udhcpd: add code which rejects lease files with suspicious or old timestamp.

*: s/time(0)/time(NULL)/g

3 files changed, 20 insertions, 18 deletions

diff --git a/networking/httpd.c b/networking/httpd.c
index 3a2e6b14b..fc8b51240 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -969,7 +969,7 @@ static void send_headers(int responseNum)
         const char *error_page = NULL;
 #endif
         unsigned i;
-        time_t timer = time(0);
+        time_t timer = time(NULL);
         char tmp_str[80];
         int len;
 
diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index d0a1eba81..ebf30178a 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -255,13 +255,13 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                         DEBUG("Received DECLINE");
                         if (lease) {
                                 memset(lease->chaddr, 0, 16);
-                                lease->expires = time(0) + server_config.decline_time;
+                                lease->expires = time(NULL) + server_config.decline_time;
                         }
                         break;
                 case DHCPRELEASE:
                         DEBUG("Received RELEASE");
                         if (lease)
-                                lease->expires = time(0);
+                                lease->expires = time(NULL);
                         break;
                 case DHCPINFORM:
                         DEBUG("Received INFORM");
diff --git a/networking/udhcp/files.c b/networking/udhcp/files.c
index 64edcbb25..fb6fe01ae 100644
--- a/networking/udhcp/files.c
+++ b/networking/udhcp/files.c
@@ -36,6 +36,7 @@ static int read_ip(const char *line, void *arg)
         return 1;
 }
 
+
 static int read_mac(const char *line, void *arg)
 {
         return NULL == ether_aton_r(line, (struct ether_addr *)arg);
@@ -362,7 +363,7 @@ void FAST_FUNC write_leases(void)
                 if (leases[i].yiaddr == 0)
                         continue;
 
-                /* screw with the time in the struct, for easier writing */
+                /* Screw with the time in the struct, for easier writing */
                 tmp_time = leases[i].expires;
 
                 leases[i].expires -= curr;
@@ -374,7 +375,7 @@ void FAST_FUNC write_leases(void)
                  * we lose some leases on restart. Oh well. */
                 full_write(fd, &leases[i], sizeof(leases[i]));
 
-                /* then restore it when done */
+                /* Then restore it when done */
                 leases[i].expires = tmp_time;
         }
         close(fd);
@@ -390,10 +391,10 @@ void FAST_FUNC write_leases(void)
 
 void FAST_FUNC read_leases(const char *file)
 {
-        int fd;
-        unsigned i;
         struct dhcpOfferedAddr lease;
-        int64_t written_at, curr;
+        int64_t written_at, time_passed;
+        int fd;
+        USE_UDHCP_DEBUG(unsigned i;)
 
         fd = open_or_warn(file, O_RDONLY);
         if (fd < 0)
@@ -402,18 +403,19 @@ void FAST_FUNC read_leases(const char *file)
         if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at))
                 goto ret;
         written_at = ntoh64(written_at);
-        curr = time(NULL);
-        if (curr < written_at)
-                written_at = curr; /* lease file from future! :) */
-
-        i = 0;
-        while (i < server_config.max_leases
-         && full_read(fd, &lease, sizeof(lease)) == sizeof(lease)
-        ) {
+
+        time_passed = time(NULL) - written_at;
+        /* Strange written_at, or lease file from old version of udhcpd
+         * which had no "written_at" field? */
+        if ((uint64_t)time_passed > 12 * 60 * 60)
+                goto ret;
+
+        USE_UDHCP_DEBUG(i = 0;)
+        while (full_read(fd, &lease, sizeof(lease)) == sizeof(lease)) {
                 /* ADDME: what if it matches some static lease? */
                 uint32_t y = ntohl(lease.yiaddr);
                 if (y >= server_config.start_ip && y <= server_config.end_ip) {
-                        int64_t expires = ntohl(lease.expires) + written_at - curr;
+                        signed_leasetime_t expires = ntohl(lease.expires) - (signed_leasetime_t)time_passed;
                         if (expires <= 0)
                                 continue;
                         /* NB: add_lease takes "relative time", IOW,
@@ -422,7 +424,7 @@ void FAST_FUNC read_leases(const char *file)
                                 bb_error_msg("too many leases while loading %s", file);
                                 break;
                         }
-                        i++;
+                        USE_UDHCP_DEBUG(i++;)
                 }
         }
         DEBUG("Read %d leases", i);