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Hallyn" Cc: linux-integrity@vger.kernel.org, zohar@linux.ibm.com, christian.brauner@ubuntu.com, containers@lists.linux.dev, dmitry.kasatkin@gmail.com, ebiederm@xmission.com, krzysztof.struczynski@huawei.com, roberto.sassu@huawei.com, mpeters@redhat.com, lhinds@redhat.com, lsturman@redhat.com, puiterwi@redhat.com, jejb@linux.ibm.com, jamjoom@us.ibm.com, linux-kernel@vger.kernel.org, paul@paul-moore.com, rgb@redhat.com, linux-security-module@vger.kernel.org, jmorris@namei.org, Denis Semakin References: <20220201203735.164593-1-stefanb@linux.ibm.com> <20220201203735.164593-13-stefanb@linux.ibm.com> <20220205055826.GA15072@mail.hallyn.com> From: Stefan Berger In-Reply-To: <20220205055826.GA15072@mail.hallyn.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: aagAQgTRfkLb-Lq3exPImckM-UJqhyU1 X-Proofpoint-ORIG-GUID: otIMV6j2_uervesGtk77m3IwpIO9v2vH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-06_05,2022-02-03_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 spamscore=0 priorityscore=1501 clxscore=1015 mlxlogscore=999 adultscore=0 bulkscore=0 suspectscore=0 impostorscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202060127 Precedence: bulk List-ID: On 2/5/22 00:58, Serge E. Hallyn wrote: > On Tue, Feb 01, 2022 at 03:37:20PM -0500, Stefan Berger wrote: >> Define mac_admin_ns_capable() as a wrapper for the combined ns_capable() >> checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return >> true on the check if either capability or both are available. >> >> Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will allow >> an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has >> less privileges than CAP_SYS_ADMIN. >> >> Signed-off-by: Denis Semakin >> Signed-off-by: Stefan Berger >> --- >> include/linux/capability.h | 6 ++++++ >> security/integrity/ima/ima.h | 6 ++++++ >> security/integrity/ima/ima_fs.c | 5 ++++- >> 3 files changed, 16 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/capability.h b/include/linux/capability.h >> index 65efb74c3585..991579178f32 100644 >> --- a/include/linux/capability.h >> +++ b/include/linux/capability.h >> @@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns) >> ns_capable(ns, CAP_SYS_ADMIN); >> } >> >> +static inline bool mac_admin_ns_capable(struct user_namespace *ns) >> +{ >> + return ns_capable(ns, CAP_MAC_ADMIN) || >> + ns_capable(ns, CAP_SYS_ADMIN); > Do you care about audit warnings? If the task has CAP_SYS_ADMIN but > not CAP_MAC_ADMIN, is it desirable that selinux_capable() will audit the > CAP_MAC_ADMIN failure? Good point.  I will switch both to ns_capable_noaudit() so that the user cannot provoke unnecessary audit message. Thanks.     Stefan > >> +} >> + >> /* audit system wants to get cap info from files as well */ >> int get_vfs_caps_from_disk(struct user_namespace *mnt_userns, >> const struct dentry *dentry, >> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h >> index fb6bd054d899..0057b1fd6c18 100644 >> --- a/security/integrity/ima/ima.h >> +++ b/security/integrity/ima/ima.h >> @@ -487,4 +487,10 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op, >> #define POLICY_FILE_FLAGS S_IWUSR >> #endif /* CONFIG_IMA_READ_POLICY */ >> >> +static inline >> +struct user_namespace *ima_user_ns_from_file(const struct file *filp) >> +{ >> + return file_inode(filp)->i_sb->s_user_ns; >> +} >> + >> #endif /* __LINUX_IMA_H */ >> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c >> index 89d3113ceda1..c41aa61b7393 100644 >> --- a/security/integrity/ima/ima_fs.c >> +++ b/security/integrity/ima/ima_fs.c >> @@ -377,6 +377,9 @@ static const struct seq_operations ima_policy_seqops = { >> */ >> static int ima_open_policy(struct inode *inode, struct file *filp) >> { >> +#ifdef CONFIG_IMA_READ_POLICY >> + struct user_namespace *user_ns = ima_user_ns_from_file(filp); >> +#endif >> struct ima_namespace *ns = &init_ima_ns; >> >> if (!(filp->f_flags & O_WRONLY)) { >> @@ -385,7 +388,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp) >> #else >> if ((filp->f_flags & O_ACCMODE) != O_RDONLY) >> return -EACCES; >> - if (!capable(CAP_SYS_ADMIN)) >> + if (!mac_admin_ns_capable(user_ns)) >> return -EPERM; >> return seq_open(filp, &ima_policy_seqops); >> #endif >> -- >> 2.31.1