[apparmor] [PATCH] libapparmor: Export a label-based query interface
Seth Arnold
seth.arnold at canonical.com
Mon Jul 29 23:36:25 UTC 2013
On Mon, Jul 29, 2013 at 02:24:15AM -0700, Tyler Hicks wrote:
> Add an interface for trusted applications to use when they need to query
> AppArmor kernel policy to determine if an action should be allowed.
>
> This is a simplified interface that tries to make it as easy as possible
> for applications to use. They provide a permissions mask and query
> string and they get a pair of booleans back that let them know if the
> action should be allowed and/or audited.
>
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
Acked-by: Seth Arnold <seth.arnold at canonical.com>
with a few comments inline...
> ---
> libraries/libapparmor/src/Makefile.am | 2 +-
> libraries/libapparmor/src/apparmor.h | 41 +++++++++++
> libraries/libapparmor/src/kernel_interface.c | 98 +++++++++++++++++++++++++++
> libraries/libapparmor/src/libapparmor.map | 7 ++
> libraries/libapparmor/swig/SWIG/libapparmor.i | 2 +
> 5 files changed, 149 insertions(+), 1 deletion(-)
>
> diff --git a/libraries/libapparmor/src/Makefile.am b/libraries/libapparmor/src/Makefile.am
> index 6507673..48bf2f4 100644
> --- a/libraries/libapparmor/src/Makefile.am
> +++ b/libraries/libapparmor/src/Makefile.am
> @@ -47,7 +47,7 @@ lib_LTLIBRARIES = libapparmor.la
> noinst_HEADERS = grammar.h parser.h scanner.h af_protos.h
>
> libapparmor_la_SOURCES = grammar.y libaalogparse.c kernel_interface.c scanner.c
> -libapparmor_la_LDFLAGS = -version-info $(AA_LIB_CURRENT):$(AA_LIB_REVISION):$(AA_LIB_AGE) -XCClinker -dynamic \
> +libapparmor_la_LDFLAGS = -version-info $(AA_LIB_CURRENT):$(AA_LIB_REVISION):$(AA_LIB_AGE) -XCClinker -dynamic -pthread \
> -Wl,--version-script=$(top_srcdir)/src/libapparmor.map -Wl,-soname=libapparmor.so.1
>
> pkgconfigdir = $(libdir)/pkgconfig
> diff --git a/libraries/libapparmor/src/apparmor.h b/libraries/libapparmor/src/apparmor.h
> index 79bc69c..387e197 100644
> --- a/libraries/libapparmor/src/apparmor.h
> +++ b/libraries/libapparmor/src/apparmor.h
> @@ -18,10 +18,41 @@
> #ifndef _SYS_APPARMOR_H_
> #define _SYS_APPARMOR_H 1
>
> +#include <stdint.h>
> #include <sys/types.h>
>
> __BEGIN_DECLS
>
> +/*
> + * Class of mediation types in the AppArmor policy db
> + */
> +#define AA_CLASS_COND 0
> +#define AA_CLASS_UNKNOWN 1
> +#define AA_CLASS_FILE 2
> +#define AA_CLASS_CAP 3
> +#define AA_CLASS_NET 4
> +#define AA_CLASS_RLIMITS 5
> +#define AA_CLASS_DOMAIN 6
> +#define AA_CLASS_MOUNT 7
> +#define AA_CLASS_NS_DOMAIN 8
> +#define AA_CLASS_PTRACE 9
> +
> +#define AA_CLASS_ENV 16
> +
> +#define AA_CLASS_DBUS 32
> +#define AA_CLASS_X 33
> +
> +
> +/* Permission Flags for Mediation classes */
> +#define AA_MAY_WRITE (1 << 1)
> +#define AA_MAY_READ (1 << 2)
> +#define AA_MAY_BIND (1 << 6)
> +
> +#define AA_DBUS_SEND AA_MAY_WRITE
> +#define AA_DBUS_RECEIVE AA_MAY_READ
> +#define AA_DBUS_BIND AA_MAY_BIND
> +
> +
> /* Prototypes for apparmor state queries */
> extern int aa_is_enabled(void);
> extern int aa_find_mountpoint(char **mnt);
> @@ -51,6 +82,16 @@ extern int aa_getcon(char **con, char **mode);
> extern int aa_getpeercon_raw(int fd, char *buf, int *len, char **mode);
> extern int aa_getpeercon(int fd, char **con, char **mode);
>
> +/* A NUL character is used to separate the query command prefix string from the
> + * rest of the query string. The query command sizes intentionally include the
> + * NUL-terminator in their values.
> + */
> +#define AA_QUERY_CMD_LABEL "label"
> +#define AA_QUERY_CMD_LABEL_SIZE sizeof(AA_QUERY_CMD_LABEL)
> +
> +extern int aa_query_label(uint32_t mask, char *query, size_t size, int *allow,
> + int *audit);
> +
> #define __macroarg_counter(Y...) __macroarg_count1 ( , ##Y)
> #define __macroarg_count1(Y...) __macroarg_count2 (Y, 16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0)
> #define __macroarg_count2(_,x0,x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12,x13,x14,x15,n,Y...) n
> diff --git a/libraries/libapparmor/src/kernel_interface.c b/libraries/libapparmor/src/kernel_interface.c
> index ea1659d..356307e 100644
> --- a/libraries/libapparmor/src/kernel_interface.c
> +++ b/libraries/libapparmor/src/kernel_interface.c
> @@ -28,6 +28,9 @@
> #include <limits.h>
> #include <stdarg.h>
> #include <mntent.h>
> +#include <inttypes.h>
> +#include <stdint.h>
inttypes.h already includes stdint.h.
> +#include <pthread.h>
>
> #include "apparmor.h"
>
> @@ -650,3 +653,98 @@ int aa_getpeercon(int fd, char **con, char **mode)
>
> return size;
> }
> +
> +static pthread_once_t aafs_access_control = PTHREAD_ONCE_INIT;
> +static char *aafs_access = NULL;
> +
> +static void aafs_access_init_once(void)
> +{
> + char *aafs;
> + int ret;
> +
> + ret = aa_find_mountpoint(&aafs);
> + if (ret < 0)
> + return;
> +
> + ret = asprintf(&aafs_access, "%s/.access", aafs);
> + if (ret < 0)
> + aafs_access = NULL;
> +
> + free(aafs);
> +}
> +
> +/* "allow 0x00000000\ndeny 0x00000000\naudit 0x00000000\nquiet 0x00000000\n" */
> +#define QUERY_LABEL_REPLY_LEN 67
> +
> +/**
> + * aa_query_label - query the access(es) of a label
> + * @mask: permission bits to query
> + * @query: binary query string, must be offset by AA_QUERY_CMD_LABEL_SIZE
> + * @size: size of the query string must include AA_QUERY_CMD_LABEL_SIZE
> + * @allowed: upon successful return, will be 1 if query is allowed and 0 if not
> + * @audited: upon successful return, will be 1 if query should be audited and 0
> + * if not
> + *
> + * Returns: 0 on success else -1 and sets errno
> + */
> +int aa_query_label(uint32_t mask, char *query, size_t size, int *allowed,
> + int *audited)
> +{
> + char buf[QUERY_LABEL_REPLY_LEN];
> + uint32_t allow, deny, audit, quiet;
> + int fd, ret, saved;
> +
> + if (!mask || size <= AA_QUERY_CMD_LABEL_SIZE) {
> + errno = EINVAL;
> + return -1;
> + }
> +
> + ret = pthread_once(&aafs_access_control, aafs_access_init_once);
> + if (ret) {
> + errno = EINVAL;
> + return -1;
> + } else if (!aafs_access) {
> + errno = ENOMEM;
> + return -1;
> + }
> +
> + fd = open(aafs_access, O_RDWR);
> + if (fd == -1)
> + return -1;
> +
> + memcpy(query, AA_QUERY_CMD_LABEL, AA_QUERY_CMD_LABEL_SIZE);
> + errno = 0;
> + ret = write(fd, query, size);
> + if (ret != size) {
> + if (ret >= 0)
> + errno = EPROTO;
> + return -1;
> + }
> +
> + ret = read(fd, buf, QUERY_LABEL_REPLY_LEN);
> + saved = errno;
> + (void)close(fd);
This may not be enough to silence the new-fangled warnings.
> + errno = saved;
> + if (ret != QUERY_LABEL_REPLY_LEN) {
> + if (ret >= 0)
> + errno = EPROTO;
> + return -1;
> + }
> +
> + ret = sscanf(buf, "allow 0x%8" SCNx32 "\n"
> + "deny 0x%8" SCNx32 "\n"
> + "audit 0x%8" SCNx32 "\n"
> + "quiet 0x%8" SCNx32 "\n",
> + &allow, &deny, &audit, &quiet);
> + if (ret != 4) {
> + errno = EPROTONOSUPPORT;
> + return -1;
> + }
> +
> + *allowed = mask & ~(allow & ~deny) ? 0 : 1;
> + if (!(*allowed))
> + audit = 0xFFFFFFFF;
> + *audited = mask & ~(audit & ~quiet) ? 0 : 1;
I already broke my head thinking this bit through once -- and I came to
the wrong conclusion last time :) -- so I hope this has the fix you
found you needed last time through. :)
> +
> + return 0;
> +}
> diff --git a/libraries/libapparmor/src/libapparmor.map b/libraries/libapparmor/src/libapparmor.map
> index c4fcf8f..df696a7 100644
> --- a/libraries/libapparmor/src/libapparmor.map
> +++ b/libraries/libapparmor/src/libapparmor.map
> @@ -37,3 +37,10 @@ APPARMOR_1.1 {
> local:
> *;
> } APPARMOR_1.0;
> +
> +APPARMOR_3.0 {
> + global:
> + aa_query_label;
> + local:
> + *;
> +} APPARMOR_1.1;
> diff --git a/libraries/libapparmor/swig/SWIG/libapparmor.i b/libraries/libapparmor/swig/SWIG/libapparmor.i
> index 1d3ca07..a94cb23 100644
> --- a/libraries/libapparmor/swig/SWIG/libapparmor.i
> +++ b/libraries/libapparmor/swig/SWIG/libapparmor.i
> @@ -27,3 +27,5 @@ extern int aa_gettaskcon(pid_t target, char **con, char **mode);
> extern int aa_getcon(char **con, char **mode);
> extern int aa_getpeercon_raw(int fd, char *buf, int *len, char **mode);
> extern int aa_getpeercon(int fd, char **con, char **mode);
> +extern int aa_query_label(uint32_t mask, char *query, size_t size, int *allow,
> + int *audit);
> --
Thanks!
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