tftpd: support full 512-byte requests

Some HP PA-RISC firmware always sends fixed 512-byte requests,
with trailing garbage.

function                                             old     new   delta
tftpd_main                                           578     572      -6

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/networking/tftp.c b/networking/tftp.c
index 630fdaf9a..8e3b0a2dc 100644
--- a/networking/tftp.c
+++ b/networking/tftp.c
@@ -119,6 +119,7 @@ struct globals {
         struct passwd *pw;
         /* used in tftpd_main(), a bit big for stack: */
         char block_buf[TFTP_BLKSIZE_DEFAULT];
+        char block_buf_tail[1];
 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
         off_t pos;
         off_t size;
@@ -793,14 +794,16 @@ int tftpd_main(int argc UNUSED_PARAM, char **argv)
                 xchroot(argv[0]);
         }
 
-        result = recv_from_to(STDIN_FILENO, G.block_buf, sizeof(G.block_buf),
+        result = recv_from_to(STDIN_FILENO,
+                        G.block_buf, sizeof(G.block_buf) + 1,
+                        /* ^^^ sizeof+1 to reliably detect oversized input */
                         0 /* flags */,
                         &peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
 
         error_msg = "malformed packet";
         opcode = ntohs(*(uint16_t*)G.block_buf);
-        if (result < 4 || result >= sizeof(G.block_buf)
-         || G.block_buf[result-1] != '\0'
+        if (result < 4 || result > sizeof(G.block_buf)
+        /*|| G.block_buf[result-1] != '\0' - bug compatibility, see below */
          || (IF_FEATURE_TFTP_PUT(opcode != TFTP_RRQ) /* not download */
              IF_GETPUT(&&)
              IF_FEATURE_TFTP_GET(opcode != TFTP_WRQ) /* not upload */
@@ -808,6 +811,13 @@ int tftpd_main(int argc UNUSED_PARAM, char **argv)
         ) {
                 goto err;
         }
+        /* Some HP PA-RISC firmware always sends fixed 512-byte requests,
+         * with trailing garbage.
+         * Support that by not requiring NUL to be the last byte (see above).
+         * To make strXYZ() ops safe, force NUL termination:
+         */
+        G.block_buf_tail[0] = '\0';
+
         local_file = G.block_buf + 2;
         if (local_file[0] == '.' || strstr(local_file, "/.")) {
                 error_msg = "dot in file name";