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Date: Mon, 18 May 2015 12:48:28 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: t.vivek@...sung.com, james.l.morris@...cle.com, serge@...lyn.com
CC: linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
"a.sahrawat@...sung.com" <a.sahrawat@...sung.com>
Subject: Re: [EDT] [PATCH] smack: allow mount opts setting over filesystems
with binary mount data
On 5/17/2015 10:14 PM, VIVEK TRIVEDI wrote:
> EP-79F327334E67427298A99177E8F035A1
>
> Add support for setting smack mount labels(using smackfsdef, smackfsroot,
> smackfshat, smackfsfloor, smackfstransmute) for filesystems with binary
> mount data like NFS.
>
> To achieve this, implement sb_parse_opts_str and sb_set_mnt_opts security
> operations in smack LSM similar to SELinux.
>
> Signed-off-by: Vivek Trivedi <t.vivek@...sung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
Please use a plain text format. This patch is unreadable as text.
> ---
> security/smack/smack.h | 18 ++++
> security/smack/smack_lsm.c | 250 ++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 223 insertions(+), 45 deletions(-)
>
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index b8c1a86..f5db743 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -138,6 +138,24 @@ struct smk_port_label {
> struct smack_known *smk_out; /* outgoing label */
> };
>
> +/* Super block security struct flags for mount options */
> +#define FSDEFAULT_MNT 0x01
> +#define FSFLOOR_MNT 0x02
> +#define FSHAT_MNT 0x04
> +#define FSROOT_MNT 0x08
> +#define FSTRANS_MNT 0x10
> +
> +#define NUM_SMK_MNT_OPTS 5
> +
> +enum {
> + Opt_error = -1,
> + Opt_fsdefault = 1,
> + Opt_fsfloor = 2,
> + Opt_fshat = 3,
> + Opt_fsroot = 4,
> + Opt_fstransmute = 5,
> +};
> +
> /*
> * Mount options
> */
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 5eae42c..d88c27e 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -41,6 +41,7 @@
> #include <linux/msg.h>
> #include <linux/shm.h>
> #include <linux/binfmts.h>
> +#include <linux/parser.h>
> #include "smack.h"
>
> #define TRANS_TRUE "TRUE"
> @@ -64,6 +65,15 @@ static char *smk_bu_mess[] = {
> "Unconfined Object", /* SMACK_UNCONFINED_OBJECT */
> };
>
> +static const match_table_t tokens = {
> + {Opt_fsdefault, SMK_FSDEFAULT "%s"},
> + {Opt_fsfloor, SMK_FSFLOOR "%s"},
> + {Opt_fshat, SMK_FSHAT "%s"},
> + {Opt_fsroot, SMK_FSROOT "%s"},
> + {Opt_fstransmute, SMK_FSTRANS "%s"},
> + {Opt_error, NULL},
> +};
> +
> static void smk_bu_mode(int mode, char *s)
> {
> int i = 0;
> @@ -573,72 +583,188 @@ static int smack_sb_copy_data(char *orig, char *smackopts)
> }
>
> /**
> - * smack_sb_kern_mount - Smack specific mount processing
> + * smack_parse_opts_str - parse Smack specific mount options
> + * @options: mount options string
> + * @opts: where to store converted mount opts
> + *
> + * Returns 0 on success or -ENOMEM on error.
> + *
> + * converts Smack specific mount options to generic security option format
> + */
> +static int smack_parse_opts_str(char *options,
> + struct security_mnt_opts *opts)
> +{
> + char *p;
> + char *fsdefault = NULL, *fsfloor = NULL;
> + char *fshat = NULL, *fsroot = NULL, *fstransmute = NULL;
> + int rc = -ENOMEM, num_mnt_opts = 0;
> +
> + opts->num_mnt_opts = 0;
> +
> + if (!options)
> + return 0;
> +
> + while ((p = strsep(&options, ",")) != NULL) {
> + int token;
> + substring_t args[MAX_OPT_ARGS];
> +
> + if (!*p)
> + continue;
> +
> + token = match_token(p, tokens, args);
> +
> + switch (token) {
> + case Opt_fsdefault:
> + if (fsdefault)
> + goto out_opt_err;
> + fsdefault = match_strdup(&args[0]);
> + if (!fsdefault)
> + goto out_err;
> + break;
> + case Opt_fsfloor:
> + if (fsfloor)
> + goto out_opt_err;
> + fsfloor = match_strdup(&args[0]);
> + if (!fsfloor)
> + goto out_err;
> + break;
> + case Opt_fshat:
> + if (fshat)
> + goto out_opt_err;
> + fshat = match_strdup(&args[0]);
> + if (!fshat)
> + goto out_err;
> + break;
> + case Opt_fsroot:
> + if (fsroot)
> + goto out_opt_err;
> + fsroot = match_strdup(&args[0]);
> + if (!fsroot)
> + goto out_err;
> + break;
> + case Opt_fstransmute:
> + if (fstransmute)
> + goto out_opt_err;
> + fstransmute = match_strdup(&args[0]);
> + if (!fstransmute)
> + goto out_err;
> + break;
> + default:
> + rc = -EINVAL;
> + pr_warn("SMACK: unknown mount option\n");
> + goto out_err;
> + }
> + }
> +
> + opts->mnt_opts = kcalloc(NUM_SMK_MNT_OPTS, sizeof(char *), GFP_ATOMIC);
> + if (!opts->mnt_opts)
> + goto out_err;
> +
> + opts->mnt_opts_flags = kcalloc(NUM_SMK_MNT_OPTS, sizeof(int),
> + GFP_ATOMIC);
> + if (!opts->mnt_opts_flags) {
> + kfree(opts->mnt_opts);
> + goto out_err;
> + }
> +
> + if (fsdefault) {
> + opts->mnt_opts[num_mnt_opts] = fsdefault;
> + opts->mnt_opts_flags[num_mnt_opts++] = FSDEFAULT_MNT;
> + }
> + if (fsfloor) {
> + opts->mnt_opts[num_mnt_opts] = fsfloor;
> + opts->mnt_opts_flags[num_mnt_opts++] = FSFLOOR_MNT;
> + }
> + if (fshat) {
> + opts->mnt_opts[num_mnt_opts] = fshat;
> + opts->mnt_opts_flags[num_mnt_opts++] = FSHAT_MNT;
> + }
> + if (fsroot) {
> + opts->mnt_opts[num_mnt_opts] = fsroot;
> + opts->mnt_opts_flags[num_mnt_opts++] = FSROOT_MNT;
> + }
> + if (fstransmute) {
> + opts->mnt_opts[num_mnt_opts] = fstransmute;
> + opts->mnt_opts_flags[num_mnt_opts++] = FSTRANS_MNT;
> + }
> +
> + opts->num_mnt_opts = num_mnt_opts;
> + return 0;
> +
> +out_opt_err:
> + rc = -EINVAL;
> + pr_warn("SMACK: duplicate mount options\n");
> +
> +out_err:
> + kfree(fsdefault);
> + kfree(fsfloor);
> + kfree(fshat);
> + kfree(fsroot);
> + kfree(fstransmute);
> + return rc;
> +}
> +
> +/**
> + * smack_set_mnt_opts - set Smack specific mount options
> * @sb: the file system superblock
> - * @flags: the mount flags
> - * @data: the smack mount options
> + * @opts: Smack mount options
> + * @kern_flags: mount option from kernel space or user space
> + * @set_kern_flags: where to store converted mount opts
> *
> - * Returns 0 on success, an error code on failure
> + * Returns 0 on success or -EPERM/ENOMEM on error.
> + *
> + * Allow filesystems with binary mount data to explicitly set Smack mount
> + * labels.
> */
> -static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> +static int smack_set_mnt_opts(struct super_block *sb,
> + struct security_mnt_opts *opts,
> + unsigned long kern_flags,
> + unsigned long *set_kern_flags)
> {
> struct dentry *root = sb->s_root;
> struct inode *inode = d_backing_inode(root);
> struct superblock_smack *sp = sb->s_security;
> struct inode_smack *isp;
> struct smack_known *skp;
> - char *op;
> - char *commap;
> + int i, num_opts = opts->num_mnt_opts;
> int transmute = 0;
> - int specified = 0;
>
> if (sp->smk_initialized)
> return 0;
>
> sp->smk_initialized = 1;
>
> - for (op = data; op != NULL; op = commap) {
> - commap = strchr(op, ',');
> - if (commap != NULL)
> - *commap++ = '\0';
> -
> - if (strncmp(op, SMK_FSHAT, strlen(SMK_FSHAT)) == 0) {
> - op += strlen(SMK_FSHAT);
> - skp = smk_import_entry(op, 0);
> - if (skp != NULL) {
> - sp->smk_hat = skp;
> - specified = 1;
> - }
> - } else if (strncmp(op, SMK_FSFLOOR, strlen(SMK_FSFLOOR)) == 0) {
> - op += strlen(SMK_FSFLOOR);
> - skp = smk_import_entry(op, 0);
> - if (skp != NULL) {
> - sp->smk_floor = skp;
> - specified = 1;
> - }
> - } else if (strncmp(op, SMK_FSDEFAULT,
> - strlen(SMK_FSDEFAULT)) == 0) {
> - op += strlen(SMK_FSDEFAULT);
> - skp = smk_import_entry(op, 0);
> - if (skp != NULL) {
> + for (i = 0; i < num_opts; i++) {
> + switch (opts->mnt_opts_flags[i]) {
> + case FSDEFAULT_MNT:
> + skp = smk_import_entry(opts->mnt_opts[i], 0);
> + if (skp != NULL)
> sp->smk_default = skp;
> - specified = 1;
> - }
> - } else if (strncmp(op, SMK_FSROOT, strlen(SMK_FSROOT)) == 0) {
> - op += strlen(SMK_FSROOT);
> - skp = smk_import_entry(op, 0);
> - if (skp != NULL) {
> + break;
> + case FSFLOOR_MNT:
> + skp = smk_import_entry(opts->mnt_opts[i], 0);
> + if (skp != NULL)
> + sp->smk_floor = skp;
> + break;
> + case FSHAT_MNT:
> + skp = smk_import_entry(opts->mnt_opts[i], 0);
> + if (skp != NULL)
> + sp->smk_hat = skp;
> + break;
> + case FSROOT_MNT:
> + skp = smk_import_entry(opts->mnt_opts[i], 0);
> + if (skp != NULL)
> sp->smk_root = skp;
> - specified = 1;
> - }
> - } else if (strncmp(op, SMK_FSTRANS, strlen(SMK_FSTRANS)) == 0) {
> - op += strlen(SMK_FSTRANS);
> - skp = smk_import_entry(op, 0);
> + break;
> + case FSTRANS_MNT:
> + skp = smk_import_entry(opts->mnt_opts[i], 0);
> if (skp != NULL) {
> sp->smk_root = skp;
> transmute = 1;
> - specified = 1;
> }
> + break;
> + default:
> + break;
> }
> }
>
> @@ -646,7 +772,7 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> /*
> * Unprivileged mounts don't get to specify Smack values.
> */
> - if (specified)
> + if (num_opts)
> return -EPERM;
> /*
> * Unprivileged mounts get root and default from the caller.
> @@ -655,6 +781,7 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> sp->smk_root = skp;
> sp->smk_default = skp;
> }
> +
> /*
> * Initialize the root inode.
> */
> @@ -674,6 +801,37 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> }
>
> /**
> + * smack_sb_kern_mount - Smack specific mount processing
> + * @sb: the file system superblock
> + * @flags: the mount flags
> + * @data: the smack mount options
> + *
> + * Returns 0 on success, an error code on failure
> + */
> +static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
> +{
> + int rc = 0;
> + char *options = data;
> + struct security_mnt_opts opts;
> +
> + security_init_mnt_opts(&opts);
> +
> + if (!options)
> + goto out;
> +
> + rc = smack_parse_opts_str(options, &opts);
> + if (rc)
> + goto out_err;
> +
> +out:
> + rc = smack_set_mnt_opts(sb, &opts, 0, NULL);
> +
> +out_err:
> + security_free_mnt_opts(&opts);
> + return rc;
> +}
> +
> +/**
> * smack_sb_statfs - Smack check on statfs
> * @dentry: identifies the file system in question
> *
> @@ -4246,6 +4404,8 @@ struct security_hook_list smack_hooks[] = {
> LSM_HOOK_INIT(sb_copy_data, smack_sb_copy_data),
> LSM_HOOK_INIT(sb_kern_mount, smack_sb_kern_mount),
> LSM_HOOK_INIT(sb_statfs, smack_sb_statfs),
> + LSM_HOOK_INIT(sb_set_mnt_opts, smack_set_mnt_opts),
> + LSM_HOOK_INIT(sb_parse_opts_str, smack_parse_opts_str),
>
> LSM_HOOK_INIT(bprm_set_creds, smack_bprm_set_creds),
> LSM_HOOK_INIT(bprm_committing_creds, smack_bprm_committing_creds),
--
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