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sftp: fix range downloads in both SSH backends

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When asking for the last N bytes of a file, and that size was larger
than the file size, it would miss the first byte due to a logic error.

The fixed range parser is now made a common function in the file now
renamed to vssh.c (from curl_path.c) - used by both backends.

Unit test 2605 verifies the parser.

Reported-by: Stanislav Fort (Aisle Research)
Closes #19460
This commit is contained in:
Daniel Stenberg 2025-11-11 09:42:16 +01:00
parent 67ef4a34f2
commit c545e10fa7
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GPG key ID: 5CC908FDB71E12C2
12 changed files with 204 additions and 84 deletions
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43
lib/vssh/libssh2.c
View file

@ -63,7 +63,7 @@
#include "../select.h"
#include "../curlx/fopen.h"
#include "../curlx/warnless.h"
#include "curl_path.h"
#include "vssh.h"
#include "../curlx/strparse.h"
#include "../curlx/base64.h" /* for base64 encoding/decoding */
@ -1434,42 +1434,11 @@ sftp_download_stat(struct Curl_easy *data,
return CURLE_BAD_DOWNLOAD_RESUME;
}
if(data->state.use_range) {
curl_off_t from, to;
const char *p = data->state.range;
int to_t, from_t;
from_t = curlx_str_number(&p, &from, CURL_OFF_T_MAX);
if(from_t == STRE_OVERFLOW)
return CURLE_RANGE_ERROR;
curlx_str_passblanks(&p);
(void)curlx_str_single(&p, '-');
to_t = curlx_str_numblanks(&p, &to);
if(to_t == STRE_OVERFLOW)
return CURLE_RANGE_ERROR;
if((to_t == STRE_NO_NUM) /* no "to" value given */
|| (to >= size)) {
to = size - 1;
}
if(from_t) {
/* from is relative to end of file */
from = size - to;
to = size - 1;
}
if(from > size) {
failf(data, "Offset (%" FMT_OFF_T ") was beyond file size (%"
FMT_OFF_T ")", from, (curl_off_t)attrs.filesize);
return CURLE_BAD_DOWNLOAD_RESUME;
}
if(from > to) {
from = to;
size = 0;
}
else {
if((to - from) == CURL_OFF_T_MAX)
return CURLE_RANGE_ERROR;
size = to - from + 1;
}
curl_off_t from;
CURLcode result = Curl_ssh_range(data, data->state.range, size,
&from, &size);
if(result)
return result;
libssh2_sftp_seek64(sshc->sftp_handle, (libssh2_uint64_t)from);
}