| Message ID | 1696457386-3010-9-git-send-email-wufan@linux.microsoft.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | Integrity Policy Enforcement LSM (IPE) | expand |
On Oct 4, 2023 Fan Wu <wufan@linux.microsoft.com> wrote: > > Users of IPE require a way to identify when and why an operation fails, > allowing them to both respond to violations of policy and be notified > of potentially malicious actions on their systems with respect to IPE > itself. > > This patch introduces 3 new audit events. > > AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation > of a resource. > AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy > has been changed to another loaded policy. > AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded > into the kernel. > > This patch also adds support for success auditing, allowing users to > identify why an allow decision was made for a resource. However, it is > recommended to use this option with caution, as it is quite noisy. > > Here are some examples of the new audit record types: > > AUDIT_IPE_ACCESS(1420): > > audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda" > ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW" > > audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0" > ino=2 rule="DEFAULT action=DENY" > > audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs" > ino=131 rule="DEFAULT action=DENY" > > The above three records were generated when the active IPE policy only > allows binaries from the initial booted drive(sda) to run. The three > identical `hello` binary were placed at different locations, only the > first hello from sda was allowed. > > Field path followed by the file's path name. > > Field dev followed by the device name as found in /dev where the file is > from. > Note that for device mappers it will use the name `dm-X` instead of > the name in /dev/mapper. > For a file in a temp file system, which is not from a device, it will use > `tmpfs` for the field. > The implementation of this part is following another existing use case > LSM_AUDIT_DATA_INODE in security/lsm_audit.c > > Field ino followed by the file's inode number. > > Field rule followed by the IPE rule made the access decision. The whole > rule must be audited because the decision is based on the combination of > all property conditions in the rule. > > Along with the syscall audit event, user can know why a blocked > happened. For example: > > audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0" > ino=2 rule="DEFAULT action=DENY" > audit[1956]: SYSCALL arch=c000003e syscall=59 > success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0 > a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 auid=4294967295 uid=0 > gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 > ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null) > > The above two records showed bash used execve to run "hello" and got > blocked by IPE. Note that the IPE records are always prior to a SYSCALL > record. > > AUDIT_IPE_CONFIG_CHANGE(1421): > > audit: AUDIT1421 > old_active_pol_name="Allow_All" old_active_pol_version=0.0.0 > old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649 > new_active_pol_name="boot_verified" new_active_pol_version=0.0.0 > new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F > auid=4294967295 ses=4294967295 lsm=ipe res=1 > > The above record showed the current IPE active policy switch from > `Allow_All` to `boot_verified` along with the version and the hash > digest of the two policies. Note IPE can only have one policy active > at a time, all access decision evaluation is based on the current active > policy. > The normal procedure to deploy a policy is loading the policy to deploy > into the kernel first, then switch the active policy to it. > > AUDIT_IPE_POLICY_LOAD(1422): > > audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0 > policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD > auid=4294967295 ses=4294967295 lsm=ipe res=1 > > The above record showed a new policy has been loaded into the kernel > with the policy name, policy version and policy hash. > > Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> > Signed-off-by: Fan Wu <wufan@linux.microsoft.com> > --- > > v2: > + Split evaluation loop, access control hooks, > and evaluation loop from policy parser and userspace > interface to pass mailing list character limit > > v3: > + Move ipe_load_properties to patch 04. > + Remove useless 0-initializations > + Prefix extern variables with ipe_ > + Remove kernel module parameters, as these are > exposed through sysctls. > + Add more prose to the IPE base config option > help text. > + Use GFP_KERNEL for audit_log_start. > + Remove unnecessary caching system. > + Remove comments from headers > + Use rcu_access_pointer for rcu-pointer null check > + Remove usage of reqprot; use prot only. > + Move policy load and activation audit event to 03/12 > > v4: > + Remove sysctls in favor of securityfs nodes > + Re-add kernel module parameters, as these are now > exposed through securityfs. > + Refactor property audit loop to a separate function. > > v5: > + fix minor grammatical errors > + do not group rule by curly-brace in audit record, > reconstruct the exact rule. > > v6: > + No changes > > v7: > + Further split lsm creation, the audit system, the evaluation loop, > and access control hooks into separate patches. > + Further split audit system patch into two separate patches; one > for include/uapi, and the usage of the new defines. > + Split out the permissive functionality into another separate patch, > for easier review. > + Correct misuse of audit_log_n_untrusted string to audit_log_format > + Use get_task_comm instead of comm directly. > + Quote certain audit values > + Remove unnecessary help text on choice options - these were > previously > idented at the wrong level > + Correct a stale string constant (ctx_ns_enforce to ctx_enforce) > > v8: > > + Change dependency for CONFIG_AUDIT to CONFIG_AUDITSYSCALL > + Drop ctx_* prefix > + Reuse, where appropriate, the audit fields from the field > dictionary. This transforms: > ctx_pathname -> path > ctx_ino -> ino > ctx_dev -> dev > > + Add audit records and event examples to commit description. > + Remove new_audit_ctx, replace with audit_log_start. All data that > would provided by new_audit_ctx is already present in the syscall > audit record, that is always emitted on these actions. The audit > records should be correlated as such. > + Change audit types: > + AUDIT_TRUST_RESULT -> AUDIT_IPE_ACCESS > + This prevents overloading of the AVC type. > + AUDIT_TRUST_POLICY_ACTIVATE -> AUDIT_MAC_CONFIG_CHANGE > + AUDIT_TRUST_POLICY_LOAD -> AUDIT_MAC_POLICY_LOAD > + There were no significant difference in meaning between > these types. > > + Remove enforcing parameter passed from the context structure > for AUDIT_IPE_ACCESS. > + This field can be inferred from the SYSCALL audit event, > based on the success field. > > + Remove all fields already captured in the syscall record. "hook", > an IPE specific field, can be determined via the syscall field in > the syscall record itself, so it has been removed. > + ino, path, and dev in IPE's record refer to the subject of the > syscall, while the syscall record refers to the calling process. > > + remove IPE prefix from policy load/policy activation events > + fix a bug wherein a policy change audit record was not fired when > updating a policy > > v9: > + Merge the AUDIT_IPE_ACCESS definition with the audit support commit > + Change the audit format of policy load and switch > + Remove the ipe audit kernel switch > > v10: > + Create AUDIT_IPE_CONFIG_CHANGE and AUDIT_IPE_POLICY_LOAD > + Change field names per upstream feedback > > v11: > + Fix style issues > --- > include/uapi/linux/audit.h | 3 + > security/ipe/Kconfig | 2 +- > security/ipe/Makefile | 1 + > security/ipe/audit.c | 195 +++++++++++++++++++++++++++++++++++++ > security/ipe/audit.h | 18 ++++ > security/ipe/eval.c | 32 ++++-- > security/ipe/eval.h | 8 ++ > security/ipe/fs.c | 70 +++++++++++++ > security/ipe/policy.c | 5 + > 9 files changed, 327 insertions(+), 7 deletions(-) > create mode 100644 security/ipe/audit.c > create mode 100644 security/ipe/audit.h ... > diff --git a/security/ipe/audit.c b/security/ipe/audit.c > new file mode 100644 > index 000000000000..e123701d5e3b > --- /dev/null > +++ b/security/ipe/audit.c > @@ -0,0 +1,195 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) Microsoft Corporation. All rights reserved. > + */ > + > +#include <linux/slab.h> > +#include <linux/audit.h> > +#include <linux/types.h> > +#include <crypto/hash.h> > + > +#include "ipe.h" > +#include "eval.h" > +#include "hooks.h" > +#include "policy.h" > +#include "audit.h" > + > +#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY") > + > +#define IPE_AUDIT_HASH_ALG "sha256" > + > +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\ > + "policy_digest=" IPE_AUDIT_HASH_ALG ":" > +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\ > + "old_active_pol_version=%hu.%hu.%hu "\ > + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":" > +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\ > + "new_active_pol_version=%hu.%hu.%hu "\ > + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":" > + > +static const char *const audit_op_names[__IPE_OP_MAX] = { > + "EXECUTE", > + "FIRMWARE", > + "KMODULE", > + "KEXEC_IMAGE", > + "KEXEC_INITRAMFS", > + "IMA_POLICY", > + "IMA_X509_CERT", > +}; > + > +static const char *const audit_prop_names[__IPE_PROP_MAX] = { > + "boot_verified=FALSE", > + "boot_verified=TRUE", > +}; I would suggest taking the same approach for both @audit_op_names and @audit_prop_names; either include the field name in the string array for both or leave it out of both. > +/** > + * audit_rule - audit an IPE policy rule approximation. > + * @ab: Supplies a pointer to the audit_buffer to append to. > + * @r: Supplies a pointer to the ipe_rule to approximate a string form for. > + */ > +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r) > +{ > + const struct ipe_prop *ptr; > + > + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]); > + > + list_for_each_entry(ptr, &r->props, next) > + audit_log_format(ab, "%s ", audit_prop_names[ptr->type]); > + > + audit_log_format(ab, "action=%s\"", ACTSTR(r->action)); > +} > + > +/** > + * ipe_audit_match - audit a match for IPE policy. > + * @ctx: Supplies a pointer to the evaluation context that was used in the > + * evaluation. > + * @match_type: Supplies the scope of the match: rule, operation default, > + * global default. > + * @act: Supplies the IPE's evaluation decision, deny or allow. > + * @r: Supplies a pointer to the rule that was matched, if possible. > + * @enforce: Supplies the enforcement/permissive state at the point > + * the enforcement decision was made. > + */ Does it make sense to move @match_type into the ipe_eval_ctx struct? > +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, > + enum ipe_match match_type, > + enum ipe_action_type act, const struct ipe_rule *const r) > +{ > + struct inode *inode; > + struct audit_buffer *ab; > + const char *op = audit_op_names[ctx->op]; > + > + if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit)) > + return; > + > + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS); > + if (!ab) > + return; > + > + if (ctx->file) { > + audit_log_d_path(ab, "path=", &ctx->file->f_path); > + inode = file_inode(ctx->file); > + if (inode) { > + audit_log_format(ab, " dev="); > + audit_log_untrustedstring(ab, inode->i_sb->s_id); > + audit_log_format(ab, " ino=%lu ", inode->i_ino); > + } > + } > + > + if (match_type == IPE_MATCH_RULE) > + audit_rule(ab, r); > + else if (match_type == IPE_MATCH_TABLE) > + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op, > + ACTSTR(act)); > + else > + audit_log_format(ab, "rule=\"DEFAULT action=%s\"", > + ACTSTR(act)); > + > + audit_log_end(ab); > +} -- paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote: > On Oct 4, 2023 Fan Wu <wufan@linux.microsoft.com> wrote: >> >> Users of IPE require a way to identify when and why an operation fails, >> allowing them to both respond to violations of policy and be notified >> of potentially malicious actions on their systems with respect to IPE >> itself. >> >> This patch introduces 3 new audit events. >> >> AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation >> of a resource. >> AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy >> has been changed to another loaded policy. >> AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded >> into the kernel. >> >> This patch also adds support for success auditing, allowing users to >> identify why an allow decision was made for a resource. However, it is >> recommended to use this option with caution, as it is quite noisy. >> >> Here are some examples of the new audit record types: >> >> AUDIT_IPE_ACCESS(1420): >> >> audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda" >> ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW" >> >> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0" >> ino=2 rule="DEFAULT action=DENY" >> >> audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs" >> ino=131 rule="DEFAULT action=DENY" >> >> The above three records were generated when the active IPE policy only >> allows binaries from the initial booted drive(sda) to run. The three >> identical `hello` binary were placed at different locations, only the >> first hello from sda was allowed. >> >> Field path followed by the file's path name. >> >> Field dev followed by the device name as found in /dev where the file is >> from. >> Note that for device mappers it will use the name `dm-X` instead of >> the name in /dev/mapper. >> For a file in a temp file system, which is not from a device, it will use >> `tmpfs` for the field. >> The implementation of this part is following another existing use case >> LSM_AUDIT_DATA_INODE in security/lsm_audit.c >> >> Field ino followed by the file's inode number. >> >> Field rule followed by the IPE rule made the access decision. The whole >> rule must be audited because the decision is based on the combination of >> all property conditions in the rule. >> >> Along with the syscall audit event, user can know why a blocked >> happened. For example: >> >> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0" >> ino=2 rule="DEFAULT action=DENY" >> audit[1956]: SYSCALL arch=c000003e syscall=59 >> success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0 >> a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 auid=4294967295 uid=0 >> gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 >> ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null) >> >> The above two records showed bash used execve to run "hello" and got >> blocked by IPE. Note that the IPE records are always prior to a SYSCALL >> record. >> >> AUDIT_IPE_CONFIG_CHANGE(1421): >> >> audit: AUDIT1421 >> old_active_pol_name="Allow_All" old_active_pol_version=0.0.0 >> old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649 >> new_active_pol_name="boot_verified" new_active_pol_version=0.0.0 >> new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F >> auid=4294967295 ses=4294967295 lsm=ipe res=1 >> >> The above record showed the current IPE active policy switch from >> `Allow_All` to `boot_verified` along with the version and the hash >> digest of the two policies. Note IPE can only have one policy active >> at a time, all access decision evaluation is based on the current active >> policy. >> The normal procedure to deploy a policy is loading the policy to deploy >> into the kernel first, then switch the active policy to it. >> >> AUDIT_IPE_POLICY_LOAD(1422): >> >> audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0 >> policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD >> auid=4294967295 ses=4294967295 lsm=ipe res=1 >> >> The above record showed a new policy has been loaded into the kernel >> with the policy name, policy version and policy hash. >> >> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> >> Signed-off-by: Fan Wu <wufan@linux.microsoft.com> ... >> --- >> include/uapi/linux/audit.h | 3 + >> security/ipe/Kconfig | 2 +- >> security/ipe/Makefile | 1 + >> security/ipe/audit.c | 195 +++++++++++++++++++++++++++++++++++++ >> security/ipe/audit.h | 18 ++++ >> security/ipe/eval.c | 32 ++++-- >> security/ipe/eval.h | 8 ++ >> security/ipe/fs.c | 70 +++++++++++++ >> security/ipe/policy.c | 5 + >> 9 files changed, 327 insertions(+), 7 deletions(-) >> create mode 100644 security/ipe/audit.c >> create mode 100644 security/ipe/audit.h > > ... > >> diff --git a/security/ipe/audit.c b/security/ipe/audit.c >> new file mode 100644 >> index 000000000000..e123701d5e3b >> --- /dev/null >> +++ b/security/ipe/audit.c >> @@ -0,0 +1,195 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (C) Microsoft Corporation. All rights reserved. >> + */ >> + >> +#include <linux/slab.h> >> +#include <linux/audit.h> >> +#include <linux/types.h> >> +#include <crypto/hash.h> >> + >> +#include "ipe.h" >> +#include "eval.h" >> +#include "hooks.h" >> +#include "policy.h" >> +#include "audit.h" >> + >> +#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY") >> + >> +#define IPE_AUDIT_HASH_ALG "sha256" >> + >> +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\ >> + "policy_digest=" IPE_AUDIT_HASH_ALG ":" >> +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\ >> + "old_active_pol_version=%hu.%hu.%hu "\ >> + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":" >> +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\ >> + "new_active_pol_version=%hu.%hu.%hu "\ >> + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":" >> + >> +static const char *const audit_op_names[__IPE_OP_MAX] = { >> + "EXECUTE", >> + "FIRMWARE", >> + "KMODULE", >> + "KEXEC_IMAGE", >> + "KEXEC_INITRAMFS", >> + "IMA_POLICY", >> + "IMA_X509_CERT", >> +}; >> + >> +static const char *const audit_prop_names[__IPE_PROP_MAX] = { >> + "boot_verified=FALSE", >> + "boot_verified=TRUE", >> +}; > > I would suggest taking the same approach for both @audit_op_names and > @audit_prop_names; either include the field name in the string array > for both or leave it out of both. > Yes sure, I will move the "op=" into audit_op_names. >> +/** >> + * audit_rule - audit an IPE policy rule approximation. >> + * @ab: Supplies a pointer to the audit_buffer to append to. >> + * @r: Supplies a pointer to the ipe_rule to approximate a string form for. >> + */ >> +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r) >> +{ >> + const struct ipe_prop *ptr; >> + >> + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]); >> + >> + list_for_each_entry(ptr, &r->props, next) >> + audit_log_format(ab, "%s ", audit_prop_names[ptr->type]); >> + >> + audit_log_format(ab, "action=%s\"", ACTSTR(r->action)); >> +} >> + >> +/** >> + * ipe_audit_match - audit a match for IPE policy. >> + * @ctx: Supplies a pointer to the evaluation context that was used in the >> + * evaluation. >> + * @match_type: Supplies the scope of the match: rule, operation default, >> + * global default. >> + * @act: Supplies the IPE's evaluation decision, deny or allow. >> + * @r: Supplies a pointer to the rule that was matched, if possible. >> + * @enforce: Supplies the enforcement/permissive state at the point >> + * the enforcement decision was made. >> + */ > > Does it make sense to move @match_type into the ipe_eval_ctx struct? > I feel the @match_type is part of the evaluation result information, which is the result of the context against the active policy. So I prefer keeping it as a local variable in the evaluation loop. -Fan >> +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, >> + enum ipe_match match_type, >> + enum ipe_action_type act, const struct ipe_rule *const r) >> +{ >> + struct inode *inode; >> + struct audit_buffer *ab; >> + const char *op = audit_op_names[ctx->op]; >> + >> + if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit)) >> + return; >> + >> + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS); >> + if (!ab) >> + return; >> + >> + if (ctx->file) { >> + audit_log_d_path(ab, "path=", &ctx->file->f_path); >> + inode = file_inode(ctx->file); >> + if (inode) { >> + audit_log_format(ab, " dev="); >> + audit_log_untrustedstring(ab, inode->i_sb->s_id); >> + audit_log_format(ab, " ino=%lu ", inode->i_ino); >> + } >> + } >> + >> + if (match_type == IPE_MATCH_RULE) >> + audit_rule(ab, r); >> + else if (match_type == IPE_MATCH_TABLE) >> + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op, >> + ACTSTR(act)); >> + else >> + audit_log_format(ab, "rule=\"DEFAULT action=%s\"", >> + ACTSTR(act)); >> + >> + audit_log_end(ab); >> +} > > -- > paul-moore.com
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h index d676ed2b246e..75e21a135483 100644 --- a/include/uapi/linux/audit.h +++ b/include/uapi/linux/audit.h @@ -143,6 +143,9 @@ #define AUDIT_MAC_UNLBL_STCDEL 1417 /* NetLabel: del a static label */ #define AUDIT_MAC_CALIPSO_ADD 1418 /* NetLabel: add CALIPSO DOI entry */ #define AUDIT_MAC_CALIPSO_DEL 1419 /* NetLabel: del CALIPSO DOI entry */ +#define AUDIT_IPE_ACCESS 1420 /* IPE denial or grant */ +#define AUDIT_IPE_CONFIG_CHANGE 1421 /* IPE config change */ +#define AUDIT_IPE_POLICY_LOAD 1422 /* IPE policy load */ #define AUDIT_FIRST_KERN_ANOM_MSG 1700 #define AUDIT_LAST_KERN_ANOM_MSG 1799 diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig index e4875fb04883..ac4d558e69d5 100644 --- a/security/ipe/Kconfig +++ b/security/ipe/Kconfig @@ -5,7 +5,7 @@ menuconfig SECURITY_IPE bool "Integrity Policy Enforcement (IPE)" - depends on SECURITY && SECURITYFS + depends on SECURITY && SECURITYFS && AUDIT && AUDITSYSCALL select PKCS7_MESSAGE_PARSER select SYSTEM_DATA_VERIFICATION help diff --git a/security/ipe/Makefile b/security/ipe/Makefile index cfbed03a8885..2279eaa3cea3 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -13,3 +13,4 @@ obj-$(CONFIG_SECURITY_IPE) += \ policy.o \ policy_fs.o \ policy_parser.o \ + audit.o \ diff --git a/security/ipe/audit.c b/security/ipe/audit.c new file mode 100644 index 000000000000..e123701d5e3b --- /dev/null +++ b/security/ipe/audit.c @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include <linux/slab.h> +#include <linux/audit.h> +#include <linux/types.h> +#include <crypto/hash.h> + +#include "ipe.h" +#include "eval.h" +#include "hooks.h" +#include "policy.h" +#include "audit.h" + +#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY") + +#define IPE_AUDIT_HASH_ALG "sha256" + +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\ + "policy_digest=" IPE_AUDIT_HASH_ALG ":" +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\ + "old_active_pol_version=%hu.%hu.%hu "\ + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":" +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\ + "new_active_pol_version=%hu.%hu.%hu "\ + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":" + +static const char *const audit_op_names[__IPE_OP_MAX] = { + "EXECUTE", + "FIRMWARE", + "KMODULE", + "KEXEC_IMAGE", + "KEXEC_INITRAMFS", + "IMA_POLICY", + "IMA_X509_CERT", +}; + +static const char *const audit_prop_names[__IPE_PROP_MAX] = { + "boot_verified=FALSE", + "boot_verified=TRUE", +}; + +/** + * audit_rule - audit an IPE policy rule approximation. + * @ab: Supplies a pointer to the audit_buffer to append to. + * @r: Supplies a pointer to the ipe_rule to approximate a string form for. + */ +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r) +{ + const struct ipe_prop *ptr; + + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]); + + list_for_each_entry(ptr, &r->props, next) + audit_log_format(ab, "%s ", audit_prop_names[ptr->type]); + + audit_log_format(ab, "action=%s\"", ACTSTR(r->action)); +} + +/** + * ipe_audit_match - audit a match for IPE policy. + * @ctx: Supplies a pointer to the evaluation context that was used in the + * evaluation. + * @match_type: Supplies the scope of the match: rule, operation default, + * global default. + * @act: Supplies the IPE's evaluation decision, deny or allow. + * @r: Supplies a pointer to the rule that was matched, if possible. + * @enforce: Supplies the enforcement/permissive state at the point + * the enforcement decision was made. + */ +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action_type act, const struct ipe_rule *const r) +{ + struct inode *inode; + struct audit_buffer *ab; + const char *op = audit_op_names[ctx->op]; + + if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit)) + return; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS); + if (!ab) + return; + + if (ctx->file) { + audit_log_d_path(ab, "path=", &ctx->file->f_path); + inode = file_inode(ctx->file); + if (inode) { + audit_log_format(ab, " dev="); + audit_log_untrustedstring(ab, inode->i_sb->s_id); + audit_log_format(ab, " ino=%lu ", inode->i_ino); + } + } + + if (match_type == IPE_MATCH_RULE) + audit_rule(ab, r); + else if (match_type == IPE_MATCH_TABLE) + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op, + ACTSTR(act)); + else + audit_log_format(ab, "rule=\"DEFAULT action=%s\"", + ACTSTR(act)); + + audit_log_end(ab); +} + +/** + * audit_policy - Audit a policy's name, version and thumbprint to @ab. + * @ab: Supplies a pointer to the audit buffer to append to. + * @p: Supplies a pointer to the policy to audit. + */ +static void audit_policy(struct audit_buffer *ab, + const char *audit_format, + const struct ipe_policy *const p) +{ + u8 *digest = NULL; + struct crypto_shash *tfm; + SHASH_DESC_ON_STACK(desc, tfm); + + tfm = crypto_alloc_shash(IPE_AUDIT_HASH_ALG, 0, 0); + if (IS_ERR(tfm)) + return; + + desc->tfm = tfm; + + digest = kzalloc(crypto_shash_digestsize(tfm), GFP_KERNEL); + if (!digest) + goto out; + + if (crypto_shash_init(desc)) + goto out; + + if (crypto_shash_update(desc, p->pkcs7, p->pkcs7len)) + goto out; + + if (crypto_shash_final(desc, digest)) + goto out; + + audit_log_format(ab, audit_format, p->parsed->name, + p->parsed->version.major, p->parsed->version.minor, + p->parsed->version.rev); + audit_log_n_hex(ab, digest, crypto_shash_digestsize(tfm)); + +out: + kfree(digest); + crypto_free_shash(tfm); +} + +/** + * ipe_audit_policy_activation - Audit a policy being made the active policy. + * @p: Supplies a pointer to the policy to audit. + */ +void ipe_audit_policy_activation(const struct ipe_policy *const op, + const struct ipe_policy *const np) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, + AUDIT_IPE_CONFIG_CHANGE); + if (!ab) + return; + + audit_policy(ab, AUDIT_OLD_ACTIVE_POLICY_FMT, op); + audit_log_format(ab, " "); + audit_policy(ab, AUDIT_NEW_ACTIVE_POLICY_FMT, np); + audit_log_format(ab, " auid=%u ses=%u lsm=ipe res=1", + from_kuid(&init_user_ns, audit_get_loginuid(current)), + audit_get_sessionid(current)); + + audit_log_end(ab); +} + +/** + * ipe_audit_policy_load - Audit a policy being loaded into the kernel. + * @p: Supplies a pointer to the policy to audit. + */ +void ipe_audit_policy_load(const struct ipe_policy *const p) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, + AUDIT_IPE_POLICY_LOAD); + if (!ab) + return; + + audit_policy(ab, AUDIT_POLICY_LOAD_FMT, p); + audit_log_format(ab, " auid=%u ses=%u lsm=ipe res=1", + from_kuid(&init_user_ns, audit_get_loginuid(current)), + audit_get_sessionid(current)); + + audit_log_end(ab); +} diff --git a/security/ipe/audit.h b/security/ipe/audit.h new file mode 100644 index 000000000000..0ff5a06808de --- /dev/null +++ b/security/ipe/audit.h @@ -0,0 +1,18 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef _IPE_AUDIT_H +#define _IPE_AUDIT_H + +#include "policy.h" + +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action_type act, const struct ipe_rule *const r); +void ipe_audit_policy_load(const struct ipe_policy *const p); +void ipe_audit_policy_activation(const struct ipe_policy *const op, + const struct ipe_policy *const np); + +#endif /* _IPE_AUDIT_H */ diff --git a/security/ipe/eval.c b/security/ipe/eval.c index bdac4abc0ddb..499b6b3338f2 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -10,12 +10,15 @@ #include <linux/sched.h> #include <linux/rcupdate.h> #include <linux/spinlock.h> +#include <linux/moduleparam.h> #include "ipe.h" #include "eval.h" #include "policy.h" +#include "audit.h" struct ipe_policy __rcu *ipe_active_policy; +bool success_audit; static const struct super_block *pinned_sb; static DEFINE_SPINLOCK(pin_lock); @@ -112,6 +115,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) { bool match = false; enum ipe_action_type action; + enum ipe_match match_type; struct ipe_policy *pol = NULL; const struct ipe_rule *rule = NULL; const struct ipe_op_table *rules = NULL; @@ -127,9 +131,9 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) if (ctx->op == IPE_OP_INVALID) { rcu_read_unlock(); - if (pol->parsed->global_default_action == IPE_ACTION_DENY) - return -EACCES; - return 0; + action = pol->parsed->global_default_action; + match_type = IPE_MATCH_GLOBAL; + goto eval; } rules = &pol->parsed->rules[ctx->op]; @@ -147,14 +151,21 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) break; } - if (match) + if (match) { action = rule->action; - else if (rules->default_action != IPE_ACTION_INVALID) + match_type = IPE_MATCH_RULE; + } else if (rules->default_action != IPE_ACTION_INVALID) { action = rules->default_action; - else + match_type = IPE_MATCH_TABLE; + } else { action = pol->parsed->global_default_action; + match_type = IPE_MATCH_GLOBAL; + } rcu_read_unlock(); +eval: + ipe_audit_match(ctx, match_type, action, rule); + if (action == IPE_ACTION_DENY) return -EACCES; @@ -178,3 +189,12 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb) spin_unlock(&pin_lock); } + +/* Set the right module name */ +#ifdef KBUILD_MODNAME +#undef KBUILD_MODNAME +#define KBUILD_MODNAME "ipe" +#endif + +module_param(success_audit, bool, 0400); +MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled"); diff --git a/security/ipe/eval.h b/security/ipe/eval.h index 9769da42c65f..5473f712566c 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -14,6 +14,7 @@ #define IPE_EVAL_CTX_INIT ((struct ipe_eval_ctx){ 0 }) extern struct ipe_policy __rcu *ipe_active_policy; +extern bool success_audit; struct ipe_eval_ctx { enum ipe_op_type op; @@ -22,6 +23,13 @@ struct ipe_eval_ctx { bool from_init_sb; }; +enum ipe_match { + IPE_MATCH_RULE = 0, + IPE_MATCH_TABLE, + IPE_MATCH_GLOBAL, + __IPE_MATCH_MAX +}; + void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op); int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx); void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb); diff --git a/security/ipe/fs.c b/security/ipe/fs.c index 522162af741a..dda7a5afc60c 100644 --- a/security/ipe/fs.c +++ b/security/ipe/fs.c @@ -8,11 +8,64 @@ #include "ipe.h" #include "fs.h" +#include "eval.h" #include "policy.h" +#include "audit.h" static struct dentry *np __ro_after_init; static struct dentry *root __ro_after_init; struct dentry *policy_root __ro_after_init; +static struct dentry *audit_node __ro_after_init; + +/** + * setaudit - Write handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall. + * @len: Supplies the length of @data. + * @offset: unused. + * + * Return: + * * >0 - Success, Length of buffer written + * * <0 - Error + */ +static ssize_t setaudit(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + bool value; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + rc = kstrtobool_from_user(data, len, &value); + if (rc) + return rc; + + WRITE_ONCE(success_audit, value); + + return len; +} + +/** + * getaudit - Read handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the read syscall. + * @len: Supplies the length of @data. + * @offset: unused. + * + * Return: + * * >0 - Success, Length of buffer written + * * <0 - Error + */ +static ssize_t getaudit(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + const char *result; + + result = ((READ_ONCE(success_audit)) ? "1" : "0"); + + return simple_read_from_buffer(data, len, offset, result, 1); +} /** * new_policy - Write handler for the securityfs node, "ipe/new_policy". @@ -46,6 +99,10 @@ static ssize_t new_policy(struct file *f, const char __user *data, } rc = ipe_new_policyfs_node(p); + if (rc) + goto out; + + ipe_audit_policy_load(p); out: if (rc < 0 && !IS_ERR(p)) @@ -58,6 +115,11 @@ static const struct file_operations np_fops = { .write = new_policy, }; +static const struct file_operations audit_fops = { + .write = setaudit, + .read = getaudit, +}; + /** * ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit. * @@ -78,6 +140,13 @@ static int __init ipe_init_securityfs(void) goto err; } + audit_node = securityfs_create_file("success_audit", 0600, root, + NULL, &audit_fops); + if (IS_ERR(audit_node)) { + rc = PTR_ERR(audit_node); + goto err; + } + policy_root = securityfs_create_dir("policies", root); if (IS_ERR(policy_root)) { rc = PTR_ERR(policy_root); @@ -94,6 +163,7 @@ static int __init ipe_init_securityfs(void) err: securityfs_remove(np); securityfs_remove(policy_root); + securityfs_remove(audit_node); securityfs_remove(root); return rc; } diff --git a/security/ipe/policy.c b/security/ipe/policy.c index 33bbc43f0d6f..7a0729246bbd 100644 --- a/security/ipe/policy.c +++ b/security/ipe/policy.c @@ -11,6 +11,7 @@ #include "fs.h" #include "policy.h" #include "policy_parser.h" +#include "audit.h" /* lock for synchronizing writers across ipe policy */ DEFINE_MUTEX(ipe_policy_lock); @@ -124,6 +125,8 @@ struct ipe_policy *ipe_update_policy(struct inode *root, swap(new->policyfs, old->policyfs); + ipe_audit_policy_load(new); + return old; err: ipe_free_policy(new); @@ -209,5 +212,7 @@ int ipe_set_active_pol(const struct ipe_policy *p) rcu_assign_pointer(ipe_active_policy, p); + ipe_audit_policy_activation(ap, p); + return 0; }