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nwfilter: avoid failure with noexec /tmp

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If /tmp is mounted with the noexec flag (common on security-conscious
systems), then nwfilter will fail to initialize, because we cannot
run any temporary script via virRun("/tmp/script"); but we _can_
use "/bin/sh /tmp/script".  For that matter, using /tmp risks collisions
with other unrelated programs; we already have /var/run/libvirt as a
dedicated temporary directory for use by libvirt.

* src/nwfilter/nwfilter_ebiptables_driver.c
(ebiptablesWriteToTempFile): Use internal directory, not /tmp;
drop attempts to make script executable; and detect close error.
(ebiptablesExecCLI): Switch to virCommand, and invoke the shell to
read the script, rather than requiring an executable script.
This commit is contained in:
Eric Blake 2011-11-09 10:23:49 -07:00
parent 0eee075dc7
commit bd6083c9ba
1 changed files with 25 additions and 59 deletions
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84
src/nwfilter/nwfilter_ebiptables_driver.c
View File

@ -40,6 +40,7 @@
#include "nwfilter_ebiptables_driver.h"
#include "virfile.h"
#include "command.h"
#include "configmake.h"
#define VIR_FROM_THIS VIR_FROM_NWFILTER
@ -2482,29 +2483,17 @@ ebiptablesDisplayRuleInstance(virConnectPtr conn ATTRIBUTE_UNUSED,
* NULL in case of error with the error reported.
*
* Write the string into a temporary file and return the name of
* the temporary file. The string is assumed to contain executable
* commands. A line '#!/bin/sh' will automatically be written
* as the first line in the file. The permissions of the file are
* set so that the file can be run as an executable script.
* the temporary file. The file can then be read as a /bin/sh script.
* No '#!/bin/sh' header is needed, since the file will be read and not
* directly executed.
*/
static char *
ebiptablesWriteToTempFile(const char *string) {
char filename[] = "/tmp/virtdXXXXXX";
int len;
char filename[] = LOCALSTATEDIR "/run/libvirt/nwfilt-XXXXXX";
size_t len;
char *filnam;
virBuffer buf = VIR_BUFFER_INITIALIZER;
char *header;
size_t written;
virBufferAddLit(&buf, "#!/bin/sh\n");
if (virBufferError(&buf)) {
virBufferFreeAndReset(&buf);
virReportOOMError();
return NULL;
}
header = virBufferContentAndReset(&buf);
int fd = mkstemp(filename);
if (fd < 0) {
@ -2514,22 +2503,6 @@ ebiptablesWriteToTempFile(const char *string) {
goto err_exit;
}
if (fchmod(fd, S_IXUSR| S_IRUSR | S_IWUSR) < 0) {
virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
"%s",
_("cannot change permissions on temp. file"));
goto err_exit;
}
len = strlen(header);
written = safewrite(fd, header, len);
if (written != len) {
virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
"%s",
_("cannot write string to file"));
goto err_exit;
}
len = strlen(string);
written = safewrite(fd, string, len);
if (written != len) {
@ -2539,18 +2512,22 @@ ebiptablesWriteToTempFile(const char *string) {
goto err_exit;
}
if (VIR_CLOSE(fd) < 0) {
virNWFilterReportError(VIR_ERR_INTERNAL_ERROR,
"%s",
_("cannot write string to file"));
goto err_exit;
}
filnam = strdup(filename);
if (!filnam) {
virReportOOMError();
goto err_exit;
}
VIR_FREE(header);
VIR_FORCE_CLOSE(fd);
return filnam;
err_exit:
VIR_FREE(header);
VIR_FORCE_CLOSE(fd);
unlink(filename);
return NULL;
@ -2564,7 +2541,7 @@ err_exit:
* @status: Pointer to an integer for returning the WEXITSTATUS of the
* commands executed via the script the was run.
*
* Returns 0 in case of success, != 0 in case of an error. The returned
* Returns 0 in case of success, < 0 in case of an error. The returned
* value is NOT the result of running the commands inside the shell
* script.
*
@ -2577,53 +2554,42 @@ ebiptablesExecCLI(virBufferPtr buf,
{
char *cmds;
char *filename;
int rc;
const char *argv[] = {NULL, NULL};
int rc = -1;
virCommandPtr cmd;
if (virBufferError(buf)) {
virReportOOMError();
virBufferFreeAndReset(buf);
return 1;
return -1;
}
*status = 0;
cmds = virBufferContentAndReset(buf);
VIR_DEBUG("%s", NULLSTR(cmds));
if (!cmds)
return 0;
filename = ebiptablesWriteToTempFile(cmds);
VIR_FREE(cmds);
if (!filename)
return 1;
goto cleanup;
argv[0] = filename;
cmd = virCommandNew("/bin/sh");
virCommandAddArg(cmd, filename);
virMutexLock(&execCLIMutex);
rc = virRun(argv, status);
rc = virCommandRun(cmd, status);
virMutexUnlock(&execCLIMutex);
if (rc == 0) {
if (WIFEXITED(*status)) {
*status = WEXITSTATUS(*status);
} else {
rc = -1;
*status = 1;
}
}
VIR_DEBUG("rc = %d, status = %d", rc, *status);
unlink(filename);
VIR_FREE(filename);
cleanup:
VIR_FREE(cmds);
virCommandFree(cmd);
return rc;
}