| Message ID | 20240115181809.885385-1-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | security: Move IMA and EVM to the LSM infrastructure | expand |
On Jan 15, 2024 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote: > > IMA and EVM are not effectively LSMs, especially due to the fact that in > the past they could not provide a security blob while there is another LSM > active. > > That changed in the recent years, the LSM stacking feature now makes it > possible to stack together multiple LSMs, and allows them to provide a > security blob for most kernel objects. While the LSM stacking feature has > some limitations being worked out, it is already suitable to make IMA and > EVM as LSMs. > > The main purpose of this patch set is to remove IMA and EVM function calls, > hardcoded in the LSM infrastructure and other places in the kernel, and to > register them as LSM hook implementations, so that those functions are > called by the LSM infrastructure like other regular LSMs. Thanks Roberto, this is looking good. I appreciate all the work you've put into making this happen; when I first mentioned this idea I figured it would be something that would happen much farther into the future, I wasn't expecting to see you pick this up and put in the work to make it happen - thank you. I had some pretty minor comments but I think the only thing I saw that I think needs a change/addition is a comment in the Makefile regarding the IMA/EVM ordering; take a look and let me know what you think. There are also a few patches in the patchset that don't have an ACK/review tag from Mimi, although now that you are co-maininting IMA/EVM with Mimi I don't know if that matters. If the two of you can let me know how you want me to handle LSM patches that are IMA/EVM related I would appreciate it (two ACKs, one or other, something else?). Once you add a Makefile commane and we sort out the IMA/EVM approval process I think we're good to get this into linux-next. A while back Mimi and I had a chat offline and if I recall everything correctly she preferred that I take this patchset via the LSM tree. I don't have a problem with that, and to be honest I would probably prefer that too, but I wanted to check with everyone that is still the case. Just in case, I've added my ACKs/reviews to this patchset in case this needs to be merged via the integrity tree. -- paul-moore.com
On Wed, 2024-02-07 at 22:18 -0500, Paul Moore wrote: > On Jan 15, 2024 Roberto Sassu <roberto.sassu@huaweicloud.com> wrote: > > > > IMA and EVM are not effectively LSMs, especially due to the fact that in > > the past they could not provide a security blob while there is another LSM > > active. > > > > That changed in the recent years, the LSM stacking feature now makes it > > possible to stack together multiple LSMs, and allows them to provide a > > security blob for most kernel objects. While the LSM stacking feature has > > some limitations being worked out, it is already suitable to make IMA and > > EVM as LSMs. > > > > The main purpose of this patch set is to remove IMA and EVM function calls, > > hardcoded in the LSM infrastructure and other places in the kernel, and to > > register them as LSM hook implementations, so that those functions are > > called by the LSM infrastructure like other regular LSMs. > > Thanks Roberto, this is looking good. I appreciate all the work you've > put into making this happen; when I first mentioned this idea I figured > it would be something that would happen much farther into the future, I > wasn't expecting to see you pick this up and put in the work to make it > happen - thank you. Thanks! I also appreciate a lot your guidance and suggestions. > I had some pretty minor comments but I think the only thing I saw that > I think needs a change/addition is a comment in the Makefile regarding > the IMA/EVM ordering; take a look and let me know what you think. Oh, I remember well, it is there but difficult to spot... --- a/security/integrity/Makefile +++ b/security/integrity/Makefile @@ -18,5 +18,6 @@ integrity-$(CONFIG_LOAD_IPL_KEYS) += platform_certs/load_ipl_s390.o integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \ platform_certs/load_powerpc.o \ platform_certs/keyring_handler.o +# The relative order of the 'ima' and 'evm' LSMs depends on the order below. obj-$(CONFIG_IMA) += ima/ obj-$(CONFIG_EVM) += evm/ > There are also a few patches in the patchset that don't have an > ACK/review tag from Mimi, although now that you are co-maininting IMA/EVM > with Mimi I don't know if that matters. If the two of you can let me > know how you want me to handle LSM patches that are IMA/EVM related I > would appreciate it (two ACKs, one or other, something else?). Ok, we will come back to you about this. > Once you add a Makefile commane and we sort out the IMA/EVM approval > process I think we're good to get this into linux-next. A while back > Mimi and I had a chat offline and if I recall everything correctly she > preferred that I take this patchset via the LSM tree. I don't have a > problem with that, and to be honest I would probably prefer > that too, but I wanted to check with everyone that is still the case. > Just in case, I've added my ACKs/reviews to this patchset in case this > needs to be merged via the integrity tree. Ok, given that there is the comment in the Makefile, the last thing to do from your side is to remove the vague comment in the file_release patch. Other than that, I think Mimi wanted to give a last look. If that is ok, then the patches should be ready for your repo and linux-next. Thanks Roberto
On Thu, Feb 8, 2024 at 3:06 AM Roberto Sassu <roberto.sassu@huaweicloud.com> wrote: > On Wed, 2024-02-07 at 22:18 -0500, Paul Moore wrote: ... > > I had some pretty minor comments but I think the only thing I saw that > > I think needs a change/addition is a comment in the Makefile regarding > > the IMA/EVM ordering; take a look and let me know what you think. > > Oh, I remember well, it is there but difficult to spot... > > --- a/security/integrity/Makefile > +++ b/security/integrity/Makefile > @@ -18,5 +18,6 @@ integrity-$(CONFIG_LOAD_IPL_KEYS) += platform_certs/load_ipl_s390.o > integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \ > platform_certs/load_powerpc.o \ > platform_certs/keyring_handler.o > +# The relative order of the 'ima' and 'evm' LSMs depends on the order below. > obj-$(CONFIG_IMA) += ima/ > obj-$(CONFIG_EVM) += evm/ Great, thanks for that. Not sure how I missed that ... ? > > Once you add a Makefile commane and we sort out the IMA/EVM approval > > process I think we're good to get this into linux-next. A while back > > Mimi and I had a chat offline and if I recall everything correctly she > > preferred that I take this patchset via the LSM tree. I don't have a > > problem with that, and to be honest I would probably prefer > > that too, but I wanted to check with everyone that is still the case. > > Just in case, I've added my ACKs/reviews to this patchset in case this > > needs to be merged via the integrity tree. > > Ok, given that there is the comment in the Makefile, the last thing to > do from your side is to remove the vague comment in the file_release > patch. > > Other than that, I think Mimi wanted to give a last look. If that is > ok, then the patches should be ready for your repo and linux-next. If Mimi is okay with the patchset as-is, and both of you would prefer this to in via the LSM tree, don't worry about the file_release comment, I'll just remove that when merging.
From: Roberto Sassu <roberto.sassu@huawei.com> IMA and EVM are not effectively LSMs, especially due to the fact that in the past they could not provide a security blob while there is another LSM active. That changed in the recent years, the LSM stacking feature now makes it possible to stack together multiple LSMs, and allows them to provide a security blob for most kernel objects. While the LSM stacking feature has some limitations being worked out, it is already suitable to make IMA and EVM as LSMs. The main purpose of this patch set is to remove IMA and EVM function calls, hardcoded in the LSM infrastructure and other places in the kernel, and to register them as LSM hook implementations, so that those functions are called by the LSM infrastructure like other regular LSMs. This patch set introduces two new LSMs 'ima' and 'evm', so that functions can be registered to their respective LSM, and removes the 'integrity' LSM. integrity_kernel_module_request() was moved to IMA, since deadlock could occur only there. integrity_inode_free() was replaced with ima_inode_free() (EVM does not need to free memory). In order to make 'ima' and 'evm' independent LSMs, it was necessary to split integrity metadata used by both IMA and EVM, and to let them manage their own. The special case of the IMA_NEW_FILE flag, managed by IMA and used by EVM, was handled by introducing a new flag in EVM, EVM_NEW_FILE, managed by two additional LSM hooks, evm_post_path_mknod() and evm_file_release(), equivalent to their counterparts ima_post_path_mknod() and ima_file_free(). In addition to splitting metadata, it was decided to embed the evm_iint_inode structure into the inode security blob, since it is small and because anyway it cannot rely on IMA anymore allocating it (since it uses a different structure). On the other hand, to avoid memory pressure concerns, only a pointer to the ima_iint_cache structure is stored in the inode security blob, and the structure is allocated on demand, like before. Another follow-up change was removing the iint parameter from evm_verifyxattr(), that IMA used to pass integrity metadata to EVM. After splitting metadata, and aligning EVM_NEW_FILE with IMA_NEW_FILE, this parameter was not necessary anymore. The last part was to ensure that the order of IMA and EVM functions is respected after they become LSMs. Since the order of lsm_info structures in the .lsm_info.init section depends on the order object files containing those structures are passed to the linker of the kernel image, and since IMA is before EVM in the Makefile, that is sufficient to assert that IMA functions are executed before EVM ones. The patch set is organized as follows. Patches 1-9 make IMA and EVM functions suitable to be registered to the LSM infrastructure, by aligning function parameters. Patches 10-18 add new LSM hooks in the same places where IMA and EVM functions are called, if there is no LSM hook already. Patch 19 moves integrity_kernel_module_request() to IMA, as a prerequisite for removing the 'integrity' LSM. Patches 20-22 introduce the new standalone LSMs 'ima' and 'evm', and move hardcoded calls to IMA, EVM and integrity functions to those LSMs. Patches 23-24 remove the dependency on the 'integrity' LSM by splitting integrity metadata, so that the 'ima' and 'evm' LSMs can use their own. They also duplicate iint_lockdep_annotate() in ima_main.c, since the mutex field was moved from integrity_iint_cache to ima_iint_cache. Patch 25 finally removes the 'integrity' LSM, since 'ima' and 'evm' are now self-contained and independent. The patch set applies on top of lsm/dev, commit f1bb47a31dff ("lsm: new security_file_ioctl_compat() hook"). The linux-integrity/next-integrity at commit c00f94b3a5be ("overlay: disable EVM") was merged. Changelog: v8: - Restore dynamic allocation of IMA integrity metadata, and store only the pointer in the inode security blob - Select SECURITY_PATH both in IMA and EVM - Rename evm_file_free() to evm_file_release() - Unconditionally register evm_post_path_mknod() - Introduce the new ima_iint.c file for the management of IMA integrity metadata - Introduce ima_inode_set_iint()/ima_inode_get_iint() in ima.h to respectively store/retrieve the IMA integrity metadata pointer - Replace ima_iint_inode() with ima_inode_get() and ima_iint_find(), with same behavior of integrity_inode_get() and integrity_iint_find() - Initialize the ima_iint_cache in ima_iintcache_init() and call it from init_ima_lsm() - Move integrity_kernel_module_request() to IMA in a separate patch (suggested by Mimi) - Compile ima_kernel_module_request() if CONFIG_INTEGRITY_ASYMMETRIC_KEYS is enabled - Remove ima_inode_alloc_security() and ima_inode_free_security(), since the IMA integrity metadata is not fully embedded in the inode security blob - Fixed the missed initialization of ima_iint_cache in process_measurement() and __ima_inode_hash() - Add a sentence in 'evm: Move to LSM infrastructure' to mention about moving evm_inode_remove_acl(), evm_inode_post_remove_acl() and evm_inode_post_set_acl() to evm_main.c - Add a sentence in 'ima: Move IMA-Appraisal to LSM infrastructure' to mention about moving ima_inode_remove_acl() to ima_appraise.c v7: - Use return instead of goto in __vfs_removexattr_locked() (suggested by Casey) - Clarify in security/integrity/Makefile that the order of 'ima' and 'evm' LSMs depends on the order in which IMA and EVM are compiled - Move integrity_iint_cache flags to ima.h and evm.h in security/ and duplicate IMA_NEW_FILE to EVM_NEW_FILE - Rename evm_inode_get_iint() to evm_iint_inode() and ima_inode_get_iint() to ima_iint_inode(), check if inode->i_security is NULL, and just return the pointer from the inode security blob - Restore the non-NULL checks after ima_iint_inode() and evm_iint_inode() (suggested by Casey) - Introduce evm_file_free() to clear EVM_NEW_FILE - Remove comment about LSM_ORDER_LAST not guaranteeing the order of 'ima' and 'evm' LSMs - Lock iint->mutex before reading IMA_COLLECTED flag in __ima_inode_hash() and restored ima_policy_flag check - Remove patch about the hardcoded ordering of 'ima' and 'evm' LSMs in security.c - Add missing ima_inode_free_security() to free iint->ima_hash - Add the cases for LSM_ID_IMA and LSM_ID_EVM in lsm_list_modules_test.c - Mention about the change in IMA and EVM post functions for private inodes v6: - See v7 v5: - Rename security_file_pre_free() to security_file_release() and the LSM hook file_pre_free_security to file_release (suggested by Paul) - Move integrity_kernel_module_request() to ima_main.c (renamed to ima_kernel_module_request()) - Split the integrity_iint_cache structure into ima_iint_cache and evm_iint_cache, so that IMA and EVM can use disjoint metadata and reserve space with the LSM infrastructure - Reserve space for the entire ima_iint_cache and evm_iint_cache structures, not just the pointer (suggested by Paul) - Introduce ima_inode_get_iint() and evm_inode_get_iint() to retrieve respectively the ima_iint_cache and evm_iint_cache structure from the security blob - Remove the various non-NULL checks for the ima_iint_cache and evm_iint_cache structures, since the LSM infrastructure ensure that they always exist - Remove the iint parameter from evm_verifyxattr() since IMA and EVM use disjoint integrity metaddata - Introduce the evm_post_path_mknod() to set the IMA_NEW_FILE flag - Register the inode_alloc_security LSM hook in IMA and EVM to initialize the respective integrity metadata structures - Remove the 'integrity' LSM completely and instead make 'ima' and 'evm' proper standalone LSMs - Add the inode parameter to ima_get_verity_digest(), since the inode field is not present in ima_iint_cache - Move iint_lockdep_annotate() to ima_main.c (renamed to ima_iint_lockdep_annotate()) - Remove ima_get_lsm_id() and evm_get_lsm_id(), since IMA and EVM directly register the needed LSM hooks - Enforce 'ima' and 'evm' LSM ordering at LSM infrastructure level v4: - Improve short and long description of security_inode_post_create_tmpfile(), security_inode_post_set_acl(), security_inode_post_remove_acl() and security_file_post_open() (suggested by Mimi) - Improve commit message of 'ima: Move to LSM infrastructure' (suggested by Mimi) v3: - Drop 'ima: Align ima_post_path_mknod() definition with LSM infrastructure' and 'ima: Align ima_post_create_tmpfile() definition with LSM infrastructure', define the new LSM hooks with the same IMA parameters instead (suggested by Mimi) - Do IS_PRIVATE() check in security_path_post_mknod() and security_inode_post_create_tmpfile() on the new inode rather than the parent directory (in the post method it is available) - Don't export ima_file_check() (suggested by Stefan) - Remove redundant check of file mode in ima_post_path_mknod() (suggested by Mimi) - Mention that ima_post_path_mknod() is now conditionally invoked when CONFIG_SECURITY_PATH=y (suggested by Mimi) - Mention when a LSM hook will be introduced in the IMA/EVM alignment patches (suggested by Mimi) - Simplify the commit messages when introducing a new LSM hook - Still keep the 'extern' in the function declaration, until the declaration is removed (suggested by Mimi) - Improve documentation of security_file_pre_free() - Register 'ima' and 'evm' as standalone LSMs (suggested by Paul) - Initialize the 'ima' and 'evm' LSMs from 'integrity', to keep the original ordering of IMA and EVM functions as when they were hardcoded - Return the IMA and EVM LSM IDs to 'integrity' for registration of the integrity-specific hooks - Reserve an xattr slot from the 'evm' LSM instead of 'integrity' - Pass the LSM ID to init_ima_appraise_lsm() v2: - Add description for newly introduced LSM hooks (suggested by Casey) - Clarify in the description of security_file_pre_free() that actions can be performed while the file is still open v1: - Drop 'evm: Complete description of evm_inode_setattr()', 'fs: Fix description of vfs_tmpfile()' and 'security: Introduce LSM_ORDER_LAST', they were sent separately (suggested by Christian Brauner) - Replace dentry with file descriptor parameter for security_inode_post_create_tmpfile() - Introduce mode_stripped and pass it as mode argument to security_path_mknod() and security_path_post_mknod() - Use goto in do_mknodat() and __vfs_removexattr_locked() (suggested by Mimi) - Replace __lsm_ro_after_init with __ro_after_init - Modify short description of security_inode_post_create_tmpfile() and security_inode_post_set_acl() (suggested by Stefan) - Move security_inode_post_setattr() just after security_inode_setattr() (suggested by Mimi) - Modify short description of security_key_post_create_or_update() (suggested by Mimi) - Add back exported functions ima_file_check() and evm_inode_init_security() respectively to ima.h and evm.h (reported by kernel robot) - Remove extern from prototype declarations and fix style issues - Remove unnecessary include of linux/lsm_hooks.h in ima_main.c and ima_appraise.c Roberto Sassu (25): ima: Align ima_inode_post_setattr() definition with LSM infrastructure ima: Align ima_file_mprotect() definition with LSM infrastructure ima: Align ima_inode_setxattr() definition with LSM infrastructure ima: Align ima_inode_removexattr() definition with LSM infrastructure ima: Align ima_post_read_file() definition with LSM infrastructure evm: Align evm_inode_post_setattr() definition with LSM infrastructure evm: Align evm_inode_setxattr() definition with LSM infrastructure evm: Align evm_inode_post_setxattr() definition with LSM infrastructure security: Align inode_setattr hook definition with EVM security: Introduce inode_post_setattr hook security: Introduce inode_post_removexattr hook security: Introduce file_post_open hook security: Introduce file_release hook security: Introduce path_post_mknod hook security: Introduce inode_post_create_tmpfile hook security: Introduce inode_post_set_acl hook security: Introduce inode_post_remove_acl hook security: Introduce key_post_create_or_update hook integrity: Move integrity_kernel_module_request() to IMA ima: Move to LSM infrastructure ima: Move IMA-Appraisal to LSM infrastructure evm: Move to LSM infrastructure evm: Make it independent from 'integrity' LSM ima: Make it independent from 'integrity' LSM integrity: Remove LSM fs/attr.c | 5 +- fs/file_table.c | 3 +- fs/namei.c | 12 +- fs/nfsd/vfs.c | 3 +- fs/open.c | 1 - fs/posix_acl.c | 5 +- fs/xattr.c | 9 +- include/linux/evm.h | 117 +------- include/linux/ima.h | 142 ---------- include/linux/integrity.h | 27 -- include/linux/lsm_hook_defs.h | 20 +- include/linux/security.h | 59 ++++ include/uapi/linux/lsm.h | 2 + security/integrity/Makefile | 1 + security/integrity/digsig_asymmetric.c | 23 -- security/integrity/evm/Kconfig | 1 + security/integrity/evm/evm.h | 19 ++ security/integrity/evm/evm_crypto.c | 4 +- security/integrity/evm/evm_main.c | 195 ++++++++++--- security/integrity/iint.c | 197 +------------ security/integrity/ima/Kconfig | 1 + security/integrity/ima/Makefile | 2 +- security/integrity/ima/ima.h | 148 ++++++++-- security/integrity/ima/ima_api.c | 23 +- security/integrity/ima/ima_appraise.c | 66 +++-- security/integrity/ima/ima_iint.c | 142 ++++++++++ security/integrity/ima/ima_init.c | 2 +- security/integrity/ima/ima_main.c | 144 +++++++--- security/integrity/ima/ima_policy.c | 2 +- security/integrity/integrity.h | 80 +----- security/keys/key.c | 10 +- security/security.c | 263 +++++++++++------- security/selinux/hooks.c | 3 +- security/smack/smack_lsm.c | 4 +- .../selftests/lsm/lsm_list_modules_test.c | 6 + 35 files changed, 902 insertions(+), 839 deletions(-) create mode 100644 security/integrity/ima/ima_iint.c