On 03/06/2015 01:48 PM, Tyler Hicks wrote:
> 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 <[email protected]>
Acked-by: John Johansen <[email protected]>
> ---
> 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 */
>
--
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