dhcp: get_option_uint* only accept options with correct len (#357)

RFC8925 mentions "The client MUST ignore the IPv6-Only Preferred option
if the length field value is not 4."

diff --git a/src/dhcp.c b/src/dhcp.c
index 85d2c56fd9162d27bd09f415ae74659e9f022ea4..4ec81a50d967af77229b30fc52eea30040c5969e 100644 (file)
--- a/src/dhcp.c
+++ b/src/dhcp.c
@@ -304,7 +304,7 @@ get_option_uint32(struct dhcpcd_ctx *ctx,
        uint32_t d;
 
        p = get_option(ctx, bootp, bootp_len, option, &len);
-       if (!p || len < (ssize_t)sizeof(d))
+       if (!p || len != (ssize_t)sizeof(d))
                return -1;
        memcpy(&d, p, sizeof(d));
        if (i)
@@ -321,7 +321,7 @@ get_option_uint16(struct dhcpcd_ctx *ctx,
        uint16_t d;
 
        p = get_option(ctx, bootp, bootp_len, option, &len);
-       if (!p || len < (ssize_t)sizeof(d))
+       if (!p || len != (ssize_t)sizeof(d))
                return -1;
        memcpy(&d, p, sizeof(d));
        if (i)
@@ -337,7 +337,7 @@ get_option_uint8(struct dhcpcd_ctx *ctx,
        size_t len;
 
        p = get_option(ctx, bootp, bootp_len, option, &len);
-       if (!p || len < (ssize_t)sizeof(*p))
+       if (!p || len != (ssize_t)sizeof(*p))
                return -1;
        if (i)
                *i = *(p);
@@ -3158,8 +3158,7 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
        /* Ensure that no reject options are present */
        for (i = 1; i < 255; i++) {
                if (has_option_mask(ifo->rejectmask, i) &&
-                   get_option_uint8(ifp->ctx, &tmp,
-                   bootp, bootp_len, (uint8_t)i) == 0)
+                   get_option(ifp->ctx, bootp, bootp_len, (uint8_t)i, NULL))
                {
                        LOGDHCP(LOG_WARNING, "reject DHCP");
                        return;
@@ -3207,8 +3206,7 @@ dhcp_handledhcp(struct interface *ifp, struct bootp *bootp, size_t bootp_len,
        /* Ensure that all required options are present */
        for (i = 1; i < 255; i++) {
                if (has_option_mask(ifo->requiremask, i) &&
-                   get_option_uint8(ifp->ctx, &tmp,
-                   bootp, bootp_len, (uint8_t)i) != 0)
+                   !get_option(ifp->ctx, bootp, bootp_len, (uint8_t)i, NULL))
                {
                        /* If we are BOOTP, then ignore the need for serverid.
                         * To ignore BOOTP, require dhcp_message_type.