/* * Copyright (c) 2001-2002 Damien Miller. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "includes.h" #include #include #include /* SunOS 4.4.4 needs this */ #ifdef HAVE_FLOATINGPOINT_H # include #endif /* HAVE_FLOATINGPOINT_H */ #include "misc.h" #include "xmalloc.h" #include "atomicio.h" #include "pathnames.h" #include "log.h" RCSID("$Id: ssh-rand-helper.c,v 1.8 2002/07/28 20:42:24 stevesk Exp $"); /* Number of bytes we write out */ #define OUTPUT_SEED_SIZE 48 /* Length of on-disk seedfiles */ #define SEED_FILE_SIZE 1024 /* Maximum number of command-line arguments to read from file */ #define NUM_ARGS 10 /* Minimum number of usable commands to be considered sufficient */ #define MIN_ENTROPY_SOURCES 16 /* Path to on-disk seed file (relative to user's home directory */ #ifndef SSH_PRNG_SEED_FILE # define SSH_PRNG_SEED_FILE _PATH_SSH_USER_DIR"/prng_seed" #endif /* Path to PRNG commands list */ #ifndef SSH_PRNG_COMMAND_FILE # define SSH_PRNG_COMMAND_FILE SSHDIR "/ssh_prng_cmds" #endif #ifdef HAVE___PROGNAME extern char *__progname; #else char *__progname; #endif #ifndef offsetof # define offsetof(type, member) ((size_t) &((type *)0)->member) #endif #define WHITESPACE " \t\n" #ifndef RUSAGE_SELF # define RUSAGE_SELF 0 #endif #ifndef RUSAGE_CHILDREN # define RUSAGE_CHILDREN 0 #endif #if !defined(PRNGD_SOCKET) && !defined(PRNGD_PORT) # define USE_SEED_FILES #endif typedef struct { /* Proportion of data that is entropy */ double rate; /* Counter goes positive if this command times out */ unsigned int badness; /* Increases by factor of two each timeout */ unsigned int sticky_badness; /* Path to executable */ char *path; /* argv to pass to executable */ char *args[NUM_ARGS]; /* XXX: arbitrary limit */ /* full command string (debug) */ char *cmdstring; } entropy_cmd_t; /* slow command timeouts (all in milliseconds) */ /* static int entropy_timeout_default = ENTROPY_TIMEOUT_MSEC; */ static int entropy_timeout_current = ENTROPY_TIMEOUT_MSEC; /* this is initialised from a file, by prng_read_commands() */ static entropy_cmd_t *entropy_cmds = NULL; /* Prototypes */ double stir_from_system(void); double stir_from_programs(void); double stir_gettimeofday(double entropy_estimate); double stir_clock(double entropy_estimate); double stir_rusage(int who, double entropy_estimate); double hash_command_output(entropy_cmd_t *src, unsigned char *hash); int get_random_bytes_prngd(unsigned char *buf, int len, unsigned short tcp_port, char *socket_path); /* * Collect 'len' bytes of entropy into 'buf' from PRNGD/EGD daemon * listening either on 'tcp_port', or via Unix domain socket at * * 'socket_path'. * Either a non-zero tcp_port or a non-null socket_path must be * supplied. * Returns 0 on success, -1 on error */ int get_random_bytes_prngd(unsigned char *buf, int len, unsigned short tcp_port, char *socket_path) { int fd, addr_len, rval, errors; char msg[2]; struct sockaddr_storage addr; struct sockaddr_in *addr_in = (struct sockaddr_in *)&addr; struct sockaddr_un *addr_un = (struct sockaddr_un *)&addr; mysig_t old_sigpipe; /* Sanity checks */ if (socket_path == NULL && tcp_port == 0) fatal("You must specify a port or a socket"); if (socket_path != NULL && strlen(socket_path) >= sizeof(addr_un->sun_path)) fatal("Random pool path is too long"); if (len > 255) fatal("Too many bytes to read from PRNGD"); memset(&addr, '\0', sizeof(addr)); if (tcp_port != 0) { addr_in->sin_family = AF_INET; addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK); addr_in->sin_port = htons(tcp_port); addr_len = sizeof(*addr_in); } else { addr_un->sun_family = AF_UNIX; strlcpy(addr_un->sun_path, socket_path, sizeof(addr_un->sun_path)); addr_len = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path) + 1; } old_sigpipe = mysignal(SIGPIPE, SIG_IGN); errors = 0; rval = -1; reopen: fd = socket(addr.ss_family, SOCK_STREAM, 0); if (fd == -1) { error("Couldn't create socket: %s", strerror(errno)); goto done; } if (connect(fd, (struct sockaddr*)&addr, addr_len) == -1) { if (tcp_port != 0) { error("Couldn't connect to PRNGD port %d: %s", tcp_port, strerror(errno)); } else { error("Couldn't connect to PRNGD socket \"%s\": %s", addr_un->sun_path, strerror(errno)); } goto done; } /* Send blocking read request to PRNGD */ msg[0] = 0x02; msg[1] = len; if (atomicio(write, fd, msg, sizeof(msg)) != sizeof(msg)) { if (errno == EPIPE && errors < 10) { close(fd); errors++; goto reopen; } error("Couldn't write to PRNGD socket: %s", strerror(errno)); goto done; } if (atomicio(read, fd, buf, len) != len) { if (errno == EPIPE && errors < 10) { close(fd); errors++; goto reopen; } error("Couldn't read from PRNGD socket: %s", strerror(errno)); goto done; } rval = 0; done: mysignal(SIGPIPE, old_sigpipe); if (fd != -1) close(fd); return rval; } double stir_gettimeofday(double entropy_estimate) { struct timeval tv; if (gettimeofday(&tv, NULL) == -1) fatal("Couldn't gettimeofday: %s", strerror(errno)); RAND_add(&tv, sizeof(tv), entropy_estimate); return entropy_estimate; } double stir_clock(double entropy_estimate) { #ifdef HAVE_CLOCK clock_t c; c = clock(); RAND_add(&c, sizeof(c), entropy_estimate); return entropy_estimate; #else /* _HAVE_CLOCK */ return 0; #endif /* _HAVE_CLOCK */ } double stir_rusage(int who, double entropy_estimate) { #ifdef HAVE_GETRUSAGE struct rusage ru; if (getrusage(who, &ru) == -1) return 0; RAND_add(&ru, sizeof(ru), entropy_estimate); return entropy_estimate; #else /* _HAVE_GETRUSAGE */ return 0; #endif /* _HAVE_GETRUSAGE */ } static int timeval_diff(struct timeval *t1, struct timeval *t2) { int secdiff, usecdiff; secdiff = t2->tv_sec - t1->tv_sec; usecdiff = (secdiff*1000000) + (t2->tv_usec - t1->tv_usec); return (int)(usecdiff / 1000); } double hash_command_output(entropy_cmd_t *src, unsigned char *hash) { char buf[8192]; fd_set rdset; int bytes_read, cmd_eof, error_abort, msec_elapsed, p[2]; int status, total_bytes_read; static int devnull = -1; pid_t pid; SHA_CTX sha; struct timeval tv_start, tv_current; debug3("Reading output from \'%s\'", src->cmdstring); if (devnull == -1) { devnull = open("/dev/null", O_RDWR); if (devnull == -1) fatal("Couldn't open /dev/null: %s", strerror(errno)); } if (pipe(p) == -1) fatal("Couldn't open pipe: %s", strerror(errno)); (void)gettimeofday(&tv_start, NULL); /* record start time */ switch (pid = fork()) { case -1: /* Error */ close(p[0]); close(p[1]); fatal("Couldn't fork: %s", strerror(errno)); /* NOTREACHED */ case 0: /* Child */ dup2(devnull, STDIN_FILENO); dup2(p[1], STDOUT_FILENO); dup2(p[1], STDERR_FILENO); close(p[0]); close(p[1]); close(devnull); execv(src->path, (char**)(src->args)); debug("(child) Couldn't exec '%s': %s", src->cmdstring, strerror(errno)); _exit(-1); default: /* Parent */ break; } RAND_add(&pid, sizeof(&pid), 0.0); close(p[1]); /* Hash output from child */ SHA1_Init(&sha); cmd_eof = error_abort = msec_elapsed = total_bytes_read = 0; while (!error_abort && !cmd_eof) { int ret; struct timeval tv; int msec_remaining; (void) gettimeofday(&tv_current, 0); msec_elapsed = timeval_diff(&tv_start, &tv_current); if (msec_elapsed >= entropy_timeout_current) { error_abort=1; continue; } msec_remaining = entropy_timeout_current - msec_elapsed; FD_ZERO(&rdset); FD_SET(p[0], &rdset); tv.tv_sec = msec_remaining / 1000; tv.tv_usec = (msec_remaining % 1000) * 1000; ret = select(p[0] + 1, &rdset, NULL, NULL, &tv); RAND_add(&tv, sizeof(tv), 0.0); switch (ret) { case 0: /* timer expired */ error_abort = 1; break; case 1: /* command input */ do { bytes_read = read(p[0], buf, sizeof(buf)); } while (bytes_read == -1 && errno == EINTR); RAND_add(&bytes_read, sizeof(&bytes_read), 0.0); if (bytes_read == -1) { error_abort = 1; break; } else if (bytes_read) { SHA1_Update(&sha, buf, bytes_read); total_bytes_read += bytes_read; } else { cmd_eof = 1; } break; case -1: default: /* error */ debug("Command '%s': select() failed: %s", src->cmdstring, strerror(errno)); error_abort = 1; break; } } SHA1_Final(hash, &sha); close(p[0]); debug3("Time elapsed: %d msec", msec_elapsed); if (waitpid(pid, &status, 0) == -1) { error("Couldn't wait for child '%s' completion: %s", src->cmdstring, strerror(errno)); return 0.0; } RAND_add(&status, sizeof(&status), 0.0); if (error_abort) { /* * Closing p[0] on timeout causes the entropy command to * SIGPIPE. Take whatever output we got, and mark this * command as slow */ debug2("Command '%s' timed out", src->cmdstring); src->sticky_badness *= 2; src->badness = src->sticky_badness; return total_bytes_read; } if (WIFEXITED(status)) { if (WEXITSTATUS(status) == 0) { return total_bytes_read; } else { debug2("Command '%s' exit status was %d", src->cmdstring, WEXITSTATUS(status)); src->badness = src->sticky_badness = 128; return 0.0; } } else if (WIFSIGNALED(status)) { debug2("Command '%s' returned on uncaught signal %d !", src->cmdstring, status); src->badness = src->sticky_badness = 128; return 0.0; } else return 0.0; } double stir_from_system(void) { double total_entropy_estimate; long int i; total_entropy_estimate = 0; i = getpid(); RAND_add(&i, sizeof(i), 0.5); total_entropy_estimate += 0.1; i = getppid(); RAND_add(&i, sizeof(i), 0.5); total_entropy_estimate += 0.1; i = getuid(); RAND_add(&i, sizeof(i), 0.0); i = getgid(); RAND_add(&i, sizeof(i), 0.0); total_entropy_estimate += stir_gettimeofday(1.0); total_entropy_estimate += stir_clock(0.5); total_entropy_estimate += stir_rusage(RUSAGE_SELF, 2.0); return total_entropy_estimate; } double stir_from_programs(void) { int c; double entropy, total_entropy; unsigned char hash[SHA_DIGEST_LENGTH]; total_entropy = 0; for(c = 0; entropy_cmds[c].path != NULL; c++) { if (!entropy_cmds[c].badness) { /* Hash output from command */ entropy = hash_command_output(&entropy_cmds[c], hash); /* Scale back estimate by command's rate */ entropy *= entropy_cmds[c].rate; /* Upper bound of entropy is SHA_DIGEST_LENGTH */ if (entropy > SHA_DIGEST_LENGTH) entropy = SHA_DIGEST_LENGTH; /* Stir it in */ RAND_add(hash, sizeof(hash), entropy); debug3("Got %0.2f bytes of entropy from '%s'", entropy, entropy_cmds[c].cmdstring); total_entropy += entropy; /* Execution time should be a bit unpredictable */ total_entropy += stir_gettimeofday(0.05); total_entropy += stir_clock(0.05); total_entropy += stir_rusage(RUSAGE_SELF, 0.1); total_entropy += stir_rusage(RUSAGE_CHILDREN, 0.1); } else { debug2("Command '%s' disabled (badness %d)", entropy_cmds[c].cmdstring, entropy_cmds[c].badness); if (entropy_cmds[c].badness > 0) entropy_cmds[c].badness--; } } return total_entropy; } /* * prng seedfile functions */ int prng_check_seedfile(char *filename) { struct stat st; /* * XXX raceable: eg replace seed between this stat and subsequent * open. Not such a problem because we don't really trust the * seed file anyway. * XXX: use secure path checking as elsewhere in OpenSSH */ if (lstat(filename, &st) == -1) { /* Give up on hard errors */ if (errno != ENOENT) debug("WARNING: Couldn't stat random seed file " "\"%.100s\": %s", filename, strerror(errno)); return 0; } /* regular file? */ if (!S_ISREG(st.st_mode)) fatal("PRNG seedfile %.100s is not a regular file", filename); /* mode 0600, owned by root or the current user? */ if (((st.st_mode & 0177) != 0) || !(st.st_uid == getuid())) { debug("WARNING: PRNG seedfile %.100s must be mode 0600, " "owned by uid %d", filename, getuid()); return 0; } return 1; } void prng_write_seedfile(void) { int fd; unsigned char seed[SEED_FILE_SIZE]; char filename[MAXPATHLEN]; struct passwd *pw; pw = getpwuid(getuid()); if (pw == NULL) fatal("Couldn't get password entry for current user " "(%i): %s", getuid(), strerror(errno)); /* Try to ensure that the parent directory is there */ snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir, _PATH_SSH_USER_DIR); mkdir(filename, 0700); snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir, SSH_PRNG_SEED_FILE); debug("writing PRNG seed to file %.100s", filename); RAND_bytes(seed, sizeof(seed)); /* Don't care if the seed doesn't exist */ prng_check_seedfile(filename); if ((fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0600)) == -1) { debug("WARNING: couldn't access PRNG seedfile %.100s " "(%.100s)", filename, strerror(errno)); } else { if (atomicio(write, fd, &seed, sizeof(seed)) < sizeof(seed)) fatal("problem writing PRNG seedfile %.100s " "(%.100s)", filename, strerror(errno)); close(fd); } } void prng_read_seedfile(void) { int fd; char seed[SEED_FILE_SIZE], filename[MAXPATHLEN]; struct passwd *pw; pw = getpwuid(getuid()); if (pw == NULL) fatal("Couldn't get password entry for current user " "(%i): %s", getuid(), strerror(errno)); snprintf(filename, sizeof(filename), "%.512s/%s", pw->pw_dir, SSH_PRNG_SEED_FILE); debug("loading PRNG seed from file %.100s", filename); if (!prng_check_seedfile(filename)) { verbose("Random seed file not found or invalid, ignoring."); return; } /* open the file and read in the seed */ fd = open(filename, O_RDONLY); if (fd == -1) fatal("could not open PRNG seedfile %.100s (%.100s)", filename, strerror(errno)); if (atomicio(read, fd, &seed, sizeof(seed)) < sizeof(seed)) { verbose("invalid or short read from PRNG seedfile " "%.100s - ignoring", filename); memset(seed, '\0', sizeof(seed)); } close(fd); /* stir in the seed, with estimated entropy zero */ RAND_add(&seed, sizeof(seed), 0.0); } /* * entropy command initialisation functions */ int prng_read_commands(char *cmdfilename) { char cmd[SEED_FILE_SIZE], *cp, line[1024], path[SEED_FILE_SIZE]; double est; entropy_cmd_t *entcmd; FILE *f; int cur_cmd, linenum, num_cmds, arg; if ((f = fopen(cmdfilename, "r")) == NULL) { fatal("couldn't read entropy commands file %.100s: %.100s", cmdfilename, strerror(errno)); } num_cmds = 64; entcmd = xmalloc(num_cmds * sizeof(entropy_cmd_t)); memset(entcmd, '\0', num_cmds * sizeof(entropy_cmd_t)); /* Read in file */ cur_cmd = linenum = 0; while (fgets(line, sizeof(line), f)) { linenum++; /* Skip leading whitespace, blank lines and comments */ cp = line + strspn(line, WHITESPACE); if ((*cp == 0) || (*cp == '#')) continue; /* done with this line */ /* * The first non-whitespace char should be a double quote * delimiting the commandline */ if (*cp != '"') { error("bad entropy command, %.100s line %d", cmdfilename, linenum); continue; } /* * First token, command args (incl. argv[0]) in double * quotes */ cp = strtok(cp, "\""); if (cp == NULL) { error("missing or bad command string, %.100s " "line %d -- ignored", cmdfilename, linenum); continue; } strlcpy(cmd, cp, sizeof(cmd)); /* Second token, full command path */ if ((cp = strtok(NULL, WHITESPACE)) == NULL) { error("missing command path, %.100s " "line %d -- ignored", cmdfilename, linenum); continue; } /* Did configure mark this as dead? */ if (strncmp("undef", cp, 5) == 0) continue; strlcpy(path, cp, sizeof(path)); /* Third token, entropy rate estimate for this command */ if ((cp = strtok(NULL, WHITESPACE)) == NULL) { error("missing entropy estimate, %.100s " "line %d -- ignored", cmdfilename, linenum); continue; } est = strtod(cp, NULL); /* end of line */ if ((cp = strtok(NULL, WHITESPACE)) != NULL) { error("garbage at end of line %d in %.100s " "-- ignored", linenum, cmdfilename); continue; } /* save the command for debug messages */ entcmd[cur_cmd].cmdstring = xstrdup(cmd); /* split the command args */ cp = strtok(cmd, WHITESPACE); arg = 0; do { entcmd[cur_cmd].args[arg] = xstrdup(cp); arg++; } while(arg < NUM_ARGS && (cp = strtok(NULL, WHITESPACE))); if (strtok(NULL, WHITESPACE)) error("ignored extra commands (max %d), %.100s " "line %d", NUM_ARGS, cmdfilename, linenum); /* Copy the command path and rate estimate */ entcmd[cur_cmd].path = xstrdup(path); entcmd[cur_cmd].rate = est; /* Initialise other values */ entcmd[cur_cmd].sticky_badness = 1; cur_cmd++; /* * If we've filled the array, reallocate it twice the size * Do this now because even if this we're on the last * command we need another slot to mark the last entry */ if (cur_cmd == num_cmds) { num_cmds *= 2; entcmd = xrealloc(entcmd, num_cmds * sizeof(entropy_cmd_t)); } } /* zero the last entry */ memset(&entcmd[cur_cmd], '\0', sizeof(entropy_cmd_t)); /* trim to size */ entropy_cmds = xrealloc(entcmd, (cur_cmd + 1) * sizeof(entropy_cmd_t)); debug("Loaded %d entropy commands from %.100s", cur_cmd, cmdfilename); return cur_cmd < MIN_ENTROPY_SOURCES ? -1 : 0; } void usage(void) { fprintf(stderr, "Usage: %s [options]\n", __progname); fprintf(stderr, " -v Verbose; display verbose debugging messages.\n"); fprintf(stderr, " Multiple -v increases verbosity.\n"); fprintf(stderr, " -x Force output in hexidecimal (for debugging)\n"); fprintf(stderr, " -X Force output in binary\n"); fprintf(stderr, " -b bytes Number of bytes to output (default %d)\n", OUTPUT_SEED_SIZE); } int main(int argc, char **argv) { unsigned char *buf; int ret, ch, debug_level, output_hex, bytes; extern char *optarg; LogLevel ll; __progname = get_progname(argv[0]); log_init(argv[0], SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_USER, 1); ll = SYSLOG_LEVEL_INFO; debug_level = output_hex = 0; bytes = OUTPUT_SEED_SIZE; /* Don't write binary data to a tty, unless we are forced to */ if (isatty(STDOUT_FILENO)) output_hex = 1; while ((ch = getopt(argc, argv, "vxXhb:")) != -1) { switch (ch) { case 'v': if (debug_level < 3) ll = SYSLOG_LEVEL_DEBUG1 + debug_level++; break; case 'x': output_hex = 1; break; case 'X': output_hex = 0; break; case 'b': if ((bytes = atoi(optarg)) <= 0) fatal("Invalid number of output bytes"); break; case 'h': usage(); exit(0); default: error("Invalid commandline option"); usage(); } } log_init(argv[0], ll, SYSLOG_FACILITY_USER, 1); #ifdef USE_SEED_FILES prng_read_seedfile(); #endif buf = xmalloc(bytes); /* * Seed the RNG from wherever we can */ /* Take whatever is on the stack, but don't credit it */ RAND_add(buf, bytes, 0); debug("Seeded RNG with %i bytes from system calls", (int)stir_from_system()); #ifdef PRNGD_PORT if (get_random_bytes_prngd(buf, bytes, PRNGD_PORT, NULL) == -1) fatal("Entropy collection failed"); RAND_add(buf, bytes, bytes); #elif defined(PRNGD_SOCKET) if (get_random_bytes_prngd(buf, bytes, 0, PRNGD_SOCKET) == -1) fatal("Entropy collection failed"); RAND_add(buf, bytes, bytes); #else /* Read in collection commands */ if (prng_read_commands(SSH_PRNG_COMMAND_FILE) == -1) fatal("PRNG initialisation failed -- exiting."); debug("Seeded RNG with %i bytes from programs", (int)stir_from_programs()); #endif #ifdef USE_SEED_FILES prng_write_seedfile(); #endif /* * Write the seed to stdout */ if (!RAND_status()) fatal("Not enough entropy in RNG"); RAND_bytes(buf, bytes); if (output_hex) { for(ret = 0; ret < bytes; ret++) printf("%02x", (unsigned char)(buf[ret])); printf("\n"); } else ret = atomicio(write, STDOUT_FILENO, buf, bytes); memset(buf, '\0', bytes); xfree(buf); return ret == bytes ? 0 : 1; }