linux-kernel - Re: [PATCH v1 2/3] evm: skip integrity verification for newly created files

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Date:	Tue, 15 Jul 2014 10:01:55 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Dmitry Kasatkin <d.kasatkin@...sung.com>
Cc:	linux-ima-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, dmitry.kasatkin@...il.com
Subject: Re: [PATCH v1 2/3] evm: skip integrity verification for newly
 created files

On Fri, 2014-07-11 at 14:47 +0300, Dmitry Kasatkin wrote: 
> Newly created files do not get initial security.ima until close.
> Setting xattr value before close fails because EVM fails to verify
> integrity due to missing xattrs. Following is the example when it
> happens:
>   fd = open("foo", O_CREAT | O_WRONLY, 0644);
>   setxattr("foo", "security.SMACK64", value, sizeof(value), 0);
>   close(fd);
> 
> This patch skips integrity verification if IMA_NEW_FILE flag is set.

Right, unless the LSM initially created the security xattr at
d_instantiate(), security.evm will not have been created.

Mimi

> 
> Signed-off-by: Dmitry Kasatkin <d.kasatkin@...sung.com>
> ---
>  security/integrity/evm/evm_main.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index 3bcb80d..682e640 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -248,10 +248,14 @@ EXPORT_SYMBOL_GPL(evm_verifyxattr);
>  static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
>  {
>  	struct inode *inode = dentry->d_inode;
> +	struct integrity_iint_cache *iint;
> 
>  	if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
>  		return 0;
> -	return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
> +	iint = integrity_iint_find(inode);
> +	if (iint && (iint->flags & IMA_NEW_FILE))
> +		return 0;
> +	return evm_verify_hmac(dentry, NULL, NULL, 0, iint);
>  }
> 
>  /*


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