| 1 |
#undef _GNU_SOURCE |
| 2 |
#define _GNU_SOURCE |
| 3 |
|
| 4 |
#include <limits.h> |
| 5 |
#include <sys/types.h> |
| 6 |
#include <sys/stat.h> |
| 7 |
#include <sys/wait.h> |
| 8 |
#include <dlfcn.h> |
| 9 |
#include <errno.h> |
| 10 |
#include <unistd.h> |
| 11 |
#include <sys/socket.h> |
| 12 |
#include <sys/socket.h> |
| 13 |
#include <stdio.h> |
| 14 |
#include <stdlib.h> |
| 15 |
#include <string.h> |
| 16 |
#include <arpa/inet.h> |
| 17 |
|
| 18 |
#include <string> |
| 19 |
#include <unordered_map> |
| 20 |
#include <mutex> |
| 21 |
|
| 22 |
#define PATHBUFSIZE 4097 |
| 23 |
#define NAMEMAX 255 |
| 24 |
#define DEFAULT_SHORTENER "/root/enametoolong/shortener-prod" |
| 25 |
|
| 26 |
static std::mutex shorten_mutex; |
| 27 |
|
| 28 |
static int shortener_fd = -1; |
| 29 |
static pid_t shortener_pid; |
| 30 |
|
| 31 |
static void |
| 32 |
die (const char *msg) |
| 33 |
{ |
| 34 |
perror ("socketpair"); |
| 35 |
exit (EXIT_FAILURE); |
| 36 |
} |
| 37 |
|
| 38 |
static bool |
| 39 |
xread (int fd, void *buf, size_t count) |
| 40 |
{ |
| 41 |
while (count > 0) |
| 42 |
{ |
| 43 |
ssize_t bytesRead = read (fd, buf, count); |
| 44 |
|
| 45 |
if (bytesRead < 0) |
| 46 |
{ |
| 47 |
if (errno == EINTR) |
| 48 |
continue; |
| 49 |
|
| 50 |
return false; |
| 51 |
} |
| 52 |
else if (bytesRead == 0) |
| 53 |
return false; |
| 54 |
|
| 55 |
buf = (char *)buf + bytesRead; |
| 56 |
count -= bytesRead; |
| 57 |
} |
| 58 |
|
| 59 |
return true; |
| 60 |
} |
| 61 |
|
| 62 |
static bool |
| 63 |
xwrite(int fd, const void *buf, size_t count) |
| 64 |
{ |
| 65 |
while (count > 0) |
| 66 |
{ |
| 67 |
ssize_t bytesWritten = send (fd, buf, count, MSG_NOSIGNAL); |
| 68 |
|
| 69 |
if (bytesWritten < 0) |
| 70 |
{ |
| 71 |
if (errno == EINTR) |
| 72 |
continue; |
| 73 |
|
| 74 |
return false; |
| 75 |
} |
| 76 |
|
| 77 |
buf = (char *)buf + bytesWritten; |
| 78 |
count -= bytesWritten; |
| 79 |
} |
| 80 |
|
| 81 |
return true; |
| 82 |
} |
| 83 |
|
| 84 |
static void |
| 85 |
shortener_open (void) |
| 86 |
{ |
| 87 |
int sp[2]; |
| 88 |
|
| 89 |
if (socketpair (AF_UNIX, SOCK_STREAM, 0, sp) < 0) |
| 90 |
die ("socketpair"); |
| 91 |
|
| 92 |
shortener_pid = vfork (); |
| 93 |
|
| 94 |
if (shortener_pid < 0) |
| 95 |
die ("vfork"); |
| 96 |
|
| 97 |
if (shortener_pid == 0) |
| 98 |
{ |
| 99 |
dup2 (sp[1], 0); |
| 100 |
dup2 (sp[1], 1); |
| 101 |
close (sp[0]); |
| 102 |
|
| 103 |
static const char *const argv[2] = { "-", 0 }; |
| 104 |
const char *shortener_path = secure_getenv ("ENAMETOOLONG_SHORTENER"); |
| 105 |
execve (shortener_path ? shortener_path : DEFAULT_SHORTENER, const_cast<char *const *>(argv), 0); |
| 106 |
_exit (126); |
| 107 |
} |
| 108 |
|
| 109 |
close (sp[1]); |
| 110 |
|
| 111 |
shortener_fd = sp[0]; |
| 112 |
} |
| 113 |
|
| 114 |
static void |
| 115 |
shortener_close (void) |
| 116 |
{ |
| 117 |
if (shortener_fd < 0) |
| 118 |
return; |
| 119 |
|
| 120 |
close (shortener_fd); |
| 121 |
shortener_fd = -1; |
| 122 |
|
| 123 |
if (shortener_pid > 0) |
| 124 |
{ |
| 125 |
int wstatus; |
| 126 |
waitpid (shortener_pid, &wstatus, 0); |
| 127 |
shortener_pid = -1; |
| 128 |
} |
| 129 |
|
| 130 |
sleep (1); // rate limit retries |
| 131 |
} |
| 132 |
|
| 133 |
static std::unordered_map<std::string, std::string> cache; |
| 134 |
|
| 135 |
__attribute__ ((__cold__, __noinline__)) |
| 136 |
static const char * |
| 137 |
shorten (const char *path) |
| 138 |
{ |
| 139 |
std::lock_guard<std::mutex> guard (shorten_mutex); |
| 140 |
|
| 141 |
std::string &shorter = cache[path]; |
| 142 |
|
| 143 |
if (shorter.size ()) |
| 144 |
return shorter.c_str (); |
| 145 |
|
| 146 |
for (;;) |
| 147 |
{ |
| 148 |
if (shortener_fd < 0) |
| 149 |
shortener_open (); |
| 150 |
|
| 151 |
uint32_t slen = strlen (path); |
| 152 |
uint32_t nlen = htonl (slen); |
| 153 |
xwrite (shortener_fd, &nlen, sizeof nlen); |
| 154 |
xwrite (shortener_fd, path, slen); |
| 155 |
|
| 156 |
if (xread (shortener_fd, &nlen, sizeof nlen)) |
| 157 |
{ |
| 158 |
nlen = ntohl (nlen); |
| 159 |
|
| 160 |
if (nlen < PATHBUFSIZE) |
| 161 |
{ |
| 162 |
shorter.resize (nlen); |
| 163 |
|
| 164 |
if (xread (shortener_fd, shorter.data (), nlen)) |
| 165 |
return shorter.c_str (); |
| 166 |
} |
| 167 |
} |
| 168 |
|
| 169 |
shortener_close (); |
| 170 |
} |
| 171 |
} |
| 172 |
|
| 173 |
static bool |
| 174 |
toolong (const char *path) |
| 175 |
{ |
| 176 |
size_t clen = 0; |
| 177 |
|
| 178 |
for (;;) |
| 179 |
{ |
| 180 |
if (*path == '/') |
| 181 |
clen = 0; |
| 182 |
else if (!*path) |
| 183 |
return false; |
| 184 |
else if (++clen > NAMEMAX) |
| 185 |
return true; |
| 186 |
|
| 187 |
++path; |
| 188 |
} |
| 189 |
} |
| 190 |
|
| 191 |
// paths starting with the MAGIC_PREFIX return the shortened |
| 192 |
// version of the part after the prefix (a relative path) |
| 193 |
// in readlink and readlinkat. |
| 194 |
|
| 195 |
#define MAGIC_PREFIX "/dev/enametoolong/" |
| 196 |
|
| 197 |
static ssize_t |
| 198 |
magic_readlink (const char *path, char *buf, size_t len) |
| 199 |
{ |
| 200 |
size_t slen = strlen (path); |
| 201 |
slen -= sizeof (MAGIC_PREFIX) - 1; |
| 202 |
path += sizeof (MAGIC_PREFIX) - 1; |
| 203 |
strncpy (buf, path, len < slen ? len : slen); |
| 204 |
return slen; |
| 205 |
} |
| 206 |
|
| 207 |
#define MAGIC_READLINK(path, buf, len) \ |
| 208 |
if (strncmp (path, MAGIC_PREFIX, sizeof (MAGIC_PREFIX) - 1) == 0) \ |
| 209 |
return magic_readlink (path, buf, len); |
| 210 |
|
| 211 |
#include "wrap.C" |
| 212 |
|
