944d27517
Vladimir Dronnikov
2009-10-15
Subject
sendmail: update by Vladimir
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mailutils/sendmail.c+41 -12
| @@ -9,6 +9,10 @@ | |
| #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 int smtp_checkp(const char *fmt, const char *param, int code) | |
| { | |
| char *answer; | |
| @@ -55,7 +59,9 @@ static char *sane_address(char *str) | |
| static void rcptto(const char *s) | |
| { | |
| - | smtp_checkp("RCPT TO:<%s>", s, 250); |
| + | // 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); |
| } | |
| int sendmail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; | |
| @@ -66,6 +72,7 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv) | |
| char *s; | |
| llist_t *list = NULL; | |
| char *domain = sane_address(safe_getdomainname()); | |
| + | unsigned nheaders = 0; |
| int code; | |
| enum { | |
| @@ -197,6 +204,7 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv) | |
| // 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 | |
| @@ -215,41 +223,62 @@ int sendmail_main(int argc UNUSED_PARAM, char **argv) | |
| // To: or Cc: headers add recipients | |
| if (0 == strncasecmp("To: ", s, 4) || 0 == strncasecmp("Bcc: " + 1, s, 4)) { | |
| rcptto(sane_address(s+4)); | |
| - | // goto addh; |
| - | llist_add_to_end(&list, s); |
| + | goto addheader; |
| // Bcc: header adds blind copy (hidden) recipient | |
| } else if (0 == strncasecmp("Bcc: ", s, 5)) { | |
| rcptto(sane_address(s+5)); | |
| free(s); | |
| // N.B. Bcc: vanishes from headers! | |
| // other headers go verbatim | |
| - | } else if (s[0]) { |
| - | // addh: |
| + | // N.B. we allow MAX_HEADERS generic headers at most to prevent attacks |
| + | } else if (strchr(s, ':')) { |
| + | addheader: |
| + | if (MAX_HEADERS && ++nheaders >= MAX_HEADERS) |
| + | goto bail; |
| llist_add_to_end(&list, s); | |
| - | // the empty line stops analyzing headers |
| + | // a line without ":" (an empty line too, by definition) doesn't look like a valid header |
| + | // so stop "analyze headers" mode |
| } else { | |
| - | free(s); |
| + | reenter: |
| // put recipients specified on cmdline | |
| while (*argv) { | |
| - | s = sane_address(*argv); |
| - | rcptto(s); |
| - | llist_add_to_end(&list, xasprintf("To: %s", s)); |
| + | char *t = sane_address(*argv); |
| + | rcptto(t); |
| + | //if (MAX_HEADERS && ++nheaders >= MAX_HEADERS) |
| + | // goto bail; |
| + | llist_add_to_end(&list, xasprintf("To: %s", t)); |
| argv++; | |
| } | |
| // enter "put message" mode | |
| - | smtp_check("DATA", 354); |
| + | // 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) { | |
| printf("%s\r\n", (char *) llist_pop(&list)); | |
| } | |
| - | printf("%s\r\n" + 2); // quirk for format string to be reused |
| // 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) { |
| + | puts("\r"); |
| + | 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 | |