From 42c63330f2b05aa6077c1bfc2798c04afe54f6b2 Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Thu, 10 Mar 2011 18:54:15 -0500 Subject: [PATCH] ima: add ima_inode_setxattr/removexattr function and calls 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 Signed-off-by: Dmitry Kasatkin --- include/linux/ima.h | 17 +++++++++++ security/integrity/ima/ima_appraise.c | 57 +++++++++++++++++++++++++++++++++++ security/security.c | 6 ++++ 3 files changed, 80 insertions(+) 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 68c1b9b..d23b435 100644 --- a/security/security.c +++ b/security/security.c @@ -573,6 +573,9 @@ 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); } @@ -608,6 +611,9 @@ 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); } -- 2.7.4