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
column.h
#ifndef COLUMN_H
#define COLUMN_H
#define COL_LAYOUT_MASK 0x000F
#define COL_ENABLE_MASK 0x0030 /* always, never or auto */
#define COL_PARSEOPT 0x0040 /* --column is given from cmdline */
#define COL_DENSE 0x0080 /* Shrink columns when possible,
making space for more columns */
#define COL_DISABLED 0x0000 /* must be zero */
#define COL_ENABLED 0x0010
#define COL_AUTO 0x0020
#define COL_LAYOUT(c) ((c) & COL_LAYOUT_MASK)
#define COL_COLUMN 0 /* Fill columns before rows */
#define COL_ROW 1 /* Fill rows before columns */
#define COL_PLAIN 15 /* one column */
#define explicitly_enable_column(c) \
(((c) & COL_PARSEOPT) && column_active(c))
struct column_options {
int width;
int padding;
const char *indent;
const char *nl;
};
struct option;
extern int parseopt_column_callback(const struct option *, const char *, int);
extern int git_column_config(const char *var, const char *value,
const char *command, unsigned int *colopts);
extern int finalize_colopts(unsigned int *colopts, int stdout_is_tty);
static inline int column_active(unsigned int colopts)
{
return (colopts & COL_ENABLE_MASK) == COL_ENABLED;
}
extern void print_columns(const struct string_list *list, unsigned int colopts,
const struct column_options *opts);
extern int run_column_filter(int colopts, const struct column_options *);
extern int stop_column_filter(void);
#endif
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