pop3

commit b27996f61e27d1416dcd11ee3143146f4fdeb8b8
Author: Jacob R. Edwards <jacob@jacobedwards.org>
Date:   Mon,  7 Mar 2022 07:42:39 +0000

Add pop3 client

Diffstat:
A
Makefile
 | 
36
++++++++++++++++++++++++++++++++++++
A
pop3.1
 | 
127
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
pop3.c
 | 
493
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

3 files changed, 656 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -0,0 +1,36 @@
+#	$Id: Makefile,v 1.1 2022/03/07 07:42:39 jacob Exp $
+
+NAME = pop3
+SRC = pop3.c
+OBJ = ${SRC:.c=.o}
+
+PREFIX = /usr/local
+MANPREFIX = ${PREFIX}/man
+
+CC = cc
+CFLAGS = -Wall -Wno-write-strings
+LDFLAGS = -static
+
+all: ${NAME}
+
+${NAME}: ${OBJ}
+	${CC} -o $@ ${OBJ} ${LDFLAGS}
+
+${OBJ}: Makefile
+
+.c.o:
+	${CC} ${CFLAGS} -c -o $@ $<
+
+clean:
+	rm -f ${NAME} ${OBJ}
+
+install: ${NAME}
+	cp -f ${NAME} ${PREFIX}/bin
+	cp -f ${NAME}.1 ${MANPREFIX}/man1
+
+uninstall:
+	rm -f ${PREFIX}/bin/${NAME}
+	rm -f ${MANPREFIX}/man1/${NAME}.1
+
+.SUFFIXES: .c .o
+.PHONY: clean install uninstall
diff --git a/pop3.1 b/pop3.1
@@ -0,0 +1,127 @@
+.\"	$Id: pop3.1,v 1.1 2022/03/07 07:42:39 jacob Exp $
+.\"
+.\" Copyright (c) 2022 Jacob R. Edwards
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.Dd March 6, 2022
+.Dt POP3 1
+.Os
+.Sh NAME
+.Nm pop3
+.Nd fetch mail from POP3 server
+.Sh SYNOPSIS
+.Nm
+.Op Fl kqst
+.Op Fl p Ar port
+.Op Fl u Ar user
+.Ar host
+.Sh DESCRIPTION
+The
+.Nm
+utility retrieves mail from a POP3 server on
+.Ar host ,
+outputting all mail in the mbox format. See
+.Sx SECURITY CONSIDERATIONS
+before use.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl k
+Don't delete mail after retreiving it.
+.It Fl q
+Query maildrop statistics. Output is of the form:
+.Bd -literal -offset indent -compact
+M message(s) B byte(s)
+.Ed
+where M is the number of messages and B is the number of bytes.
+.It Fl s
+Read passphrase from
+.Pa /dev/stdin ,
+by default
+.Pa /dev/tty
+is used.
+.It Fl t
+Trace POP3 communication.
+.It Fl p Ar port
+Connect to
+.Ar host
+on port
+.Ar port .
+Defaults to 110 (pop3).
+.It Fl u Ar user
+Login to POP3
+.Ar user
+uesr. By default your login name (as returned by
+.Xr getlogin 2 )
+is used.
+.El
+.Sh EXIT STATUS
+.Ex -std
+.Sh EXAMPLES
+Retrieve mail from pop3.xyz, append it to
+.Pa mbox ,
+and delete it from the server
+.Bd -literal -offset indent
+$ pop3 pop3.xyz >> mbox
+.Ed
+.Pp
+The same, except don't delete the mail
+.Bd -literal -offset indent
+$ pop3 -k pop3.xyz >> mbox
+.Ed
+.Pp
+Like the last example, except read the passphrase from the
+.Pa pass
+file
+.Bd -literal -offset indent
+$ pop3 -ks < pass >> mbox
+.Ed
+.Pp
+Like the first example, except communication is tunneled
+through
+.Xr ssh 1
+.Bd -literal -offset indent
+$ ssh -f -L 1110:localhost:110 pop3.xyz sleep 10
+$ pop3 -p 1110 localhost >> mbox
+.Ed
+.Pp
+Emulate pop3s support using
+.Xr stunnel 8
+.Bd -literal -offset indent
+$ stunnel -fd 0 < stunnel.conf
+$ pop3 -p 1110 localhost
+.Ed
+where
+.Pa stunnel.conf
+contains
+.Bd -literal -offset indent
+[pop3s]
+client = yes
+connect = pop3.xyz
+accept = 1110
+.Ed
+.Sh SEE ALSO
+.Xr popa3d 8 ,
+.Xr ssh 1 ,
+.Xr stunnel 8
+.Sh STANDARDS
+.Nm
+tries to comply with Internet Standard STD 53 (RFC 1939).
+.St "STD 53"
+.Sh AUTHORS
+.An Jacob R. Edwards
+.Sh SECURITY CONSIDERATIONS
+.Nm
+communicates in cleartext; an encrypted tunnel should be used if
+security is a concern.
diff --git a/pop3.c b/pop3.c
@@ -0,0 +1,493 @@
+/*	$Id: pop3.c,v 1.1 2022/03/07 07:42:39 jacob Exp $	*/
+
+/*
+ * Copyright (c) 2022 Jacob R. Edwards
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* ignore const */
+#define const
+
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <netdb.h>
+
+#include <ctype.h>
+#include <errno.h>
+#include <libgen.h>
+#include <limits.h>
+#include <readpassphrase.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* Limits */
+#define LISTMAX	9999	/* Maximum number of messages (see scanlisting struct) */
+#define LINEMAX	1002	/* Includes CRLF and nul (see RFC 5321 5.4.3.1.6.)  */
+#define POPMAX	513	/* POP3 status size including CRLF and nul */
+#define ARGMAX	40	/* POP3 argument size excluding nul */
+#define KEYMAX	4	/* POP3 keyword size excluding nul */
+
+/* Messy global error buffers */
+static char poperr[128];
+static int gaierr;
+
+/* Flag variables */
+static int keep;
+static int query;
+static int usestdin;
+static int trace;
+
+/* Option and argument variables */
+static char *port = "110";
+static char *user;
+static char *host;
+
+struct scanlisting {
+	char msg[4 + 1]; /* See LISTMAX */
+	int bytes;
+};
+
+void
+die(char *fmt, ...)
+{
+	va_list ap;
+	char *info;
+
+	if (gaierr && gaierr != EAI_SYSTEM)
+		info = gai_strerror(gaierr);
+	else if (*poperr)
+		info = poperr;
+	else
+		info = strerror(errno);
+
+	fprintf(stderr, "%s: ", getprogname());
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+	fprintf(stderr, ": %s\n", info);
+	exit(1);
+}
+
+void
+usage(char *why)
+{
+	if (why)
+		fprintf(stderr, "%s\n", why);
+	fprintf(stderr, "usage: %s [-kqst] [-u user] [-p port] host\n",
+	    getprogname());
+	exit(1);
+}
+
+int
+resolve(char *host, char *serv)
+{
+	struct addrinfo hints;
+	struct addrinfo *res, *res0;
+	int fd;
+	int errno2;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_protocol = IPPROTO_TCP;
+	hints.ai_flags = AI_PASSIVE;
+ 
+	if ((gaierr = getaddrinfo(host, serv, &hints, &res0)) != 0)
+		return -1;
+
+	fd = -1;
+	errno2 = errno;
+	for (res = res0; fd < 0 && res; res = res->ai_next) {
+		fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+		if (fd >= 0) {
+			if (connect(fd, res->ai_addr, res->ai_addrlen)) {
+				close(fd);
+				fd = -1;
+			}
+		}
+	}
+
+	if (fd >= 0)
+		errno = errno2;
+	freeaddrinfo(res0);
+
+	return fd;
+}
+
+int
+pop_split(char **ap, int len, char *buf)
+{
+	int i;
+	char *p;
+
+	for (i = 0; (p = strsep(&buf, " ")); ++i)
+		if (i < len)
+			ap[i] = p;
+	return i;
+}
+
+char *
+pop_okay(char *buf)
+{
+	if (!buf)
+		return NULL;
+
+	if (strncmp(buf, "+OK", 3) == 0)
+		return buf + ((buf[3] == ' ') ? 4 : 3);
+	if (strncmp(buf, "-ERR ", 5) == 0)
+		strlcpy(poperr, buf + 5, sizeof(poperr));
+	return NULL;
+}
+
+char *
+pop_charcheck(char *buf)
+{
+        /*
+	 * The RFC doesn't seem to specify what servers are allowed
+         * to send.  It DOES specify that clients can only send
+         * "printable ASCII characters". I'll just allow printable
+         * characters and tab.
+	 */
+	while (isprint(*buf) || *buf == '\t')
+		++buf;
+	return buf;
+}
+
+char *
+pop_read(FILE *fp, char *buf, int size)
+{
+	char *p;
+
+	if (!fgets(buf, size, fp))
+		return NULL;
+
+	p = pop_charcheck(buf);
+	if (strcmp(p, "\r\n") != 0) {
+		errno = EFTYPE;
+		return NULL;
+	}
+
+	*p = '\0';
+	if (trace)
+		fprintf(stderr, "<S %s\n", buf);
+	return buf;
+}
+
+int
+pop_write(FILE *fp, char *keyword, char *arg) 
+{
+	char buf[KEYMAX + 1 + ARGMAX + 1];
+	int len;
+
+	if (arg)
+		len = snprintf(buf, sizeof(buf), "%s %s", keyword, arg);
+	else
+		len = snprintf(buf, sizeof(buf), "%s", keyword);
+
+	if (len < 0)
+		return -1;
+
+	if (len >= sizeof(buf)) {
+		errno = ENOBUFS;
+		return -1;
+	}
+
+	if (*pop_charcheck(buf)) {
+		errno = EFTYPE;
+		return -1;
+	}
+
+	if (trace)
+		fprintf(stderr, "C> %s\n", buf);
+	return fprintf(fp, "%s\r\n", buf) != len + 2;
+}
+
+FILE *
+pop_open(char *host, char *serv)
+{
+	FILE *fp;
+	char buf[POPMAX];
+	int fd;
+
+	fd = resolve(host, serv);
+	if (fd < 0)
+		return NULL;
+
+	if ((fp = fdopen(fd, "r+")) == NULL) {
+		close(fd);
+		return NULL;
+	}
+
+	if (!pop_okay(pop_read(fp, buf, sizeof(buf)))) {
+		fclose(fp);
+		return NULL;
+	}
+	return fp;
+}
+
+char *
+pop_comd(FILE *fp, char *buf, int size, char *keyword, char *arg)
+{
+	if (pop_write(fp, keyword, arg))
+		return NULL;
+	if (!pop_read(fp, buf, size))
+		return NULL;
+	return buf;
+}
+
+int
+pop_quit(FILE *fp)
+{
+	char buf[POPMAX];
+
+	if (!pop_okay(pop_comd(fp, buf, sizeof(buf), "QUIT", NULL))) {
+		fclose(fp);
+		return 1;
+	}
+	return fclose(fp) < 0;
+}
+
+int
+pop_auth(FILE *fp, char *user, char *pass)
+{
+	char buf[POPMAX];
+
+	if (!pop_okay(pop_comd(fp, buf, sizeof(buf), "USER", user)))
+		return 1;
+	if (!pop_okay(pop_comd(fp, buf, sizeof(buf), "PASS", pass)))
+		return 1;
+	return 0;
+}
+
+int
+pop_stat(FILE *fp, int *msgs, int *bytes)
+{
+	char buf[POPMAX];
+	char *ap[2];
+	int nums[2];
+	char *p;
+	int i;
+
+	if (!pop_comd(fp, buf, sizeof(buf), "STAT", NULL))
+		return 1;
+
+	if (!(p = pop_okay(buf)) || pop_split(ap, 2, p) < 2) {
+		errno = EFTYPE;
+		return 1;
+	}
+
+	for (i = 0; i < 2; ++i) {
+		nums[i] = strtonum(ap[i], 0, INT_MAX, &p);
+		if (p)
+			return 1;
+	}
+
+	if (msgs)
+		*msgs = nums[0];
+	if (bytes)
+		*bytes = nums[1];
+	return 0;
+}
+
+struct scanlisting *
+pop_list(FILE *fp, int *_len)
+{
+	char *ap[2];
+	char buf[POPMAX];
+	struct scanlisting *listings;
+	int len, i;
+
+	if (pop_stat(fp, &len, NULL))
+		return NULL;
+
+	if (len > LISTMAX) {
+		/* More descriptive errors would be nice,
+		 * maybe just print them out.
+		 */
+		errno = EOVERFLOW;
+		return NULL;
+	}
+	listings = calloc(len, sizeof(*listings));
+	if (len == 0 || listings == NULL)
+		return listings;
+
+	if (!pop_okay(pop_comd(fp, buf, sizeof(buf), "LIST", NULL)))
+		return NULL;
+
+	for (i = 0; i < len && pop_read(fp, buf, sizeof(buf)) &&
+	    strcmp(buf, ".") != 0; ++i) {
+		/* Beginning . would be invalid anyway,
+		 * so strtonum can check it.
+		 */
+		if (pop_split(ap, 2, buf) != 2) {
+			free(listings);
+			errno = EFTYPE;
+			return NULL;
+		}
+
+		if (strlcpy(listings[i].msg, ap[0], sizeof(listings[i].msg)) >=
+		    sizeof(listings[i].msg)) {
+			free(listings);
+			errno = ENOBUFS;
+			return NULL;
+		}
+
+		listings[i].bytes = strtonum(ap[1], 0, INT_MAX, &ap[0]);
+		if (ap[0]) {
+			free(listings);
+			return NULL;
+		}
+	}
+
+	if (_len)
+		*_len = len;
+	return listings;
+}
+
+int
+pop_retr(FILE *fp, char *msg)
+{
+	char buf[LINEMAX], *p;
+
+	if (!pop_okay(pop_comd(fp, buf, sizeof(buf), "RETR", msg)))
+		return 1;
+
+	while ((p = pop_read(fp, buf, sizeof(buf))) && strcmp(p, ".") != 0) {
+		if (*p == '.')
+			++p;
+		if (puts(p) < 0)
+			return 1;
+	}
+	if (p == NULL)
+		return 1;
+	return puts("") < 0;
+}
+
+int
+pop_dele(FILE *fp, char *msg)
+{
+	char buf[POPMAX];
+
+	return pop_okay(pop_comd(fp, buf, sizeof(buf), "DELE", msg)) == NULL;
+}
+
+int
+mbox(FILE *fp, int delete)
+{
+	int len, i;
+	struct scanlisting *listings;
+
+	listings = pop_list(fp, &len);
+	if (listings == NULL)
+		return 1;
+
+	for (i = 0; i < len; ++i) {
+		if (pop_retr(fp, listings[i].msg) ||
+		    (delete && pop_dele(fp, listings[i].msg))) {
+			free(listings);
+			return 1;
+		}
+	}
+
+	free(listings);
+	return 0;
+}
+
+int
+stat(FILE *fp)
+{
+	int msgs, bytes;
+	if (pop_stat(fp, &msgs, &bytes))
+		return 1;;
+	return printf("%d %s %d %s\n",
+	    msgs, msgs == 1 ? "message" : "messages",
+	    bytes, bytes == 1 ? "byte" : "bytes") < 0;
+}
+
+int
+auth(FILE *fp, char *user, int usestdin)
+{
+	char pass[ARGMAX + 1];
+	int status;
+
+	if (!readpassphrase("Passphrase: ", pass, sizeof(pass),
+	    usestdin ? RPP_STDIN : RPP_REQUIRE_TTY))
+		die("unable to read passphrase");
+	status = pop_auth(fp, user, pass);
+	explicit_bzero(pass, sizeof(pass));
+
+	return status;
+}
+
+int
+main(int argc, char *argv[])
+{
+	FILE *fp;
+	int c;
+
+	if (pledge("stdio tty inet dns", NULL))
+		die("pledge");
+
+	user = getlogin();
+	while ((c = getopt(argc, argv, "kp:qstu:")) >= 0) {
+		switch (c) {
+		case 'k':
+			keep = 1;
+			break;
+		case 'p':
+			port = optarg;
+			break;
+		case 'q':
+			query = 1;
+			break;
+		case 's':
+			usestdin = 1;
+			break;
+		case 't':
+			trace = 1;
+			break;
+		case 'u':
+			user = optarg;
+			break;
+		default:
+			usage(NULL);
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (argc > 1)
+		usage("Too many arguments");
+	if (argc < 1)
+		usage("No host");
+	host = argv[0];
+
+	fp = pop_open(host, port);
+	if (fp == NULL)
+		die("'%s'", host);
+
+	if (auth(fp, user, usestdin))
+		die("unable to authenticate for '%s'", user);
+
+	if (pledge("stdio", NULL))
+		die("pledge");
+
+	if (query ?  stat(fp) : mbox(fp, !keep))
+		die("unable to complete transaction");
+	return !pop_quit(fp);
+}