leandrof/u-boot
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

env: Add support for explicit write access list

Browse Source 
This option marks any U-Boot variable which does not have explicit 'w'
writeable flag set as read-only. This way the environment can be locked
down and only variables explicitly configured to be writeable can ever
be changed by either 'env import', 'env set' or loading user environment
from environment storage.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
This commit is contained in:
Marek Vasut 2020-07-07 20:51:39 +02:00 committed by Tom Rini
parent 47f3b1f243
commit d045cbacf2
4 changed files with 68 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
env/Kconfig vendored
View File

@ -623,6 +623,14 @@ config ENV_APPEND
with newly imported data. This may be used in combination with static
flags to e.g. to protect variables which must not be modified.
config ENV_WRITEABLE_LIST
bool "Permit write access only to listed variables"
default n
help
If defined, only environment variables which explicitly set the 'w'
writeable flag can be written and modified at runtime. No variables
can be otherwise created, written or imported into the environment.
config ENV_ACCESS_IGNORE_FORCE
bool "Block forced environment operations"
default n

62
env/flags.c vendored
View File

@ -28,8 +28,15 @@
#define ENV_FLAGS_NET_VARTYPE_REPS ""
#endif
#ifdef CONFIG_ENV_WRITEABLE_LIST
#define ENV_FLAGS_WRITEABLE_VARACCESS_REPS "w"
#else
#define ENV_FLAGS_WRITEABLE_VARACCESS_REPS ""
#endif
static const char env_flags_vartype_rep[] = "sdxb" ENV_FLAGS_NET_VARTYPE_REPS;
static const char env_flags_varaccess_rep[] = "aroc";
static const char env_flags_varaccess_rep[] =
"aroc" ENV_FLAGS_WRITEABLE_VARACCESS_REPS;
static const int env_flags_varaccess_mask[] = {
0,
ENV_FLAGS_VARACCESS_PREVENT_DELETE |
@ -38,7 +45,11 @@ static const int env_flags_varaccess_mask[] = {
ENV_FLAGS_VARACCESS_PREVENT_DELETE |
ENV_FLAGS_VARACCESS_PREVENT_OVERWR,
ENV_FLAGS_VARACCESS_PREVENT_DELETE |
ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR};
ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR,
#ifdef CONFIG_ENV_WRITEABLE_LIST
ENV_FLAGS_VARACCESS_WRITEABLE,
#endif
};
#ifdef CONFIG_CMD_ENV_FLAGS
static const char * const env_flags_vartype_names[] = {
@ -56,6 +67,9 @@ static const char * const env_flags_varaccess_names[] = {
"read-only",
"write-once",
"change-default",
#ifdef CONFIG_ENV_WRITEABLE_LIST
"writeable",
#endif
};
/*
@ -130,21 +144,25 @@ enum env_flags_vartype env_flags_parse_vartype(const char *flags)
*/
enum env_flags_varaccess env_flags_parse_varaccess(const char *flags)
{
enum env_flags_varaccess va_default = env_flags_varaccess_any;
enum env_flags_varaccess va;
char *access;
if (strlen(flags) <= ENV_FLAGS_VARACCESS_LOC)
return env_flags_varaccess_any;
return va_default;
access = strchr(env_flags_varaccess_rep,
flags[ENV_FLAGS_VARACCESS_LOC]);
if (access != NULL)
return (enum env_flags_varaccess)
if (access != NULL) {
va = (enum env_flags_varaccess)
(access - &env_flags_varaccess_rep[0]);
return va;
}
printf("## Warning: Unknown environment variable access method '%c'\n",
flags[ENV_FLAGS_VARACCESS_LOC]);
return env_flags_varaccess_any;
return va_default;
}
/*
@ -152,17 +170,21 @@ enum env_flags_varaccess env_flags_parse_varaccess(const char *flags)
*/
enum env_flags_varaccess env_flags_parse_varaccess_from_binflags(int binflags)
{
enum env_flags_varaccess va_default = env_flags_varaccess_any;
enum env_flags_varaccess va;
int i;
for (i = 0; i < ARRAY_SIZE(env_flags_varaccess_mask); i++)
if (env_flags_varaccess_mask[i] ==
(binflags & ENV_FLAGS_VARACCESS_BIN_MASK))
return (enum env_flags_varaccess)i;
(binflags & ENV_FLAGS_VARACCESS_BIN_MASK)) {
va = (enum env_flags_varaccess)i;
return va;
}
printf("Warning: Non-standard access flags. (0x%x)\n",
binflags & ENV_FLAGS_VARACCESS_BIN_MASK);
return env_flags_varaccess_any;
return va_default;
}
static inline int is_hex_prefix(const char *value)
@ -326,13 +348,14 @@ enum env_flags_vartype env_flags_get_type(const char *name)
enum env_flags_varaccess env_flags_get_varaccess(const char *name)
{
const char *flags_list = env_get(ENV_FLAGS_VAR);
enum env_flags_varaccess va_default = env_flags_varaccess_any;
char flags[ENV_FLAGS_ATTR_MAX_LEN + 1];
if (env_flags_lookup(flags_list, name, flags))
return env_flags_varaccess_any;
return va_default;
if (strlen(flags) <= ENV_FLAGS_VARACCESS_LOC)
return env_flags_varaccess_any;
return va_default;
return env_flags_parse_varaccess(flags);
}
@ -426,7 +449,11 @@ void env_flags_init(struct env_entry *var_entry)
int ret = 1;
if (first_call) {
#ifdef CONFIG_ENV_WRITEABLE_LIST
flags_list = ENV_FLAGS_LIST_STATIC;
#else
flags_list = env_get(ENV_FLAGS_VAR);
#endif
first_call = 0;
}
/* look in the ".flags" and static for a reference to this variable */
@ -523,6 +550,19 @@ int env_flags_validate(const struct env_entry *item, const char *newval,
}
/* check for access permission */
#ifdef CONFIG_ENV_WRITEABLE_LIST
if (flag & H_DEFAULT)
return 0; /* Default env is always OK */
/*
* External writeable variables can be overwritten by external env,
* anything else can not be overwritten by external env.
*/
if ((flag & H_EXTERNAL) &&
!(item->flags & ENV_FLAGS_VARACCESS_WRITEABLE))
return 1;
#endif
#ifndef CONFIG_ENV_ACCESS_IGNORE_FORCE
if (flag & H_FORCE) {
printf("## Error: Can't force access to \"%s\"\n", name);

6
include/env_flags.h
View File

@ -24,6 +24,9 @@ enum env_flags_varaccess {
env_flags_varaccess_readonly,
env_flags_varaccess_writeonce,
env_flags_varaccess_changedefault,
#ifdef CONFIG_ENV_WRITEABLE_LIST
env_flags_varaccess_writeable,
#endif
env_flags_varaccess_end
};
@ -173,6 +176,7 @@ int env_flags_validate(const struct env_entry *item, const char *newval,
#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
#define ENV_FLAGS_VARACCESS_WRITEABLE 0x00000080
#define ENV_FLAGS_VARACCESS_BIN_MASK 0x000000f8
#endif /* __ENV_FLAGS_H__ */

5
lib/hashtable.c
View File

@ -950,9 +950,12 @@ int himport_r(struct hsearch_data *htab,
e.data = value;
hsearch_r(e, ENV_ENTER, &rv, htab, flag);
if (rv == NULL)
#if !CONFIG_IS_ENABLED(ENV_WRITEABLE_LIST)
if (rv == NULL) {
printf("himport_r: can't insert \"%s=%s\" into hash table\n",
name, value);
}
#endif
debug("INSERT: table %p, filled %d/%d rv %p ==> name=\"%s\" value=\"%s\"\n",
htab, htab->filled, htab->size,