Smack: check permissions from user space (v2)
Adds a new file into SmackFS called 'access'. Wanted Smack permission is written into /smack/access. After that result can be read from the opened file. If access applies result contains 1 and otherwise 0. File access is protected from race conditions by using simple_transaction_get()/set() API. Fixes from the previous version: - Removed smack.h changes, refactoring left-over from previous version. - Removed #include <linux/smack.h>, refactoring left-over from previous version. Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com> Signed-off-by: Casey Schaufler <cschaufler@cschaufler-intel.(none)>
This commit is contained in:
Jarkko Sakkinen
Casey Schaufler
parent
545a726034
commit
828716c28f
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@ -44,6 +44,7 @@ enum smk_inos {
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SMK_ONLYCAP = 9, /* the only "capable" label */
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SMK_LOGGING = 10, /* logging */
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SMK_LOAD_SELF = 11, /* task specific rules */
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SMK_ACCESSES = 12, /* access policy */
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};
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/*
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@ -175,6 +176,81 @@ static int smk_set_access(struct smack_rule *srp, struct list_head *rule_list,
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return found;
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}
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/**
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* smk_parse_rule - parse subject, object and access type
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* @data: string to be parsed whose size is SMK_LOADLEN
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* @rule: parsed entities are stored in here
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*/
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static int smk_parse_rule(const char *data, struct smack_rule *rule)
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{
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rule->smk_subject = smk_import(data, 0);
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if (rule->smk_subject == NULL)
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return -1;
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rule->smk_object = smk_import(data + SMK_LABELLEN, 0);
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if (rule->smk_object == NULL)
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return -1;
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rule->smk_access = 0;
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switch (data[SMK_LABELLEN + SMK_LABELLEN]) {
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case '-':
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break;
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case 'r':
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case 'R':
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rule->smk_access |= MAY_READ;
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break;
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default:
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return -1;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 1]) {
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case '-':
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break;
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case 'w':
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case 'W':
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rule->smk_access |= MAY_WRITE;
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break;
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default:
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return -1;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 2]) {
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case '-':
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break;
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case 'x':
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case 'X':
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rule->smk_access |= MAY_EXEC;
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break;
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default:
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return -1;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 3]) {
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case '-':
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break;
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case 'a':
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case 'A':
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rule->smk_access |= MAY_APPEND;
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break;
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default:
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return -1;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 4]) {
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case '-':
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break;
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case 't':
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case 'T':
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rule->smk_access |= MAY_TRANSMUTE;
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break;
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default:
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return -1;
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}
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return 0;
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}
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/**
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* smk_write_load_list - write() for any /smack/load
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* @file: file pointer, not actually used
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@ -234,71 +310,9 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf,
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goto out;
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}
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rule->smk_subject = smk_import(data, 0);
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if (rule->smk_subject == NULL)
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if (smk_parse_rule(data, rule))
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goto out_free_rule;
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rule->smk_object = smk_import(data + SMK_LABELLEN, 0);
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if (rule->smk_object == NULL)
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goto out_free_rule;
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rule->smk_access = 0;
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switch (data[SMK_LABELLEN + SMK_LABELLEN]) {
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case '-':
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break;
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case 'r':
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case 'R':
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rule->smk_access |= MAY_READ;
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break;
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default:
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goto out_free_rule;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 1]) {
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case '-':
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break;
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case 'w':
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case 'W':
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rule->smk_access |= MAY_WRITE;
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break;
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default:
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goto out_free_rule;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 2]) {
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case '-':
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break;
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case 'x':
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case 'X':
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rule->smk_access |= MAY_EXEC;
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break;
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default:
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goto out_free_rule;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 3]) {
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case '-':
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break;
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case 'a':
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case 'A':
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rule->smk_access |= MAY_APPEND;
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break;
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default:
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goto out_free_rule;
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}
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switch (data[SMK_LABELLEN + SMK_LABELLEN + 4]) {
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case '-':
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break;
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case 't':
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case 'T':
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rule->smk_access |= MAY_TRANSMUTE;
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break;
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default:
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goto out_free_rule;
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}
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rc = count;
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/*
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* smk_set_access returns true if there was already a rule
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@ -1425,6 +1439,44 @@ static const struct file_operations smk_load_self_ops = {
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.write = smk_write_load_self,
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.release = seq_release,
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};
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/**
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* smk_write_access - handle access check transaction
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* @file: file pointer
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* @buf: data from user space
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* @count: bytes sent
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* @ppos: where to start - must be 0
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*/
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static ssize_t smk_write_access(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct smack_rule rule;
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char *data;
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if (!capable(CAP_MAC_ADMIN))
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return -EPERM;
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data = simple_transaction_get(file, buf, count);
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if (IS_ERR(data))
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return PTR_ERR(data);
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if (count < SMK_LOADLEN || smk_parse_rule(data, &rule))
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return -EINVAL;
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data[0] = smk_access(rule.smk_subject, rule.smk_object,
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rule.smk_access, NULL) == 0;
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simple_transaction_set(file, 1);
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return SMK_LOADLEN;
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}
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static const struct file_operations smk_access_ops = {
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.write = smk_write_access,
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.read = simple_transaction_read,
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.release = simple_transaction_release,
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.llseek = generic_file_llseek,
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};
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/**
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* smk_fill_super - fill the /smackfs superblock
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* @sb: the empty superblock
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@ -1459,6 +1511,8 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent)
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"logging", &smk_logging_ops, S_IRUGO|S_IWUSR},
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[SMK_LOAD_SELF] = {
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"load-self", &smk_load_self_ops, S_IRUGO|S_IWUGO},
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[SMK_ACCESSES] = {
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"access", &smk_access_ops, S_IRUGO|S_IWUSR},
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/* last one */
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{""}
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};
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