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    SubjectRe: [PATCH v3 09/12] ima: add ima_inode_setxattr/removexattr function and calls
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    On Wed, Mar 21, 2012 at 8:54 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
    > Based on xattr_permission comments, the restriction to modify 'security'
    > xattr is left up to the underlying fs or lsm. Ensure that not just anyone
    > can modify or remove 'security.ima'.
    >
    > Changelog v1:
    > - Unless IMA-APPRAISE is configured, use stub ima_inode_removexattr()/setxattr()
    >  functions.  (Moved ima_inode_removexattr()/setxattr() to ima_appraise.c)
    >
    > Changelog:
    >  - take i_mutex to fix locking (Dmitry Kasatkin)
    >  - ima_reset_appraise_flags should only be called when modifying or
    >    removing the 'security.ima' xattr. Requires CAP_SYS_ADMIN privilege.
    >    (Incorporated fix from Roberto Sassu)
    >  - Even if allowed to update security.ima, reset the appraisal flags,
    >    forcing re-appraisal.
    >  - Replace CAP_MAC_ADMIN with CAP_SYS_ADMIN
    >  - static inline ima_inode_setxattr()/ima_inode_removexattr() stubs
    >  - ima_protect_xattr should be static
    >
    > Signed-off-by: Mimi Zohar <zohar@us.ibm.com>

    Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>

    > ---
    >  include/linux/ima.h                   |   17 ++++++++++
    >  security/integrity/ima/ima_appraise.c |   57 +++++++++++++++++++++++++++++++++
    >  security/security.c                   |    6 +++
    >  3 files changed, 80 insertions(+), 0 deletions(-)
    >
    > diff --git a/include/linux/ima.h b/include/linux/ima.h
    > index e2bfbb1..2c7223d 100644
    > --- a/include/linux/ima.h
    > +++ b/include/linux/ima.h
    > @@ -44,10 +44,27 @@ static inline int ima_file_mmap(struct file *file, unsigned long prot)
    >
    >  #ifdef CONFIG_IMA_APPRAISE
    >  extern void ima_inode_post_setattr(struct dentry *dentry);
    > +extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
    > +                      const void *xattr_value, size_t xattr_value_len);
    > +extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
    >  #else
    >  static inline void ima_inode_post_setattr(struct dentry *dentry)
    >  {
    >        return;
    >  }
    > +
    > +static inline int ima_inode_setxattr(struct dentry *dentry,
    > +                                    const char *xattr_name,
    > +                                    const void *xattr_value,
    > +                                    size_t xattr_value_len)
    > +{
    > +       return 0;
    > +}
    > +
    > +static inline int ima_inode_removexattr(struct dentry *dentry,
    > +                                       const char *xattr_name)
    > +{
    > +       return 0;
    > +}
    >  #endif /* CONFIG_IMA_APPRAISE_H */
    >  #endif /* _LINUX_IMA_H */
    > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
    > index 681cb6e..becc7e0 100644
    > --- a/security/integrity/ima/ima_appraise.c
    > +++ b/security/integrity/ima/ima_appraise.c
    > @@ -169,3 +169,60 @@ void ima_inode_post_setattr(struct dentry *dentry)
    >                rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA);
    >        return;
    >  }
    > +
    > +/*
    > + * ima_protect_xattr - protect 'security.ima'
    > + *
    > + * Ensure that not just anyone can modify or remove 'security.ima'.
    > + */
    > +static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
    > +                            const void *xattr_value, size_t xattr_value_len)
    > +{
    > +       if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
    > +               if (!capable(CAP_SYS_ADMIN))
    > +                       return -EPERM;
    > +               return 1;
    > +       }
    > +       return 0;
    > +}
    > +
    > +static void ima_reset_appraise_flags(struct inode *inode)
    > +{
    > +       struct integrity_iint_cache *iint;
    > +
    > +       if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode))
    > +               return;
    > +
    > +       iint = integrity_iint_find(inode);
    > +       if (!iint)
    > +               return;
    > +
    > +       iint->flags &= ~(IMA_COLLECTED | IMA_APPRAISED | IMA_MEASURED);
    > +       return;
    > +}
    > +
    > +int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
    > +                      const void *xattr_value, size_t xattr_value_len)
    > +{
    > +       int result;
    > +
    > +       result = ima_protect_xattr(dentry, xattr_name, xattr_value,
    > +                                  xattr_value_len);
    > +       if (result == 1) {
    > +               ima_reset_appraise_flags(dentry->d_inode);
    > +               result = 0;
    > +       }
    > +       return result;
    > +}
    > +
    > +int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
    > +{
    > +       int result;
    > +
    > +       result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
    > +       if (result == 1) {
    > +               ima_reset_appraise_flags(dentry->d_inode);
    > +               result = 0;
    > +       }
    > +       return result;
    > +}
    > diff --git a/security/security.c b/security/security.c
    > index e50bbf4..7bb127e 100644
    > --- a/security/security.c
    > +++ b/security/security.c
    > @@ -557,6 +557,9 @@ int security_inode_setxattr(struct dentry *dentry, const char *name,
    >        ret = security_ops->inode_setxattr(dentry, name, value, size, flags);
    >        if (ret)
    >                return ret;
    > +       ret = ima_inode_setxattr(dentry, name, value, size);
    > +       if (ret)
    > +               return ret;
    >        return evm_inode_setxattr(dentry, name, value, size);
    >  }
    >
    > @@ -592,6 +595,9 @@ int security_inode_removexattr(struct dentry *dentry, const char *name)
    >        ret = security_ops->inode_removexattr(dentry, name);
    >        if (ret)
    >                return ret;
    > +       ret = ima_inode_removexattr(dentry, name);
    > +       if (ret)
    > +               return ret;
    >        return evm_inode_removexattr(dentry, name);
    >  }
    >
    > --
    > 1.7.6.5
    >
    --
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