diff options
Diffstat (limited to 'imap.c')
| -rw-r--r-- | imap.c | 327 |
1 files changed, 297 insertions, 30 deletions
@@ -16,6 +16,11 @@ #include "fetchmail.h" #include "socket.h" +#ifdef KERBEROS_V4 +#include <krb.h> +#include "base64.h" +#endif /* KERBEROS_V4 */ + extern char *strstr(); /* needed on sysV68 R3V7.1. */ /* imap_version values */ @@ -76,45 +81,307 @@ int imap_ok (int sock, char *argbuf) } } -int imap_getauth(int sock, struct query *ctl, char *buf) -/* apply for connection authorization */ +#ifdef KERBEROS_V4 +static int do_rfc1731(int sock, struct query *ctl, char *buf) +/* authenticate as per RFC1731 + * note 32-bit integer requirement here... + * sizeof int must be 4! + * + * Note: Base64 conversion routines come from Cyrus IMAPd and have + * possibly too-restrictive redistribution requirements. See base64.c + * for details. Base64 is defined in RFC2045 section 6.8, "Base64 + * Content-Transfer-Encoding", but lines must not be broken in the + * scheme used here. + */ { - char rbuf [POPBUFSIZE+1]; + int result = 0, len; + char buf1[4096], buf2[4096]; + union { + int 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. + */ - /* try to get authorized */ - int ok = gen_transact(sock, - "LOGIN %s \"%s\"", - ctl->remotename, ctl->password); + if (result = gen_recv(sock, buf1, sizeof buf1)) { + return result; + } - if (ok) - return(ok); + len = from64(challenge1.cstr, buf1); + if (len < 0) { + error(0, -1, "could not decode initial BASE64 challenge"); + return PS_AUTHFAIL; + } - /* 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"); + /* 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.names->id, (sizeof srvinst)-1); + srvinst[(sizeof srvinst)-1] = '\0'; + for (p = srvinst; *p; p++) { + if (isupper(*p)) { + *p = tolower(*p); + } } - else if (strstr(rbuf, "IMAP4rev1")) - { - imap_version = IMAP4rev1; - if (outlevel == O_VERBOSE) - error(0, 0, "Protocol identified as IMAP4 rev 1"); + + strncpy(srvrealm, krb_realmofhost(srvinst), (sizeof srvrealm)-1); + srvrealm[(sizeof srvrealm)-1] = '\0'; + if (p = strchr(srvinst, '.')) { + *p = '\0'; } - else - { - imap_version = IMAP4; - if (outlevel == O_VERBOSE) - error(0, 0, "Protocol identified as IMAP4 rev 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; } - peek_capable = (imap_version >= IMAP4); + 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; + } - return(PS_SUCCESS); + 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; + } + + to64(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 = from64(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); + + to64(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"); + } + else if (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, |