| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Allow open(2) to work on Unix-domain sockets |
| 4 | * |
| 5 | * (c) 2008 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of the preload-hacks package. |
| 11 | * |
| 12 | * Preload-hacks are free software; you can redistribute it and/or modify |
| 13 | * them under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 2 of the License, or (at |
| 15 | * your option) any later version. |
| 16 | * |
| 17 | * Preload-hacks are distributed in the hope that it will be useful, but |
| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| 19 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 20 | * for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License along |
| 23 | * with preload-hacks; if not, write to the Free Software Foundation, Inc., |
| 24 | * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | */ |
| 26 | |
| 27 | #define _GNU_SOURCE |
| 28 | #undef sun |
| 29 | |
| 30 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <errno.h> |
| 33 | #include <stdarg.h> |
| 34 | #include <stdio.h> |
| 35 | #include <string.h> |
| 36 | |
| 37 | #include <unistd.h> |
| 38 | #include <dlfcn.h> |
| 39 | #include <fcntl.h> |
| 40 | |
| 41 | #include <sys/socket.h> |
| 42 | #include <sys/stat.h> |
| 43 | #include <sys/un.h> |
| 44 | |
| 45 | /*----- Import the real versions of functions -----------------------------*/ |
| 46 | |
| 47 | /* The list of functions to immport. */ |
| 48 | #define IMPORTS(_) \ |
| 49 | _(open, int, (const char *, int, ...)) \ |
| 50 | _(open64, int, (const char *, int, ...)) \ |
| 51 | _(fopen, FILE *, (const char *, const char *)) \ |
| 52 | _(freopen, FILE *, (const char *, const char *, FILE *)) |
| 53 | |
| 54 | /* Function pointers to set up. */ |
| 55 | #define DECL(imp, ret, args) static ret (*real_##imp) args; |
| 56 | IMPORTS(DECL) |
| 57 | #undef DECL |
| 58 | |
| 59 | /* Import the system calls. */ |
| 60 | static void import(void) |
| 61 | { |
| 62 | #define IMPORT(imp, ret, args) \ |
| 63 | real_##imp = (ret (*)args)dlsym(RTLD_NEXT, #imp); |
| 64 | IMPORTS(IMPORT) |
| 65 | #undef IMPORT |
| 66 | } |
| 67 | /*----- Utilities ---------------------------------------------------------*/ |
| 68 | |
| 69 | /* Socket address casts */ |
| 70 | #define SA(sa) ((struct sockaddr *)(sa)) |
| 71 | |
| 72 | /* Preservation of error status */ |
| 73 | #define PRESERVING_ERRNO(body) do { \ |
| 74 | int _err = errno; { body } errno = _err; \ |
| 75 | } while (0) |
| 76 | |
| 77 | /*----- Connecting to Unix-domain sockets ---------------------------------*/ |
| 78 | |
| 79 | /* If FN refers to a Unix-domain socket, connect to it, stash the socket |
| 80 | * (or -1 on error) in *FDP, and return 1. Otherwise return 0. |
| 81 | */ |
| 82 | static int maybe_connect(const char *fn, int *fdp) |
| 83 | { |
| 84 | int fd; |
| 85 | struct sockaddr_un sun; |
| 86 | struct stat st; |
| 87 | |
| 88 | if (stat(fn, &st) || !S_ISSOCK(st.st_mode)) |
| 89 | return (0); |
| 90 | *fdp = -1; |
| 91 | if (strlen(fn) >= sizeof(sun.sun_path)) { |
| 92 | errno = EINVAL; |
| 93 | return (1); |
| 94 | } |
| 95 | strncpy(sun.sun_path, fn, sizeof(sun.sun_path)); |
| 96 | sun.sun_family = AF_UNIX; |
| 97 | if ((fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0 || |
| 98 | connect(fd, SA(&sun), SUN_LEN(&sun))) { |
| 99 | PRESERVING_ERRNO( if (fd >= 0) close(fd); ); |
| 100 | return (1); |
| 101 | } |
| 102 | *fdp = fd; |
| 103 | return (1); |
| 104 | } |
| 105 | |
| 106 | /*----- Intercepted system calls ------------------------------------------*/ |
| 107 | |
| 108 | /* Create an open(2)-like function OPEN. */ |
| 109 | #define OPEN_VENEER(open) \ |
| 110 | int open(const char *fn, int how, ...) \ |
| 111 | { \ |
| 112 | int mode = 0; \ |
| 113 | int fd; \ |
| 114 | va_list ap; \ |
| 115 | \ |
| 116 | PRESERVING_ERRNO({ \ |
| 117 | if (how & O_CREAT) \ |
| 118 | { va_start(ap, how); mode = va_arg(ap, int); va_end(ap); } \ |
| 119 | if (!maybe_connect(fn, &fd)) fd = real_##open(fn, how, mode); \ |
| 120 | if (fd < 0) return (-1); \ |
| 121 | }); \ |
| 122 | return (fd); \ |
| 123 | } |
| 124 | |
| 125 | /* open(2) and open64(2). */ |
| 126 | OPEN_VENEER(open) |
| 127 | OPEN_VENEER(open64) |
| 128 | |
| 129 | FILE *fopen(const char *fn, const char *how) |
| 130 | { |
| 131 | int fd; |
| 132 | FILE *fp = 0; |
| 133 | |
| 134 | PRESERVING_ERRNO({ |
| 135 | if (!maybe_connect(fn, &fd)) |
| 136 | fp = real_fopen(fn, how); |
| 137 | else if (fd >= 0 && (fp = fdopen(fd, how)) == 0) |
| 138 | PRESERVING_ERRNO( close(fd); ); |
| 139 | }); |
| 140 | return (fp); |
| 141 | } |
| 142 | |
| 143 | FILE *freopen(const char *fn, const char *how, FILE *fp) |
| 144 | { |
| 145 | int fd; |
| 146 | |
| 147 | PRESERVING_ERRNO({ |
| 148 | if (!maybe_connect(fn, &fd)) |
| 149 | fp = real_freopen(fn, how, fp); |
| 150 | else if (fd >= 0) { |
| 151 | if (fflush(fp) || dup2(fd, fileno(fp))) fp = 0; |
| 152 | PRESERVING_ERRNO( close(fd); ); |
| 153 | } |
| 154 | }); |
| 155 | return (fp); |
| 156 | } |
| 157 | |
| 158 | /*----- Initialization ----------------------------------------------------*/ |
| 159 | |
| 160 | static void setup(void) __attribute__((constructor)); |
| 161 | static void setup(void) |
| 162 | { |
| 163 | PRESERVING_ERRNO({ |
| 164 | import(); |
| 165 | }); |
| 166 | } |
| 167 | |
| 168 | /*----- That's all, folks -------------------------------------------------*/ |