From: Deven Bowers <deven.desai@linux.microsoft.com>

IPE's interpretation of the what the user trusts is accomplished through
its policy. IPE's design is to not provide support for a single trust
provider, but to support multiple providers to enable the end-user to
choose the best one to seek their needs.

This requires the policy to be rather flexible and modular so that
integrity providers, like fs-verity, dm-verity, dm-integrity, or
some other system, can plug into the policy with minimal code changes.

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 policy load and activation audit event to 03/12
  + Fix a potential panic when a policy failed to load.
  + use pr_warn for a failure to parse instead of an
    audit record
  + Remove comments from headers
  + Add lockdep assertions to ipe_update_active_policy and
    ipe_activate_policy
  + Fix up warnings with checkpatch --strict
  + Use file_ns_capable for CAP_MAC_ADMIN for securityfs
    nodes.
  + Use memdup_user instead of kzalloc+simple_write_to_buffer.
  + Remove strict_parse command line parameter, as it is added
    by the sysctl command line.
  + Prefix extern variables with ipe_

v4:
  + Remove securityfs to reverse-dependency
  + Add SHA1 reverse dependency.
  + Add versioning scheme for IPE properties, and associated
    interface to query the versioning scheme.
  + Cause a parser to always return an error on unknown syntax.
  + Remove strict_parse option
  + Change active_policy interface from sysctl, to securityfs,
    and change scheme.

v5:
  + Cause an error if a default action is not defined for each
    operation.
  + Minor function renames

v6:
  + No changes

v7:
  + Further split parser and userspace interface into two
    separate commits, for easier review.
  + Refactor policy parser to make code cleaner via introducing a
    more modular design, for easier extension of policy, and
    easier review.

v8:
  + remove unnecessary pr_info emission on parser loading
  + add explicit newline to the pr_err emitted when a parser
    fails to load.

v9:
  + switch to match table to parse policy
  + remove quote syntax and KERNEL_READ operation

v10:
  + Fix memory leaks in parser
  + Fix typos and change code styles
---
 security/ipe/Makefile        |   2 +
 security/ipe/policy.c        |  97 +++++++
 security/ipe/policy.h        |  83 ++++++
 security/ipe/policy_parser.c | 488 +++++++++++++++++++++++++++++++++++
 security/ipe/policy_parser.h |  11 +
 5 files changed, 681 insertions(+)
 create mode 100644 security/ipe/policy.c
 create mode 100644 security/ipe/policy.h
 create mode 100644 security/ipe/policy_parser.c
 create mode 100644 security/ipe/policy_parser.h

diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 571648579991..16bbe80991f1 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -8,3 +8,5 @@
 obj-$(CONFIG_SECURITY_IPE) += \
 	hooks.o \
 	ipe.o \
+	policy.o \
+	policy_parser.o \
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
new file mode 100644
index 000000000000..4069ff075093
--- /dev/null
+++ b/security/ipe/policy.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/errno.h>
+#include <linux/verification.h>
+
+#include "ipe.h"
+#include "policy.h"
+#include "policy_parser.h"
+
+/**
+ * ipe_free_policy - Deallocate a given IPE policy.
+ * @p: Supplies the policy to free.
+ *
+ * Safe to call on IS_ERR/NULL.
+ */
+void ipe_free_policy(struct ipe_policy *p)
+{
+	if (IS_ERR_OR_NULL(p))
+		return;
+
+	free_parsed_policy(p->parsed);
+	if (!p->pkcs7)
+		kfree(p->text);
+	kfree(p->pkcs7);
+	kfree(p);
+}
+
+static int set_pkcs7_data(void *ctx, const void *data, size_t len,
+			  size_t asn1hdrlen)
+{
+	struct ipe_policy *p = ctx;
+
+	p->text = (const char *)data;
+	p->textlen = len;
+
+	return 0;
+}
+
+/**
+ * ipe_new_policy - Allocate and parse an ipe_policy structure.
+ *
+ * @text: Supplies a pointer to the plain-text policy to parse.
+ * @textlen: Supplies the length of @text.
+ * @pkcs7: Supplies a pointer to a pkcs7-signed IPE policy.
+ * @pkcs7len: Supplies the length of @pkcs7.
+ *
+ * @text/@textlen Should be NULL/0 if @pkcs7/@pkcs7len is set.
+ *
+ * Return:
+ * * !IS_ERR	- Success
+ * * -EBADMSG	- Policy is invalid
+ * * -ENOMEM	- Out of memory
+ */
+struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
+				  const char *pkcs7, size_t pkcs7len)
+{
+	int rc = 0;
+	struct ipe_policy *new = NULL;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (!new)
+		return ERR_PTR(-ENOMEM);
+
+	if (!text) {
+		new->pkcs7len = pkcs7len;
+		new->pkcs7 = kmemdup(pkcs7, pkcs7len, GFP_KERNEL);
+		if (!new->pkcs7) {
+			rc = -ENOMEM;
+			goto err;
+		}
+
+		rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL,
+					    VERIFYING_UNSPECIFIED_SIGNATURE,
+					    set_pkcs7_data, new);
+		if (rc)
+			goto err;
+	} else {
+		new->textlen = textlen;
+		new->text = kstrdup(text, GFP_KERNEL);
+		if (!new->text) {
+			rc = -ENOMEM;
+			goto err;
+		}
+	}
+
+	rc = parse_policy(new);
+	if (rc)
+		goto err;
+
+	return new;
+err:
+	ipe_free_policy(new);
+	return ERR_PTR(rc);
+}
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
new file mode 100644
index 000000000000..113a037f0d71
--- /dev/null
+++ b/security/ipe/policy.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_POLICY_H
+#define _IPE_POLICY_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+
+enum ipe_op_type {
+	__IPE_OP_EXEC = 0,
+	__IPE_OP_FIRMWARE,
+	__IPE_OP_KERNEL_MODULE,
+	__IPE_OP_KEXEC_IMAGE,
+	__IPE_OP_KEXEC_INITRAMFS,
+	__IPE_OP_IMA_POLICY,
+	__IPE_OP_IMA_X509,
+	__IPE_OP_MAX
+};
+
+#define __IPE_OP_INVALID __IPE_OP_MAX
+
+enum ipe_action_type {
+	__IPE_ACTION_ALLOW = 0,
+	__IPE_ACTION_DENY,
+	__IPE_ACTION_MAX
+};
+
+#define __IPE_ACTION_INVALID __IPE_ACTION_MAX
+
+enum ipe_prop_type {
+	__IPE_PROP_MAX
+};
+
+#define __IPE_PROP_INVALID __IPE_PROP_MAX
+
+struct ipe_prop {
+	struct list_head next;
+	enum ipe_prop_type type;
+	void *value;
+};
+
+struct ipe_rule {
+	enum ipe_op_type op;
+	enum ipe_action_type action;
+	struct list_head props;
+	struct list_head next;
+};
+
+struct ipe_op_table {
+	struct list_head rules;
+	enum ipe_action_type default_action;
+};
+
+struct ipe_parsed_policy {
+	const char *name;
+	struct {
+		u16 major;
+		u16 minor;
+		u16 rev;
+	} version;
+
+	enum ipe_action_type global_default_action;
+
+	struct ipe_op_table rules[__IPE_OP_MAX];
+};
+
+struct ipe_policy {
+	const char *pkcs7;
+	size_t pkcs7len;
+
+	const char *text;
+	size_t textlen;
+
+	struct ipe_parsed_policy *parsed;
+};
+
+struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
+				  const char *pkcs7, size_t pkcs7len);
+void ipe_free_policy(struct ipe_policy *pol);
+
+#endif /* _IPE_POLICY_H */
diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
new file mode 100644
index 000000000000..27e5767480b0
--- /dev/null
+++ b/security/ipe/policy_parser.c
@@ -0,0 +1,488 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/types.h>
+#include <linux/parser.h>
+
+#include "policy.h"
+#include "policy_parser.h"
+
+#define START_COMMENT	'#'
+
+/**
+ * new_parsed_policy - Allocate and initialize a parsed policy.
+ *
+ * Return:
+ * * !IS_ERR	- OK
+ * * -ENOMEM	- Out of memory
+ */
+static struct ipe_parsed_policy *new_parsed_policy(void)
+{
+	size_t i = 0;
+	struct ipe_parsed_policy *p = NULL;
+	struct ipe_op_table *t = NULL;
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return ERR_PTR(-ENOMEM);
+
+	p->global_default_action = __IPE_ACTION_INVALID;
+
+	for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
+		t = &p->rules[i];
+
+		t->default_action = __IPE_ACTION_INVALID;
+		INIT_LIST_HEAD(&t->rules);
+	}
+
+	return p;
+}
+
+/**
+ * remove_comment - Truncate all chars following START_COMMENT in a string.
+ *
+ * @line: Supplies a poilcy line string for preprocessing.
+ */
+static void remove_comment(char *line)
+{
+	line = strchr(line, START_COMMENT);
+
+	if (line)
+		*line = '\0';
+}
+
+/**
+ * remove_trailing_spaces - Truncate all trailing spaces in a string.
+ *
+ * @line: Supplies a poilcy line string for preprocessing.
+ *
+ * Return: The length of truncated string.
+ */
+static size_t remove_trailing_spaces(char *line)
+{
+	size_t i = 0;
+
+	for (i = strlen(line); i > 0 && (line[i - 1] == ' ' || line[i - 1] == '\t'); --i)
+		;
+
+	line[i] = '\0';
+
+	return i;
+}
+
+/**
+ * parse_version - Parse policy version.
+ * @ver: Supplies a version string to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * 0	- OK
+ * * !0	- Standard errno
+ */
+static int parse_version(char *ver, struct ipe_parsed_policy *p)
+{
+	int rc = 0;
+	size_t sep_count = 0;
+	char *token;
+	u16 *const cv[] = { &p->version.major, &p->version.minor, &p->version.rev };
+
+	while ((token = strsep(&ver, ".")) != NULL) {
+		/* prevent overflow */
+		if (sep_count >= ARRAY_SIZE(cv))
+			return -EBADMSG;
+
+		rc = kstrtou16(token, 10, cv[sep_count]);
+		if (rc)
+			return rc;
+
+		++sep_count;
+	}
+
+	/* prevent underflow */
+	if (sep_count != ARRAY_SIZE(cv))
+		rc = -EBADMSG;
+
+	return rc;
+}
+
+enum header_opt {
+	__IPE_HEADER_POLICY_NAME = 0,
+	__IPE_HEADER_POLICY_VERSION,
+	__IPE_HEADER_MAX
+};
+
+static const match_table_t header_tokens = {
+	{__IPE_HEADER_POLICY_NAME,	"policy_name=%s"},
+	{__IPE_HEADER_POLICY_VERSION,	"policy_version=%s"},
+	{__IPE_HEADER_MAX,		NULL}
+};
+
+/**
+ * parse_header - Parse policy header information.
+ * @line: Supplies header line to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * 0	- OK
+ * * !0	- Standard errno
+ */
+static int parse_header(char *line, struct ipe_parsed_policy *p)
+{
+	int rc = 0;
+	char *t, *ver = NULL;
+	substring_t args[MAX_OPT_ARGS];
+	size_t idx = 0;
+
+	while ((t = strsep(&line, " \t")) != NULL) {
+		int token;
+
+		if (*t == '\0')
+			continue;
+		if (idx >= __IPE_HEADER_MAX) {
+			rc = -EBADMSG;
+			goto err;
+		}
+
+		token = match_token(t, header_tokens, args);
+		if (token != idx) {
+			rc = -EBADMSG;
+			goto err;
+		}
+
+		switch (token) {
+		case __IPE_HEADER_POLICY_NAME:
+			p->name = match_strdup(&args[0]);
+			if (!p->name)
+				rc = -ENOMEM;
+			break;
+		case __IPE_HEADER_POLICY_VERSION:
+			ver = match_strdup(&args[0]);
+			if (!ver) {
+				rc = -ENOMEM;
+				break;
+			}
+			rc = parse_version(ver, p);
+			break;
+		default:
+			rc = -EBADMSG;
+		}
+		if (rc)
+			goto err;
+		++idx;
+	}
+
+	if (idx != __IPE_HEADER_MAX) {
+		rc = -EBADMSG;
+		goto err;
+	}
+
+out:
+	kfree(ver);
+	return rc;
+err:
+	kfree(p->name);
+	p->name = NULL;
+	goto out;
+}
+
+/**
+ * token_default - Determine if the given token is "DEFAULT".
+ * @token: Supplies the token string to be compared.
+ *
+ * Return:
+ * * 0	- The token is not "DEFAULT"
+ * * !0	- The token is "DEFAULT"
+ */
+static bool token_default(char *token)
+{
+	return !strcmp(token, "DEFAULT");
+}
+
+/**
+ * free_rule - Free the supplied ipe_rule struct.
+ * @r: Supplies the ipe_rule struct to be freed.
+ *
+ * Free a ipe_rule struct @r. Note @r must be removed from any lists before
+ * calling this function.
+ */
+static void free_rule(struct ipe_rule *r)
+{
+	struct ipe_prop *p, *t;
+
+	if (IS_ERR_OR_NULL(r))
+		return;
+
+	list_for_each_entry_safe(p, t, &r->props, next) {
+		list_del(&p->next);
+		kfree(p);
+	}
+
+	kfree(r);
+}
+
+static const match_table_t operation_tokens = {
+	{__IPE_OP_EXEC,			"op=EXECUTE"},
+	{__IPE_OP_FIRMWARE,		"op=FIRMWARE"},
+	{__IPE_OP_KERNEL_MODULE,	"op=KMODULE"},
+	{__IPE_OP_KEXEC_IMAGE,		"op=KEXEC_IMAGE"},
+	{__IPE_OP_KEXEC_INITRAMFS,	"op=KEXEC_INITRAMFS"},
+	{__IPE_OP_IMA_POLICY,		"op=IMA_POLICY"},
+	{__IPE_OP_IMA_X509,		"op=IMA_X509_CERT"},
+	{__IPE_OP_INVALID,		NULL}
+};
+
+/**
+ * parse_operation - Parse the operation type given a token string.
+ * @t: Supplies the token string to be parsed.
+ *
+ * Return: The parsed operation type.
+ */
+static enum ipe_op_type parse_operation(char *t)
+{
+	substring_t args[MAX_OPT_ARGS];
+
+	return match_token(t, operation_tokens, args);
+}
+
+static const match_table_t action_tokens = {
+	{__IPE_ACTION_ALLOW,	"action=ALLOW"},
+	{__IPE_ACTION_DENY,	"action=DENY"},
+	{__IPE_ACTION_INVALID,	NULL}
+};
+
+/**
+ * parse_action - Parse the action type given a token string.
+ * @t: Supplies the token string to be parsed.
+ *
+ * Return: The parsed action type.
+ */
+static enum ipe_action_type parse_action(char *t)
+{
+	substring_t args[MAX_OPT_ARGS];
+
+	return match_token(t, action_tokens, args);
+}
+
+/**
+ * parse_property - Parse the property type given a token string.
+ * @t: Supplies the token string to be parsed.
+ * @r: Supplies the ipe_rule the parsed property will be associated with.
+ *
+ * Return:
+ * * !IS_ERR	- OK
+ * * -ENOMEM	- Out of memory
+ * * -EBADMSG	- The supplied token cannot be parsed
+ */
+static int parse_property(char *t, struct ipe_rule *r)
+{
+	return -EBADMSG;
+}
+
+/**
+ * parse_rule - parse a policy rule line.
+ * @line: Supplies rule line to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * !IS_ERR	- OK
+ * * -ENOMEM	- Out of memory
+ * * -EBADMSG	- Policy syntax error
+ */
+static int parse_rule(char *line, struct ipe_parsed_policy *p)
+{
+	int rc = 0;
+	bool first_token = true, is_default_rule = false;
+	bool op_parsed = false;
+	enum ipe_op_type op = __IPE_OP_INVALID;
+	enum ipe_action_type action = __IPE_ACTION_INVALID;
+	struct ipe_rule *r = NULL;
+	char *t;
+
+	r = kzalloc(sizeof(*r), GFP_KERNEL);
+	if (!r)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&r->next);
+	INIT_LIST_HEAD(&r->props);
+
+	while (t = strsep(&line, " \t"), line) {
+		if (*t == '\0')
+			continue;
+		if (first_token && token_default(t)) {
+			is_default_rule = true;
+		} else {
+			if (!op_parsed) {
+				op = parse_operation(t);
+				if (op == __IPE_OP_INVALID)
+					rc = -EBADMSG;
+				else
+					op_parsed = true;
+			} else {
+				rc = parse_property(t, r);
+			}
+		}
+
+		if (rc)
+			goto err;
+		first_token = false;
+	}
+
+	action = parse_action(t);
+	if (action == __IPE_ACTION_INVALID) {
+		rc = -EBADMSG;
+		goto err;
+	}
+
+	if (is_default_rule) {
+		if (!list_empty(&r->props)) {
+			rc = -EBADMSG;
+		} else if (op == __IPE_OP_INVALID) {
+			if (p->global_default_action != __IPE_ACTION_INVALID)
+				rc = -EBADMSG;
+			else
+				p->global_default_action = action;
+		} else {
+			if (p->rules[op].default_action != __IPE_ACTION_INVALID)
+				rc = -EBADMSG;
+			else
+				p->rules[op].default_action = action;
+		}
+	} else if (op != __IPE_OP_INVALID && action != __IPE_ACTION_INVALID) {
+		r->op = op;
+		r->action = action;
+	} else {
+		rc = -EBADMSG;
+	}
+
+	if (rc)
+		goto err;
+	if (!is_default_rule)
+		list_add_tail(&r->next, &p->rules[op].rules);
+	else
+		free_rule(r);
+
+out:
+	return rc;
+err:
+	free_rule(r);
+	goto out;
+}
+
+/**
+ * free_parsed_policy - free a parsed policy structure.
+ * @p: Supplies the parsed policy.
+ */
+void free_parsed_policy(struct ipe_parsed_policy *p)
+{
+	size_t i = 0;
+	struct ipe_rule *pp, *t;
+
+	if (IS_ERR_OR_NULL(p))
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(p->rules); ++i)
+		list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) {
+			list_del(&pp->next);
+			free_rule(pp);
+		}
+
+	kfree(p->name);
+	kfree(p);
+}
+
+/**
+ * validate_policy - validate a parsed policy.
+ * @p: Supplies the fully parsed policy.
+ *
+ * Given a policy structure that was just parsed, validate that all
+ * necessary fields are present, initialized correctly.
+ *
+ * A parsed policy can be in an invalid state for use (a default was
+ * undefined) by just parsing the policy.
+ *
+ * Return:
+ * * 0		- OK
+ * * -EBADMSG	- Policy is invalid
+ */
+static int validate_policy(const struct ipe_parsed_policy *p)
+{
+	int i = 0;
+
+	if (p->global_default_action != __IPE_ACTION_INVALID)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
+		if (p->rules[i].default_action == __IPE_ACTION_INVALID)
+			return -EBADMSG;
+	}
+
+	return 0;
+}
+
+/**
+ * parse_policy - Given a string, parse the string into an IPE policy.
+ * @p: partially filled ipe_policy structure to populate with the result.
+ *     it must have text and textlen set.
+ *
+ * Return:
+ * * 0		- OK
+ * * -EBADMSG	- Policy is invalid
+ * * -ENOMEM	- Out of Memory
+ */
+int parse_policy(struct ipe_policy *p)
+{
+	int rc = 0;
+	size_t len;
+	char *policy = NULL, *dup = NULL;
+	char *line = NULL;
+	bool header_parsed = false;
+	struct ipe_parsed_policy *pp = NULL;
+
+	if (!p->textlen)
+		return -EBADMSG;
+
+	policy = kmemdup_nul(p->text, p->textlen, GFP_KERNEL);
+	if (!policy)
+		return -ENOMEM;
+	dup = policy;
+
+	pp = new_parsed_policy();
+	if (IS_ERR(pp)) {
+		rc = PTR_ERR(pp);
+		goto out;
+	}
+
+	while ((line = strsep(&policy, "\n\r")) != NULL) {
+		remove_comment(line);
+		len = remove_trailing_spaces(line);
+		if (!len)
+			continue;
+
+		if (!header_parsed) {
+			rc = parse_header(line, pp);
+			if (rc)
+				goto err;
+			header_parsed = true;
+		} else {
+			rc = parse_rule(line, pp);
+			if (rc)
+				goto err;
+		}
+	}
+
+	if (!header_parsed || validate_policy(pp)) {
+		rc = -EBADMSG;
+		goto err;
+	}
+
+	p->parsed = pp;
+
+out:
+	kfree(dup);
+	return rc;
+err:
+	free_parsed_policy(pp);
+	goto out;
+}
diff --git a/security/ipe/policy_parser.h b/security/ipe/policy_parser.h
new file mode 100644
index 000000000000..2b744103d06a
--- /dev/null
+++ b/security/ipe/policy_parser.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_POLICY_PARSER_H
+#define _IPE_POLICY_PARSER_H
+
+int parse_policy(struct ipe_policy *p);
+void free_parsed_policy(struct ipe_parsed_policy *p);
+
+#endif /* _IPE_POLICY_PARSER_H */
-- 
2.25.1

On Jun 28, 2023 Fan Wu <wufan@linux.microsoft.com> wrote:
> 
> IPE's interpretation of the what the user trusts is accomplished through
> its policy. IPE's design is to not provide support for a single trust
> provider, but to support multiple providers to enable the end-user to
> choose the best one to seek their needs.
> 
> This requires the policy to be rather flexible and modular so that
> integrity providers, like fs-verity, dm-verity, dm-integrity, or
> some other system, can plug into the policy with minimal code changes.
> 
> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
> ---
>  security/ipe/Makefile        |   2 +
>  security/ipe/policy.c        |  97 +++++++
>  security/ipe/policy.h        |  83 ++++++
>  security/ipe/policy_parser.c | 488 +++++++++++++++++++++++++++++++++++
>  security/ipe/policy_parser.h |  11 +
>  5 files changed, 681 insertions(+)
>  create mode 100644 security/ipe/policy.c
>  create mode 100644 security/ipe/policy.h
>  create mode 100644 security/ipe/policy_parser.c
>  create mode 100644 security/ipe/policy_parser.h

...

> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
> new file mode 100644
> index 000000000000..4069ff075093
> --- /dev/null
> +++ b/security/ipe/policy.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/verification.h>
> +
> +#include "ipe.h"
> +#include "policy.h"
> +#include "policy_parser.h"
> +
> +/**
> + * ipe_free_policy - Deallocate a given IPE policy.
> + * @p: Supplies the policy to free.
> + *
> + * Safe to call on IS_ERR/NULL.
> + */
> +void ipe_free_policy(struct ipe_policy *p)
> +{
> +	if (IS_ERR_OR_NULL(p))
> +		return;
> +
> +	free_parsed_policy(p->parsed);
> +	if (!p->pkcs7)
> +		kfree(p->text);

Since it's safe to kfree(NULL), you could kfree(p->text) without
having to check if p->pkcs7 was non-NULL, correct?

> +	kfree(p->pkcs7);
> +	kfree(p);
> +}

...

> diff --git a/security/ipe/policy.h b/security/ipe/policy.h
> new file mode 100644
> index 000000000000..113a037f0d71
> --- /dev/null
> +++ b/security/ipe/policy.h
> @@ -0,0 +1,83 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +#ifndef _IPE_POLICY_H
> +#define _IPE_POLICY_H
> +
> +#include <linux/list.h>
> +#include <linux/types.h>
> +
> +enum ipe_op_type {
> +	__IPE_OP_EXEC = 0,
> +	__IPE_OP_FIRMWARE,
> +	__IPE_OP_KERNEL_MODULE,
> +	__IPE_OP_KEXEC_IMAGE,
> +	__IPE_OP_KEXEC_INITRAMFS,
> +	__IPE_OP_IMA_POLICY,
> +	__IPE_OP_IMA_X509,
> +	__IPE_OP_MAX
> +};

Thanks for capitalizing the enums, that helps make IPE consistent with
the majority of the kernel.  However, when I talked about using
underscores for "__IPE_OP_MAX", I was talking about *only*
"__IPE_OP_MAX" to help indicate it is a sentinel value and not an enum
value that would normally be used by itself.

Here is what I was intending:

enum ipe_op_type {
  IPE_OP_EXEC = 0,
  IPE_OP_FIRMWARE,
  ...
  IPE_OP_IMA_X509,
  __IPE_OP_MAX
};

> +#define __IPE_OP_INVALID __IPE_OP_MAX

Similarly, I would remove the underscores from "__IPE_OP_INVALID":

#define IPE_OP_INVALID __IPE_OP_MAX

Both of these comments would apply to the other IPE enums as well.

> diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
> new file mode 100644
> index 000000000000..27e5767480b0
> --- /dev/null
> +++ b/security/ipe/policy_parser.c
> @@ -0,0 +1,488 @@

...

> +/**
> + * parse_header - Parse policy header information.
> + * @line: Supplies header line to be parsed.
> + * @p: Supplies the partial parsed policy.
> + *
> + * Return:
> + * * 0	- OK
> + * * !0	- Standard errno
> + */
> +static int parse_header(char *line, struct ipe_parsed_policy *p)
> +{
> +	int rc = 0;
> +	char *t, *ver = NULL;
> +	substring_t args[MAX_OPT_ARGS];
> +	size_t idx = 0;
> +
> +	while ((t = strsep(&line, " \t")) != NULL) {

It might be nice to define a macro to help reinforce that " \t" are
the IPE policy delimiters, how about IPE_POLICY_DELIM?

#define IPE_POLICY_DELIM " \t"

> +		int token;
> +
> +		if (*t == '\0')
> +			continue;

Why would you want to continue if you run into a NUL byte?  You would
only run into a NUL byte if the line was trimmed due to comments or
whitespace, correct?  If that is the case, wouldn't you want to
break out of this loop when hitting a NUL byte?

> +		if (idx >= __IPE_HEADER_MAX) {
> +			rc = -EBADMSG;
> +			goto err;
> +		}
> +
> +		token = match_token(t, header_tokens, args);
> +		if (token != idx) {
> +			rc = -EBADMSG;
> +			goto err;
> +		}
> +
> +		switch (token) {
> +		case __IPE_HEADER_POLICY_NAME:
> +			p->name = match_strdup(&args[0]);
> +			if (!p->name)
> +				rc = -ENOMEM;
> +			break;
> +		case __IPE_HEADER_POLICY_VERSION:
> +			ver = match_strdup(&args[0]);
> +			if (!ver) {
> +				rc = -ENOMEM;
> +				break;
> +			}
> +			rc = parse_version(ver, p);
> +			break;
> +		default:
> +			rc = -EBADMSG;
> +		}
> +		if (rc)
> +			goto err;
> +		++idx;
> +	}
> +
> +	if (idx != __IPE_HEADER_MAX) {
> +		rc = -EBADMSG;
> +		goto err;
> +	}
> +
> +out:
> +	kfree(ver);
> +	return rc;
> +err:
> +	kfree(p->name);
> +	p->name = NULL;
> +	goto out;

Do we need to worry about ipe_parsed_policy::name here?  If we are
returning an error the caller will call free_parsed_policy() for us,
right?  This would allow us to get rid of the 'err' jump label and
simply use 'out' for both success and failure.

> +}

...

> +/**
> + * parse_rule - parse a policy rule line.
> + * @line: Supplies rule line to be parsed.
> + * @p: Supplies the partial parsed policy.
> + *
> + * Return:
> + * * !IS_ERR	- OK
> + * * -ENOMEM	- Out of memory
> + * * -EBADMSG	- Policy syntax error
> + */
> +static int parse_rule(char *line, struct ipe_parsed_policy *p)
> +{
> +	int rc = 0;
> +	bool first_token = true, is_default_rule = false;
> +	bool op_parsed = false;
> +	enum ipe_op_type op = __IPE_OP_INVALID;
> +	enum ipe_action_type action = __IPE_ACTION_INVALID;
> +	struct ipe_rule *r = NULL;
> +	char *t;
> +
> +	r = kzalloc(sizeof(*r), GFP_KERNEL);
> +	if (!r)
> +		return -ENOMEM;
> +
> +	INIT_LIST_HEAD(&r->next);
> +	INIT_LIST_HEAD(&r->props);
> +
> +	while (t = strsep(&line, " \t"), line) {

See my previous comment about IPE_POLICY_DELIM.

> +		if (*t == '\0')
> +			continue;

I still wonder why continuing here is the desired behavior, can you
help me understand?

> +		if (first_token && token_default(t)) {
> +			is_default_rule = true;
> +		} else {
> +			if (!op_parsed) {
> +				op = parse_operation(t);
> +				if (op == __IPE_OP_INVALID)
> +					rc = -EBADMSG;
> +				else
> +					op_parsed = true;
> +			} else {
> +				rc = parse_property(t, r);
> +			}
> +		}
> +
> +		if (rc)
> +			goto err;
> +		first_token = false;
> +	}
> +
> +	action = parse_action(t);
> +	if (action == __IPE_ACTION_INVALID) {
> +		rc = -EBADMSG;
> +		goto err;
> +	}
> +
> +	if (is_default_rule) {
> +		if (!list_empty(&r->props)) {
> +			rc = -EBADMSG;
> +		} else if (op == __IPE_OP_INVALID) {
> +			if (p->global_default_action != __IPE_ACTION_INVALID)
> +				rc = -EBADMSG;
> +			else
> +				p->global_default_action = action;
> +		} else {
> +			if (p->rules[op].default_action != __IPE_ACTION_INVALID)
> +				rc = -EBADMSG;
> +			else
> +				p->rules[op].default_action = action;
> +		}
> +	} else if (op != __IPE_OP_INVALID && action != __IPE_ACTION_INVALID) {
> +		r->op = op;
> +		r->action = action;
> +	} else {
> +		rc = -EBADMSG;
> +	}
> +
> +	if (rc)
> +		goto err;
> +	if (!is_default_rule)
> +		list_add_tail(&r->next, &p->rules[op].rules);
> +	else
> +		free_rule(r);
> +
> +out:
> +	return rc;
> +err:
> +	free_rule(r);
> +	goto out;

In keeping with the rule of not jumping to a label only to
immediately return, and considering that the only place where we jump
to 'out' is in the 'err' code, let's get rid of the 'out' label and
have 'err' "return rc" instead of "goto out".

> +}

--
paul-moore.com