[apparmor] [PATCH] libapparmor: Export a label-based query interface
Tyler Hicks
tyhicks at canonical.com
Mon Jul 29 23:47:27 UTC 2013
On 2013-07-29 16:36:25, Seth Arnold wrote:
> 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.
Ah, nice catch. I'll drop the stdint.h include in my local copy. (I'm
not going to send out a v2)
>
> > +#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.
It seems to be enough on Saucy, both with a simple make and with a PPA
build, which I assume has more hardening flags enabled.
>
> > + 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. :)
Luckily for the both of us, I kept the patch updated. :)
Thanks for the review!
Tyler
>
> > +
> > + 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!
> --
> AppArmor mailing list
> AppArmor at lists.ubuntu.com
> Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/apparmor
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: Digital signature
URL: <https://lists.ubuntu.com/archives/apparmor/attachments/20130729/42bdbf0f/attachment-0001.pgp>
More information about the AppArmor
mailing list