/* * imap.c -- IMAP2bis/IMAP4 protocol methods * * Copyright 1997 by Eric S. Raymond * For license terms, see the file COPYING in this directory. */ #include "config.h" #include #include #include #if defined(STDC_HEADERS) #include #endif #include "fetchmail.h" #include "socket.h" #ifdef KERBEROS_V4 #if defined (__bsdi__) #include #define krb_get_err_text(e) (krb_err_txt[e]) #endif #if defined (__FreeBSD__) #define krb_get_err_text(e) (krb_err_txt[e]) #endif #include #endif /* KERBEROS_V4 */ extern char *strstr(); /* needed on sysV68 R3V7.1. */ /* imap_version values */ #define IMAP2 -1 /* IMAP2 or IMAP2BIS, RFC1176 */ #define IMAP4 0 /* IMAP4 rev 0, RFC1730 */ #define IMAP4rev1 1 /* IMAP4 rev 1, RFC2060 */ static int count, seen, recent, unseen, deletecount, imap_version; int imap_ok (int sock, char *argbuf) /* parse command response */ { char buf [POPBUFSIZE+1]; seen = 0; do { int ok; if ((ok = gen_recv(sock, buf, sizeof(buf)))) return(ok); /* interpret untagged status responses */ if (strstr(buf, "EXISTS")) count = atoi(buf+2); if (strstr(buf, "RECENT")) recent = atoi(buf+2); if (strstr(buf, "UNSEEN")) { char *cp; /* * Handle both "* 42 UNSEEN" (if tha ever happens) and * "* OK [UNSEEN 42] 42". Note that what this gets us is * a minimum index, not a count. */ unseen = 0; for (cp = buf; *cp && !isdigit(*cp); cp++) continue; unseen = atoi(cp); } if (strstr(buf, "FLAGS")) seen = (strstr(buf, "Seen") != (char *)NULL); } while (tag[0] != '\0' && strncmp(buf, tag, strlen(tag))); if (tag[0] == '\0') { strcpy(argbuf, buf); return(PS_SUCCESS); } else { char *cp; /* skip the tag */ for (cp = buf; !isspace(*cp); cp++) continue; while (isspace(*cp)) cp++; if (strncmp(cp, "OK", 2) == 0) { strcpy(argbuf, cp); return(PS_SUCCESS); } else if (strncmp(cp, "BAD", 2) == 0) return(PS_ERROR); else return(PS_PROTOCOL); } } #ifdef KERBEROS_V4 #if SIZEOF_INT == 4 typedef int int32; #elif SIZEOF_SHORT == 4 typedef short int32; #elif SIZEOF_LONG == 4 typedef long int32; #else #error Cannot deduce a 32-bit-type #endif static int do_rfc1731(int sock, struct query *ctl, char *buf) /* authenticate as per RFC1731 -- note 32-bit integer requirement here */ { int result = 0, len; char buf1[4096], buf2[4096]; union { int32 cint; char cstr[4]; } challenge1, challenge2; char srvinst[INST_SZ]; char *p; char srvrealm[REALM_SZ]; KTEXT_ST authenticator; CREDENTIALS credentials; char tktuser[MAX_K_NAME_SZ+1+INST_SZ+1+REALM_SZ+1]; char tktinst[INST_SZ]; char tktrealm[REALM_SZ]; des_cblock session; des_key_schedule schedule; gen_send(sock, "AUTHENTICATE KERBEROS_V4"); /* The data encoded in the first ready response contains a random * 32-bit number in network byte order. The client should respond * with a Kerberos ticket and an authenticator for the principal * "imap.hostname@realm", where "hostname" is the first component * of the host name of the server with all letters in lower case * and where "realm" is the Kerberos realm of the server. The * encrypted checksum field included within the Kerberos * authenticator should contain the server provided 32-bit number * in network byte order. */ if (result = gen_recv(sock, buf1, sizeof buf1)) { return result; } len = from64tobits(challenge1.cstr, buf1); if (len < 0) { error(0, -1, "could not decode initial BASE64 challenge"); return PS_AUTHFAIL; } /* Client responds with a Kerberos ticket and an authenticator for * the principal "imap.hostname@realm" where "hostname" is the * first component of the host name of the server with all letters * in lower case and where "realm" is the Kerberos realm of the * server. The encrypted checksum field included within the * Kerberos authenticator should contain the server-provided * 32-bit number in network byte order. */ strncpy(srvinst, ctl->server.truename, (sizeof srvinst)-1); srvinst[(sizeof srvinst)-1] = '\0'; for (p = srvinst; *p; p++) { if (isupper(*p)) { *p = tolower(*p); } } strncpy(srvrealm, krb_realmofhost(srvinst), (sizeof srvrealm)-1); srvrealm[(sizeof srvrealm)-1] = '\0'; if (p = strchr(srvinst, '.')) { *p = '\0'; } result = krb_mk_req(&authenticator, "imap", srvinst, srvrealm, 0); if (result) { error(0, -1, "krb_mq_req: %s", krb_get_err_text(result)); return PS_AUTHFAIL; } result = krb_get_cred("imap", srvinst, srvrealm, &credentials); if (result) { error(0, -1, "krb_get_cred: %s", krb_get_err_text(result)); return PS_AUTHFAIL; } memcpy(session, credentials.session, sizeof session); memset(&credentials, 0, sizeof credentials); des_key_sched(session, schedule); result = krb_get_tf_fullname(TKT_FILE, tktuser, tktinst, tktrealm); if (result) { error(0, -1, "krb_get_tf_fullname: %s", krb_get_err_text(result)); return PS_AUTHFAIL; } if (strcmp(tktuser, user) != 0) { error(0, -1, "principal %s in ticket does not match -u %s", tktuser, user); return PS_AUTHFAIL; } if (tktinst[0]) { error(0, 0, "non-null instance (%s) might cause strange behavior", tktinst); strcat(tktuser, "."); strcat(tktuser, tktinst); } if (strcmp(tktrealm, srvrealm) != 0) { strcat(tktuser, "@"); strcat(tktuser, tktrealm); } result = krb_mk_req(&authenticator, "imap", srvinst, srvrealm, challenge1.cint); if (result) { error(0, -1, "krb_mq_req: %s", krb_get_err_text(result)); return PS_AUTHFAIL; } to64frombits(buf1, authenticator.dat, authenticator.length); if (outlevel == O_VERBOSE) { error(0, 0, "IMAP> %s", buf1); } SockWrite(sock, buf1, strlen(buf1)); SockWrite(sock, "\r\n", 2); /* Upon decrypting and verifying the ticket and authenticator, the * server should verify that the contained checksum field equals * the original server provided random 32-bit number. Should the * verification be successful, the server must add one to the * checksum and construct 8 octets of data, with the first four * octets containing the incremented checksum in network byte * order, the fifth octet containing a bit-mask specifying the * protection mechanisms supported by the server, and the sixth * through eighth octets containing, in network byte order, the * maximum cipher-text buffer size the server is able to receive. * The server must encrypt the 8 octets of data in the session key * and issue that encrypted data in a second ready response. The * client should consider the server authenticated if the first * four octets the un-encrypted data is equal to one plus the * checksum it previously sent. */ if (result = gen_recv(sock, buf1, sizeof buf1)) return result; /* The client must construct data with the first four octets * containing the original server-issued checksum in network byte * order, the fifth octet containing the bit-mask specifying the * selected protection mechanism, the sixth through eighth octets * containing in network byte order the maximum cipher-text buffer * size the client is able to receive, and the following octets * containing a user name string. The client must then append * from one to eight octets so that the length of the data is a * multiple of eight octets. The client must then PCBC encrypt the * data with the session key and respond to the second ready * response with the encrypted data. The server decrypts the data * and verifies the contained checksum. The username field * identifies the user for whom subsequent IMAP operations are to * be performed; the server must verify that the principal * identified in the Kerberos ticket is authorized to connect as * that user. After these verifications, the authentication * process is complete. */ len = from64tobits(buf2, buf1); if (len < 0) { error(0, -1, "could not decode BASE64 ready response"); return PS_AUTHFAIL; } des_ecb_encrypt((des_cblock *)buf2, (des_cblock *)buf2, schedule, 0); memcpy(challenge2.cstr, buf2, 4); if (ntohl(challenge2.cint) != challenge1.cint + 1) { error(0, -1, "challenge mismatch"); return PS_AUTHFAIL; } memset(authenticator.dat, 0, sizeof authenticator.dat); result = htonl(challenge1.cint); memcpy(authenticator.dat, &result, sizeof result); /* The protection mechanisms and their corresponding bit-masks are as * follows: * * 1 No protection mechanism * 2 Integrity (krb_mk_safe) protection * 4 Privacy (krb_mk_priv) protection */ authenticator.dat[4] = 1; len = strlen(tktuser); strncpy(authenticator.dat+8, tktuser, len); authenticator.length = len + 8 + 1; while (authenticator.length & 7) { authenticator.length++; } des_pcbc_encrypt((des_cblock *)authenticator.dat, (des_cblock *)authenticator.dat, authenticator.length, schedule, &session, 1); to64frombits(buf1, authenticator.dat, authenticator.length); if (outlevel == O_VERBOSE) { error(0, 0, "IMAP> %s", buf1); } SockWrite(sock, buf1, strlen(buf1)); SockWrite(sock, "\r\n", 2); if (result = gen_recv(sock, buf1, sizeof buf1)) return result; if (strstr(buf1, "OK")) { return PS_SUCCESS; } else { return PS_AUTHFAIL; } } #endif /* KERBEROS_V4 */ int imap_getauth(int sock, struct query *ctl, char *buf) /* apply for connection authorization */ { char rbuf [POPBUFSIZE+1]; int ok = 0; #ifdef KERBEROS_V4 int kerbok = 0; if (ctl->server.protocol != P_IMAP_K4) #endif /* KERBEROS_V4 */ /* try to get authorized */ ok = gen_transact(sock, "LOGIN %s \"%s\"", ctl->remotename, ctl->password); if (ok) return(ok); /* probe to see if we're running IMAP4 and can use RFC822.PEEK */ gen_send(sock, "CAPABILITY"); if ((ok = gen_recv(sock, rbuf, sizeof(rbuf)))) return(ok); if (strstr(rbuf, "BAD")) { imap_version = IMAP2; if (outlevel == O_VERBOSE) error(0, 0, "Protocol identified as IMAP2 or IMAP2BIS"); } /* UW-IMAP server 10.173 notifies in all caps */ else if (strstr(rbuf, "IMAP4rev1") || strstr(rbuf, "IMAP4REV1")) { imap_version = IMAP4rev1; if (outlevel == O_VERBOSE) error(0, 0, "Protocol identified as IMAP4 rev 1"); } else { imap_version = IMAP4; if (outlevel == O_VERBOSE) error(0, 0, "Protocol identified as IMAP4 rev 0"); } peek_capable = (imap_version >= IMAP4); #ifdef KERBEROS_V4 if (strstr(rbuf, "AUTH=KERBEROS_V4")) { kerbok++; if (outlevel == O_VERBOSE) error(0, 0, "KERBEROS_V4 authentication is supported"); } /* eat OK response */ if ((ok = gen_recv(sock, rbuf, sizeof(rbuf)))) return(ok); if (!strstr(rbuf, "OK")) return(PS_AUTHFAIL); if ((imap_version >= IMAP4) && (ctl->server.protocol == P_IMAP_K4)) { if (!kerbok) { error(0, -1, "Required KERBEROS_V4 capability not supported by server"); return(PS_AUTHFAIL); } if ((ok = do_rfc1731(sock, ctl, buf))) { if (outlevel == O_VERBOSE) error(0, 0, "IMAP> *"); SockWrite(sock, "*\r\n", 3); return(ok); } } #endif /* KERBEROS_V4 */ return(PS_SUCCESS); } static int imap_getrange(int sock, struct query *ctl, const char *folder, int *countp, int *newp) /* get range of messages to be fetched */ { int ok; /* find out how many messages are waiting */ recent = unseen = -1; ok = gen_transact(sock, "SELECT %s", folder ? folder : "INBOX"); if (ok != 0) { error(0, 0, "mailbox selection failed"); return(ok); } *countp = count; /* * Note: because IMAP has an is_old method, this number is used * only for the "X messages (Y unseen)" notification. Accordingly * it doesn't matter much that it can be wrong (e.g. if we see an * UNSEEN response but not all messages above the first UNSEEN one * are likewise). */ if (unseen >= 0) /* optional, but better if we see it */ *newp = count - unseen + 1; else if (recent >= 0) /* mandatory */ *newp = recent; else *newp = -1; /* should never happen, RECENT is mandatory */ deletecount = 0; return(PS_SUCCESS); } static int imap_getsizes(int sock, int count, int *sizes) /* capture the sizes of all messages */ { char buf [POPBUFSIZE+1]; gen_send(sock, "FETCH 1:%d RFC822.SIZE", count); while (SockRead(sock, buf, sizeof(buf))) { int num, size, ok; if ((ok = gen_recv(sock, buf, sizeof(buf)))) return(ok); if (strstr(buf, "OK")) break; else if (sscanf(buf, "* %d FETCH (RFC822.SIZE %d)", &num, &size) == 2) sizes[num - 1] = size; else sizes[num - 1] = -1; } return(PS_SUCCESS); } static int imap_is_old(int sock, struct query *ctl, int number) /* is the given message old? */ { int ok; /* expunges change the fetch numbers */ number -= deletecount; if ((ok = gen_transact(sock, "FETCH %d FLAGS", number)) != 0) return(PS_ERROR); return(seen); } static int imap_fetch_headers(int sock, struct query *ctl,int number,int *lenp) /* request headers of nth message */ { char buf [POPBUFSIZE+1]; int num; /* expunges change the fetch numbers */ number -= deletecount; /* * This is blessed by RFC 1176, RFC1730, RFC2060. * According to the RFCs, it should *not* set the \Seen flag. */ gen_send(sock, "FETCH %d RFC822.HEADER", number); /* looking for FETCH response */ do { int ok; if ((ok = gen_recv(sock, buf, sizeof(buf)))) return(ok); } while (sscanf(buf+2, "%d FETCH (%*s {%d}", &num, lenp) != 2); if (num != number) return(PS_ERROR); else return(PS_SUCCESS); } static int imap_fetch_body(int sock, struct query *ctl, int number, int *lenp) /* request body of nth message */ { char buf [POPBUFSIZE+1], *cp; int num; /* expunges change the fetch numbers */ number -= deletecount; /* * If we're using IMAP4, we can fetch the message without setting its * seen flag. This is good! It means that if the protocol exchange * craps out during the message, it will still be marked `unseen' on * the server. * * However...*don't* do this if we're using keep to suppress deletion! * In that case, marking the seen flag is the only way to prevent the * message from being re-fetched on subsequent runs. */ switch (imap_version) { case IMAP4rev1: /* RFC 2060 */ if (!ctl->keep) gen_send(sock, "FETCH %d BODY.PEEK[TEXT]", number); else gen_send(sock, "FETCH %d BODY[TEXT]", number); break; case IMAP4: /* RFC 1730 */ if (!ctl->keep) gen_send(sock, "FETCH %d RFC822.TEXT.PEEK", number); else gen_send(sock, "FETCH %d RFC822.TEXT", number); break; default: /* RFC 1176 */ gen_send(sock, "FETCH %d RFC822.TEXT", number); break; } /* looking for FETCH response */ do { int ok; if ((ok = gen_recv(sock, buf, sizeof(buf)))) return(ok); } while (sscanf(buf+2, "%d FETCH", &num) != 1); if (num != number) return(PS_ERROR); /* try to extract a length */ if ((cp = strchr(buf, '{'))) *lenp = atoi(cp + 1); else *lenp = 0; return(PS_SUCCESS); } static int imap_trail(int sock, struct query *ctl, int number) /* discard tail of FETCH response after reading message text */ { /* expunges change the fetch numbers */ /* number -= deletecount; */ for (;;) { char buf[POPBUFSIZE+1]; int ok; if ((ok = gen_recv(sock, buf, sizeof(buf)))) return(ok); /* UW IMAP returns "OK FETCH", Cyrus returns "OK Completed" */ if (strstr(buf, "OK")) break; } return(PS_SUCCESS); } static int imap_delete(int sock, struct query *ctl, int number) /* set delete flag for given message */ { int ok; /* expunges change the fetch numbers */ number -= deletecount; /* * Use SILENT if possible as a minor throughput optimization. * Note: this has been dropped from IMAP4rev1. */ if ((ok = gen_transact(sock, imap_version == IMAP4 ? "STORE %d +FLAGS.SILENT (\\Deleted)" : "STORE %d +FLAGS (\\Deleted)", number))) return(ok); /* * We do an expunge after each message, rather than just before quit, * so that a line hit during a long session won't result in lots of * messages being fetched again during the next session. */ if ((ok = gen_transact(sock, "EXPUNGE"))) return(ok); deletecount++; return(PS_SUCCESS); } static flag imap_retain_check(int num, char *buf) /* is this a special message that should be retained? */ { /* * The University of Washington IMAP server (the reference * implementation of IMAP4 written by Mark Crispin) relies * on being able to keep base-UID information in a special * message at the head of the mailbox. This message should * neither be deleted nor forwarded. */ return (num == 1 && !strncasecmp(buf, "X-IMAP:", 7)); } const static struct method imap = { "IMAP", /* Internet Message Access Protocol */ 143, /* standard IMAP2bis/IMAP4 port */ TRUE, /* this is a tagged protocol */ FALSE, /* no message delimiter */ imap_ok, /* parse command response */ imap_getauth, /* get authorization */ imap_getrange, /* query range of messages */ imap_getsizes, /* get sizes of messages (used for --limit option */ imap_is_old, /* no UID check */ imap_fetch_headers, /* request given message headers */ imap_fetch_body, /* request given message body */ imap_trail, /* eat message trailer */ imap_delete, /* delete the message */ imap_retain_check, /* leave this message alone? */ "LOGOUT", /* the IMAP exit command */ }; int doIMAP(struct query *ctl) /* retrieve messages using IMAP Version 2bis or Version 4 */ { return(do_protocol(ctl, &imap)); } /* imap.c ends here */