X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/yaid/blobdiff_plain/9da480be78586152866e0421a61994aab9adeaf3..2abfa39366012d4fd46dd8f026fbce1be56a5533:/yaid.c diff --git a/yaid.c b/yaid.c index 385ce38..da015e1 100644 --- a/yaid.c +++ b/yaid.c @@ -30,117 +30,130 @@ /*----- Data structures ---------------------------------------------------*/ -struct listen { - int af; - const char *proto; - sel_file f; -}; - +/* A write buffer is the gadget which keeps track of our output and writes + * portions of it out as and when connections are ready for it. + */ #define WRBUFSZ 1024 struct writebuf { - size_t o, n; - sel_file wr; - void (*func)(int, void *); - void *p; - unsigned char buf[WRBUFSZ]; + size_t o; /* Offset of remaining data */ + size_t n; /* Length of remaining data */ + sel_file wr; /* Write selector */ + void (*func)(int /*err*/, void *); /* Function to call on completion */ + void *p; /* Context for `func' */ + unsigned char buf[WRBUFSZ]; /* Output buffer */ }; -struct proxy { - struct client *c; - int fd; - conn cn; - selbuf b; - struct writebuf wb; - char nat[ADDRLEN]; +/* Structure for a listening socket. There's one of these for each address + * family we're looking after. + */ +struct listen { + const struct addrops *ao; /* Address family operations */ + sel_file f; /* Watch for incoming connections */ }; +/* The main structure for a client. */ struct client { - selbuf b; - int fd; - struct query q; - struct listen *l; - struct writebuf wb; - struct proxy *px; + int fd; /* The connection to the client */ + selbuf b; /* Accumulate lines of input */ + union addr raddr; /* Remote address */ + struct query q; /* The clients query and our reply */ + struct sel_timer t; /* Timeout for idle or doomed conn */ + struct listen *l; /* Back to the listener (and ops) */ + struct writebuf wb; /* Write buffer for our reply */ + struct proxy *px; /* Proxy if conn goes via NAT */ + struct client *next; /* Next in a chain of clients */ +}; + +/* A proxy connection. */ +struct proxy { + int fd; /* Connection; -1 if in progress */ + struct client *c; /* Back to the client */ + conn cn; /* Nonblocking connection */ + selbuf b; /* Accumulate the response line */ + struct writebuf wb; /* Write buffer for query */ + char nat[ADDRLEN]; /* Server address, as text */ + struct proxy *next; /* Next in a chain of proxies */ }; /*----- Static variables --------------------------------------------------*/ -static sel_state sel; +static sel_state sel; /* I/O multiplexer state */ -static policy_v policy = DA_INIT; -static fwatch polfw; +static const char *pidfile = 0; /* Where to write daemon's pid */ -static unsigned char tokenbuf[4096]; -static size_t tokenptr = sizeof(tokenbuf); -static int randfd; +static const char *policyfile = POLICYFILE; /* Filename for global policy */ +static const struct policy default_policy = POLICY_INIT(A_NAME); +static policy_v policy = DA_INIT; /* Vector of global policy rules */ +static fwatch polfw; /* Watch policy file for changes */ -/*----- Main code ---------------------------------------------------------*/ +static unsigned char tokenbuf[4096]; /* Random-ish data for tokens */ +static size_t tokenptr = sizeof(tokenbuf); /* Current read position */ +static int randfd; /* File descriptor for random data */ -static void socket_to_sockaddr(int af, const struct socket *s, - struct sockaddr *sa, size_t *ssz) -{ - sa->sa_family = af; - switch (af) { - case AF_INET: { - struct sockaddr_in *sin = (struct sockaddr_in *)sa; - sin->sin_addr = s->addr.ipv4; - sin->sin_port = htons(s->port); - *ssz = sizeof(*sin); - } break; - case AF_INET6: { - struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa; - sin6->sin6_addr = s->addr.ipv6; - sin6->sin6_port = htons(s->port); - sin6->sin6_flowinfo = 0; - sin6->sin6_scope_id = 0; - *ssz = sizeof(*sin6); - } break; - default: abort(); - } -} +static struct client *dead_clients = 0; /* List of defunct clients */ +static struct proxy *dead_proxies = 0; /* List of defunct proxies */ -static void sockaddr_to_addr(const struct sockaddr *sa, union addr *a) -{ - switch (sa->sa_family) { - case AF_INET: a->ipv4 = ((struct sockaddr_in *)sa)->sin_addr; break; - case AF_INET6: a->ipv6 = ((struct sockaddr_in6 *)sa)->sin6_addr; break; - default: abort(); - } -} +static unsigned flags = 0; /* Various interesting flags */ +#define F_SYSLOG 1u /* Use syslog for logging */ +#define F_RUNNING 2u /* Running properly now */ + +/*----- Ident protocol parsing --------------------------------------------*/ + +/* Advance *PP over whitespace characters. */ +static void skipws(const char **pp) + { while (isspace((unsigned char )**pp)) (*pp)++; } -static void dputsock(dstr *d, int af, const struct socket *s) +/* Copy a token of no more than N bytes starting at *PP into Q, advancing *PP + * over it. + */ +static int idtoken(const char **pp, char *q, size_t n) { - char buf[ADDRLEN]; + const char *p = *pp; - inet_ntop(af, &s->addr, buf, sizeof(buf)); - if (!s->port || af != AF_INET6) dstr_puts(d, buf); - else { dstr_putc(d, '['); dstr_puts(d, buf); dstr_putc(d, ']'); } - if (s->port) dstr_putf(d, ":%d", s->port); + skipws(&p); + n--; + for (;;) { + if (*p == ':' || *p <= 32 || *p >= 127) break; + if (!n) return (-1); + *q++ = *p++; + n--; + } + *q++ = 0; + *pp = p; + return (0); } -void logmsg(const struct query *q, int prio, const char *msg, ...) +/* Read an unsigned decimal number from *PP, and store it in *II. Check that + * it's between MIN and MAX, and advance *PP over it. Return zero for + * success, or nonzero if something goes wrong. + */ +static int unum(const char **pp, unsigned *ii, unsigned min, unsigned max) { - va_list ap; - dstr d = DSTR_INIT; + char *q; + unsigned long i; + int e; - va_start(ap, msg); - if (q) { - dputsock(&d, q->af, &q->s[L]); - dstr_puts(&d, " <-> "); - dputsock(&d, q->af, &q->s[R]); - dstr_puts(&d, ": "); - } - dstr_vputf(&d, msg, &ap); - va_end(ap); - fprintf(stderr, "yaid: %s\n", d.buf); - dstr_destroy(&d); + skipws(pp); + if (!isdigit((unsigned char)**pp)) return (-1); + e = errno; errno = 0; + i = strtoul(*pp, &q, 10); + if (errno) return (-1); + *pp = q; + errno = e; + if (i < min || i > max) return (-1); + *ii = i; + return (0); } +/*----- Asynchronous writing ----------------------------------------------*/ + +/* Callback for actually writing stuff from a `writebuf'. */ static void write_out(int fd, unsigned mode, void *p) { ssize_t n; struct writebuf *wb = p; + /* Try to write something. */ if ((n = write(fd, wb->buf + wb->o, wb->n)) < 0) { if (errno == EAGAIN || errno == EWOULDBLOCK) return; wb->n = 0; @@ -149,6 +162,8 @@ static void write_out(int fd, unsigned mode, void *p) } wb->o += n; wb->n -= n; + + /* If there's nothing left then restore the buffer to its empty state. */ if (!wb->n) { wb->o = 0; sel_rmfile(&wb->wr); @@ -156,26 +171,47 @@ static void write_out(int fd, unsigned mode, void *p) } } +/* Queue N bytes starting at P to be written. */ static int queue_write(struct writebuf *wb, const void *p, size_t n) { + /* Maybe there's nothing to actually do. */ if (!n) return (0); + + /* Make sure it'll fit. */ if (wb->n - wb->o + n > WRBUFSZ) return (-1); + + /* If there's anything there already, then make sure it's at the start of + * the available space. + */ if (wb->o) { memmove(wb->buf, wb->buf + wb->o, wb->n); wb->o = 0; } - memcpy(wb->buf + wb->n, p, n); + + /* If there's nothing currently there, then we're not requesting write + * notifications, so set that up, and force an initial wake-up. + */ if (!wb->n) { sel_addfile(&wb->wr); sel_force(&wb->wr); } + + /* Copy the new material over. */ + memcpy(wb->buf + wb->n, p, n); wb->n += n; + + /* Done. */ return (0); } +/* Release resources allocated to WB. */ static void free_writebuf(struct writebuf *wb) { if (wb->n) sel_rmfile(&wb->wr); } +/* Initialize a writebuf in *WB, writing to file descriptor FD. On + * completion, call FUNC, passing it P and an error indicator: either 0 for + * success or an `errno' value on failure. + */ static void init_writebuf(struct writebuf *wb, int fd, void (*func)(int, void *), void *p) { @@ -185,29 +221,73 @@ static void init_writebuf(struct writebuf *wb, wb->n = wb->o = 0; } -static void cancel_proxy(struct proxy *px) +/*----- General utilities -------------------------------------------------*/ + +/* Format and log MSG somewhere sensible, at the syslog(3) priority PRIO. + * Prefix it with a description of the query Q, if non-null. + */ +void logmsg(const struct query *q, int prio, const char *msg, ...) { - if (px->fd == -1) - conn_kill(&px->cn); + va_list ap; + dstr d = DSTR_INIT; + time_t t; + struct tm *tm; + char buf[64]; + + va_start(ap, msg); + if (q) { + dputsock(&d, q->ao, &q->s[L]); + dstr_puts(&d, " <-> "); + dputsock(&d, q->ao, &q->s[R]); + dstr_puts(&d, ": "); + } + dstr_vputf(&d, msg, &ap); + va_end(ap); + + if (!(flags & F_RUNNING)) + moan("%s", d.buf); + else if (flags & F_SYSLOG) + syslog(prio, "%s", d.buf); else { - close(px->fd); - selbuf_destroy(&px->b); - free_writebuf(&px->wb); + t = time(0); + tm = localtime(&t); + strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S %z", tm); + fprintf(stderr, "%s %s: %s\n", buf, QUIS, d.buf); } - selbuf_enable(&px->c->b); - px->c->px = 0; - xfree(px); + + dstr_destroy(&d); } -static void disconnect_client(struct client *c) +/* Fix up a socket FD so that it won't bite us. Returns zero on success, or + * nonzero on error. + */ +static int fix_up_socket(int fd, const char *what) { - close(c->fd); - selbuf_destroy(&c->b); - free_writebuf(&c->wb); - if (c->px) cancel_proxy(c->px); - xfree(c); + int yes = 1; + + if (fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0)) { + logmsg(0, LOG_ERR, "failed to set %s connection nonblocking: %s", + what, strerror(errno)); + return (-1); + } + + if (setsockopt(fd, SOL_SOCKET, SO_OOBINLINE, &yes, sizeof(yes))) { + logmsg(0, LOG_ERR, + "failed to disable `out-of-band' data on %s connection: %s", + what, strerror(errno)); + return (-1); + } + + return (0); } +/*----- Client output functions -------------------------------------------*/ + +static void disconnect_client(struct client *c); + +/* Notification that output has been written. If successful, re-enable the + * input buffer and prepare for another query. + */ static void done_client_write(int err, void *p) { struct client *c = p; @@ -220,7 +300,11 @@ static void done_client_write(int err, void *p) } } -static void write_to_client(struct client *c, const char *fmt, ...) +/* Format the message FMT and queue it to be sent to the client. Client + * input will be disabled until the write completes. + */ +static void PRINTF_LIKE(2, 3) + write_to_client(struct client *c, const char *fmt, ...) { va_list ap; char buf[WRBUFSZ]; @@ -245,56 +329,72 @@ static void write_to_client(struct client *c, const char *fmt, ...) } } -static void reply(struct client *c, const char *ty, const char *msg) +/* Format a reply to the client, with the form LPORT:RPORT:TY:TOK0[:TOK1]. + * Typically, TY will be `ERROR' or `USERID'. In the former case, TOK0 will + * be the error token and TOK1 will be null; in the latter case, TOK0 will be + * the operating system and TOK1 the user name. + */ +static void reply(struct client *c, const char *ty, + const char *tok0, const char *tok1) { - write_to_client(c, "%u,%u:%s:%s\r\n", - c->q.s[L].port, c->q.s[R].port, ty, msg); + write_to_client(c, "%u,%u:%s:%s%s%s\r\n", + c->q.s[L].port, c->q.s[R].port, ty, + tok0, tok1 ? ":" : "", tok1 ? tok1 : ""); } +/* Mapping from error codes to their protocol tokens. */ +const char *const errtok[] = { +#define DEFTOK(err, tok) tok, + ERROR(DEFTOK) +#undef DEFTOK +}; + +/* Report an error with code ERR to the client. */ static void reply_error(struct client *c, unsigned err) { assert(err < E_LIMIT); - reply(c, "ERROR", errtok[err]); + reply(c, "ERROR", errtok[err], 0); } -static void skipws(const char **pp) - { while (isspace((unsigned char )**pp)) (*pp)++; } +/*----- NAT proxy functions -----------------------------------------------*/ -static int idtoken(const char **pp, char *q, size_t n) +/* Cancel the proxy operation PX, closing the connection and releasing + * resources. This is used for both normal and unexpected closures. + */ +static void cancel_proxy(struct proxy *px) { - const char *p = *pp; - - skipws(&p); - n--; - for (;;) { - if (*p == ':' || *p <= 32 || *p >= 127) break; - if (!n) return (-1); - *q++ = *p++; - n--; + if (px->fd == -1) + conn_kill(&px->cn); + else { + close(px->fd); + selbuf_disable(&px->b); } - *q++ = 0; - *pp = p; - return (0); + px->c->px = 0; + selbuf_enable(&px->c->b); + px->next = dead_proxies; + dead_proxies = px; } -static int unum(const char **pp, unsigned *ii, unsigned min, unsigned max) +/* Delayed destruction of unsafe parts of proxies. */ +static void reap_dead_proxies(void) { - char *q; - unsigned long i; - int e; + struct proxy *px, *pp; - skipws(pp); - if (!isdigit((unsigned char)**pp)) return (-1); - e = errno; errno = 0; - i = strtoul(*pp, &q, 10); - if (errno) return (-1); - *pp = q; - errno = e; - if (i < min || i > max) return (-1); - *ii = i; - return (0); + for (px = dead_proxies; px; px = pp) { + pp = px->next; + if (px->fd != -1) { + selbuf_destroy(&px->b); + free_writebuf(&px->wb); + } + xfree(px); + } + dead_proxies = 0; } +/* Notification that a line (presumably a reply) has been received from the + * server. We should check it, log it, and propagate the answer back. + * Whatever happens, this proxy operation is now complete. + */ static void proxy_line(char *line, size_t sz, void *p) { struct proxy *px = p; @@ -302,39 +402,55 @@ static void proxy_line(char *line, size_t sz, void *p) const char *q = line; unsigned lp, rp; + /* Trim trailing space. */ while (sz && isspace((unsigned char)line[sz - 1])) sz--; - printf("received proxy line from %s: %s\n", px->nat, line); + /* Parse the port numbers. These should match the request. */ if (unum(&q, &lp, 1, 65535)) goto syntax; skipws(&q); if (*q != ',') goto syntax; q++; if (unum(&q, &rp, 1, 65535)) goto syntax; skipws(&q); if (*q != ':') goto syntax; q++; if (lp != px->c->q.u.nat.port || rp != px->c->q.s[R].port) goto syntax; + + /* Find out what kind of reply this is. */ if (idtoken(&q, buf, sizeof(buf))) goto syntax; skipws(&q); if (*q != ':') goto syntax; q++; + if (strcmp(buf, "ERROR") == 0) { + + /* Report the error without interpreting it. It might be meaningful to + * the client. + */ skipws(&q); logmsg(&px->c->q, LOG_ERR, "proxy error from %s: %s", px->nat, q); - reply(px->c, "ERROR", q); + reply(px->c, "ERROR", q, 0); + } else if (strcmp(buf, "USERID") == 0) { + + /* Parse out the operating system and user name, and pass them on. */ if (idtoken(&q, buf, sizeof(buf))) goto syntax; skipws(&q); if (*q != ':') goto syntax; q++; skipws(&q); logmsg(&px->c->q, LOG_ERR, "user `%s'; proxy = %s, os = %s", q, px->nat, buf); - write_to_client(px->c, "%u,%u:USERID:%s:%s\r\n", - px->c->q.s[L].port, px->c->q.s[R].port, buf, q); + reply(px->c, "USERID", buf, q); + } else goto syntax; goto done; syntax: + /* We didn't understand the message from the client. */ logmsg(&px->c->q, LOG_ERR, "failed to parse response from %s", px->nat); reply_error(px->c, E_UNKNOWN); done: + /* All finished, no matter what. */ cancel_proxy(px); } +/* Notification that we have written the query to the server. Await a + * response if successful. + */ static void done_proxy_write(int err, void *p) { struct proxy *px = p; @@ -349,71 +465,91 @@ static void done_proxy_write(int err, void *p) selbuf_enable(&px->b); } +/* Notification that the connection to the server is either established or + * failed. In the former case, queue the right query. + */ static void proxy_connected(int fd, void *p) { struct proxy *px = p; char buf[16]; int n; + /* If the connection failed then report the problem and give up. */ if (fd < 0) { logmsg(&px->c->q, LOG_ERR, "failed to make %s proxy connection to %s: %s", - px->c->l->proto, px->nat, strerror(errno)); + px->c->l->ao->name, px->nat, strerror(errno)); reply_error(px->c, E_UNKNOWN); cancel_proxy(px); return; } + /* We're now ready to go, so set things up. */ px->fd = fd; selbuf_init(&px->b, &sel, fd, proxy_line, px); selbuf_setsize(&px->b, 1024); selbuf_disable(&px->b); init_writebuf(&px->wb, fd, done_proxy_write, px); + /* Write the query. This buffer is large enough because we've already + * range-checked the remote the port number and the local one came from the + * kernel, which we trust not to do anything stupid. + */ n = sprintf(buf, "%u,%u\r\n", px->c->q.u.nat.port, px->c->q.s[R].port); queue_write(&px->wb, buf, n); } +/* Proxy the query through to a client machine for which we're providing NAT + * disservice. + */ static void proxy_query(struct client *c) { struct socket s; struct sockaddr_storage ss; size_t ssz; struct proxy *px; - int o; int fd; + /* Allocate the context structure for the NAT. */ px = xmalloc(sizeof(*px)); - inet_ntop(c->q.af, &c->q.u.nat.addr, px->nat, sizeof(px->nat)); - if ((fd = socket(c->q.af, SOCK_STREAM, 0)) < 0) { + /* We'll use the client host's address in lots of log messages, so we may + * as well format it once and use it over and over. + */ + inet_ntop(c->q.ao->af, &c->q.u.nat.addr, px->nat, sizeof(px->nat)); + + /* Create the socket for the connection. */ + if ((fd = socket(c->q.ao->af, SOCK_STREAM, 0)) < 0) { logmsg(&c->q, LOG_ERR, "failed to make %s socket for proxy: %s", - c->l->proto, strerror(errno)); + c->l->ao->name, strerror(errno)); goto err_0; } - - if ((o = fcntl(fd, F_GETFL)) < 0 || - fcntl(fd, F_SETFL, o | O_NONBLOCK)) { - logmsg(&c->q, LOG_ERR, "failed to set %s proxy socket nonblocking: %s", - c->l->proto, strerror(errno)); - goto err_1; - } - + if (fix_up_socket(fd, "proxy")) goto err_1; + + /* Set up the connection to the client host. The connection interface is a + * bit broken: if the connection completes immediately, then the callback + * function is called synchronously, and that might decide to shut + * everything down. So we must have fully initialized our context before + * calling `conn_init', and mustn't touch it again afterwards -- since the + * block may have been freed. + */ s = c->q.u.nat; s.port = 113; - socket_to_sockaddr(c->q.af, &s, (struct sockaddr *)&ss, &ssz); + c->l->ao->socket_to_sockaddr(&s, &ss, &ssz); selbuf_disable(&c->b); + c->px = px; px->c = c; + px->fd = -1; if (conn_init(&px->cn, &sel, fd, (struct sockaddr *)&ss, ssz, proxy_connected, px)) { logmsg(&c->q, LOG_ERR, "failed to make %s proxy connection to %s: %s", - c->l->proto, px->nat, strerror(errno)); + c->l->ao->name, px->nat, strerror(errno)); goto err_2; } - c->px = px; px->c = c; - px->fd = -1; + /* All ready to go. */ return; + /* Tidy up after various kinds of failures. */ err_2: selbuf_enable(&c->b); err_1: @@ -423,35 +559,103 @@ err_0: reply_error(c, E_UNKNOWN); } -static const struct policy default_policy = POLICY_INIT(A_NAME); +/*----- Client connection functions ---------------------------------------*/ + +/* Disconnect a client, freeing up any associated resources. */ +static void disconnect_client(struct client *c) +{ + selbuf_disable(&c->b); + close(c->fd); + sel_rmtimer(&c->t); + free_writebuf(&c->wb); + if (c->px) cancel_proxy(c->px); + c->next = dead_clients; + dead_clients = c; +} + +/* Throw away dead clients now that we've reached a safe point in the + * program. + */ +static void reap_dead_clients(void) +{ + struct client *c, *cc; + for (c = dead_clients; c; c = cc) { + cc = c->next; + selbuf_destroy(&c->b); + xfree(c); + } + dead_clients = 0; +} + +/* Time out a client because it's been idle for too long. */ +static void timeout_client(struct timeval *tv, void *p) +{ + struct client *c = p; + logmsg(&c->q, LOG_NOTICE, "timing out idle or stuck client"); + sel_addtimer(&sel, &c->t, tv, timeout_client, 0); + disconnect_client(c); +} + +/* Reset the client idle timer, as a result of activity. Set EXISTP if + * there is an existing timer which needs to be removed. + */ +static void reset_client_timer(struct client *c, int existp) +{ + struct timeval tv; + + gettimeofday(&tv, 0); + tv.tv_sec += 30; + if (existp) sel_rmtimer(&c->t); + sel_addtimer(&sel, &c->t, &tv, timeout_client, c); +} +/* Write a pseudorandom token into the buffer at P, which must have space for + * at least TOKENSZ bytes. + */ +#define TOKENRANDSZ 8 +#define TOKENSZ ((4*TOKENRANDSZ + 5)/3) static void user_token(char *p) { - static const char tokmap[64] = - "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-"; unsigned a = 0; unsigned b = 0; int i; -#define TOKENSZ 8 + static const char tokmap[64] = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-"; - if (tokenptr + TOKENSZ >= sizeof(tokenbuf)) { + /* If there's not enough pseudorandom stuff lying around, then read more + * from the kernel. + */ + if (tokenptr + TOKENRANDSZ >= sizeof(tokenbuf)) { if (read(randfd, tokenbuf, sizeof(tokenbuf)) < sizeof(tokenbuf)) die(1, "unexpected short read or error from `/dev/urandom'"); tokenptr = 0; } - for (i = 0; i < TOKENSZ; i++) { + /* Now encode the bytes using a slightly tweaked base-64 encoding. Read + * bytes into the accumulator and write out characters while there's + * enough material. + */ + for (i = 0; i < TOKENRANDSZ; i++) { a = (a << 8) | tokenbuf[tokenptr++]; b += 8; while (b >= 6) { b -= 6; *p++ = tokmap[(a >> b) & 0x3f]; } } + + /* If there's anything left in the accumulator then flush it out. */ if (b) *p++ = tokmap[(a << (6 - b)) & 0x3f]; + + /* Null-terminate the token. */ *p++ = 0; } +/* Notification that a line has been received from the client. Parse it, + * find out about the connection it's referring to, apply the relevant + * policy rules, and produce a response. This is where almost everything + * interesting happens. + */ static void client_line(char *line, size_t len, void *p) { struct client *c = p; @@ -462,107 +666,171 @@ static void client_line(char *line, size_t len, void *p) struct policy upol = POLICY_INIT(A_LIMIT); struct policy_file pf; char buf[16]; - int i; + int i, t; + /* If the connection has closed, then tidy stuff away. */ + c->q.s[R].addr = c->raddr; c->q.s[L].port = c->q.s[R].port = 0; if (!line) { disconnect_client(c); return; } - if (fwatch_update(&polfw, "yaid.policy")) { - logmsg(0, LOG_INFO, "reload master policy file `%s'", "yaid.policy"); - load_policy_file("yaid.policy", &policy); + /* Client activity, so update the timer. */ + reset_client_timer(c, 1); + + /* See if the policy file has changed since we last looked. If so, try to + * read the new version. + */ + if (fwatch_update(&polfw, policyfile)) { + logmsg(0, LOG_INFO, "reload master policy file `%s'", policyfile); + load_policy_file(policyfile, &policy); } + /* Read the local and remote port numbers into the query structure. */ q = line; if (unum(&q, &c->q.s[L].port, 1, 65535)) goto bad; skipws(&q); if (*q != ',') goto bad; q++; if (unum(&q, &c->q.s[R].port, 1, 65535)) goto bad; skipws(&q); if (*q) goto bad; + /* Identify the connection. Act on the result. */ identify(&c->q); switch (c->q.resp) { + case R_UID: + /* We found a user. Track down the user's password entry, because + * we'll want that later. Most of the processing for this case is + * below. + */ if ((pw = getpwuid(c->q.u.uid)) == 0) { logmsg(&c->q, LOG_ERR, "no passwd entry for user %d", c->q.u.uid); reply_error(c, E_NOUSER); return; } break; + case R_NAT: + /* We've acted as a NAT for this connection. Proxy the query through + * to the actal client host. + */ proxy_query(c); return; + case R_ERROR: - /* Should already be logged. */ + /* We failed to identify the connection for some reason. We should + * already have logged an error, so there's not much to do here. + */ reply_error(c, c->q.u.error); return; + default: + /* Something happened that we don't understand. */ abort(); } + /* Search the table of policy rules to find a match. */ for (i = 0; i < DA_LEN(&policy); i++) { pol = &DA(&policy)[i]; if (!match_policy(pol, &c->q)) continue; - if (pol->act.act != A_USER) - goto match; + + /* If this is something simple, then apply the resulting policy rule. */ + if (pol->act.act != A_USER) goto match; + + /* The global policy has decided to let the user have a say, so we must + * parse the user file. + */ DRESET(&d); dstr_putf(&d, "%s/.yaid.policy", pw->pw_dir); - if (open_policy_file(&pf, d.buf, "user policy file", &c->q)) + if (open_policy_file(&pf, d.buf, "user policy file", &c->q, OPF_NOENTOK)) continue; - while (!read_policy_file(&pf)) { + while ((t = read_policy_file(&pf)) < T_ERROR) { + + /* Give up after 100 lines or if there's an error. If the user's + * policy is that complicated, something's gone very wrong. Or there's + * too much commentary or something. + */ if (pf.lno > 100) { logmsg(&c->q, LOG_ERR, "%s:%d: user policy file too long", pf.name, pf.lno); break; } + + /* If this was a blank line, just go around again. */ + if (t != T_OK) continue; + + /* If this isn't a match, go around for the next rule. */ if (!match_policy(&pf.p, &c->q)) continue; + + /* Check that the user is allowed to request this action. If not, see + * if there's a more acceptable action later on. + */ if (!(pol->act.u.user & (1 << pf.p.act.act))) { logmsg(&c->q, LOG_ERR, "%s:%d: user action forbidden by global policy", pf.name, pf.lno); continue; } + + /* We've found a match, so grab it, close the file, and say we're + * done. + */ upol = pf.p; pol = &upol; init_policy(&pf.p); close_policy_file(&pf); + DDESTROY(&d); goto match; } close_policy_file(&pf); + DDESTROY(&d); } + + /* No match: apply the built-in default policy. */ pol = &default_policy; match: - DDESTROY(&d); switch (pol->act.act) { + case A_NAME: + /* Report the actual user's name. */ logmsg(&c->q, LOG_INFO, "user `%s' (%d)", pw->pw_name, c->q.u.uid); - reply(c, "USERID:UNIX", pw->pw_name); + reply(c, "USERID", "UNIX", pw->pw_name); break; + case A_TOKEN: + /* Report an arbitrary token which we can look up in our log file. */ user_token(buf); logmsg(&c->q, LOG_INFO, "user `%s' (%d); token = %s", pw->pw_name, c->q.u.uid, buf); - reply(c, "USERID:OTHER", buf); + reply(c, "USERID", "OTHER", buf); break; + case A_DENY: + /* Deny that there's anyone there at all. */ logmsg(&c->q, LOG_INFO, "user `%s' (%d); denying", pw->pw_name, c->q.u.uid); break; + case A_HIDE: + /* Report the user as being hidden. */ logmsg(&c->q, LOG_INFO, "user `%s' (%d); hiding", pw->pw_name, c->q.u.uid); reply_error(c, E_HIDDEN); break; + case A_LIE: + /* Tell an egregious lie about who the user is. */ logmsg(&c->q, LOG_INFO, "user `%s' (%d); lie = `%s'", pw->pw_name, c->q.u.uid, pol->act.u.lie); - reply(c, "USERID:UNIX", pol->act.u.lie); + reply(c, "USERID", "UNIX", pol->act.u.lie); break; + default: + /* Something has gone very wrong. */ abort(); } + /* All done. */ free_policy(&upol); return; @@ -571,6 +839,7 @@ bad: disconnect_client(c); } +/* Notification that a new client has connected. Prepare to read a query. */ static void accept_client(int fd, unsigned mode, void *p) { struct listen *l = p; @@ -579,124 +848,307 @@ static void accept_client(int fd, unsigned mode, void *p) size_t ssz = sizeof(ssr); int sk; + /* Accept the new connection. */ if ((sk = accept(fd, (struct sockaddr *)&ssr, &ssz)) < 0) { if (errno != EAGAIN && errno == EWOULDBLOCK) { logmsg(0, LOG_ERR, "failed to accept incoming %s connection: %s", - l->proto, strerror(errno)); + l->ao->name, strerror(errno)); } return; } + if (fix_up_socket(sk, "incoming client")) { close(sk); return; } + /* Build a client block and fill it in. */ c = xmalloc(sizeof(*c)); c->l = l; - c->q.af = l->af; - sockaddr_to_addr((struct sockaddr *)&ssr, &c->q.s[R].addr); + c->q.ao = l->ao; + + /* Collect the local and remote addresses. */ + l->ao->sockaddr_to_addr(&ssr, &c->raddr); ssz = sizeof(ssl); if (getsockname(sk, (struct sockaddr *)&ssl, &ssz)) { logmsg(0, LOG_ERR, "failed to read local address for incoming %s connection: %s", - l->proto, strerror(errno)); + l->ao->name, strerror(errno)); close(sk); xfree(c); return; } - sockaddr_to_addr((struct sockaddr *)&ssl, &c->q.s[L].addr); + l->ao->sockaddr_to_addr(&ssl, &c->q.s[L].addr); c->q.s[L].port = c->q.s[R].port = 0; - /* logmsg(&c->q, LOG_INFO, "accepted %s connection", l->proto); */ - + /* Set stuff up for reading the query and sending responses. */ selbuf_init(&c->b, &sel, sk, client_line, c); selbuf_setsize(&c->b, 1024); + reset_client_timer(c, 0); c->fd = sk; c->px = 0; init_writebuf(&c->wb, sk, done_client_write, c); } -static int make_listening_socket(int af, int port, const char *proto) +/*----- Main code ---------------------------------------------------------*/ + +/* Set up a listening socket for the address family described by AO, + * listening on PORT. + */ +static int make_listening_socket(const struct addrops *ao, int port) { int fd; - int o; + int yes = 1; + struct socket s; struct sockaddr_storage ss; struct listen *l; size_t ssz; - if ((fd = socket(af, SOCK_STREAM, 0)) < 0) { + /* Make the socket. */ + if ((fd = socket(ao->af, SOCK_STREAM, 0)) < 0) { + if (errno == EAFNOSUPPORT) return (-1); die(1, "failed to create %s listening socket: %s", - proto, strerror(errno)); - } - o = 1; setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &o, sizeof(o)); - ss.ss_family = af; - switch (af) { - case AF_INET: { - struct sockaddr_in *sin = (struct sockaddr_in *)&ss; - sin->sin_addr.s_addr = INADDR_ANY; - sin->sin_port = htons(port); - ssz = sizeof(*sin); - } break; - case AF_INET6: { - struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&ss; - o = 1; setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &o, sizeof(o)); - sin6->sin6_family = AF_INET6; - sin6->sin6_addr = in6addr_any; - sin6->sin6_scope_id = 0; - sin6->sin6_flowinfo = 0; - ssz = sizeof(*sin6); - } break; - default: - abort(); + ao->name, strerror(errno)); + } + + /* Build the appropriate local address. */ + s.addr = *ao->any; + s.port = port; + ao->socket_to_sockaddr(&s, &ss, &ssz); + + /* Perform any initialization specific to the address type. */ + if (ao->init_listen_socket(fd)) { + die(1, "failed to initialize %s listening socket: %s", + ao->name, strerror(errno)); + } + + /* Bind to the address. */ + setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)); + if (bind(fd, (struct sockaddr *)&ss, ssz)) { + die(1, "failed to bind %s listening socket: %s", + ao->name, strerror(errno)); } - if (bind(fd, (struct sockaddr *)&ss, ssz)) - die(1, "failed to bind %s listening socket: %s", proto, strerror(errno)); - if ((o = fcntl(fd, F_GETFL)) < 0 || - fcntl(fd, F_SETFL, o | O_NONBLOCK)) { + + /* Avoid unpleasant race conditions. */ + if (fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0)) { die(1, "failed to set %s listening socket nonblocking: %s", - proto, strerror(errno)); + ao->name, strerror(errno)); } + + /* Prepare to listen. */ if (listen(fd, 5)) - die(1, "failed to listen for %s: %s", proto, strerror(errno)); + die(1, "failed to listen for %s: %s", ao->name, strerror(errno)); + /* Make a record of all of this. */ l = xmalloc(sizeof(*l)); - l->af = af; - l->proto = proto; + l->ao = ao; sel_initfile(&sel, &l->f, fd, SEL_READ, accept_client, l); sel_addfile(&l->f); - return (fd); + /* Done. */ + return (0); +} + +/* Quit because of a fatal signal. */ +static void NORETURN quit(int sig, void *p) +{ + const char *signame = p; + + logmsg(0, LOG_NOTICE, "shutting down on %s", signame); + if (pidfile) unlink(pidfile); + exit(0); +} + +/* Answer whether the string pointed to by P consists entirely of digits. */ +static int numericp(const char *p) +{ + while (*p) + if (!isdigit((unsigned char)*p++)) return (0); + return (1); +} + +static void usage(FILE *fp) +{ + pquis(fp, "Usage: $ [-Dl] [-G GROUP] [-U USER] [-P FILE] " + "[-c FILE] [-p PORT]\n"); +} + +static void version(FILE *fp) + { pquis(fp, "$, version " VERSION "\n"); } + +static void help(FILE *fp) +{ + version(fp); fputc('\n', fp); + usage(fp); + fputs("\n\ +Yet Another Ident Daemon. Really, the world doesn't need such a thing.\n\ +It's just a shame none of the others do the right things.\n\ +\n\ +Options:\n\ +\n\ + -h, --help Show this help message.\n\ + -v, --version Show the version number.\n\ + -u, --usage Show a very short usage summary.\n\ +\n\ + -D, --daemon Become a daemon, running in the background.\n\ + -G, --group=GROUP Set group after initialization.\n\ + -P, --pidfile=FILE Write process id to FILE.\n\ + -U, --user=USER Set user after initialization.\n\ + -c, --config=FILE Read global policy from FILE.\n\ + -l, --syslog Write log messages using syslog(3).\n\ + -p, --port=PORT Listen for connections on this port.\n", + fp); } int main(int argc, char *argv[]) { int port = 113; - char buf[ADDRLEN]; - union addr a; + uid_t u = -1; + gid_t g = -1; + struct passwd *pw = 0; + struct group *gr; + struct servent *s; + sig sigint, sigterm; + FILE *fp = 0; + int i; + unsigned f = 0; +#define f_bogus 1u +#define f_daemon 2u + const struct addrops *ao; + int any = 0; ego(argv[0]); - fwatch_init(&polfw, "yaid.policy"); - if (load_policy_file("yaid.policy", &policy)) - exit(1); - { int i; - for (i = 0; i < DA_LEN(&policy); i++) - print_policy(&DA(&policy)[i]); + /* Parse command-line options. */ + for (;;) { + const struct option opts[] = { + { "help", 0, 0, 'h' }, + { "version", 0, 0, 'v' }, + { "usage", 0, 0, 'u' }, + { "daemon", 0, 0, 'D' }, + { "group", OPTF_ARGREQ, 0, 'G' }, + { "pidfile", OPTF_ARGREQ, 0, 'P' }, + { "user", OPTF_ARGREQ, 0, 'U' }, + { "config", OPTF_ARGREQ, 0, 'c' }, + { "syslog", 0, 0, 'l' }, + { "port", OPTF_ARGREQ, 0, 'p' }, + { 0, 0, 0, 0 } + }; + + if ((i = mdwopt(argc, argv, "hvuDG:P:U:c:lp:", opts, 0, 0, 0)) < 0) + break; + switch (i) { + case 'h': help(stdout); exit(0); + case 'v': version(stdout); exit(0); + case 'u': usage(stdout); exit(0); + case 'D': f |= f_daemon; break; + case 'P': pidfile = optarg; break; + case 'c': policyfile = optarg; break; + case 'l': flags |= F_SYSLOG; break; + case 'G': + if (numericp(optarg)) + g = atoi(optarg); + else if ((gr = getgrnam(optarg)) == 0) + die(1, "unknown group `%s'", optarg); + else + g = gr->gr_gid; + break; + case 'U': + if (numericp(optarg)) + u = atoi(optarg); + else if ((pw = getpwnam(optarg)) == 0) + die(1, "unknown user `%s'", optarg); + else + u = pw->pw_uid; + break; + case 'p': + if (numericp(optarg)) + port = atoi(optarg); + else if ((s = getservbyname(optarg, "tcp")) == 0) + die(1, "unknown service name `%s'", optarg); + else + port = ntohs(s->s_port); + break; + default: f |= f_bogus; break; + } } + if (optind < argc) f |= f_bogus; + if (f & f_bogus) { usage(stderr); exit(1); } + + /* If a user has been requested, but no group, then find the user's primary + * group. If the user was given by name, then we already have a password + * entry and should use that, in case two differently-named users have the + * same uid but distinct gids. + */ + if (u != -1 && g == -1) { + if (!pw && (pw = getpwuid(u)) == 0) { + die(1, "failed to find password entry for user %d: " + "request group explicitly", u); + } + g = pw->pw_gid; + } + + /* Initialize system-specific machinery. */ + init_sys(); + /* Load the global policy rules. */ + fwatch_init(&polfw, policyfile); + if (load_policy_file(policyfile, &policy)) + exit(1); + + /* Open the random data source. */ if ((randfd = open("/dev/urandom", O_RDONLY)) < 0) { die(1, "failed to open `/dev/urandom' for reading: %s", strerror(errno)); } - if (get_default_gw(AF_INET, &a)) - printf("ipv4 gw = %s\n", inet_ntop(AF_INET, &a, buf, sizeof(buf))); - if (get_default_gw(AF_INET6, &a)) - printf("ipv6 gw = %s\n", inet_ntop(AF_INET6, &a, buf, sizeof(buf))); - + /* Set up the I/O event system. */ sel_init(&sel); - make_listening_socket(AF_INET, port, "IPv4"); - make_listening_socket(AF_INET6, port, "IPv6"); - for (;;) - if (sel_select(&sel)) die(1, "select failed: %s", strerror(errno)); + /* Watch for some interesting signals. */ + sig_init(&sel); + sig_add(&sigint, SIGINT, quit, "SIGINT"); + sig_add(&sigterm, SIGTERM, quit, "SIGTERM"); + + /* Listen for incoming connections. */ + for (ao = addroptab; ao->name; ao++) + if (!make_listening_socket(ao, port)) any = 1; + if (!any) die(1, "no IP protocols supported"); + + /* Open the pidfile now, in case it's somewhere we can't write. */ + if (pidfile && (fp = fopen(pidfile, "w")) == 0) { + die(1, "failed to open pidfile `%s' for writing: %s", + pidfile, strerror(errno)); + } + + /* If we're meant to use syslog, then open the log. */ + if (flags & F_SYSLOG) + openlog(QUIS, 0, LOG_DAEMON); + + /* Drop privileges. */ + if ((g != -1 && (setegid(g) || setgid(g) || + (getuid() == 0 && setgroups(1, &g)))) || + (u != -1 && setuid(u))) + die(1, "failed to drop privileges: %s", strerror(errno)); + + /* Become a background process, if requested. */ + if ((f & f_daemon) && daemonize()) + die(1, "failed to become daemon: %s", strerror(errno)); + + /* Write the process id to the pidfile. */ + if (fp) { + fprintf(fp, "%d\n", getpid()); + fclose(fp); + } + + /* And now we're going. */ + flags |= F_RUNNING; + + /* Read events and process them. */ + for (;;) { + if (sel_select(&sel) && errno != EINTR) + die(1, "select failed: %s", strerror(errno)); + reap_dead_proxies(); + reap_dead_clients(); + } + /* This just keeps the compiler happy. */ return (0); }