5:16 p.m.
Since the kernel sets a number of dynamic rlimits based on the system
properties (e.g. physical memory for nproc), these rlimits should be
respected by PAM. Parse /proc/1/limits for the kernel-defined rlimits.
Signed-off-by: Kees Cook <kees.cook(a)canonical.com>
---
modules/pam_limits/pam_limits.c | 157 +++++++++++++++++++++++++++++++++++++-
1 files changed, 152 insertions(+), 5 deletions(-)
diff --git a/modules/pam_limits/pam_limits.c b/modules/pam_limits/pam_limits.c
index 8814652..fa1d35f 100644
--- a/modules/pam_limits/pam_limits.c
+++ b/modules/pam_limits/pam_limits.c
@@ -51,9 +51,10 @@
#define LIMITS_DEF_USER 0 /* limit was set by an user entry */
#define LIMITS_DEF_GROUP 1 /* limit was set by a group entry */
#define LIMITS_DEF_ALLGROUP 2 /* limit was set by a group entry */
-#define LIMITS_DEF_ALL 3 /* limit was set by an default entry */
-#define LIMITS_DEF_DEFAULT 4 /* limit was set by an default entry */
-#define LIMITS_DEF_NONE 5 /* this limit was not set yet */
+#define LIMITS_DEF_ALL 3 /* limit was set by an all entry */
+#define LIMITS_DEF_DEFAULT 4 /* limit was set by a default entry */
+#define LIMITS_DEF_KERNEL 5 /* limit was set from /proc/1/limits */
+#define LIMITS_DEF_NONE 6 /* this limit was not set yet */
#define LIMIT_RANGE_ERR -1 /* error in specified uid/gid range */
#define LIMIT_RANGE_NONE 0 /* no range specified */
@@ -67,6 +68,7 @@ static const char *limits_def_names[] = {
"ALLGROUP",
"ALL",
"DEFAULT",
+ "KERNEL",
"NONE",
NULL
};
@@ -292,7 +294,139 @@ check_logins (pam_handle_t *pamh, const char *name, int limit, int
ctrl,
return 0;
}
-static int init_limits(struct pam_limit_s *pl)
+static const char * lnames[RLIM_NLIMITS] = {
+ [RLIMIT_CPU] = "Max cpu time",
+ [RLIMIT_FSIZE] = "Max file size",
+ [RLIMIT_DATA] = "Max data size",
+ [RLIMIT_STACK] = "Max stack size",
+ [RLIMIT_CORE] = "Max core file size",
+ [RLIMIT_RSS] = "Max resident set",
+ [RLIMIT_NPROC] = "Max processes",
+ [RLIMIT_NOFILE] = "Max open files",
+ [RLIMIT_MEMLOCK] = "Max locked memory",
+#ifdef RLIMIT_AS
+ [RLIMIT_AS] = "Max address space",
+#endif
+#ifdef RLIMIT_LOCKS
+ [RLIMIT_LOCKS] = "Max file locks",
+#endif
+#ifdef RLIMIT_SIGPENDING
+ [RLIMIT_SIGPENDING] = "Max pending signals",
+#endif
+#ifdef RLIMIT_MSGQUEUE
+ [RLIMIT_MSGQUEUE] = "Max msgqueue size",
+#endif
+#ifdef RLIMIT_NICE
+ [RLIMIT_NICE] = "Max nice priority",
+#endif
+#ifdef RLIMIT_RTPRIO
+ [RLIMIT_RTPRIO] = "Max realtime priority",
+#endif
+#ifdef RLIMIT_RTTIME
+ [RLIMIT_RTTIME] = "Max realtime timeout",
+#endif
+};
+
+static int str2rlimit(char *name) {
+ int i;
+ if (!name || *name == '\0')
+ return -1;
+ for(i = 0; i < RLIM_NLIMITS; i++) {
+ if (strcmp(name, lnames[i]) == 0) return i;
+ }
+ return -1;
+}
+
+static rlim_t str2rlim_t(char *value) {
+ unsigned long long rlimit = 0;
+
+ if (!value) return (rlim_t)rlimit;
+ if (strcmp(value, "unlimited") == 0) {
+ return RLIM_INFINITY;
+ }
+ rlimit = strtoull(value, NULL, 10);
+ return (rlim_t)rlimit;
+}
+
+#define LIMITS_SKIP_WHITESPACE { \
+ /* step backwards over spaces */ \
+ pos--; \
+ while (pos && line[pos] == ' ') pos--; \
+ if (!pos) continue; \
+ line[pos+1] = '\0'; \
+}
+#define LIMITS_MARK_ITEM(item) { \
+ /* step backwards over non-spaces */ \
+ pos--; \
+ while (pos && line[pos] != ' ') pos--; \
+ if (!pos) continue; \
+ item = line + pos + 1; \
+}
+
+static void parse_kernel_limits(pam_handle_t *pamh, struct pam_limit_s *pl)
+{
+ int i, maxlen = 0;
+ FILE *limitsfile;
+ const char *proclimits = "/proc/1/limits";
+ char line[256];
+ char *units, *hard, *soft, *name;
+
+ if (!(limitsfile = fopen(proclimits, "r"))) {
+ pam_syslog(pamh, LOG_WARNING, "Could not read %s (%s), using PAM
defaults", proclimits, strerror(errno));
+ return;
+ }
+
+ while (fgets(line, 256, limitsfile)) {
+ int pos = strlen(line);
+ if (pos < 2) continue;
+
+ /* drop trailing newline */
+ if (line[pos-1] == '\n') {
+ pos--;
+ line[pos] = '\0';
+ }
+
+ /* determine formatting boundry of limits report */
+ if (!maxlen && strncmp(line, "Limit", 5) == 0) {
+ maxlen = pos;
+ continue;
+ }
+
+ if (pos == maxlen) {
+ /* step backwards over "Units" name */
+ LIMITS_SKIP_WHITESPACE;
+ LIMITS_MARK_ITEM(units);
+ }
+ else {
+ units = "";
+ }
+
+ /* step backwards over "Hard Limit" value */
+ LIMITS_SKIP_WHITESPACE;
+ LIMITS_MARK_ITEM(hard);
+
+ /* step backwards over "Soft Limit" value */
+ LIMITS_SKIP_WHITESPACE;
+ LIMITS_MARK_ITEM(soft);
+
+ /* step backwards over name of limit */
+ LIMITS_SKIP_WHITESPACE;
+ name = line;
+
+ i = str2rlimit(name);
+ if (i < 0 || i >= RLIM_NLIMITS) {
+ pam_syslog(pamh, LOG_DEBUG, "Unknown kernel rlimit '%s'
ignored", name);
+ continue;
+ }
+ pl->limits[i].limit.rlim_cur = str2rlim_t(soft);
+ pl->limits[i].limit.rlim_max = str2rlim_t(hard);
+ pl->limits[i].src_soft = LIMITS_DEF_KERNEL;
+ pl->limits[i].src_hard = LIMITS_DEF_KERNEL;
+ }
+ fclose(limitsfile);
+}
+
+static int init_limits(pam_handle_t *pamh, struct pam_limit_s *pl)
{
int i;
int retval = PAM_SUCCESS;
@@ -313,6 +447,19 @@ static int init_limits(struct pam_limit_s *pl)
}
}
+#ifdef __linux__
+ parse_kernel_limits(pamh, pl);
+#endif
+
+ for(i = 0; i < RLIM_NLIMITS; i++) {
+ if (pl->limits[i].supported &&
+ (pl->limits[i].src_soft == LIMITS_DEF_NONE ||
+ pl->limits[i].src_hard == LIMITS_DEF_NONE)) {
+#ifdef __linux__
+ pam_syslog(pamh, LOG_WARNING, "Did not find kernel RLIMIT for %s, using PAM
default", rlimit2str(i));
+#endif
+ }
+
errno = 0;
pl->priority = getpriority (PRIO_PROCESS, 0);
if (pl->priority == -1 && errno != 0)
@@ -873,7 +1020,7 @@ pam_sm_open_session (pam_handle_t *pamh, int flags UNUSED,
return PAM_USER_UNKNOWN;
}
- retval = init_limits(pl);
+ retval = init_limits(pamh, pl);
if (retval != PAM_SUCCESS) {
pam_syslog(pamh, LOG_WARNING, "cannot initialize");
return PAM_ABORT;
--
1.7.4.1
--
Kees Cook
Ubuntu Security Team