Revision e7cb0b4455c85b53aeba40f88ffddcf6d4002498 authored by Johannes Schindelin on 11 May 2018, 14:03:54 UTC, committed by Jeff King on 22 May 2018, 03:50:11 UTC
When we started to catch NTFS short names that clash with .git, we only looked for GIT~1. This is sufficient because we only ever clone into an empty directory, so .git is guaranteed to be the first subdirectory or file in that directory. However, even with a fresh clone, .gitmodules is *not* necessarily the first file to be written that would want the NTFS short name GITMOD~1: a malicious repository can add .gitmodul0000 and friends, which sorts before `.gitmodules` and is therefore checked out *first*. For that reason, we have to test not only for ~1 short names, but for others, too. It's hard to just adapt the existing checks in is_ntfs_dotgit(): since Windows 2000 (i.e., in all Windows versions still supported by Git), NTFS short names are only generated in the <prefix>~<number> form up to number 4. After that, a *different* prefix is used, calculated from the long file name using an undocumented, but stable algorithm. For example, the short name of .gitmodules would be GITMOD~1, but if it is taken, and all of ~2, ~3 and ~4 are taken, too, the short name GI7EBA~1 will be used. From there, collisions are handled by incrementing the number, shortening the prefix as needed (until ~9999999 is reached, in which case NTFS will not allow the file to be created). We'd also want to handle .gitignore and .gitattributes, which suffer from a similar problem, using the fall-back short names GI250A~1 and GI7D29~1, respectively. To accommodate for that, we could reimplement the hashing algorithm, but it is just safer and simpler to provide the known prefixes. This algorithm has been reverse-engineered and described at https://usn.pw/blog/gen/2015/06/09/filenames/, which is defunct but still available via https://web.archive.org/. These can be recomputed by running the following Perl script: -- snip -- use warnings; use strict; sub compute_short_name_hash ($) { my $checksum = 0; foreach (split('', $_[0])) { $checksum = ($checksum * 0x25 + ord($_)) & 0xffff; } $checksum = ($checksum * 314159269) & 0xffffffff; $checksum = 1 + (~$checksum & 0x7fffffff) if ($checksum & 0x80000000); $checksum -= (($checksum * 1152921497) >> 60) * 1000000007; return scalar reverse sprintf("%x", $checksum & 0xffff); } print compute_short_name_hash($ARGV[0]); -- snap -- E.g., running that with the argument ".gitignore" will result in "250a" (which then becomes "gi250a" in the code). Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Jeff King <peff@peff.net>
1 parent 0fc333b
precompose_utf8.c
/*
* Converts filenames from decomposed unicode into precomposed unicode.
* Used on MacOS X.
*/
#define PRECOMPOSE_UNICODE_C
#include "cache.h"
#include "utf8.h"
#include "precompose_utf8.h"
typedef char *iconv_ibp;
static const char *repo_encoding = "UTF-8";
static const char *path_encoding = "UTF-8-MAC";
static size_t has_non_ascii(const char *s, size_t maxlen, size_t *strlen_c)
{
const uint8_t *ptr = (const uint8_t *)s;
size_t strlen_chars = 0;
size_t ret = 0;
if (!ptr || !*ptr)
return 0;
while (*ptr && maxlen) {
if (*ptr & 0x80)
ret++;
strlen_chars++;
ptr++;
maxlen--;
}
if (strlen_c)
*strlen_c = strlen_chars;
return ret;
}
void probe_utf8_pathname_composition(void)
{
struct strbuf path = STRBUF_INIT;
static const char *auml_nfc = "\xc3\xa4";
static const char *auml_nfd = "\x61\xcc\x88";
int output_fd;
if (precomposed_unicode != -1)
return; /* We found it defined in the global config, respect it */
git_path_buf(&path, "%s", auml_nfc);
output_fd = open(path.buf, O_CREAT|O_EXCL|O_RDWR, 0600);
if (output_fd >= 0) {
close(output_fd);
git_path_buf(&path, "%s", auml_nfd);
precomposed_unicode = access(path.buf, R_OK) ? 0 : 1;
git_config_set("core.precomposeunicode",
precomposed_unicode ? "true" : "false");
git_path_buf(&path, "%s", auml_nfc);
if (unlink(path.buf))
die_errno(_("failed to unlink '%s'"), path.buf);
}
strbuf_release(&path);
}
void precompose_argv(int argc, const char **argv)
{
int i = 0;
const char *oldarg;
char *newarg;
iconv_t ic_precompose;
if (precomposed_unicode != 1)
return;
ic_precompose = iconv_open(repo_encoding, path_encoding);
if (ic_precompose == (iconv_t) -1)
return;
while (i < argc) {
size_t namelen;
oldarg = argv[i];
if (has_non_ascii(oldarg, (size_t)-1, &namelen)) {
newarg = reencode_string_iconv(oldarg, namelen, ic_precompose, NULL);
if (newarg)
argv[i] = newarg;
}
i++;
}
iconv_close(ic_precompose);
}
PREC_DIR *precompose_utf8_opendir(const char *dirname)
{
PREC_DIR *prec_dir = xmalloc(sizeof(PREC_DIR));
prec_dir->dirent_nfc = xmalloc(sizeof(dirent_prec_psx));
prec_dir->dirent_nfc->max_name_len = sizeof(prec_dir->dirent_nfc->d_name);
prec_dir->dirp = opendir(dirname);
if (!prec_dir->dirp) {
free(prec_dir->dirent_nfc);
free(prec_dir);
return NULL;
} else {
int ret_errno = errno;
prec_dir->ic_precompose = iconv_open(repo_encoding, path_encoding);
/* if iconv_open() fails, die() in readdir() if needed */
errno = ret_errno;
}
return prec_dir;
}
struct dirent_prec_psx *precompose_utf8_readdir(PREC_DIR *prec_dir)
{
struct dirent *res;
res = readdir(prec_dir->dirp);
if (res) {
size_t namelenz = strlen(res->d_name) + 1; /* \0 */
size_t new_maxlen = namelenz;
int ret_errno = errno;
if (new_maxlen > prec_dir->dirent_nfc->max_name_len) {
size_t new_len = sizeof(dirent_prec_psx) + new_maxlen -
sizeof(prec_dir->dirent_nfc->d_name);
prec_dir->dirent_nfc = xrealloc(prec_dir->dirent_nfc, new_len);
prec_dir->dirent_nfc->max_name_len = new_maxlen;
}
prec_dir->dirent_nfc->d_ino = res->d_ino;
prec_dir->dirent_nfc->d_type = res->d_type;
if ((precomposed_unicode == 1) && has_non_ascii(res->d_name, (size_t)-1, NULL)) {
if (prec_dir->ic_precompose == (iconv_t)-1) {
die("iconv_open(%s,%s) failed, but needed:\n"
" precomposed unicode is not supported.\n"
" If you want to use decomposed unicode, run\n"
" \"git config core.precomposeunicode false\"\n",
repo_encoding, path_encoding);
} else {
iconv_ibp cp = (iconv_ibp)res->d_name;
size_t inleft = namelenz;
char *outpos = &prec_dir->dirent_nfc->d_name[0];
size_t outsz = prec_dir->dirent_nfc->max_name_len;
errno = 0;
iconv(prec_dir->ic_precompose, &cp, &inleft, &outpos, &outsz);
if (errno || inleft) {
/*
* iconv() failed and errno could be E2BIG, EILSEQ, EINVAL, EBADF
* MacOS X avoids illegal byte sequences.
* If they occur on a mounted drive (e.g. NFS) it is not worth to
* die() for that, but rather let the user see the original name
*/
namelenz = 0; /* trigger strlcpy */
}
}
} else
namelenz = 0;
if (!namelenz)
strlcpy(prec_dir->dirent_nfc->d_name, res->d_name,
prec_dir->dirent_nfc->max_name_len);
errno = ret_errno;
return prec_dir->dirent_nfc;
}
return NULL;
}
int precompose_utf8_closedir(PREC_DIR *prec_dir)
{
int ret_value;
int ret_errno;
ret_value = closedir(prec_dir->dirp);
ret_errno = errno;
if (prec_dir->ic_precompose != (iconv_t)-1)
iconv_close(prec_dir->ic_precompose);
free(prec_dir->dirent_nfc);
free(prec_dir);
errno = ret_errno;
return ret_value;
}
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