is handled directly here.
+	 */
+	if (strcmp(name, "context") == 0) {
+		/*
+		 * First verify that the input is acceptable.
+		 * lsm1='v1'lsm2='v2'lsm3='v3'
+		 *
+		 * A note on the use of strncmp() below.
+		 * The check is for the substring at the beginning of cp.
+		 * The kzalloc of size + 1 ensures a terminated string.
+		 */
+		local = kzalloc(size + 1, GFP_KERNEL);
+		memcpy(local, value, size);
+		cp = local;
+		list_for_each_entry(hp, &security_hook_heads.setprocattr,
+					list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			slen = strlen(hp->lsm);
+			if (strncmp(cp, hp->lsm, slen))
+				goto free_out;
+			cp += slen;
+			if (cp[0] != '=' || cp[1] != '\'' || cp[2] == '\'')
+				goto free_out;
+			for (cp += 2; cp[0] != '\''; cp++)
+				if (cp[0] == '\0')
+					goto free_out;
+			cp++;
+		}
+		cp = local;
+		list_for_each_entry(hp, &security_hook_heads.setprocattr,
+					list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			cp += strlen(hp->lsm) + 2;
+			for (slen = 0; cp[slen] != '\''; slen++)
+				;
+			cp[slen] = '\0';
+
+			rc = hp->hook.setprocattr(p, "context", cp, slen);
+			if (rc < 0)
+				failed = rc;
+			cp += slen + 1;
+		}
+		if (failed != 0)
+			rc = failed;
+		else
+			rc = size;
+free_out:
+		kfree(local);
+		return rc;
+	}
 	list_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
 		if (lsm != NULL && strcmp(lsm, hp->lsm))
 			continue;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ed3a757..3a21c2b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5711,6 +5711,8 @@  static int selinux_getprocattr(struct task_struct *p,
 
 	if (!strcmp(name, "current"))
 		sid = __tsec->sid;
+	else if (!strcmp(name, "context"))
+		sid = __tsec->sid;
 	else if (!strcmp(name, "prev"))
 		sid = __tsec->osid;
 	else if (!strcmp(name, "exec"))
@@ -5728,7 +5730,21 @@  static int selinux_getprocattr(struct task_struct *p,
 	if (!sid)
 		return 0;
 
-	error = security_sid_to_context(sid, value, &len);
+	if (strcmp(name, "context")) {
+		error = security_sid_to_context(sid, value, &len);
+	} else {
+		char *vp;
+
+		error = security_sid_to_context(sid, &vp, &len);
+		if (!error) {
+			*value = kzalloc(len + 10, GFP_KERNEL);
+			if (*value == NULL)
+				error = -ENOMEM;
+			else
+				sprintf(*value, "selinux='%s'", vp);
+		}
+	}
+
 	if (error)
 		return error;
 	return len;
@@ -5768,6 +5784,8 @@  static int selinux_setprocattr(struct task_struct *p,
 		error = current_has_perm(p, PROCESS__SETSOCKCREATE);
 	else if (!strcmp(name, "current"))
 		error = current_has_perm(p, PROCESS__SETCURRENT);
+	else if (!strcmp(name, "context"))
+		error = current_has_perm(p, PROCESS__SETCURRENT);
 	else
 		error = -EINVAL;
 	if (error)
@@ -5827,7 +5845,7 @@  static int selinux_setprocattr(struct task_struct *p,
 		tsec->keycreate_sid = sid;
 	} else if (!strcmp(name, "sockcreate")) {
 		tsec->sockcreate_sid = sid;
-	} else if (!strcmp(name, "current")) {
+	} else if (!strcmp(name, "current") || !strcmp(name, "context")) {
 		error = -EINVAL;
 		if (sid == 0)
 			goto abort_change;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3577009..d2d8624 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3576,16 +3576,21 @@  static int smack_getprocattr(struct task_struct *p, char *name, char **value)
 	char *cp;
 	int slen;
 
-	if (strcmp(name, "current") != 0)
+	if (strcmp(name, "current") == 0) {
+		cp = kstrdup(skp->smk_known, GFP_KERNEL);
+		if (cp == NULL)
+			return -ENOMEM;
+	} else if (strcmp(name, "context") == 0) {
+		slen = strlen(skp->smk_known) + 9;
+		cp = kzalloc(slen, GFP_KERNEL);
+		if (cp == NULL)
+			return -ENOMEM;
+		sprintf(cp, "smack='%s'", skp->smk_known);
+	} else
 		return -EINVAL;
 
-	cp = kstrdup(skp->smk_known, GFP_KERNEL);
-	if (cp == NULL)
-		return -ENOMEM;
-
-	slen = strlen(cp);
 	*value = cp;
-	return slen;
+	return strlen(cp);
 }
 
 /**
@@ -3622,7 +3627,7 @@  static int smack_setprocattr(struct task_struct *p, char *name,
 	if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
 		return -EINVAL;
 
-	if (strcmp(name, "current") != 0)
+	if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0)
 		return -EINVAL;
 
 	skp = smk_import_entry(value, size);