| /* vi: set sw=4 ts=4: */ |
| /* |
| * bare bones sendmail |
| * |
| * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com> |
| * |
| * Licensed under GPLv2, see file LICENSE in this source tree. |
| */ |
| |
| //kbuild:lib-$(CONFIG_SENDMAIL) += sendmail.o mail.o |
| |
| //usage:#define sendmail_trivial_usage |
| //usage: "[-tv] [-f SENDER] [-amLOGIN 4<user_pass.txt | -auUSER -apPASS]" |
| //usage: "\n [-w SECS] [-H 'PROG ARGS' | -S HOST] [RECIPIENT_EMAIL]..." |
| //usage:#define sendmail_full_usage "\n\n" |
| //usage: "Read email from stdin and send it\n" |
| //usage: "\nStandard options:" |
| //usage: "\n -t Read additional recipients from message body" |
| //usage: "\n -f SENDER For use in MAIL FROM:<sender>. Can be empty string" |
| //usage: "\n Default: -auUSER, or username of current UID" |
| //usage: "\n -o OPTIONS Various options. -oi implied, others are ignored" |
| //usage: "\n -i -oi synonym, implied and ignored" |
| //usage: "\n" |
| //usage: "\nBusybox specific options:" |
| //usage: "\n -v Verbose" |
| //usage: "\n -w SECS Network timeout" |
| //usage: "\n -H 'PROG ARGS' Run connection helper. Examples:" |
| //usage: "\n openssl s_client -quiet -tls1 -starttls smtp -connect smtp.gmail.com:25" |
| //usage: "\n openssl s_client -quiet -tls1 -connect smtp.gmail.com:465" |
| //usage: "\n -S HOST[:PORT] Server (default $SMTPHOST or 127.0.0.1)" |
| //usage: "\n -amLOGIN Log in using AUTH LOGIN (-amCRAM-MD5 not supported)" |
| //usage: "\n -auUSER Username for AUTH" |
| //usage: "\n -apPASS Password for AUTH" |
| //usage: "\n" |
| //usage: "\nIf no -a options are given, authentication is not done." |
| //usage: "\nIf -amLOGIN is given but no -au/-ap, user/password is read from fd #4." |
| //usage: "\nOther options are silently ignored; -oi is implied." |
| //usage: IF_MAKEMIME( |
| //usage: "\nUse makemime to create emails with attachments." |
| //usage: ) |
| |
| /* Currently we don't sanitize or escape user-supplied SENDER and RECIPIENT_EMAILs. |
| * We may need to do so. For one, '.' in usernames seems to require escaping! |
| * |
| * From http://cr.yp.to/smtp/address.html: |
| * |
| * SMTP offers three ways to encode a character inside an address: |
| * |
| * "safe": the character, if it is not <>()[].,;:@, backslash, |
| * double-quote, space, or an ASCII control character; |
| * "quoted": the character, if it is not \012, \015, backslash, |
| * or double-quote; or |
| * "slashed": backslash followed by the character. |
| * |
| * An encoded box part is either (1) a sequence of one or more slashed |
| * or safe characters or (2) a double quote, a sequence of zero or more |
| * slashed or quoted characters, and a double quote. It represents |
| * the concatenation of the characters encoded inside it. |
| * |
| * For example, the encoded box parts |
| * angels |
| * \a\n\g\e\l\s |
| * "\a\n\g\e\l\s" |
| * "angels" |
| * "ang\els" |
| * all represent the 6-byte string "angels", and the encoded box parts |
| * a\,comma |
| * \a\,\c\o\m\m\a |
| * "a,comma" |
| * all represent the 7-byte string "a,comma". |
| * |
| * An encoded address contains |
| * the byte <; |
| * optionally, a route followed by a colon; |
| * an encoded box part, the byte @, and a domain; and |
| * the byte >. |
| * |
| * It represents an Internet mail address, given by concatenating |
| * the string represented by the encoded box part, the byte @, |
| * and the domain. For example, the encoded addresses |
| * <God@heaven.af.mil> |
| * <\God@heaven.af.mil> |
| * <"God"@heaven.af.mil> |
| * <@gateway.af.mil,@uucp.local:"\G\o\d"@heaven.af.mil> |
| * all represent the Internet mail address "God@heaven.af.mil". |
| */ |
| |
| #include "libbb.h" |
| #include "mail.h" |
| |
| // limit maximum allowed number of headers to prevent overflows. |
| // set to 0 to not limit |
| #define MAX_HEADERS 256 |
| |
| static void send_r_n(const char *s) |
| { |
| if (verbose) |
| bb_error_msg("send:'%s'", s); |
| printf("%s\r\n", s); |
| } |
| |
| static int smtp_checkp(const char *fmt, const char *param, int code) |
| { |
| char *answer; |
| char *msg = send_mail_command(fmt, param); |
| // read stdin |
| // if the string has a form NNN- -- read next string. E.g. EHLO response |
| // parse first bytes to a number |
| // if code = -1 then just return this number |
| // if code != -1 then checks whether the number equals the code |
| // if not equal -> die saying msg |
| while ((answer = xmalloc_fgetline(stdin)) != NULL) { |
| if (verbose) |
| bb_error_msg("recv:'%.*s'", (int)(strchrnul(answer, '\r') - answer), answer); |
| if (strlen(answer) <= 3 || '-' != answer[3]) |
| break; |
| free(answer); |
| } |
| if (answer) { |
| int n = atoi(answer); |
| if (timeout) |
| alarm(0); |
| free(answer); |
| if (-1 == code || n == code) { |
| free(msg); |
| return n; |
| } |
| } |
| bb_error_msg_and_die("%s failed", msg); |
| } |
| |
| static int smtp_check(const char *fmt, int code) |
| { |
| return smtp_checkp(fmt, NULL, code); |
| } |
| |
| // strip argument of bad chars |
| static char *sane_address(char *str) |
| { |
| char *s; |
| |
| trim(str); |
| s = str; |
| while (*s) { |
| if (!isalnum(*s) && !strchr("_-.@", *s)) { |
| bb_error_msg("bad address '%s'", str); |
| /* returning "": */ |
| str[0] = '\0'; |
| return str; |
| } |
| s++; |
| } |
| return str; |
| } |
| |
| // check for an address inside angle brackets, if not found fall back to normal |
| static char *angle_address(char *str) |
| { |
| char *s, *e; |
| |
| trim(str); |
| e = last_char_is(str, '>'); |
| if (e) { |
| s = strrchr(str, '<'); |
| if (s) { |
| *e = '\0'; |
| str = s + 1; |
| } |
| } |
| return sane_address(str); |
| } |
| |
| static void rcptto(const char *s) |
| { |
| if (!*s) |
| return; |
| // N.B. we don't die if recipient is rejected, for the other recipients may be accepted |
| if (250 != smtp_checkp("RCPT TO:<%s>", s, -1)) |
| bb_error_msg("Bad recipient: <%s>", s); |
| } |
| |
| // send to a list of comma separated addresses |
| static void rcptto_list(const char *list) |
| { |
| char *str = xstrdup(list); |
| char *s = str; |
| char prev = 0; |
| int in_quote = 0; |
| |
| while (*s) { |
| char ch = *s++; |
| |
| if (ch == '"' && prev != '\\') { |
| in_quote = !in_quote; |
| } else if (!in_quote && ch == ',') { |
| s[-1] = '\0'; |
| rcptto(angle_address(str)); |
| str = s; |
| } |
| prev = ch; |
| } |
| if (prev != ',') |
| rcptto(angle_address(str)); |
| free(str); |
| } |
| |
| int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
| int sendmail_main(int argc UNUSED_PARAM, char **argv) |
| { |
| char *opt_connect = opt_connect; |
| char *opt_from = NULL; |
| char *s; |
| llist_t *list = NULL; |
| char *host = sane_address(safe_gethostname()); |
| unsigned nheaders = 0; |
| int code; |
| enum { |
| HDR_OTHER = 0, |
| HDR_TOCC, |
| HDR_BCC, |
| } last_hdr = 0; |
| int check_hdr; |
| int has_to = 0; |
| |
| enum { |
| //--- standard options |
| OPT_t = 1 << 0, // read message for recipients, append them to those on cmdline |
| OPT_f = 1 << 1, // sender address |
| OPT_o = 1 << 2, // various options. -oi IMPLIED! others are IGNORED! |
| OPT_i = 1 << 3, // IMPLIED! |
| //--- BB specific options |
| OPT_w = 1 << 4, // network timeout |
| OPT_H = 1 << 5, // use external connection helper |
| OPT_S = 1 << 6, // specify connection string |
| OPT_a = 1 << 7, // authentication tokens |
| OPT_v = 1 << 8, // verbosity |
| }; |
| |
| // init global variables |
| INIT_G(); |
| |
| // save initial stdin since body is piped! |
| xdup2(STDIN_FILENO, 3); |
| G.fp0 = xfdopen_for_read(3); |
| |
| // parse options |
| // -v is a counter, -H and -S are mutually exclusive, -a is a list |
| opt_complementary = "vv:H--S:S--H"; |
| // N.B. since -H and -S are mutually exclusive they do not interfere in opt_connect |
| // -a is for ssmtp (http://downloads.openwrt.org/people/nico/man/man8/ssmtp.8.html) compatibility, |
| // it is still under development. |
| opts = getopt32(argv, "tf:o:iw:+H:S:a:*:v", &opt_from, NULL, |
| &timeout, &opt_connect, &opt_connect, &list, &verbose); |
| //argc -= optind; |
| argv += optind; |
| |
| // process -a[upm]<token> options |
| if ((opts & OPT_a) && !list) |
| bb_show_usage(); |
| while (list) { |
| char *a = (char *) llist_pop(&list); |
| if ('u' == a[0]) |
| G.user = xstrdup(a+1); |
| if ('p' == a[0]) |
| G.pass = xstrdup(a+1); |
| // N.B. we support only AUTH LOGIN so far |
| //if ('m' == a[0]) |
| // G.method = xstrdup(a+1); |
| } |
| // N.B. list == NULL here |
| //bb_error_msg("OPT[%x] AU[%s], AP[%s], AM[%s], ARGV[%s]", opts, au, ap, am, *argv); |
| |
| // connect to server |
| |
| // connection helper ordered? -> |
| if (opts & OPT_H) { |
| const char *args[] = { "sh", "-c", opt_connect, NULL }; |
| // plug it in |
| launch_helper(args); |
| // Now: |
| // our stdout will go to helper's stdin, |
| // helper's stdout will be available on our stdin. |
| |
| // Wait for initial server message. |
| // If helper (such as openssl) invokes STARTTLS, the initial 220 |
| // is swallowed by helper (and not repeated after TLS is initiated). |
| // We will send NOOP cmd to server and check the response. |
| // We should get 220+250 on plain connection, 250 on STARTTLSed session. |
| // |
| // The problem here is some servers delay initial 220 message, |
| // and consider client to be a spammer if it starts sending cmds |
| // before 220 reached it. The code below is unsafe in this regard: |
| // in non-STARTTLSed case, we potentially send NOOP before 220 |
| // is sent by server. |
| // Ideas? (--delay SECS opt? --assume-starttls-helper opt?) |
| code = smtp_check("NOOP", -1); |
| if (code == 220) |
| // we got 220 - this is not STARTTLSed connection, |
| // eat 250 response to our NOOP |
| smtp_check(NULL, 250); |
| else |
| if (code != 250) |
| bb_error_msg_and_die("SMTP init failed"); |
| } else { |
| // vanilla connection |
| int fd; |
| // host[:port] not explicitly specified? -> use $SMTPHOST |
| // no $SMTPHOST? -> use localhost |
| if (!(opts & OPT_S)) { |
| opt_connect = getenv("SMTPHOST"); |
| if (!opt_connect) |
| opt_connect = (char *)"127.0.0.1"; |
| } |
| // do connect |
| fd = create_and_connect_stream_or_die(opt_connect, 25); |
| // and make ourselves a simple IO filter |
| xmove_fd(fd, STDIN_FILENO); |
| xdup2(STDIN_FILENO, STDOUT_FILENO); |
| |
| // Wait for initial server 220 message |
| smtp_check(NULL, 220); |
| } |
| |
| // we should start with modern EHLO |
| if (250 != smtp_checkp("EHLO %s", host, -1)) |
| smtp_checkp("HELO %s", host, 250); |
| |
| // perform authentication |
| if (opts & OPT_a) { |
| smtp_check("AUTH LOGIN", 334); |
| // we must read credentials unless they are given via -a[up] options |
| if (!G.user || !G.pass) |
| get_cred_or_die(4); |
| encode_base64(NULL, G.user, NULL); |
| smtp_check("", 334); |
| encode_base64(NULL, G.pass, NULL); |
| smtp_check("", 235); |
| } |
| |
| // set sender |
| // N.B. we have here a very loosely defined algorythm |
| // since sendmail historically offers no means to specify secrets on cmdline. |
| // 1) server can require no authentication -> |
| // we must just provide a (possibly fake) reply address. |
| // 2) server can require AUTH -> |
| // we must provide valid username and password along with a (possibly fake) reply address. |
| // For the sake of security username and password are to be read either from console or from a secured file. |
| // Since reading from console may defeat usability, the solution is either to read from a predefined |
| // file descriptor (e.g. 4), or again from a secured file. |
| |
| // got no sender address? use auth name, then UID username as a last resort |
| if (!opt_from) { |
| opt_from = xasprintf("%s@%s", |
| G.user ? G.user : xuid2uname(getuid()), |
| xgethostbyname(host)->h_name); |
| } |
| free(host); |
| |
| smtp_checkp("MAIL FROM:<%s>", opt_from, 250); |
| |
| // process message |
| |
| // read recipients from message and add them to those given on cmdline. |
| // this means we scan stdin for To:, Cc:, Bcc: lines until an empty line |
| // and then use the rest of stdin as message body |
| code = 0; // set "analyze headers" mode |
| while ((s = xmalloc_fgetline(G.fp0)) != NULL) { |
| dump: |
| // put message lines doubling leading dots |
| if (code) { |
| // escape leading dots |
| // N.B. this feature is implied even if no -i (-oi) switch given |
| // N.B. we need to escape the leading dot regardless of |
| // whether it is single or not character on the line |
| if ('.' == s[0] /*&& '\0' == s[1] */) |
| bb_putchar('.'); |
| // dump read line |
| send_r_n(s); |
| free(s); |
| continue; |
| } |
| |
| // analyze headers |
| // To: or Cc: headers add recipients |
| check_hdr = (0 == strncasecmp("To:", s, 3)); |
| has_to |= check_hdr; |
| if (opts & OPT_t) { |
| if (check_hdr || 0 == strncasecmp("Bcc:" + 1, s, 3)) { |
| rcptto_list(s+3); |
| last_hdr = HDR_TOCC; |
| goto addheader; |
| } |
| // Bcc: header adds blind copy (hidden) recipient |
| if (0 == strncasecmp("Bcc:", s, 4)) { |
| rcptto_list(s+4); |
| free(s); |
| last_hdr = HDR_BCC; |
| continue; // N.B. Bcc: vanishes from headers! |
| } |
| } |
| check_hdr = (list && isspace(s[0])); |
| if (strchr(s, ':') || check_hdr) { |
| // other headers go verbatim |
| // N.B. RFC2822 2.2.3 "Long Header Fields" allows for headers to occupy several lines. |
| // Continuation is denoted by prefixing additional lines with whitespace(s). |
| // Thanks (stefan.seyfried at googlemail.com) for pointing this out. |
| if (check_hdr && last_hdr != HDR_OTHER) { |
| rcptto_list(s+1); |
| if (last_hdr == HDR_BCC) |
| continue; |
| // N.B. Bcc: vanishes from headers! |
| } else { |
| last_hdr = HDR_OTHER; |
| } |
| addheader: |
| // N.B. we allow MAX_HEADERS generic headers at most to prevent attacks |
| if (MAX_HEADERS && ++nheaders >= MAX_HEADERS) |
| goto bail; |
| llist_add_to_end(&list, s); |
| } else { |
| // a line without ":" (an empty line too, by definition) doesn't look like a valid header |
| // so stop "analyze headers" mode |
| reenter: |
| // put recipients specified on cmdline |
| check_hdr = 1; |
| while (*argv) { |
| char *t = sane_address(*argv); |
| rcptto(t); |
| //if (MAX_HEADERS && ++nheaders >= MAX_HEADERS) |
| // goto bail; |
| if (!has_to) { |
| const char *hdr; |
| |
| if (check_hdr && argv[1]) |
| hdr = "To: %s,"; |
| else if (check_hdr) |
| hdr = "To: %s"; |
| else if (argv[1]) |
| hdr = "To: %s," + 3; |
| else |
| hdr = "To: %s" + 3; |
| llist_add_to_end(&list, |
| xasprintf(hdr, t)); |
| check_hdr = 0; |
| } |
| argv++; |
| } |
| // enter "put message" mode |
| // N.B. DATA fails iff no recipients were accepted (or even provided) |
| // in this case just bail out gracefully |
| if (354 != smtp_check("DATA", -1)) |
| goto bail; |
| // dump the headers |
| while (list) { |
| send_r_n((char *) llist_pop(&list)); |
| } |
| // stop analyzing headers |
| code++; |
| // N.B. !s means: we read nothing, and nothing to be read in the future. |
| // just dump empty line and break the loop |
| if (!s) { |
| send_r_n(""); |
| break; |
| } |
| // go dump message body |
| // N.B. "s" already contains the first non-header line, so pretend we read it from input |
| goto dump; |
| } |
| } |
| // odd case: we didn't stop "analyze headers" mode -> message body is empty. Reenter the loop |
| // N.B. after reenter code will be > 0 |
| if (!code) |
| goto reenter; |
| |
| // finalize the message |
| smtp_check(".", 250); |
| bail: |
| // ... and say goodbye |
| smtp_check("QUIT", 221); |
| // cleanup |
| if (ENABLE_FEATURE_CLEAN_UP) |
| fclose(G.fp0); |
| |
| return EXIT_SUCCESS; |
| } |