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virtfs-proxy-helper: switch from libcap to libcap-ng

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virtfs-proxy-helper is the only user of libcap; everyone else is using
the simpler libcap-ng API.  Switch and remove the configure code to
detect libcap.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
[groug: - drop remaining -lcap from Makefile
        - fix error message in configure]
Signed-off-by: Greg Kurz <groug@kaod.org>
This commit is contained in:
Paolo Bonzini 2019-11-29 12:16:32 +01:00 • committed by Greg Kurz
parent fb2246882a
commit 7e46261368
3 changed files with 47 additions and 74 deletions
Download patch file Download diff file Expand all files Collapse all files

100
fsdev/virtfs-proxy-helper.c
View file

@ -13,7 +13,6 @@
#include <sys/resource.h>
#include <getopt.h>
#include <syslog.h>
#include <sys/capability.h>
#include <sys/fsuid.h>
#include <sys/vfs.h>
#include <sys/ioctl.h>
@ -21,6 +20,7 @@
#ifdef CONFIG_LINUX_MAGIC_H
#include <linux/magic.h>
#endif
#include <cap-ng.h>
#include "qemu-common.h"
#include "qemu/sockets.h"
#include "qemu/xattr.h"
@ -79,49 +79,10 @@ static void do_perror(const char *string)
}
}
static int do_cap_set(cap_value_t *cap_value, int size, int reset)
{
cap_t caps;
if (reset) {
/*
* Start with an empty set and set permitted and effective
*/
caps = cap_init();
if (caps == NULL) {
do_perror("cap_init");
return -1;
}
if (cap_set_flag(caps, CAP_PERMITTED, size, cap_value, CAP_SET) < 0) {
do_perror("cap_set_flag");
goto error;
}
} else {
caps = cap_get_proc();
if (!caps) {
do_perror("cap_get_proc");
return -1;
}
}
if (cap_set_flag(caps, CAP_EFFECTIVE, size, cap_value, CAP_SET) < 0) {
do_perror("cap_set_flag");
goto error;
}
if (cap_set_proc(caps) < 0) {
do_perror("cap_set_proc");
goto error;
}
cap_free(caps);
return 0;
error:
cap_free(caps);
return -1;
}
static int init_capabilities(void)
{
/* helper needs following capabilities only */
cap_value_t cap_list[] = {
int cap_list[] = {
CAP_CHOWN,
CAP_DAC_OVERRIDE,
CAP_FOWNER,
@ -130,7 +91,34 @@ static int init_capabilities(void)
CAP_MKNOD,
CAP_SETUID,
};
return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 1);
int i;
capng_clear(CAPNG_SELECT_BOTH);
for (i = 0; i < ARRAY_SIZE(cap_list); i++) {
if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
cap_list[i]) < 0) {
do_perror("capng_update");
return -1;
}
}
if (capng_apply(CAPNG_SELECT_BOTH) < 0) {
do_perror("capng_apply");
return -1;
}
/* Prepare effective set for setugid. */
for (i = 0; i < ARRAY_SIZE(cap_list); i++) {
if (cap_list[i] == CAP_DAC_OVERRIDE) {
continue;
}
if (capng_update(CAPNG_DROP, CAPNG_EFFECTIVE,
cap_list[i]) < 0) {
do_perror("capng_update");
return -1;
}
}
return 0;
}
static int socket_read(int sockfd, void *buff, ssize_t size)
@ -295,14 +283,6 @@ static int setugid(int uid, int gid, int *suid, int *sgid)
{
int retval;
/*
* We still need DAC_OVERRIDE because we don't change
* supplementary group ids, and hence may be subjected DAC rules
*/
cap_value_t cap_list[] = {
CAP_DAC_OVERRIDE,
};
*suid = geteuid();
*sgid = getegid();
@ -316,11 +296,21 @@ static int setugid(int uid, int gid, int *suid, int *sgid)
goto err_sgid;
}
if (uid != 0 || gid != 0) {
if (do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0) < 0) {
retval = -errno;
goto err_suid;
}
if (uid == 0 && gid == 0) {
/* Linux has already copied the permitted set to the effective set. */
return 0;
}
/*
* All capabilities have been cleared from the effective set. However
* we still need DAC_OVERRIDE because we don't change supplementary
* group ids, and hence may be subject to DAC rules. init_capabilities
* left the set of capabilities that we want in libcap-ng's state.
*/
if (capng_apply(CAPNG_SELECT_CAPS) < 0) {
retval = -errno;
do_perror("capng_apply");
goto err_suid;
}
return 0;