From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751966AbeCNVkt (ORCPT ); Wed, 14 Mar 2018 17:40:49 -0400 Received: from h2.hallyn.com ([78.46.35.8]:45498 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751624AbeCNVkr (ORCPT ); Wed, 14 Mar 2018 17:40:47 -0400 Date: Wed, 14 Mar 2018 16:40:45 -0500 From: "Serge E. Hallyn" To: Thiago Jung Bauermann Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, James Morris , "Serge E. Hallyn" , Mimi Zohar , Dmitry Kasatkin Subject: Re: [PATCH 3/4] ima: Improvements in ima_appraise_measurement() Message-ID: <20180314214045.GC14289@mail.hallyn.com> References: <20180314202020.3794-1-bauerman@linux.vnet.ibm.com> <20180314202020.3794-4-bauerman@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180314202020.3794-4-bauerman@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Thiago Jung Bauermann (bauerman@linux.vnet.ibm.com): > From: Mimi Zohar > > 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 and constify the > cause variable. > > Signed-off-by: Mimi Zohar > Signed-off-by: Thiago Jung Bauermann > --- > security/integrity/ima/ima_appraise.c | 33 ++++++++++++++++++++------------- > 1 file changed, 20 insertions(+), 13 deletions(-) > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index 0c5f94b7b9c3..dd10ecbdce45 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -215,7 +215,7 @@ 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; > @@ -241,16 +241,20 @@ 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_PASS_IMMUTABLE) && > - (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_PASS_IMMUTABLE: > + case INTEGRITY_UNKNOWN: Wouldn't it be more future-proof to replace this with a 'default', or to at least add a "default: BUG()" to catch new status values? > + 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) { > case IMA_XATTR_DIGEST_NG: > /* first byte contains algorithm id */ > @@ -316,17 +320,20 @@ int ima_appraise_measurement(enum ima_hooks func, > integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > op, cause, rc, 0); > } else 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)) { > 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 && This may be correct, but it's not identical to what you're replacing. Since in either case you're setting status to INTEGRITY_PASS the final result is the same, but with a few extra possible steps. Not sure whether that matters. > + xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { > status = INTEGRITY_PASS; > } > + > integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > op, cause, rc, 0); > } else { From mboxrd@z Thu Jan 1 00:00:00 1970 From: serge@hallyn.com (Serge E. Hallyn) Date: Wed, 14 Mar 2018 16:40:45 -0500 Subject: [PATCH 3/4] ima: Improvements in ima_appraise_measurement() In-Reply-To: <20180314202020.3794-4-bauerman@linux.vnet.ibm.com> References: <20180314202020.3794-1-bauerman@linux.vnet.ibm.com> <20180314202020.3794-4-bauerman@linux.vnet.ibm.com> Message-ID: <20180314214045.GC14289@mail.hallyn.com> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org Quoting Thiago Jung Bauermann (bauerman at linux.vnet.ibm.com): > From: Mimi Zohar > > 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 and constify the > cause variable. > > Signed-off-by: Mimi Zohar > Signed-off-by: Thiago Jung Bauermann > --- > security/integrity/ima/ima_appraise.c | 33 ++++++++++++++++++++------------- > 1 file changed, 20 insertions(+), 13 deletions(-) > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index 0c5f94b7b9c3..dd10ecbdce45 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -215,7 +215,7 @@ 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; > @@ -241,16 +241,20 @@ 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_PASS_IMMUTABLE) && > - (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_PASS_IMMUTABLE: > + case INTEGRITY_UNKNOWN: Wouldn't it be more future-proof to replace this with a 'default', or to at least add a "default: BUG()" to catch new status values? > + 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) { > case IMA_XATTR_DIGEST_NG: > /* first byte contains algorithm id */ > @@ -316,17 +320,20 @@ int ima_appraise_measurement(enum ima_hooks func, > integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > op, cause, rc, 0); > } else 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)) { > 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 && This may be correct, but it's not identical to what you're replacing. Since in either case you're setting status to INTEGRITY_PASS the final result is the same, but with a few extra possible steps. Not sure whether that matters. > + xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { > status = INTEGRITY_PASS; > } > + > integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, > op, cause, rc, 0); > } else { -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html