| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Privilege separation communication protocol |
| 4 | * |
| 5 | * (c) 2008 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Trivial IP Encryption (TrIPE). |
| 11 | * |
| 12 | * TrIPE is free software: you can redistribute it and/or modify it under |
| 13 | * the terms of the GNU General Public License as published by the Free |
| 14 | * Software Foundation; either version 3 of the License, or (at your |
| 15 | * option) any later version. |
| 16 | * |
| 17 | * TrIPE is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | * 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 |
| 23 | * along with TrIPE. If not, see <https://www.gnu.org/licenses/>. |
| 24 | */ |
| 25 | |
| 26 | /*----- Header files ------------------------------------------------------*/ |
| 27 | |
| 28 | #include "tripe.h" |
| 29 | #include "priv.h" |
| 30 | |
| 31 | /*----- Static variables --------------------------------------------------*/ |
| 32 | |
| 33 | static pid_t kid = -1; |
| 34 | static sig sig_chld; |
| 35 | |
| 36 | /*----- Fetching a tunnel file descriptor ---------------------------------*/ |
| 37 | |
| 38 | /* --- @ps_tunfd@ --- * |
| 39 | * |
| 40 | * Arguments: @const tunnel_ops *tops@ = pointer to tunnel operations |
| 41 | * @char **ifn@ = where to put the interface name |
| 42 | * |
| 43 | * Returns: The file descriptor, or @-1@ on error. |
| 44 | * |
| 45 | * Use: Fetches a file descriptor for a tunnel driver. |
| 46 | */ |
| 47 | |
| 48 | int ps_tunfd(const tunnel_ops *tops, char **ifn) |
| 49 | { |
| 50 | unsigned code; |
| 51 | ssize_t n; |
| 52 | dstr d = DSTR_INIT; |
| 53 | int fd; |
| 54 | |
| 55 | if (pc_fd == -1) { |
| 56 | a_warn("PRIVSEP", "helper-died", A_END); |
| 57 | return (-1); |
| 58 | } |
| 59 | T( trace(T_PRIVSEP, |
| 60 | "privsep: requesting descriptor for %s tunnel", |
| 61 | tops->name); ) |
| 62 | if (pc_putuint(PS_TUNRQ) || pc_putstring(tops->name)) { |
| 63 | a_warn("PRIVSEP", "helper-write-error", "?ERRNO", A_END); |
| 64 | goto lose; |
| 65 | } |
| 66 | for (;;) { |
| 67 | n = fdpass_recv(pc_fd, &fd, &code, sizeof(code)); |
| 68 | if (n < 0) goto readlose; |
| 69 | if (n < sizeof(code)) { |
| 70 | a_warn("PRIVSEP", "helper-short-read", A_END); |
| 71 | goto lose; |
| 72 | } |
| 73 | switch (code) { |
| 74 | case PS_TUNFD: |
| 75 | if (fd == -1) { |
| 76 | a_warn("PRIVSEP", "no-fd-from-helper", A_END); |
| 77 | goto lose; |
| 78 | } |
| 79 | if (pc_getstring(&d)) { close(fd); goto readlose; } |
| 80 | *ifn = xstrdup(d.buf); |
| 81 | T( trace(T_PRIVSEP, |
| 82 | "privsep: received winning descriptor for %s", |
| 83 | *ifn); ) |
| 84 | goto done; |
| 85 | case PS_TUNERR: |
| 86 | if (pc_geterr(&errno)) goto readlose; |
| 87 | T( trace(T_PRIVSEP, "privsep: helper lost: %s", strerror(errno)); ) |
| 88 | fd = -1; |
| 89 | goto done; |
| 90 | #ifndef NTRACE |
| 91 | case PS_TRACE: |
| 92 | if (pc_getuint(&code) || pc_getstring(&d)) goto readlose; |
| 93 | trace(code, "%s", d.buf); |
| 94 | DRESET(&d); |
| 95 | break; |
| 96 | #endif |
| 97 | case PS_WARN: |
| 98 | if (pc_getstring(&d)) goto readlose; |
| 99 | a_warn("*%s", d.buf, A_END); |
| 100 | DRESET(&d); |
| 101 | break; |
| 102 | default: |
| 103 | a_warn("PRIVSEP", "unknown-response-code", "%u", code, A_END); |
| 104 | goto lose; |
| 105 | } |
| 106 | } |
| 107 | done: |
| 108 | dstr_destroy(&d); |
| 109 | return (fd); |
| 110 | |
| 111 | readlose: |
| 112 | a_warn("PRIVSEP", "helper-read-error", "?ERRNO", A_END); |
| 113 | lose: |
| 114 | dstr_destroy(&d); |
| 115 | close(pc_fd); |
| 116 | pc_fd = -1; |
| 117 | return (-1); |
| 118 | } |
| 119 | |
| 120 | /*----- Main code ---------------------------------------------------------*/ |
| 121 | |
| 122 | /* --- @reap@ --- * |
| 123 | * |
| 124 | * Arguments: @int sig@ = signal number (always @SIGCHLD@; ignored) |
| 125 | * |
| 126 | * Returns: --- |
| 127 | * |
| 128 | * Use: Notices and reports child process death. |
| 129 | */ |
| 130 | |
| 131 | static void reap(int sig, void *p) |
| 132 | { |
| 133 | pid_t k; |
| 134 | int st; |
| 135 | |
| 136 | for (;;) { |
| 137 | k = waitpid(-1, &st, WNOHANG); |
| 138 | if (k < 0) { |
| 139 | switch (errno) { |
| 140 | case EINTR: |
| 141 | break; |
| 142 | default: |
| 143 | a_warn("SERVER", "waitpid-error", "?ERRNO", A_END); |
| 144 | case ECHILD: |
| 145 | return; |
| 146 | } |
| 147 | } |
| 148 | if (!k) |
| 149 | return; |
| 150 | if (k == kid) { |
| 151 | if (WIFEXITED(st)) |
| 152 | a_warn("PRIVSEP", "child-exited", "%d", WEXITSTATUS(st), A_END); |
| 153 | else if (WIFSIGNALED(st)) |
| 154 | a_warn("PRIVSEP", "child-killed", "%d", WTERMSIG(st), A_END); |
| 155 | else |
| 156 | a_warn("PRIVSEP", "child-died", "%d", st, A_END); |
| 157 | kid = -1; |
| 158 | } |
| 159 | } |
| 160 | } |
| 161 | |
| 162 | /* --- @ps_split@ --- * |
| 163 | * |
| 164 | * Arguments: @int detachp@ = whether to detach the child from its terminal |
| 165 | * |
| 166 | * Returns: --- |
| 167 | * |
| 168 | * Use: Separates off the privileged tunnel-opening service from the |
| 169 | * rest of the server. |
| 170 | */ |
| 171 | |
| 172 | void ps_split(int detachp) |
| 173 | { |
| 174 | pid_t kid; |
| 175 | int fd[2]; |
| 176 | mdup_fd md[1]; |
| 177 | const char *helper; |
| 178 | |
| 179 | if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd)) { |
| 180 | die(EXIT_FAILURE, |
| 181 | "failed to create socket pair for privilege separation: %s", |
| 182 | strerror(errno)); |
| 183 | } |
| 184 | helper = getenv("TRIPE_PRIVHELPER"); |
| 185 | if (!helper) helper = PRIVSEP_HELPER; |
| 186 | fdflags(fd[0], 0, 0, FD_CLOEXEC, FD_CLOEXEC); |
| 187 | fdflags(fd[1], 0, 0, FD_CLOEXEC, FD_CLOEXEC); |
| 188 | sig_add(&sig_chld, SIGCHLD, reap, 0); |
| 189 | kid = fork(); |
| 190 | if (kid == 0) { |
| 191 | signal(SIGCHLD, SIG_DFL); |
| 192 | if (detachp) detachtty(); |
| 193 | close(fd[1]); |
| 194 | md[0].cur = fd[0]; md[0].want = STDIN_FILENO; |
| 195 | if (mdup(md, 1)) goto lose; |
| 196 | execl(helper, helper, (char *)0); |
| 197 | lose: |
| 198 | fprintf(stderr, "helper: failed to run helper: %s\n", strerror(errno)); |
| 199 | _exit(127); |
| 200 | } |
| 201 | T( trace(T_PRIVSEP, "privsep: forked child successfully"); ) |
| 202 | close(fd[0]); |
| 203 | pc_fd = fd[1]; |
| 204 | } |
| 205 | |
| 206 | /* --- @ps_quit@ --- * |
| 207 | * |
| 208 | * Arguments: --- |
| 209 | * |
| 210 | * Returns: --- |
| 211 | * |
| 212 | * Use: Detaches from the helper process. |
| 213 | */ |
| 214 | |
| 215 | void ps_quit(void) { if (pc_fd != -1) close(pc_fd); } |
| 216 | |
| 217 | /*----- That's all, folks -------------------------------------------------*/ |