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tftp: on download, open local file only when first bit of data arrived

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No reason to potentially clobber existing file before absolutely necessary.

function                                             old     new   delta
tftp_protocol                                       1947    2020     +73
tftp_main                                            393     376     -17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 73/-17)             Total: 56 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2020-02-13 15:27:23 +01:00
parent 0c4e5977df
commit adc540f0db
1 changed files with 33 additions and 28 deletions
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61
networking/tftp.c
View File

@ -319,7 +319,7 @@ static int tftp_protocol(
uint16_t opcode;
uint16_t block_nr;
uint16_t recv_blk;
int open_mode, local_fd;
int local_fd = -1;
int retries, waittime_ms;
int io_bufsize = blksize + 4;
char *cp;
@ -354,19 +354,6 @@ static int tftp_protocol(
}
}
/* Prepare open mode */
if (CMD_PUT(option_mask32)) {
open_mode = O_RDONLY;
} else {
open_mode = O_WRONLY | O_TRUNC | O_CREAT;
#if ENABLE_TFTPD
if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
/* tftpd without -c */
open_mode = O_WRONLY | O_TRUNC;
}
#endif
}
/* Examples of network traffic.
* Note two cases when ACKs with block# of 0 are sent.
*
@ -400,6 +387,14 @@ static int tftp_protocol(
if (!ENABLE_TFTP || our_lsa) { /* tftpd */
/* Open file (must be after changing user) */
int open_mode = O_RDONLY;
if (CMD_GET(option_mask32)) {
open_mode = O_WRONLY | O_TRUNC | O_CREAT;
if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
/* tftpd without -c */
open_mode = O_WRONLY | O_TRUNC;
}
}
local_fd = open(local_file, open_mode, 0666);
if (local_fd < 0) {
/* sanitize name, it came from untrusted remote side */
@ -414,6 +409,7 @@ static int tftp_protocol(
strcpy(G_error_pkt_str, "can't open file");
goto send_err_pkt_nomsg;
}
/* gcc 4.3.1 would NOT optimize it out as it should! */
#if ENABLE_FEATURE_TFTP_BLOCKSIZE
if (blksize != TFTP_BLKSIZE_DEFAULT || want_transfer_size) {
@ -432,10 +428,11 @@ static int tftp_protocol(
block_nr = 0;
}
} else { /* tftp */
/* Open file (must be after changing user) */
local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
if (NOT_LONE_DASH(local_file))
local_fd = xopen(local_file, open_mode);
if (CMD_PUT(option_mask32)) {
local_fd = STDIN_FILENO;
if (local_file)
local_fd = xopen(local_file, O_RDONLY);
}
/* Removing #if, or using if() statement instead of #if may lead to
* "warning: null argument where non-null required": */
#if ENABLE_TFTP
@ -491,7 +488,7 @@ static int tftp_protocol(
}
if (want_transfer_size) {
/* add "tsize", <nul>, size, <nul> (see RFC2349) */
/* if tftp and downloading, we send "0" (since we opened local_fd with O_TRUNC)
/* if tftp and downloading, we send "0" (local_fd is not open yet)
* and this makes server to send "tsize" option with the size */
/* if tftp and uploading, we send file size (maybe dont, to not confuse old servers???) */
/* if tftpd and downloading, we are answering to client's request */
@ -500,7 +497,8 @@ static int tftp_protocol(
strcpy(cp, "tsize");
cp += sizeof("tsize");
st.st_size = 0;
fstat(local_fd, &st);
if (local_fd >= 0)
fstat(local_fd, &st);
cp += sprintf(cp, "%"OFF_FMT"u", (off_t)st.st_size) + 1;
# if ENABLE_FEATURE_TFTP_PROGRESS_BAR
/* Save for progress bar. If 0 (tftp downloading),
@ -690,7 +688,13 @@ static int tftp_protocol(
if (CMD_GET(option_mask32) && (opcode == TFTP_DATA)) {
if (recv_blk == block_nr) {
int sz = full_write(local_fd, &rbuf[4], len - 4);
int sz;
if (local_fd == -1) {
local_fd = STDOUT_FILENO;
if (local_file)
local_fd = xopen(local_file, O_WRONLY | O_TRUNC | O_CREAT);
}
sz = full_write(local_fd, &rbuf[4], len - 4);
if (sz != len - 4) {
strcpy(G_error_pkt_str, bb_msg_write_error);
G_error_pkt_reason = ERR_WRITE;
@ -739,7 +743,9 @@ static int tftp_protocol(
free(xbuf);
free(rbuf);
}
return finished == 0; /* returns 1 on failure */
if (!finished)
goto err;
return EXIT_SUCCESS;
send_read_err_pkt:
strcpy(G_error_pkt_str, bb_msg_read_error);
@ -750,6 +756,9 @@ static int tftp_protocol(
G.error_pkt[1] = TFTP_ERROR;
xsendto(socket_fd, G.error_pkt, 4 + 1 + strlen(G_error_pkt_str),
&peer_lsa->u.sa, peer_lsa->len);
err:
if (local_fd >= 0 && CMD_GET(option_mask32) && local_file)
unlink(local_file);
return EXIT_FAILURE;
#undef remote_file
}
@ -767,7 +776,6 @@ int tftp_main(int argc UNUSED_PARAM, char **argv)
# endif
int result;
int port;
IF_GETPUT(int opt;)
INIT_G();
@ -808,7 +816,7 @@ int tftp_main(int argc UNUSED_PARAM, char **argv)
}
}
IF_GETPUT(opt =) getopt32(argv, "^"
getopt32(argv, "^"
IF_FEATURE_TFTP_GET("g") IF_FEATURE_TFTP_PUT("p")
"l:r:" IF_FEATURE_TFTP_BLOCKSIZE("b:")
IF_FEATURE_TFTP_HPA_COMPAT("m:")
@ -859,15 +867,12 @@ int tftp_main(int argc UNUSED_PARAM, char **argv)
# endif
result = tftp_protocol(
NULL /*our_lsa*/, peer_lsa,
local_file, remote_file
(LONE_DASH(local_file) ? NULL : local_file), remote_file
IF_FEATURE_TFTP_BLOCKSIZE(, 1 /* want_transfer_size */)
IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
);
tftp_progress_done();
if (result != EXIT_SUCCESS && NOT_LONE_DASH(local_file) && CMD_GET(opt)) {
unlink(local_file);
}
return result;
}
#endif /* ENABLE_TFTP */