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authorRay Satiro <raysatiro@yahoo.com>2016-01-26 23:23:15 +0100
committerDaniel Stenberg <daniel@haxx.se>2016-01-26 23:42:55 +0100
commit3017d8a8d8849ebd4feae4f5eae037cd55736a61 (patch)
tree976231c185eafd16960d905dc73a7ca0c04ff59f /src/tool_doswin.c
parentcea1fd7a9414b628e3b462b08ee3b64f24a689d1 (diff)
downloadcurl-3017d8a8d8849ebd4feae4f5eae037cd55736a61.tar.gz
curl: avoid local drive traversal when saving file (Windows)
curl does not sanitize colons in a remote file name that is used as the local file name. This may lead to a vulnerability on systems where the colon is a special path character. Currently Windows/DOS is the only OS where this vulnerability applies. CVE-2016-0754 Bug: http://curl.haxx.se/docs/adv_20160127B.html
Diffstat (limited to 'src/tool_doswin.c')
-rw-r--r--src/tool_doswin.c174
1 files changed, 144 insertions, 30 deletions
diff --git a/src/tool_doswin.c b/src/tool_doswin.c
index dd6e8bb85..9c6a7a39f 100644
--- a/src/tool_doswin.c
+++ b/src/tool_doswin.c
@@ -85,42 +85,106 @@ __pragma(warning(pop))
# include <fcntl.h> /* _use_lfn(f) prototype */
#endif
-static const char *msdosify (const char *file_name);
-static char *rename_if_dos_device_name (char *file_name);
+static char *msdosify(const char *file_name);
+static char *rename_if_dos_device_name(const char *file_name);
-/*
- * sanitize_dos_name: returns a newly allocated string holding a
- * valid file name which will be a transformation of given argument
- * in case this wasn't already a valid file name.
- *
- * This function takes ownership of given argument, free'ing it before
- * returning. Caller is responsible of free'ing returned string. Upon
- * out of memory condition function returns NULL.
- */
-char *sanitize_dos_name(char *file_name)
+/*
+Sanitize *file_name.
+Success: (CURLE_OK) *file_name points to a sanitized version of the original.
+ This function takes ownership of the original *file_name and frees it.
+Failure: (!= CURLE_OK) *file_name is unchanged.
+*/
+CURLcode sanitize_file_name(char **file_name)
{
- char new_name[PATH_MAX];
+ size_t len;
+ char *p, *sanitized;
+
+ /* Calculate the maximum length of a filename.
+ FILENAME_MAX is often the same as PATH_MAX, in other words it does not
+ discount the path information. PATH_MAX size is calculated based on:
+ <drive-letter><colon><path-sep><max-filename-len><NULL> */
+ const size_t max_filename_len = PATH_MAX - 3 - 1;
+
+ if(!file_name || !*file_name)
+ return CURLE_BAD_FUNCTION_ARGUMENT;
+
+ len = strlen(*file_name);
+
+ if(len >= max_filename_len)
+ len = max_filename_len - 1;
- if(!file_name)
- return NULL;
+ sanitized = malloc(len + 1);
- if(strlen(file_name) >= PATH_MAX)
- file_name[PATH_MAX-1] = '\0'; /* truncate it */
+ if(!sanitized)
+ return CURLE_OUT_OF_MEMORY;
- strcpy(new_name, msdosify(file_name));
+ strncpy(sanitized, *file_name, len);
+ sanitized[len] = '\0';
- Curl_safefree(file_name);
+ for(p = sanitized; *p; ++p ) {
+ const char *banned;
+ if(1 <= *p && *p <= 31) {
+ *p = '_';
+ continue;
+ }
+ for(banned = "|<>/\\\":?*"; *banned; ++banned) {
+ if(*p == *banned) {
+ *p = '_';
+ break;
+ }
+ }
+ }
- return strdup(rename_if_dos_device_name(new_name));
+#ifdef MSDOS
+ /* msdosify checks for more banned characters for MSDOS, however it allows
+ for some path information to pass through. since we are sanitizing only a
+ filename and cannot allow a path it's important this call be done in
+ addition to and not instead of the banned character check above. */
+ p = msdosify(sanitized);
+ if(!p) {
+ free(sanitized);
+ return CURLE_BAD_FUNCTION_ARGUMENT;
+ }
+ sanitized = p;
+ len = strlen(sanitized);
+#endif
+
+ p = rename_if_dos_device_name(sanitized);
+ if(!p) {
+ free(sanitized);
+ return CURLE_BAD_FUNCTION_ARGUMENT;
+ }
+ sanitized = p;
+ len = strlen(sanitized);
+
+ /* dos_device_name rename will rename a device name, possibly changing the
+ length. If the length is too long now we can't truncate it because we
+ could end up with a device name. In practice this shouldn't be a problem
+ because device names are short, but you never know. */
+ if(len >= max_filename_len) {
+ free(sanitized);
+ return CURLE_BAD_FUNCTION_ARGUMENT;
+ }
+
+ *file_name = sanitized;
+ return CURLE_OK;
}
-/* The following functions are taken with modification from the DJGPP
- * port of tar 1.12. They use algorithms originally from DJTAR. */
+/* The functions msdosify, rename_if_dos_device_name and __crt0_glob_function
+ * were taken with modification from the DJGPP port of tar 1.12. They use
+ * algorithms originally from DJTAR.
+ */
-static const char *msdosify (const char *file_name)
+/*
+Extra sanitization MSDOS for file_name.
+Returns a copy of file_name that is sanitized by MSDOS standards.
+Warning: path information may pass through. For sanitizing a filename use
+sanitize_file_name which calls this function after sanitizing path info.
+*/
+static char *msdosify(const char *file_name)
{
- static char dos_name[PATH_MAX];
+ char dos_name[PATH_MAX];
static const char illegal_chars_dos[] = ".+, ;=[]" /* illegal in DOS */
"|<>\\\":?*"; /* illegal in DOS & W95 */
static const char *illegal_chars_w95 = &illegal_chars_dos[8];
@@ -201,15 +265,20 @@ static const char *msdosify (const char *file_name)
}
*d = '\0';
- return dos_name;
+ return strdup(dos_name);
}
-static char *rename_if_dos_device_name (char *file_name)
+/*
+Rename file_name if it's a representation of a device name.
+Returns a copy of file_name, and the copy will have contents different from the
+original if a device name was found.
+*/
+static char *rename_if_dos_device_name(const char *file_name)
{
/* We could have a file whose name is a device on MS-DOS. Trying to
* retrieve such a file would fail at best and wedge us at worst. We need
* to rename such files. */
- char *base;
+ char *p, *base;
struct_stat st_buf;
char fname[PATH_MAX];
@@ -219,7 +288,7 @@ static char *rename_if_dos_device_name (char *file_name)
if(((stat(base, &st_buf)) == 0) && (S_ISCHR(st_buf.st_mode))) {
size_t blen = strlen(base);
- if(strlen(fname) >= PATH_MAX-1) {
+ if(strlen(fname) == PATH_MAX-1) {
/* Make room for the '_' */
blen--;
base[blen] = '\0';
@@ -227,9 +296,54 @@ static char *rename_if_dos_device_name (char *file_name)
/* Prepend a '_'. */
memmove(base + 1, base, blen + 1);
base[0] = '_';
- strcpy(file_name, fname);
}
- return file_name;
+
+ /* The above stat check does not identify devices for me in Windows 7. For
+ example a stat on COM1 returns a regular file S_IFREG. According to MSDN
+ stat doc that is the correct behavior, so I assume the above code is
+ legacy, maybe MSDOS or DJGPP specific? */
+
+ /* Rename devices.
+ Examples: CON => _CON, CON.EXT => CON_EXT, CON:ADS => CON_ADS */
+ for(p = fname; p; p = (p == fname && fname != base ? base : NULL)) {
+ size_t p_len;
+ int x = (curl_strnequal(p, "CON", 3) ||
+ curl_strnequal(p, "PRN", 3) ||
+ curl_strnequal(p, "AUX", 3) ||
+ curl_strnequal(p, "NUL", 3)) ? 3 :
+ (curl_strnequal(p, "CLOCK$", 6)) ? 6 :
+ (curl_strnequal(p, "COM", 3) || curl_strnequal(p, "LPT", 3)) ?
+ (('1' <= p[3] && p[3] <= '9') ? 4 : 3) : 0;
+
+ if(!x)
+ continue;
+
+ /* the devices may be accessible with an extension or ADS, for
+ example CON.AIR and CON:AIR both access console */
+ if(p[x] == '.' || p[x] == ':') {
+ p[x] = '_';
+ continue;
+ }
+ else if(p[x]) /* no match */
+ continue;
+
+ p_len = strlen(p);
+
+ if(strlen(fname) == PATH_MAX-1) {
+ /* Make room for the '_' */
+ p_len--;
+ p[p_len] = '\0';
+ }
+ /* Prepend a '_'. */
+ memmove(p + 1, p, p_len + 1);
+ p[0] = '_';
+
+ /* if fname was just modified then the basename pointer must be updated */
+ if(p == fname)
+ base = basename(fname);
+ }
+
+ return strdup(fname);
}
#if defined(MSDOS) && (defined(__DJGPP__) || defined(__GO32__))