[Devel] Re: [RFC PATCH 2/2] cr: debug security_checkpoint_header and security_may_restart
Casey Schaufler
casey at schaufler-ca.com
Thu Sep 3 22:20:46 PDT 2009
Serge E. Hallyn wrote:
> This patch, for debugging only, introduces a silly admin-controlled
> 'policy version' for smack. By default the version is 1. An
> admin (with CAP_MAC_ADMIN) can change it by echoing a new value
> into /smack/version.
>
The scheme you have suggested is just one step off of completely
acceptable for real. More detail below, but if you make the "version"
a string instead of a number I'm happy with it. In particular, a
string that would itself be a valid Smack label makes everything
really simple.
It would take me a few days, but if you're not in a real hurry or
you're lazier than I am (yeah, right) I could provide a patch that
does it. Or, if I haven't been completely incomprehensible, you
could do a revision.
> It then defines security_checkpoint_header() to add this 'policy
> version' into the checkpoint header, and defines security_may_restart()
> to refuse restart if both:
> 1. the caller asked for RESTART_KEEP_LSM
> and
> 2. the checkpointed version was different from the current.
>
> This of course is easy enough to test by doing
>
> echo 1 > /smack/version
> ckpt > out
> mktree < out
> succeed
> mktree -k < out
> succeed
> echo 2 > /smack/version
> mktree < out
> succeed
> mktree -k < out
> fail
>
> Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
> ---
> security/smack/smack_lsm.c | 46 +++++++++++++++++++++++++++
> security/smack/smackfs.c | 75 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 121 insertions(+), 0 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 279fdce..f0d4a08 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -27,6 +27,7 @@
> #include <linux/udp.h>
> #include <linux/mutex.h>
> #include <linux/pipe_fs_i.h>
> +#include <linux/checkpoint.h>
> #include <net/netlabel.h>
> #include <net/cipso_ipv4.h>
> #include <linux/audit.h>
> @@ -3111,6 +3112,47 @@ static void smack_release_secctx(char *secdata, u32 seclen)
> {
> }
>
> +#ifdef CONFIG_CHECKPOINT
> +extern int smack_version;
>
Make this a char * instead of an int and set it to
smack_known_floor.smk_known (which will be "_").
> +
> +static int smack_may_restart(struct ckpt_ctx *ctx)
>
So as to reduce confusion between ctx's and checkpoint thingies,
static int smack_may_restart(struct ckpt_ctx *ckptx)
> +{
> + struct ckpt_hdr *h;
>
How about:
struct ckpt_hdr *chp;
instead for a little more consistency with Smack code.
> + char *smackv;
> + int v = 0, slen, ret;
> +
> + h = ckpt_read_buf_type(ctx, CKPT_LSM_INFO_LEN, CKPT_HDR_LSM_INFO);
> + if (IS_ERR(h))
> + return PTR_ERR(h);
> +
> + if (strcmp(ctx->lsm_name, "smack") != 0)
> + return 0;
> +
> + smackv = (char *) (h + 1);
>
And delete from here ...
> + slen = h->len - sizeof(*h);
> + if (smackv[slen-1] != '\0')
> + smackv[slen-1] = '\0';
> + ret = sscanf(smackv, "%d", &v);
>
... to here. How about we say that the version name meet the same
requirements as a label? A call to smk_import() can verify that and
take care of all the memory allocation business.
> + ckpt_hdr_put(ctx, h);
> + if (!(ctx->uflags & RESTART_KEEP_LSM))
> + return 0;
> + if (ret != 1 || v != smack_version) {
>
Make this a strcmp()
> + ckpt_debug("Smack version at checkpoint was %d, now is %d\n",
>
%s instead of %d all around.
> + v, smack_version);
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +static int smack_checkpoint_header(struct cpt_ctx *ctx)
> +{
> + char smackv[10];
> + sprintf(smackv, "%d", smack_version);
>
You can drop this ...
> + return ckpt_write_obj_type(ctx, smackv, strlen(smackv)+1,
> + CKPT_HDR_LSM_INFO);
>
And pass back smack_version, which is a string.
> +}
> +#endif
> +
> struct security_operations smack_ops = {
> .name = "smack",
>
> @@ -3245,6 +3287,10 @@ struct security_operations smack_ops = {
> .secid_to_secctx = smack_secid_to_secctx,
> .secctx_to_secid = smack_secctx_to_secid,
> .release_secctx = smack_release_secctx,
> +#ifdef CONFIG_CHECKPOINT
> + .may_restart = smack_may_restart,
> + .checkpoint_header = smack_checkpoint_header,
> +#endif
> };
>
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index f83a809..7b20ad9 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -42,6 +42,7 @@ enum smk_inos {
> SMK_NETLBLADDR = 8, /* single label hosts */
> SMK_ONLYCAP = 9, /* the only "capable" label */
> SMK_LOGGING = 10, /* logging */
> + SMK_VERSION = 11, /* logging */
> };
>
> /*
> @@ -51,6 +52,7 @@ static DEFINE_MUTEX(smack_list_lock);
> static DEFINE_MUTEX(smack_cipso_lock);
> static DEFINE_MUTEX(smack_ambient_lock);
> static DEFINE_MUTEX(smk_netlbladdr_lock);
> +static DEFINE_MUTEX(smack_version_lock);
>
> /*
> * This is the "ambient" label for network traffic.
> @@ -60,6 +62,11 @@ static DEFINE_MUTEX(smk_netlbladdr_lock);
> char *smack_net_ambient = smack_known_floor.smk_known;
>
> /*
> + * this is the policy version, a simple integer
> + */
> +int smack_version = 1;
> +
>
Make this a char * instead of an int and set it to
smack_known_floor.smk_known (which will be "_"). As above.
> +/*
> * This is the level in a CIPSO header that indicates a
> * smack label is contained directly in the category set.
> * It can be reset via smackfs/direct
> @@ -1255,6 +1262,72 @@ static const struct file_operations smk_logging_ops = {
> .read = smk_read_logging,
> .write = smk_write_logging,
> };
> +
> +#define SMK_VERSIONLEN 12
>
#define SMK_VERSIONLEN SMK_LABELLEN
> +/**
> + * smk_read_version - read() for /smack/version
> + * @filp: file pointer, not actually used
> + * @buf: where to put the result
> + * @cn: maximum to send along
> + * @ppos: where to start
> + *
> + * Returns number of bytes read or error code, as appropriate
> + */
> +static ssize_t smk_read_version(struct file *filp, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + char temp[SMK_VERSIONLEN];
> +
> + if (*ppos != 0)
> + return 0;
> +
> + mutex_lock(&smack_version_lock);
> + sprintf(temp, "%d\n", smack_version);
>
In the scheme I'm suggesting, no need for the sprintf.
> + mutex_unlock(&smack_version_lock);
> +
> + return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
> +}
> +
> +/**
> + * smk_write_version - write() for /smack/version
> + * @file: file pointer, not actually used
> + * @buf: where to get the data from
> + * @count: bytes sent
> + * @ppos: where to start
> + *
> + * Returns number of bytes written or error code, as appropriate
> + */
> +static ssize_t smk_write_version(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + char in[SMK_VERSIONLEN];
> + int tmp, ret;
> +
> + if (!capable(CAP_MAC_ADMIN))
> + return -EPERM;
> +
> + if (count >= SMK_VERSIONLEN)
> + return -EINVAL;
> +
> + if (copy_from_user(in, buf, count) != 0)
> + return -EFAULT;
>
This would become smk_import(), replacing ....
> +
> + in[count-1] = '\0';
> + ret = sscanf(in, "%d", &tmp);
> + if (ret != 1)
> + return -EINVAL;
>
... this
> + mutex_lock(&smack_version_lock);
> + smack_version = tmp;
>
and smack_version gets the return from smk_import unless it is NULL.
> + mutex_unlock(&smack_version_lock);
> +
> + return count;
> +}
> +
> +static const struct file_operations smk_version_ops = {
> + .read = smk_read_version,
> + .write = smk_write_version,
> +};
> +
> /**
> * smk_fill_super - fill the /smackfs superblock
> * @sb: the empty superblock
> @@ -1287,6 +1360,8 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent)
> {"onlycap", &smk_onlycap_ops, S_IRUGO|S_IWUSR},
> [SMK_LOGGING] =
> {"logging", &smk_logging_ops, S_IRUGO|S_IWUSR},
> + [SMK_VERSION] =
> + {"version", &smk_version_ops, S_IRUGO|S_IWUSR},
> /* last one */ {""}
> };
>
>
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