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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id u203sm4260197wme.32.2020.11.20.05.17.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Nov 2020 05:17:10 -0800 (PST) From: KP Singh To: James Morris , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Florent Revest , Brendan Jackman , Mimi Zohar Subject: [PATCH bpf-next 1/3] ima: Implement ima_inode_hash Date: Fri, 20 Nov 2020 13:17:06 +0000 Message-Id: <20201120131708.3237864-1-kpsingh@chromium.org> X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog MIME-Version: 1.0 Precedence: bulk List-ID: From: KP Singh This is in preparation to add a helper for BPF LSM programs to use IMA hashes when attached to LSM hooks. There are LSM hooks like inode_unlink which do not have a struct file * argument and cannot use the existing ima_file_hash API. An inode based API is, therefore, useful in LSM based detections like an executable trying to delete itself which rely on the inode_unlink LSM hook. Moreover, the ima_file_hash function does nothing with the struct file pointer apart from calling file_inode on it and converting it to an inode. Signed-off-by: KP Singh --- include/linux/ima.h | 6 +++ scripts/bpf_helpers_doc.py | 1 + security/integrity/ima/ima_main.c | 74 ++++++++++++++++++++++--------- 3 files changed, 59 insertions(+), 22 deletions(-) diff --git a/include/linux/ima.h b/include/linux/ima.h index 8fa7bcfb2da2..7233a2751754 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -29,6 +29,7 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size, enum kernel_read_file_id id); extern void ima_post_path_mknod(struct dentry *dentry); extern int ima_file_hash(struct file *file, char *buf, size_t buf_size); +extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size); extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size); #ifdef CONFIG_IMA_KEXEC @@ -115,6 +116,11 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size) return -EOPNOTSUPP; } +static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size) +{ + return -EOPNOTSUPP; +} + static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {} #endif /* CONFIG_IMA */ diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py index c5bc947a70ad..add7fcb32dcd 100755 --- a/scripts/bpf_helpers_doc.py +++ b/scripts/bpf_helpers_doc.py @@ -478,6 +478,7 @@ class PrinterHelpers(Printer): 'struct tcp_request_sock', 'struct udp6_sock', 'struct task_struct', + 'struct inode', 'struct path', 'struct btf_ptr', } diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 2d1af8899cab..1dd2123b5b43 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -501,37 +501,17 @@ int ima_file_check(struct file *file, int mask) } EXPORT_SYMBOL_GPL(ima_file_check); -/** - * ima_file_hash - return the stored measurement if a file has been hashed and - * is in the iint cache. - * @file: pointer to the file - * @buf: buffer in which to store the hash - * @buf_size: length of the buffer - * - * On success, return the hash algorithm (as defined in the enum hash_algo). - * If buf is not NULL, this function also outputs the hash into buf. - * If the hash is larger than buf_size, then only buf_size bytes will be copied. - * It generally just makes sense to pass a buffer capable of holding the largest - * possible hash: IMA_MAX_DIGEST_SIZE. - * The file hash returned is based on the entire file, including the appended - * signature. - * - * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. - * If the parameters are incorrect, return -EINVAL. - */ -int ima_file_hash(struct file *file, char *buf, size_t buf_size) +static int __ima_inode_hash(struct inode *inode, char *buf, size_t buf_size) { - struct inode *inode; struct integrity_iint_cache *iint; int hash_algo; - if (!file) + if (!inode) return -EINVAL; if (!ima_policy_flag) return -EOPNOTSUPP; - inode = file_inode(file); iint = integrity_iint_find(inode); if (!iint) return -EOPNOTSUPP; @@ -558,8 +538,58 @@ int ima_file_hash(struct file *file, char *buf, size_t buf_size) return hash_algo; } + +/** + * ima_file_hash - return the stored measurement if a file has been hashed and + * is in the iint cache. + * @file: pointer to the file + * @buf: buffer in which to store the hash + * @buf_size: length of the buffer + * + * On success, return the hash algorithm (as defined in the enum hash_algo). + * If buf is not NULL, this function also outputs the hash into buf. + * If the hash is larger than buf_size, then only buf_size bytes will be copied. + * It generally just makes sense to pass a buffer capable of holding the largest + * possible hash: IMA_MAX_DIGEST_SIZE. + * The file hash returned is based on the entire file, including the appended + * signature. + * + * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. + * If the parameters are incorrect, return -EINVAL. + */ +int ima_file_hash(struct file *file, char *buf, size_t buf_size) +{ + if (!file) + return -EINVAL; + + return __ima_inode_hash(file_inode(file), buf, buf_size); +} EXPORT_SYMBOL_GPL(ima_file_hash); +/** + * ima_inode_hash - return the stored measurement if the inode has been hashed + * and is in the iint cache. + * @inode: pointer to the inode + * @buf: buffer in which to store the hash + * @buf_size: length of the buffer + * + * On success, return the hash algorithm (as defined in the enum hash_algo). + * If buf is not NULL, this function also outputs the hash into buf. + * If the hash is larger than buf_size, then only buf_size bytes will be copied. + * It generally just makes sense to pass a buffer capable of holding the largest + * possible hash: IMA_MAX_DIGEST_SIZE. + * The hash returned is based on the entire contents, including the appended + * signature. + * + * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. + * If the parameters are incorrect, return -EINVAL. + */ +int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size) +{ + return __ima_inode_hash(inode, buf, buf_size); +} +EXPORT_SYMBOL_GPL(ima_inode_hash); + /** * ima_post_create_tmpfile - mark newly created tmpfile as new * @file : newly created tmpfile