From: Thiago Jung Bauermann Subject: [PATCH v5 06/18] ima: Improvements in ima_appraise_measurement Date: Tue, 17 Oct 2017 22:53:19 -0200 Message-ID: <20171018005331.2688-7-bauerman@linux.vnet.ibm.com> References: <20171018005331.2688-1-bauerman@linux.vnet.ibm.com> Cc: linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Mimi Zohar , Dmitry Kasatkin , James Morris , "Serge E. Hallyn" , David Howells , David Woodhouse , Jessica Yu , Rusty Russell , Herbert Xu , "David S. Miller" , "AKASHI, Takahiro" , Thiago Jung Bauermann To: linux-integrity@vger.kernel.org Return-path: In-Reply-To: <20171018005331.2688-1-bauerman@linux.vnet.ibm.com> Sender: owner-linux-security-module@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Replace nested ifs in the EVM xattr verification logic with a switch statement, making the code easier to understand. Also, add comments to the if statements in the out section. Signed-off-by: Mimi Zohar Signed-off-by: Thiago Jung Bauermann --- security/integrity/ima/ima.h | 5 +++++ security/integrity/ima/ima_appraise.c | 33 ++++++++++++++++++++------------- 2 files changed, 25 insertions(+), 13 deletions(-) diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index d52b487ad259..4e61d3189b72 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -155,6 +155,11 @@ unsigned long ima_get_binary_runtime_size(void); int ima_init_template(void); void ima_init_template_list(void); +static inline bool is_ima_sig(const struct evm_ima_xattr_data *xattr_value) +{ + return xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG; +} + /* * used to protect h_table and sha_table */ diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 58c6a60c7e83..2c069f47eeec 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -204,7 +204,7 @@ int ima_appraise_measurement(enum ima_hooks func, int xattr_len, int opened) { static const char op[] = "appraise_data"; - char *cause = "unknown"; + const char *cause = "unknown"; struct dentry *dentry = file_dentry(file); struct inode *inode = d_backing_inode(dentry); enum integrity_status status = INTEGRITY_UNKNOWN; @@ -229,11 +229,16 @@ int ima_appraise_measurement(enum ima_hooks func, } status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); - if (status != INTEGRITY_PASS && status != INTEGRITY_UNKNOWN) { - if (status == INTEGRITY_NOLABEL || status == INTEGRITY_NOXATTRS) - cause = "missing-HMAC"; - else if (status == INTEGRITY_FAIL) - cause = "invalid-HMAC"; + switch (status) { + case INTEGRITY_PASS: + case INTEGRITY_UNKNOWN: + break; + case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ + case INTEGRITY_NOLABEL: /* No security.evm xattr. */ + cause = "missing-HMAC"; + goto out; + case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ + cause = "invalid-HMAC"; goto out; } switch (xattr_value->type) { @@ -287,17 +292,19 @@ int ima_appraise_measurement(enum ima_hooks func, out: if (status != INTEGRITY_PASS) { + /* Fix mode, but don't replace file signatures. */ if ((ima_appraise & IMA_APPRAISE_FIX) && - (!xattr_value || - xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { + !is_ima_sig(xattr_value)) { if (!ima_fix_xattr(dentry, iint)) status = INTEGRITY_PASS; - } else if (inode->i_size == 0 && - (iint->flags & IMA_NEW_FILE) && - xattr_value && - xattr_value->type == EVM_IMA_XATTR_DIGSIG) { + } + + /* Permit new files with file signatures, but without data. */ + if (inode->i_size == 0 && (iint->flags & IMA_NEW_FILE) && + is_ima_sig(xattr_value)) { status = INTEGRITY_PASS; } + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, op, cause, rc, 0); } else { @@ -404,7 +411,7 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, if (!xattr_value_len || xvalue->type >= IMA_XATTR_LAST) return -EINVAL; ima_reset_appraise_flags(d_backing_inode(dentry), - xvalue->type == EVM_IMA_XATTR_DIGSIG); + is_ima_sig(xvalue)); result = 0; } return result;