On 7/29/2019 10:19 AM, Kees Cook wrote:
> On Fri, Jul 26, 2019 at 04:39:22PM -0700, Casey Schaufler wrote:
>> Add an entry /proc/.../attr/context which displays the full
>> process security "context" in compound format:'
>> lsm1\0value\0lsm2\0value\0...
>> This entry is not writable.
> As this is a new API, would it make sense to make this a bit more
> human readable (i.e. newlines not %NUL)?
With the far reaching discussion about what format would be
acceptable in mind I went with Simon McVittie's suggestion.
Also note that AppArmor includes newline in attr/current,
and this way we can preserve the existing value.
It's compatible with /proc/.../cmdline and easily keesized:
cat /proc/self/attr/context | tr '\0' '\n'
> (And if not, please justify the
> reasoning in the commit log).
Good idea.
>
> -Kees
>
>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> ---
>> fs/proc/base.c | 1 +
>> security/security.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 46 insertions(+)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 7bf70e041315..79600df5f7a2 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -2619,6 +2619,7 @@ static const struct pid_entry attr_dir_stuff[] = {
>> ATTR(NULL, "keycreate", 0666),
>> ATTR(NULL, "sockcreate", 0666),
>> ATTR(NULL, "display", 0666),
>> + ATTR(NULL, "context", 0666),
>> #ifdef CONFIG_SECURITY_SMACK
>> DIR("smack", 0555,
>> proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
>> diff --git a/security/security.c b/security/security.c
>> index 5551c146c035..6a89a6b90cce 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -2057,6 +2057,14 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>> char **value)
>> {
>> struct security_hook_list *hp;
>> + char *final = NULL;
>> + char *cp;
>> + char *tp;
>> + int rc = 0;
>> + int finallen = 0;
>> + int llen;
>> + int clen;
>> + int tlen;
>> int display = lsm_task_display(current);
>> int slot = 0;
>>
>> @@ -2074,6 +2082,43 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
>> return -ENOMEM;
>> }
>>
>> + if (!strcmp(name, "context")) {
>> + hlist_for_each_entry(hp, &security_hook_heads.getprocattr,
>> + list) {
>> + rc = hp->hook.getprocattr(p, "current", &cp);
>> + if (rc == -EINVAL || rc == -ENOPROTOOPT)
>> + continue;
>> + if (rc < 0) {
>> + kfree(final);
>> + return rc;
>> + }
>> + llen = strlen(hp->lsmid->lsm) + 1;
>> + clen = strlen(cp) + 1;
>> + tlen = llen + clen;
>> + if (final)
>> + tlen += finallen;
>> + tp = kzalloc(tlen, GFP_KERNEL);
>> + if (tp == NULL) {
>> + kfree(cp);
>> + kfree(final);
>> + return -ENOMEM;
>> + }
>> + if (final)
>> + memcpy(tp, final, finallen);
>> + memcpy(tp + finallen, hp->lsmid->lsm, llen);
>> + memcpy(tp + finallen + llen, cp, clen);
>> + kfree(cp);
>> + if (final)
>> + kfree(final);
>> + final = tp;
>> + finallen = tlen;
>> + }
>> + if (final == NULL)
>> + return -EINVAL;
>> + *value = final;
>> + return finallen;
>> + }
>> +
>> hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
>> if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
>> continue;
>> --
>> 2.20.1
>>
