Adding upstream version 1:4.13+dfsg1.upstream/1%4.13+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 151 insertions, 0 deletions

diff --git a/lib/nss.c b/lib/nss.c
new file mode 100644
index 0000000..23d0518
--- /dev/null
+++ b/lib/nss.c
@@ -0,0 +1,151 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+#include <stdbool.h>
+#include <string.h>
+#include <strings.h>
+#include <ctype.h>
+#include <stdatomic.h>
+#include "prototypes.h"
+#include "../libsubid/subid.h"
+#include "shadowlog_internal.h"
+#include "shadowlog.h"
+
+#define NSSWITCH "/etc/nsswitch.conf"
+
+// NSS plugin handling for subids
+// If nsswitch has a line like
+//    subid: sssd
+// then sssd will be consulted for subids.  Unlike normal NSS dbs,
+// only one db is supported at a time.  That's open to debate, but
+// the subids are a pretty limited resource, and local files seem
+// bound to step on any other allocations leading to insecure
+// conditions.
+static atomic_flag nss_init_started;
+static atomic_bool nss_init_completed;
+
+static struct subid_nss_ops *subid_nss;
+
+bool nss_is_initialized() {
+	return atomic_load(&nss_init_completed);
+}
+
+static void nss_exit(void) {
+	if (nss_is_initialized() && subid_nss) {
+		dlclose(subid_nss->handle);
+		free(subid_nss);
+		subid_nss = NULL;
+	}
+}
+
+// nsswitch_path is an argument only to support testing.
+void nss_init(const char *nsswitch_path) {
+	FILE *nssfp = NULL;
+	char *line = NULL, *p, *token, *saveptr;
+	size_t len = 0;
+	FILE *shadow_logfd = log_get_logfd();
+
+	if (atomic_flag_test_and_set(&nss_init_started)) {
+		// Another thread has started nss_init, wait for it to complete
+		while (!atomic_load(&nss_init_completed))
+			usleep(100);
+		return;
+	}
+
+	if (!nsswitch_path)
+		nsswitch_path = NSSWITCH;
+
+	// read nsswitch.conf to check for a line like:
+	//   subid:	files
+	nssfp = fopen(nsswitch_path, "r");
+	if (!nssfp) {
+		atomic_store(&nss_init_completed, true);
+		return;
+	}
+	while ((getline(&line, &len, nssfp)) != -1) {
+		if (line[0] == '\0' || line[0] == '#')
+			continue;
+		if (strlen(line) < 8)
+			continue;
+		if (strncasecmp(line, "subid:", 6) != 0)
+			continue;
+		p = &line[6];
+		while ((*p) && isspace(*p))
+			p++;
+		if (!*p)
+			continue;
+		for (token = strtok_r(p, " \n\t", &saveptr);
+		     token;
+		     token = strtok_r(NULL, " \n\t", &saveptr)) {
+			char libname[65];
+			void *h;
+			if (strcmp(token, "files") == 0) {
+				subid_nss = NULL;
+				goto done;
+			}
+			if (strlen(token) > 50) {
+				fprintf(shadow_logfd, "Subid NSS module name too long (longer than 50 characters): %s\n", token);
+				fprintf(shadow_logfd, "Using files\n");
+				subid_nss = NULL;
+				goto done;
+			}
+			snprintf(libname, 64,  "libsubid_%s.so", token);
+			h = dlopen(libname, RTLD_LAZY);
+			if (!h) {
+				fprintf(shadow_logfd, "Error opening %s: %s\n", libname, dlerror());
+				fprintf(shadow_logfd, "Using files\n");
+				subid_nss = NULL;
+				goto done;
+			}
+			subid_nss = malloc(sizeof(*subid_nss));
+			if (!subid_nss) {
+				dlclose(h);
+				goto done;
+			}
+			subid_nss->has_range = dlsym(h, "shadow_subid_has_range");
+			if (!subid_nss->has_range) {
+				fprintf(shadow_logfd, "%s did not provide @has_range@\n", libname);
+				dlclose(h);
+				free(subid_nss);
+				subid_nss = NULL;
+				goto done;
+			}
+			subid_nss->list_owner_ranges = dlsym(h, "shadow_subid_list_owner_ranges");
+			if (!subid_nss->list_owner_ranges) {
+				fprintf(shadow_logfd, "%s did not provide @list_owner_ranges@\n", libname);
+				dlclose(h);
+				free(subid_nss);
+				subid_nss = NULL;
+				goto done;
+			}
+			subid_nss->find_subid_owners = dlsym(h, "shadow_subid_find_subid_owners");
+			if (!subid_nss->find_subid_owners) {
+				fprintf(shadow_logfd, "%s did not provide @find_subid_owners@\n", libname);
+				dlclose(h);
+				free(subid_nss);
+				subid_nss = NULL;
+				goto done;
+			}
+			subid_nss->handle = h;
+			goto done;
+		}
+		fprintf(shadow_logfd, "No usable subid NSS module found, using files\n");
+		// subid_nss has to be null here, but to ease reviews:
+		free(subid_nss);
+		subid_nss = NULL;
+		goto done;
+	}
+
+done:
+	atomic_store(&nss_init_completed, true);
+	free(line);
+	if (nssfp) {
+		atexit(nss_exit);
+		fclose(nssfp);
+	}
+}
+
+struct subid_nss_ops *get_subid_nss_handle() {
+	nss_init(NULL);
+	return subid_nss;
+}