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/* Copyright (c) 2009-2016 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "str.h"
#include "realpath.h"
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
// FIXME: move/merge to Dovecot
#define REALPATH_MAX_PATH 8*1024
#define REALPATH_MAX_SYMLINKS 80
static int t_getcwd_alloc(char **dir_r, size_t *asize_r)
{
/* @UNSAFE */
char *dir;
size_t asize = 128;
dir = t_buffer_get(asize);
while (getcwd(dir, asize) == NULL) {
if (errno != ERANGE)
return -1;
asize = nearest_power(asize+1);
dir = t_buffer_get(asize);
}
*asize_r = asize;
*dir_r = dir;
return 0;
}
static int path_normalize(const char *path, bool resolve_links,
const char **npath_r)
{
/* @UNSAFE */
unsigned int link_count = 0;
char *npath, *npath_pos;
const char *p;
size_t asize;
if (path[0] != '/') {
/* relative; initialize npath with current directory */
if (t_getcwd_alloc(&npath, &asize) < 0)
return -1;
npath_pos = npath + strlen(npath);
i_assert(npath[0] == '/');
} else {
/* absolute; initialize npath with root */
asize = 128;
npath = t_buffer_get(asize);
npath[0] = '/';
npath_pos = npath + 1;
}
p = path;
while (*p != '\0') {
struct stat st;
ptrdiff_t seglen;
const char *segend;
/* skip duplicate shashes */
while (*p == '/')
p++;
/* find end of path segment */
for (segend = p; *segend != '\0' && *segend != '/'; segend++);
if (segend == p)
break; /* '\0' */
seglen = segend - p;
if (seglen == 1 && p[0] == '.') {
/* a reference to this segment; nothing to do */
} else if (seglen == 2 && p[0] == '.' && p[1] == '.') {
/* a reference to parent segment; back up to previous slash */
if (npath_pos > npath + 1) {
if (*(npath_pos-1) == '/')
npath_pos--;
for (; *(npath_pos-1) != '/'; npath_pos--);
}
} else {
/* make sure npath now ends in slash */
if (*(npath_pos-1) != '/')
*(npath_pos++) = '/';
/* allocate space if necessary */
if ((npath_pos + seglen + 1) >= (npath + asize)) {
ptrdiff_t npath_offset = npath_pos - npath;
asize = nearest_power(npath_offset + seglen + 2);
npath = t_buffer_reget(npath, asize);
npath_pos = npath + npath_offset;
}
/* copy segment to normalized path */
(void)memmove(npath_pos, p, seglen);
npath_pos += seglen;
}
if (resolve_links) {
/* stat path up to here (segend points to tail) */
*npath_pos = '\0';
if (lstat(npath, &st) < 0)
return -1;
if (S_ISLNK (st.st_mode)) {
/* symlink */
char *npath_link;
size_t lsize = 128, tlen = strlen(segend), espace;
size_t ltlen = (link_count == 0 ? 0 : tlen);
ssize_t ret;
/* limit link dereferences */
if (++link_count > REALPATH_MAX_SYMLINKS) {
errno = ELOOP;
return -1;
}
/* allocate space for preserving tail of previous symlink and
first attempt at reading symlink with room for the tail
buffer will look like this:
[npath][0][preserved tail][link buffer][room for tail][0]
*/
espace = ltlen + tlen + 2;
if ((npath_pos + espace + lsize) >= (npath + asize)) {
ptrdiff_t npath_offset = npath_pos - npath;
asize = nearest_power((npath_offset + espace + lsize) + 1);
lsize = asize - (npath_offset + espace);
npath = t_buffer_reget(npath, asize);
npath_pos = npath + npath_offset;
}
if (ltlen > 0) {
/* preserve tail just after end of npath */
(void)memmove(npath_pos + 1, segend, ltlen);
}
/* read the symlink after the preserved tail */
for (;;) {
npath_link = (npath_pos + 1) + ltlen;
/* attempt to read the link */
if ((ret=readlink(npath, npath_link, lsize)) < 0)
return -1;
if ((size_t)ret < lsize) {
/* make static analyzers happy */
npath_link[ret] = '\0';
break;
}
/* sum of new symlink content length and path tail length may not
exeed maximum */
if ((size_t)(ret + tlen) >= REALPATH_MAX_PATH) {
errno = ENAMETOOLONG;
return -1;
}
/* try again with bigger buffer */
espace = ltlen + tlen + 2;
if ((npath_pos + espace + lsize) >= (npath + asize)) {
ptrdiff_t npath_offset = npath_pos - npath;
asize = nearest_power((npath_offset + espace + lsize) + 1);
lsize = asize - (npath_offset + espace);
npath = t_buffer_reget(npath, asize);
npath_pos = npath + npath_offset;
}
}
/* add tail of previous path at end of symlink */
if (ltlen > 0)
(void)memcpy(npath_link + ret, npath_pos + 1, tlen);
else
(void)memcpy(npath_link + ret, segend, tlen);
*(npath_link+ret+tlen) = '\0';
/* use as new source path */
path = segend = npath_link;
if (path[0] == '/') {
/* absolute symlink; start over at root */
npath_pos = npath + 1;
} else {
/* relative symlink; back up to previous segment */
if (npath_pos > npath + 1) {
if (*(npath_pos-1) == '/')
npath_pos--;
for (; *(npath_pos-1) != '/'; npath_pos--);
}
}
} else if (*segend != '\0' && !S_ISDIR (st.st_mode)) {
/* not last segment, but not a directory either */
errno = ENOTDIR;
return -1;
}
}
p = segend;
}
/* remove any trailing slash */
if (npath_pos > npath + 1 && *(npath_pos-1) == '/')
npath_pos--;
*npath_pos = '\0';
t_buffer_alloc(npath_pos - npath + 1);
*npath_r = npath;
return 0;
}
int t_normpath(const char *path, const char **npath_r)
{
return path_normalize(path, FALSE, npath_r);
}
int t_normpath_to(const char *path, const char *root,
const char **npath_r)
{
if (*path == '/')
return t_normpath(path, npath_r);
return t_normpath(t_strconcat(root, "/", path, NULL), npath_r);
}
int t_realpath(const char *path, const char **npath_r)
{
return path_normalize(path, TRUE, npath_r);
}
int t_realpath_to(const char *path, const char *root,
const char **npath_r)
{
if (*path == '/')
return t_realpath(path, npath_r);
return t_realpath(t_strconcat(root, "/", path, NULL), npath_r);
}
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