env: Add support for access control to .flags

Add support for read-only, write-once, and change-default.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

README

@@ -3128,7 +3128,8 @@ Configuration Settings:
 
 	The format of the list is:
 		type_attribute = [s|d|x|b|i|m]
-		attributes = type_attribute
+		access_atribute = [a|r|o|c]
+		attributes = type_attribute[access_atribute]
 		entry = variable_name[:attributes]
 		list = entry[,list]
 
@@ -3140,6 +3141,12 @@ Configuration Settings:
 		i - IP address
 		m - MAC address
 
+	The access attributes are:
+		a - Any (default)
+		r - Read-only
+		o - Write-once
+		c - Change-default
+
 	- CONFIG_ENV_FLAGS_LIST_DEFAULT
 		Define this to a list (string) to define the ".flags"
 		envirnoment variable in the default or embedded environment.
@@ -3151,6 +3158,10 @@ Configuration Settings:
 		list, simply add an entry for the same variable name to the
 		".flags" variable.
 
+- CONFIG_ENV_ACCESS_IGNORE_FORCE
+	If defined, don't allow the -f switch to env set override variable
+	access flags.
+
 The following definitions that deal with the placement and management
 of environment data (variable area); in general, we support the
 following configurations:

common/cmd_nvedit.c

@@ -447,8 +447,11 @@ int do_env_callback(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 static int print_static_flags(const char *var_name, const char *flags)
 {
 	enum env_flags_vartype type = env_flags_parse_vartype(flags);
+	enum env_flags_varaccess access = env_flags_parse_varaccess(flags);
 
-	printf("\t%-20s %-20s\n", var_name, env_flags_get_vartype_name(type));
+	printf("\t%-20s %-20s %-20s\n", var_name,
+		env_flags_get_vartype_name(type),
+		env_flags_get_varaccess_name(access));
 
 	return 0;
 }
@@ -456,13 +459,17 @@ static int print_static_flags(const char *var_name, const char *flags)
 static int print_active_flags(ENTRY *entry)
 {
 	enum env_flags_vartype type;
+	enum env_flags_varaccess access;
 
 	if (entry->flags == 0)
 		return 0;
 
 	type = (enum env_flags_vartype)
 		(entry->flags & ENV_FLAGS_VARTYPE_BIN_MASK);
-	printf("\t%-20s %-20s\n", entry->key, env_flags_get_vartype_name(type));
+	access = env_flags_parse_varaccess_from_binflags(entry->flags);
+	printf("\t%-20s %-20s %-20s\n", entry->key,
+		env_flags_get_vartype_name(type),
+		env_flags_get_varaccess_name(access));
 
 	return 0;
 }
@@ -480,17 +487,29 @@ int do_env_flags(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	env_flags_print_vartypes();
 	puts("\n");
 
+	/* Print the available variable access types */
+	printf("Available variable access flags (position %d):\n",
+		ENV_FLAGS_VARACCESS_LOC);
+	puts("\tFlag\tVariable Access Name\n");
+	puts("\t----\t--------------------\n");
+	env_flags_print_varaccess();
+	puts("\n");
+
 	/* Print the static flags that may exist */
 	puts("Static flags:\n");
-	printf("\t%-20s %-20s\n", "Variable Name", "Variable Type");
-	printf("\t%-20s %-20s\n", "-------------", "-------------");
+	printf("\t%-20s %-20s %-20s\n", "Variable Name", "Variable Type",
+		"Variable Access");
+	printf("\t%-20s %-20s %-20s\n", "-------------", "-------------",
+		"---------------");
 	env_attr_walk(ENV_FLAGS_LIST_STATIC, print_static_flags);
 	puts("\n");
 
 	/* walk through each variable and print the flags if non-default */
 	puts("Active flags:\n");
-	printf("\t%-20s %-20s\n", "Variable Name", "Variable Type");
-	printf("\t%-20s %-20s\n", "-------------", "-------------");
+	printf("\t%-20s %-20s %-20s\n", "Variable Name", "Variable Type",
+		"Variable Access");
+	printf("\t%-20s %-20s %-20s\n", "-------------", "-------------",
+		"---------------");
 	hwalk_r(&env_htab, print_active_flags);
 	return 0;
 }

common/env_common.c

@@ -95,6 +95,24 @@ int getenv_yesno(const char *var)
 		1 : 0;
 }
 
+/*
+ * Look up the variable from the default environment
+ */
+char *getenv_default(const char *name)
+{
+	char *ret_val;
+	unsigned long really_valid = gd->env_valid;
+	unsigned long real_gd_flags = gd->flags;
+
+	/* Pretend that the image is bad. */
+	gd->flags &= ~GD_FLG_ENV_READY;
+	gd->env_valid = 0;
+	ret_val = getenv(name);
+	gd->env_valid = really_valid;
+	gd->flags = real_gd_flags;
+	return ret_val;
+}
+
 void set_default_env(const char *s)
 {
 	int flags = 0;

common/env_flags.c

@@ -43,6 +43,17 @@
 #endif
 
 static const char env_flags_vartype_rep[] = "sdxb" ENV_FLAGS_NET_VARTYPE_REPS;
+static const char env_flags_varaccess_rep[] = "aroc";
+static const int env_flags_varaccess_mask[] = {
+	0,
+	ENV_FLAGS_VARACCESS_PREVENT_DELETE |
+		ENV_FLAGS_VARACCESS_PREVENT_CREATE |
+		ENV_FLAGS_VARACCESS_PREVENT_OVERWR,
+	ENV_FLAGS_VARACCESS_PREVENT_DELETE |
+		ENV_FLAGS_VARACCESS_PREVENT_OVERWR,
+	ENV_FLAGS_VARACCESS_PREVENT_DELETE |
+		ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR};
+
 #ifdef CONFIG_CMD_ENV_FLAGS
 static const char * const env_flags_vartype_names[] = {
 	"string",
@@ -54,6 +65,12 @@ static const char * const env_flags_vartype_names[] = {
 	"MAC address",
 #endif
 };
+static const char * const env_flags_varaccess_names[] = {
+	"any",
+	"read-only",
+	"write-once",
+	"change-default",
+};
 
 /*
  * Print the whole list of available type flags.
@@ -70,12 +87,34 @@ void env_flags_print_vartypes(void)
 }
 
 /*
+ * Print the whole list of available access flags.
+ */
+void env_flags_print_varaccess(void)
+{
+	enum env_flags_varaccess curaccess = (enum env_flags_varaccess)0;
+
+	while (curaccess != env_flags_varaccess_end) {
+		printf("\t%c   -\t%s\n", env_flags_varaccess_rep[curaccess],
+			env_flags_varaccess_names[curaccess]);
+		curaccess++;
+	}
+}
+
+/*
  * Return the name of the type.
  */
 const char *env_flags_get_vartype_name(enum env_flags_vartype type)
 {
 	return env_flags_vartype_names[type];
 }
+
+/*
+ * Return the name of the access.
+ */
+const char *env_flags_get_varaccess_name(enum env_flags_varaccess access)
+{
+	return env_flags_varaccess_names[access];
+}
 #endif /* CONFIG_CMD_ENV_FLAGS */
 
 /*
@@ -100,6 +139,46 @@ enum env_flags_vartype env_flags_parse_vartype(const char *flags)
 	return env_flags_vartype_string;
 }
 
+/*
+ * Parse the flags string from a .flags attribute list into the varaccess enum.
+ */
+enum env_flags_varaccess env_flags_parse_varaccess(const char *flags)
+{
+	char *access;
+
+	if (strlen(flags) <= ENV_FLAGS_VARACCESS_LOC)
+		return env_flags_varaccess_any;
+
+	access = strchr(env_flags_varaccess_rep,
+		flags[ENV_FLAGS_VARACCESS_LOC]);
+
+	if (access != NULL)
+		return (enum env_flags_varaccess)
+			(access - &env_flags_varaccess_rep[0]);
+
+	printf("## Warning: Unknown environment variable access method '%c'\n",
+		flags[ENV_FLAGS_VARACCESS_LOC]);
+	return env_flags_varaccess_any;
+}
+
+/*
+ * Parse the binary flags from a hash table entry into the varaccess enum.
+ */
+enum env_flags_varaccess env_flags_parse_varaccess_from_binflags(int binflags)
+{
+	int i;
+
+	for (i = 0; i < sizeof(env_flags_varaccess_mask); i++)
+		if (env_flags_varaccess_mask[i] ==
+		    (binflags & ENV_FLAGS_VARACCESS_BIN_MASK))
+			return (enum env_flags_varaccess)i;
+
+	printf("Warning: Non-standard access flags. (0x%x)\n",
+		binflags & ENV_FLAGS_VARACCESS_BIN_MASK);
+
+	return env_flags_varaccess_any;
+}
+
 static inline int is_hex_prefix(const char *value)
 {
 	return value[0] == '0' && (value[1] == 'x' || value[1] == 'X');
@@ -242,6 +321,23 @@ enum env_flags_vartype env_flags_get_type(const char *name)
 }
 
 /*
+ * Look up the access of a variable directly from the .flags var.
+ */
+enum env_flags_varaccess env_flags_get_varaccess(const char *name)
+{
+	const char *flags_list = getenv(ENV_FLAGS_VAR);
+	char flags[ENV_FLAGS_ATTR_MAX_LEN + 1];
+
+	if (env_flags_lookup(flags_list, name, flags))
+		return env_flags_varaccess_any;
+
+	if (strlen(flags) <= ENV_FLAGS_VARACCESS_LOC)
+		return env_flags_varaccess_any;
+
+	return env_flags_parse_varaccess(flags);
+}
+
+/*
  * Validate that the proposed new value for "name" is valid according to the
  * defined flags for that variable, if any.
  */
@@ -262,6 +358,21 @@ int env_flags_validate_type(const char *name, const char *value)
 }
 
 /*
+ * Validate that the proposed access to variable "name" is valid according to
+ * the defined flags for that variable, if any.
+ */
+int env_flags_validate_varaccess(const char *name, int check_mask)
+{
+	enum env_flags_varaccess access;
+	int access_mask;
+
+	access = env_flags_get_varaccess(name);
+	access_mask = env_flags_varaccess_mask[access];
+
+	return (check_mask & access_mask) != 0;
+}
+
+/*
  * Validate the parameters to "env set" directly
  */
 int env_flags_validate_env_set_params(int argc, char * const argv[])
@@ -292,7 +403,12 @@ int env_flags_validate_env_set_params(int argc, char * const argv[])
  */
 static int env_parse_flags_to_bin(const char *flags)
 {
-	return env_flags_parse_vartype(flags) & ENV_FLAGS_VARTYPE_BIN_MASK;
+	int binflags;
+
+	binflags = env_flags_parse_vartype(flags) & ENV_FLAGS_VARTYPE_BIN_MASK;
+	binflags |= env_flags_varaccess_mask[env_flags_parse_varaccess(flags)];
+
+	return binflags;
 }
 
 /*
@@ -377,13 +493,10 @@ int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 	int flag)
 {
 	const char *name;
-#if !defined(CONFIG_ENV_OVERWRITE) && defined(CONFIG_OVERWRITE_ETHADDR_ONCE) \
-&& defined(CONFIG_ETHADDR)
 	const char *oldval = NULL;
 
 	if (op != env_op_create)
 		oldval = item->data;
-#endif
 
 	name = item->key;
 
@@ -422,6 +535,44 @@ int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 		}
 	}
 
+	/* check for access permission */
+#ifndef CONFIG_ENV_ACCESS_IGNORE_FORCE
+	if (flag & H_FORCE)
+		return 0;
+#endif
+	switch (op) {
+	case env_op_delete:
+		if (item->flags & ENV_FLAGS_VARACCESS_PREVENT_DELETE) {
+			printf("## Error: Can't delete \"%s\"\n", name);
+			return 1;
+		}
+		break;
+	case env_op_overwrite:
+		if (item->flags & ENV_FLAGS_VARACCESS_PREVENT_OVERWR) {
+			printf("## Error: Can't overwrite \"%s\"\n", name);
+			return 1;
+		} else if (item->flags &
+		    ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR) {
+			const char *defval = getenv_default(name);
+
+			if (defval == NULL)
+				defval = "";
+			printf("oldval: %s  defval: %s\n", oldval, defval);
+			if (strcmp(oldval, defval) != 0) {
+				printf("## Error: Can't overwrite \"%s\"\n",
+					name);
+				return 1;
+			}
+		}
+		break;
+	case env_op_create:
+		if (item->flags & ENV_FLAGS_VARACCESS_PREVENT_CREATE) {
+			printf("## Error: Can't create \"%s\"\n", name);
+			return 1;
+		}
+		break;
+	}
+
 	return 0;
 }
 

include/env_flags.h

@@ -36,9 +36,18 @@ enum env_flags_vartype {
 	env_flags_vartype_end
 };
 
+enum env_flags_varaccess {
+	env_flags_varaccess_any,
+	env_flags_varaccess_readonly,
+	env_flags_varaccess_writeonce,
+	env_flags_varaccess_changedefault,
+	env_flags_varaccess_end
+};
+
 #define ENV_FLAGS_VAR ".flags"
 #define ENV_FLAGS_ATTR_MAX_LEN 2
 #define ENV_FLAGS_VARTYPE_LOC 0
+#define ENV_FLAGS_VARACCESS_LOC 1
 
 #ifndef CONFIG_ENV_FLAGS_LIST_STATIC
 #define CONFIG_ENV_FLAGS_LIST_STATIC ""
@@ -53,15 +62,31 @@ enum env_flags_vartype {
  */
 void env_flags_print_vartypes(void);
 /*
+ * Print the whole list of available access flags.
+ */
+void env_flags_print_varaccess(void);
+/*
  * Return the name of the type.
  */
 const char *env_flags_get_vartype_name(enum env_flags_vartype type);
+/*
+ * Return the name of the access.
+ */
+const char *env_flags_get_varaccess_name(enum env_flags_varaccess access);
 #endif
 
 /*
  * Parse the flags string from a .flags attribute list into the vartype enum.
  */
 enum env_flags_vartype env_flags_parse_vartype(const char *flags);
+/*
+ * Parse the flags string from a .flags attribute list into the varaccess enum.
+ */
+enum env_flags_varaccess env_flags_parse_varaccess(const char *flags);
+/*
+ * Parse the binary flags from a hash table entry into the varaccess enum.
+ */
+enum env_flags_varaccess env_flags_parse_varaccess_from_binflags(int binflags);
 
 #ifdef USE_HOSTCC
 /*
@@ -69,11 +94,25 @@ enum env_flags_vartype env_flags_parse_vartype(const char *flags);
  */
 enum env_flags_vartype env_flags_get_type(const char *name);
 /*
+ * Look up the access of a variable directly from the .flags var.
+ */
+enum env_flags_varaccess env_flags_get_access(const char *name);
+/*
  * Validate the newval for its type to conform with the requirements defined by
  * its flags (directly looked at the .flags var).
  */
 int env_flags_validate_type(const char *name, const char *newval);
 /*
+ * Validate the newval for its access to conform with the requirements defined
+ * by its flags (directly looked at the .flags var).
+ */
+int env_flags_validate_access(const char *name, int check_mask);
+/*
+ * Validate that the proposed access to variable "name" is valid according to
+ * the defined flags for that variable, if any.
+ */
+int env_flags_validate_varaccess(const char *name, int check_mask);
+/*
  * Validate the parameters passed to "env set" for type compliance
  */
 int env_flags_validate_env_set_params(int argc, char * const argv[]);
@@ -94,13 +133,18 @@ void env_flags_init(ENTRY *var_entry);
 int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 	int flag);
 
+#endif /* USE_HOSTCC */
+
 /*
  * These are the binary flags used in the environment entry->flags variable to
  * decribe properties of veriables in the table
  */
-#define ENV_FLAGS_VARTYPE_BIN_MASK	0x00000007
+#define ENV_FLAGS_VARTYPE_BIN_MASK			0x00000007
 /* The actual variable type values use the enum value (within the mask) */
-
-#endif /* USE_HOSTCC */
+#define ENV_FLAGS_VARACCESS_PREVENT_DELETE		0x00000008
+#define ENV_FLAGS_VARACCESS_PREVENT_CREATE		0x00000010
+#define ENV_FLAGS_VARACCESS_PREVENT_OVERWR		0x00000020
+#define ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR	0x00000040
+#define ENV_FLAGS_VARACCESS_BIN_MASK			0x00000078
 
 #endif /* __ENV_FLAGS_H__ */

include/environment.h

@@ -181,6 +181,9 @@ unsigned char env_get_char_memory(int index);
 /* Function that updates CRC of the enironment */
 void env_crc_update(void);
 
+/* Look up the variable from the default environment */
+char *getenv_default(const char *name);
+
 /* [re]set to the default environment */
 void set_default_env(const char *s);
 

tools/env/fw_env.c

@@ -182,6 +182,32 @@ char *fw_getenv (char *name)
 }
 
 /*
+ * Search the default environment for a variable.
+ * Return the value, if found, or NULL, if not found.
+ */
+char *fw_getdefenv(char *name)
+{
+	char *env, *nxt;
+
+	for (env = default_environment; *env; env = nxt + 1) {
+		char *val;
+
+		for (nxt = env; *nxt; ++nxt) {
+			if (nxt >= &default_environment[ENV_SIZE]) {
+				fprintf(stderr, "## Error: "
+					"default environment not terminated\n");
+				return NULL;
+			}
+		}
+		val = envmatch(name, env);
+		if (!val)
+			continue;
+		return val;
+	}
+	return NULL;
+}
+
+/*
  * Print the current definition of one, or more, or all
  * environment variables
  */
@@ -282,6 +308,7 @@ int fw_env_write(char *name, char *value)
 	int len;
 	char *env, *nxt;
 	char *oldval = NULL;
+	int deleting, creating, overwriting;
 
 	/*
 	 * search if variable with this name already exists
@@ -299,10 +326,49 @@ int fw_env_write(char *name, char *value)
 			break;
 	}
 
-	/*
-	 * Delete any existing definition
-	 */
-	if (oldval) {
+	deleting = (oldval && !(value && strlen(value)));
+	creating = (!oldval && (value && strlen(value)));
+	overwriting = (oldval && (value && strlen(value)));
+
+	/* check for permission */
+	if (deleting) {
+		if (env_flags_validate_varaccess(name,
+		    ENV_FLAGS_VARACCESS_PREVENT_DELETE)) {
+			printf("Can't delete \"%s\"\n", name);
+			errno = EROFS;
+			return -1;
+		}
+	} else if (overwriting) {
+		if (env_flags_validate_varaccess(name,
+		    ENV_FLAGS_VARACCESS_PREVENT_OVERWR)) {
+			printf("Can't overwrite \"%s\"\n", name);
+			errno = EROFS;
+			return -1;
+		} else if (env_flags_validate_varaccess(name,
+		    ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR)) {
+			const char *defval = fw_getdefenv(name);
+
+			if (defval == NULL)
+				defval = "";
+			if (strcmp(oldval, defval)
+			    != 0) {
+				printf("Can't overwrite \"%s\"\n", name);
+				errno = EROFS;
+				return -1;
+			}
+		}
+	} else if (creating) {
+		if (env_flags_validate_varaccess(name,
+		    ENV_FLAGS_VARACCESS_PREVENT_CREATE)) {
+			printf("Can't create \"%s\"\n", name);
+			errno = EROFS;
+			return -1;
+		}
+	} else
+		/* Nothing to do */
+		return 0;
+
+	if (deleting || overwriting) {
 #ifndef CONFIG_ENV_OVERWRITE
 		/*
 		 * Ethernet Address and serial# can be set only once