| Message ID | 1519335184-17808-2-git-send-email-zohar@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Mimi Zohar <zohar@linux.vnet.ibm.com> writes: > FUSE can be mounted by unprivileged users either today with fusermount > installed with setuid, or soon with the upcoming patches to allow FUSE > mounts in a non-init user namespace. > > This patch addresses the new unprivileged non-init mounted filesystems, > which are untrusted, by failing the signature verification. > > This patch defines two new flags SB_I_IMA_UNVERIFIABLE_SIGNATURE and > SB_I_UNTRUSTED_MOUNTER. I don't belive this patch matches your intent. > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > Cc: Miklos Szeredi <miklos@szeredi.hu> > Cc: Seth Forshee <seth.forshee@canonical.com> > Cc: Eric W. Biederman <ebiederm@xmission.com> > Cc: Dongsu Park <dongsu@kinvolk.io> > Cc: Alban Crequy <alban@kinvolk.io> > Cc: Serge E. Hallyn <serge@hallyn.com> > > Changelog v2: > - Limit patch to non-init mounted filesystems. > - Define 2 sb->s_iflags > > Changelog v1: > - Merged the unprivileged and privileged patches. > - Dropped IMA fsname support. > - Introduced a new IMA builtin policy named "untrusted_fs". > - Replaced fs_type flag with sb->s_iflags flag. > --- > include/linux/fs.h | 2 ++ > security/integrity/ima/ima_appraise.c | 14 +++++++++++++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 2a815560fda0..4e1c76af7b68 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1320,6 +1320,8 @@ extern int send_sigurg(struct fown_struct *fown); > > /* sb->s_iflags to limit user namespace mounts */ > #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ > +#define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 > +#define SB_I_UNTRUSTED_MOUNTER 0x00000040 > > /* Possible states of 'frozen' field */ > enum { > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index 1b177461f20e..f34901069e78 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -302,7 +302,18 @@ int ima_appraise_measurement(enum ima_hooks func, > } > > out: > - if (status != INTEGRITY_PASS) { > + /* > + * File signatures on some filesystems can not be properly verified. > + * On these filesytems, that are mounted by an untrusted mounter, > + * fail the file signature verification. > + */ > + if (inode->i_sb->s_iflags & > + (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) > { I like this test. This test does not match your comments. This test returns true if either SB_I_IMA_UNVERIFIABLE_SIGNATURE or SB_I_UNTRUSTED_MOUNTER. > + status = INTEGRITY_FAIL; > + cause = "unverifiable-signature"; > + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > + op, cause, rc, 0); > + } else if (status != INTEGRITY_PASS) { > if ((ima_appraise & IMA_APPRAISE_FIX) && > (!xattr_value || > xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { Eric
On Mon, 2018-02-26 at 19:47 -0600, Eric W. Biederman wrote: > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > > index 1b177461f20e..f34901069e78 100644 > > --- a/security/integrity/ima/ima_appraise.c > > +++ b/security/integrity/ima/ima_appraise.c > > @@ -302,7 +302,18 @@ int ima_appraise_measurement(enum ima_hooks func, > > } > > > > out: > > - if (status != INTEGRITY_PASS) { > > + /* > > + * File signatures on some filesystems can not be properly verified. > > + * On these filesytems, that are mounted by an untrusted mounter, > > + * fail the file signature verification. > > + */ > > + if (inode->i_sb->s_iflags & > > + (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) > > { > > I like this test. > > This test does not match your comments. This test returns true if > either SB_I_IMA_UNVERIFIABLE_SIGNATURE or SB_I_UNTRUSTED_MOUNTER. Thanks, you're right. The test should have been: if ((inode->i_sb->s_iflags & (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) == (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) { Mimi > > > + status = INTEGRITY_FAIL; > > + cause = "unverifiable-signature"; > > + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > > + op, cause, rc, 0); > > + } else if (status != INTEGRITY_PASS) { > > if ((ima_appraise & IMA_APPRAISE_FIX) && > > (!xattr_value || > > xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { > > Eric >
diff --git a/include/linux/fs.h b/include/linux/fs.h index 2a815560fda0..4e1c76af7b68 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1320,6 +1320,8 @@ extern int send_sigurg(struct fown_struct *fown); /* sb->s_iflags to limit user namespace mounts */ #define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ +#define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 +#define SB_I_UNTRUSTED_MOUNTER 0x00000040 /* Possible states of 'frozen' field */ enum { diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 1b177461f20e..f34901069e78 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -302,7 +302,18 @@ int ima_appraise_measurement(enum ima_hooks func, } out: - if (status != INTEGRITY_PASS) { + /* + * File signatures on some filesystems can not be properly verified. + * On these filesytems, that are mounted by an untrusted mounter, + * fail the file signature verification. + */ + if (inode->i_sb->s_iflags & + (SB_I_IMA_UNVERIFIABLE_SIGNATURE | SB_I_UNTRUSTED_MOUNTER)) { + status = INTEGRITY_FAIL; + cause = "unverifiable-signature"; + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, + op, cause, rc, 0); + } else if (status != INTEGRITY_PASS) { if ((ima_appraise & IMA_APPRAISE_FIX) && (!xattr_value || xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { @@ -319,6 +330,7 @@ int ima_appraise_measurement(enum ima_hooks func, } else { ima_cache_flags(iint, func); } + ima_set_cache_status(iint, func, status); return status; }
FUSE can be mounted by unprivileged users either today with fusermount installed with setuid, or soon with the upcoming patches to allow FUSE mounts in a non-init user namespace. This patch addresses the new unprivileged non-init mounted filesystems, which are untrusted, by failing the signature verification. This patch defines two new flags SB_I_IMA_UNVERIFIABLE_SIGNATURE and SB_I_UNTRUSTED_MOUNTER. Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Seth Forshee <seth.forshee@canonical.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Dongsu Park <dongsu@kinvolk.io> Cc: Alban Crequy <alban@kinvolk.io> Cc: Serge E. Hallyn <serge@hallyn.com> Changelog v2: - Limit patch to non-init mounted filesystems. - Define 2 sb->s_iflags Changelog v1: - Merged the unprivileged and privileged patches. - Dropped IMA fsname support. - Introduced a new IMA builtin policy named "untrusted_fs". - Replaced fs_type flag with sb->s_iflags flag. --- include/linux/fs.h | 2 ++ security/integrity/ima/ima_appraise.c | 14 +++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-)