[apparmor] [PATCH v2 18/42] parser: Begin to flesh out library interface for features
Tyler Hicks
tyhicks at canonical.com
Fri Mar 6 21:48:34 UTC 2015
The aa_features_new_*() functions create an aa_features object. They can
be thought of as the constructor of aa_features objects. A number of
constructors are available depending on whether the features are coming
from a file in the policy cache, a string specified on the command line,
or from apparmorfs.
The aa_features_ref() and aa_features_unref() functions are used to grab
and give up references to an aa_features. When the ref count hits zero,
all allocated memory is freed. Like with free(), aa_features_unref() can
be called with a NULL pointer for convenience.
Pre-processor macros are hidden behind functions so that they don't
become part of our ABI when we move this code into libapparmor later on.
A temporary convenience function, aa_features_get_string(), is provided
while code that uses aa_features is migrated from expecting raw features
string access to something more abstract. The function will be removed
in an upcoming patch.
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
parser/features.c | 170 ++++++++++++++++++++++++++++++++++++++++----------
parser/features.h | 15 ++---
parser/parser_main.c | 36 ++++++-----
parser/policy_cache.c | 23 ++++---
parser/policy_cache.h | 4 +-
5 files changed, 183 insertions(+), 65 deletions(-)
diff --git a/parser/features.c b/parser/features.c
index a2c25c2..ccc238d 100644
--- a/parser/features.c
+++ b/parser/features.c
@@ -33,11 +33,17 @@
#include "lib.h"
#include "parser.h"
-#define FEATURES_STRING_SIZE 8192
-char *features_string = NULL;
+#define FEATURES_FILE "/sys/kernel/security/" MODULE_NAME "/features"
+
+#define STRING_SIZE 8192
+
+struct aa_features {
+ unsigned int ref_count;
+ char string[STRING_SIZE];
+};
struct features_struct {
- char **buffer;
+ char *buffer;
int size;
char *pos;
};
@@ -45,7 +51,7 @@ struct features_struct {
static int features_snprintf(struct features_struct *fst, const char *fmt, ...)
{
va_list args;
- int i, remaining = fst->size - (fst->pos - *fst->buffer);
+ int i, remaining = fst->size - (fst->pos - fst->buffer);
if (remaining < 0) {
errno = EINVAL;
@@ -86,7 +92,7 @@ static int features_dir_cb(DIR *dir, const char *name, struct stat *st,
if (S_ISREG(st->st_mode)) {
autoclose int file = -1;
int len;
- int remaining = fst->size - (fst->pos - *fst->buffer);
+ int remaining = fst->size - (fst->pos - fst->buffer);
file = openat(dirfd(dir), name, O_RDONLY);
if (file == -1) {
@@ -122,7 +128,7 @@ static int features_dir_cb(DIR *dir, const char *name, struct stat *st,
return 0;
}
-static char *handle_features_dir(const char *filename, char **buffer, int size,
+static char *handle_features_dir(const char *filename, char *buffer, int size,
char *pos)
{
struct features_struct fst = { buffer, size, pos };
@@ -135,49 +141,145 @@ static char *handle_features_dir(const char *filename, char **buffer, int size,
return fst.pos;
}
-char *load_features_file(const char *name) {
- char *buffer;
+static int load_features_file(const char *name, char *buffer, size_t size)
+{
autofclose FILE *f = NULL;
- size_t size;
+ size_t end;
f = fopen(name, "r");
if (!f)
- return NULL;
-
- buffer = (char *) malloc(FEATURES_STRING_SIZE);
- if (!buffer)
- goto fail;
-
- size = fread(buffer, 1, FEATURES_STRING_SIZE - 1, f);
- if (!size || ferror(f))
- goto fail;
- buffer[size] = 0;
+ return -1;
- return buffer;
+ errno = 0;
+ end = fread(buffer, 1, size - 1, f);
+ if (ferror(f)) {
+ if (!errno)
+ errno = EIO;
+ return -1;
+ }
+ buffer[end] = 0;
-fail:
- int save = errno;
- free(buffer);
- errno = save;
- return NULL;
+ return 0;
}
-int load_features(const char *name)
+/**
+ * aa_features_new - create a new features based on a path
+ * @features: will point to the address of an allocated and initialized
+ * aa_features object upon success
+ * @path: path to a features file or directory
+ *
+ * Returns: 0 on success, -1 on error with errno set and *@features pointing to
+ * NULL
+ */
+int aa_features_new(aa_features **features, const char *path)
{
struct stat stat_file;
+ aa_features *f;
- if (stat(name, &stat_file) == -1)
+ *features = NULL;
+
+ if (stat(path, &stat_file) == -1)
+ return -1;
+
+ f = (aa_features *) calloc(1, sizeof(*f));
+ if (!f) {
+ errno = ENOMEM;
return -1;
+ }
+ aa_features_ref(f);
if (S_ISDIR(stat_file.st_mode)) {
- /* if we have a features directory default to */
- features_string = (char *) malloc(FEATURES_STRING_SIZE);
- handle_features_dir(name, &features_string, FEATURES_STRING_SIZE, features_string);
- } else {
- features_string = load_features_file(name);
- if (!features_string)
- return -1;
+ handle_features_dir(path, f->string, STRING_SIZE, f->string);
+ } else if (load_features_file(path, f->string, STRING_SIZE)) {
+ int save = errno;
+
+ aa_features_unref(f);
+ errno = save;
+ return -1;
+ }
+
+ *features = f;
+
+ return 0;
+}
+
+/**
+ * aa_features_new_from_string - create a new features based on a string
+ * @features: will point to the address of an allocated and initialized
+ * aa_features object upon success
+ * @string: a NUL-terminated string representation of features
+ * @size: the size of @string, not counting the NUL-terminator
+ *
+ * Returns: 0 on success, -1 on error with errno set and *@features pointing to
+ * NULL
+ */
+int aa_features_new_from_string(aa_features **features,
+ const char *string, size_t size)
+{
+ aa_features *f;
+
+ *features = NULL;
+
+ /* Require size to be less than STRING_SIZE so there's room for a NUL */
+ if (size >= STRING_SIZE)
+ return ENOBUFS;
+
+ f = (aa_features *) calloc(1, sizeof(*f));
+ if (!f) {
+ errno = ENOMEM;
+ return -1;
}
+ aa_features_ref(f);
+
+ memcpy(f->string, string, size);
+ f->string[size] = '\0';
+ *features = f;
return 0;
}
+
+/**
+ * aa_features_new_from_kernel - create a new features based on the current kernel
+ * @features: will point to the address of an allocated and initialized
+ * aa_features object upon success
+ *
+ * Returns: 0 on success, -1 on error with errno set and *@features pointing to
+ * NULL
+ */
+int aa_features_new_from_kernel(aa_features **features)
+{
+ return aa_features_new(features, FEATURES_FILE);
+}
+
+/**
+ * aa_features_ref - increments the ref count of a features
+ * @features: the features
+ *
+ * Returns: the features
+ */
+aa_features *aa_features_ref(aa_features *features)
+{
+ atomic_inc(&features->ref_count);
+ return features;
+}
+
+/**
+ * aa_features_unref - decrements the ref count and frees the features when 0
+ * @features: the features (can be NULL)
+ */
+void aa_features_unref(aa_features *features)
+{
+ if (features && atomic_dec_and_test(&features->ref_count))
+ free(features);
+}
+
+/**
+ * aa_features_get_string - provides immutable string representation of features
+ * @features: the features
+ *
+ * Returns: an immutable string representation of features
+ */
+const char *aa_features_get_string(aa_features *features)
+{
+ return features->string;
+}
diff --git a/parser/features.h b/parser/features.h
index 201d8fc..100f460 100644
--- a/parser/features.h
+++ b/parser/features.h
@@ -19,13 +19,14 @@
#ifndef __AA_FEATURES_H
#define __AA_FEATURES_H
-#include "parser.h"
+typedef struct aa_features aa_features;
-#define FEATURES_FILE "/sys/kernel/security/" MODULE_NAME "/features"
-
-extern char *features_string;
-
-char *load_features_file(const char *name);
-int load_features(const char *name);
+int aa_features_new(aa_features **features, const char *path);
+int aa_features_new_from_string(aa_features **features,
+ const char *string, size_t size);
+int aa_features_new_from_kernel(aa_features **features);
+aa_features *aa_features_ref(aa_features *features);
+void aa_features_unref(aa_features *features);
+const char *aa_features_get_string(aa_features *features);
#endif /* __AA_FEATURES_H */
diff --git a/parser/parser_main.c b/parser/parser_main.c
index 2455103..3f8ca6a 100644
--- a/parser/parser_main.c
+++ b/parser/parser_main.c
@@ -82,6 +82,8 @@ struct timespec mru_tstamp;
static char *cacheloc = NULL;
+static aa_features *features = NULL;
+
/* Make sure to update BOTH the short and long_options */
static const char *short_options = "adf:h::rRVvI:b:BCD:NSm:M:qQn:XKTWkL:O:po:";
struct option long_options[] = {
@@ -389,11 +391,17 @@ static int process_arg(int c, char *optarg)
}
break;
case 'm':
- features_string = strdup(optarg);
+ if (aa_features_new_from_string(&features,
+ optarg, strlen(optarg))) {
+ fprintf(stderr,
+ "Failed to parse features string: %m\n");
+ exit(1);
+ }
break;
case 'M':
- if (load_features(optarg) == -1) {
- fprintf(stderr, "Failed to load features from '%s'\n",
+ if (aa_features_new(&features, optarg)) {
+ fprintf(stderr,
+ "Failed to load features from '%s': %m\n",
optarg);
exit(1);
}
@@ -564,16 +572,17 @@ no_match:
perms_create = 1;
}
-static void set_supported_features(void) {
+static void set_supported_features(void)
+{
+ const char *features_string;
/* has process_args() already assigned a match string? */
- if (!features_string) {
- if (load_features(FEATURES_FILE) == -1) {
- set_features_by_match_file();
- return;
- }
+ if (!features && aa_features_new_from_kernel(&features) == -1) {
+ set_features_by_match_file();
+ return;
}
+ features_string = aa_features_get_string(features);
perms_create = 1;
/* TODO: make this real parsing and config setting */
@@ -865,10 +874,9 @@ static void setup_flags(void)
set_supported_features();
/* Gracefully handle AppArmor kernel without compatibility patch */
- if (!features_string) {
- PERROR("Cache read/write disabled: %s interface file missing. "
- "(Kernel needs AppArmor 2.4 compatibility patch.)\n",
- FEATURES_FILE);
+ if (!features) {
+ PERROR("Cache read/write disabled: interface file missing. "
+ "(Kernel needs AppArmor 2.4 compatibility patch.)\n");
write_cache = 0;
skip_read_cache = 1;
return;
@@ -924,7 +932,7 @@ int main(int argc, char *argv[])
return 0;
}
- retval = setup_cache(cacheloc);
+ retval = setup_cache(features, cacheloc);
if (retval) {
PERROR(_("Failed setting up policy cache (%s): %s\n"),
cacheloc, strerror(errno));
diff --git a/parser/policy_cache.c b/parser/policy_cache.c
index 469d884..8d34f34 100644
--- a/parser/policy_cache.c
+++ b/parser/policy_cache.c
@@ -30,7 +30,6 @@
#define _(s) gettext(s)
#include "lib.h"
-#include "features.h"
#include "parser.h"
#include "policy_cache.h"
@@ -228,10 +227,11 @@ void install_cache(const char *cachetmpname, const char *cachename)
}
}
-int setup_cache(const char *cacheloc)
+int setup_cache(aa_features *kernel_features, const char *cacheloc)
{
autofree char *cache_features_path = NULL;
- autofree char *cache_flags = NULL;
+ aa_features *cache_features;
+ const char *kernel_features_string;
if (!cacheloc) {
errno = EINVAL;
@@ -250,22 +250,27 @@ int setup_cache(const char *cacheloc)
return -1;
}
- cache_flags = load_features_file(cache_features_path);
- if (cache_flags) {
- if (strcmp(features_string, cache_flags) != 0) {
+ kernel_features_string = aa_features_get_string(kernel_features);
+ if (!aa_features_new(&cache_features, cache_features_path)) {
+ const char *cache_features_string;
+
+ cache_features_string = aa_features_get_string(cache_features);
+ if (strcmp(kernel_features_string, cache_features_string) != 0) {
if (write_cache && cond_clear_cache) {
if (create_cache(cacheloc, cache_features_path,
- features_string))
+ kernel_features_string))
skip_read_cache = 1;
} else {
if (show_cache)
- PERROR("Cache read/write disabled: %s does not match %s\n", FEATURES_FILE, cache_features_path);
+ PERROR("Cache read/write disabled: Police cache is invalid\n");
write_cache = 0;
skip_read_cache = 1;
}
}
+ aa_features_unref(cache_features);
} else if (write_cache) {
- create_cache(cacheloc, cache_features_path, features_string);
+ create_cache(cacheloc, cache_features_path,
+ kernel_features_string);
}
return 0;
diff --git a/parser/policy_cache.h b/parser/policy_cache.h
index 68d45a4..728de57 100644
--- a/parser/policy_cache.h
+++ b/parser/policy_cache.h
@@ -19,6 +19,8 @@
#ifndef __AA_POLICY_CACHE_H
#define __AA_POLICY_CACHE_H
+#include "features.h"
+
extern struct timespec mru_tstamp;
/* returns true if time is more recent than mru_tstamp */
@@ -46,6 +48,6 @@ void valid_read_cache(const char *cachename);
int cache_hit(const char *cachename);
int setup_cache_tmp(const char **cachetmpname, const char *cachename);
void install_cache(const char *cachetmpname, const char *cachename);
-int setup_cache(const char *cacheloc);
+int setup_cache(aa_features *kernel_features, const char *cacheloc);
#endif /* __AA_POLICY_CACHE_H */
--
2.1.4
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