diff options
Diffstat (limited to 'qmail-smtpd.c')
| -rw-r--r-- | qmail-smtpd.c | 292 |
1 files changed, 291 insertions, 1 deletions
diff --git a/qmail-smtpd.c b/qmail-smtpd.c index 582a695..b545760 100644 --- a/qmail-smtpd.c +++ b/qmail-smtpd.c @@ -37,9 +37,27 @@ unsigned int databytes = 0; int timeout = 1200; +const char *protocol = "SMTP"; + +#ifdef TLS +#include <sys/stat.h> +#include "tls.h" +#include "ssl_timeoutio.h" + +void tls_init(); +int tls_verify(); +void tls_nogateway(); +int ssl_rfd = -1, ssl_wfd = -1; /* SSL_get_Xfd() are broken */ +#endif + int safewrite(fd,buf,len) int fd; char *buf; int len; { int r; +#ifdef TLS + if (ssl && fd == ssl_wfd) + r = ssl_timeoutwrite(timeout, ssl_rfd, ssl_wfd, ssl, buf, len); + else +#endif r = timeoutwrite(timeout,fd,buf,len); if (r <= 0) _exit(1); return r; @@ -60,7 +78,16 @@ void straynewline() { out("451 See http://pobox.com/~djb/docs/smtplf.html.\r\n") void err_badbounce() { out("550 sorry, bounce messages should have a single envelope recipient (#5.7.1)\r\n"); } void err_bmf() { out("553 sorry, your envelope sender is in my badmailfrom list (#5.7.1)\r\n"); } +#ifndef TLS void err_nogateway() { out("553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)\r\n"); } +#else +void err_nogateway() +{ + out("553 sorry, that domain isn't in my list of allowed rcpthosts"); + tls_nogateway(); + out(" (#5.7.1)\r\n"); +} +#endif void err_unimpl(arg) char *arg; { out("502 unimplemented (#5.5.1)\r\n"); } void err_syntax() { out("555 syntax error (#5.5.4)\r\n"); } void err_relay() { out("553 we don't relay (#5.7.1)\r\n"); } @@ -151,6 +178,11 @@ void setup() if (!remotehost) remotehost = "unknown"; remoteinfo = env_get("TCPREMOTEINFO"); relayclient = env_get("RELAYCLIENT"); + +#ifdef TLS + if (env_get("SMTPS")) { smtps = 1; tls_init(); } + else +#endif dohelo(remotehost); } @@ -236,6 +268,9 @@ int addrallowed() int r; r = rcpthosts(addr.s,str_len(addr.s)); if (r == -1) die_control(); +#ifdef TLS + if (r == 0) if (tls_verify()) r = -2; +#endif return r; } @@ -268,9 +303,17 @@ void smtp_helo(arg) char *arg; smtp_greet("250 "); out("\r\n"); seenmail = 0; dohelo(arg); } +/* ESMTP extensions are published here */ void smtp_ehlo(arg) char *arg; { +#ifdef TLS + struct stat st; +#endif smtp_greet("250-"); +#ifdef TLS + if (!ssl && (stat("control/servercert.pem",&st) == 0)) + out("\r\n250-STARTTLS"); +#endif out("\r\n250-PIPELINING\r\n250 8BITMIME\r\n"); seenmail = 0; dohelo(arg); } @@ -313,6 +356,11 @@ int saferead(fd,buf,len) int fd; char *buf; int len; { int r; flush(); +#ifdef TLS + if (ssl && fd == ssl_rfd) + r = ssl_timeoutread(timeout, ssl_rfd, ssl_wfd, ssl, buf, len); + else +#endif r = timeoutread(timeout,fd,buf,len); if (r == -1) if (errno == error_timeout) die_alarm(); if (r <= 0) die_read(); @@ -321,6 +369,9 @@ int saferead(fd,buf,len) int fd; char *buf; int len; char ssinbuf[1024]; substdio ssin = SUBSTDIO_FDBUF(saferead,0,ssinbuf,sizeof ssinbuf); +#ifdef TLS +void flush_io() { ssin.p = 0; flush(); } +#endif struct qmail qqt; unsigned int bytestooverflow = 0; @@ -423,7 +474,7 @@ void smtp_data(arg) char *arg; { qp = qmail_qp(&qqt); out("354 go ahead\r\n"); - received(&qqt,"SMTP",local,remoteip,remotehost,remoteinfo,fakehelo); + received(&qqt,protocol,local,remoteip,remotehost,remoteinfo,fakehelo); blast(&hops); hops = (hops >= MAXHOPS); if (hops) qmail_fail(&qqt); @@ -659,6 +710,242 @@ char *arg; } } +#ifdef TLS +stralloc proto = {0}; +int ssl_verified = 0; +const char *ssl_verify_err = 0; + +void smtp_tls(char *arg) +{ + if (ssl) err_unimpl(); + else if (*arg) out("501 Syntax error (no parameters allowed) (#5.5.4)\r\n"); + else tls_init(); +} + +RSA *tmp_rsa_cb(SSL *ssl, int export, int keylen) +{ + if (!export) keylen = 2048; + if (keylen == 2048) { + FILE *in = fopen("control/rsa2048.pem", "r"); + if (in) { + RSA *rsa = PEM_read_RSAPrivateKey(in, NULL, NULL, NULL); + fclose(in); + if (rsa) return rsa; + } + } + return RSA_generate_key(keylen, RSA_F4, NULL, NULL); +} + +DH *tmp_dh_cb(SSL *ssl, int export, int keylen) +{ + if (!export) keylen = 2048; + if (keylen == 2048) { + FILE *in = fopen("control/dh2048.pem", "r"); + if (in) { + DH *dh = PEM_read_DHparams(in, NULL, NULL, NULL); + fclose(in); + if (dh) return dh; + } + } + return DH_generate_parameters(keylen, DH_GENERATOR_2, NULL, NULL); +} + +/* don't want to fail handshake if cert isn't verifiable */ +int verify_cb(int preverify_ok, X509_STORE_CTX *ctx) { return 1; } + +void tls_nogateway() +{ + /* there may be cases when relayclient is set */ + if (!ssl || relayclient) return; + out("; no valid cert for gatewaying"); + if (ssl_verify_err) { out(": "); out(ssl_verify_err); } +} +void tls_out(const char *s1, const char *s2) +{ + out("454 TLS "); out(s1); + if (s2) { out(": "); out(s2); } + out(" (#4.3.0)\r\n"); flush(); +} +void tls_err(const char *s) { tls_out(s, ssl_error()); if (smtps) die_read(); } + +# define CLIENTCA "control/clientca.pem" +# define CLIENTCRL "control/clientcrl.pem" +# define SERVERCERT "control/servercert.pem" + +int tls_verify() +{ + stralloc clients = {0}; + struct constmap mapclients; + + if (!ssl || relayclient || ssl_verified) return 0; + ssl_verified = 1; /* don't do this twice */ + + /* request client cert to see if it can be verified by one of our CAs + * and the associated email address matches an entry in tlsclients */ + switch (control_readfile(&clients, "control/tlsclients", 0)) + { + case 1: + if (constmap_init(&mapclients, clients.s, clients.len, 0)) { + /* if CLIENTCA contains all the standard root certificates, a + * 0.9.6b client might fail with SSL_R_EXCESSIVE_MESSAGE_SIZE; + * it is probably due to 0.9.6b supporting only 8k key exchange + * data while the 0.9.6c release increases that limit to 100k */ + STACK_OF(X509_NAME) *sk = SSL_load_client_CA_file(CLIENTCA); + if (sk) { + SSL_set_client_CA_list(ssl, sk); + SSL_set_verify(ssl, SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE, NULL); + break; + } + constmap_free(&mapclients); + } + case 0: alloc_free(clients.s); return 0; + case -1: die_control(); + } + + if (ssl_timeoutrehandshake(timeout, ssl_rfd, ssl_wfd, ssl) <= 0) { + const char *err = ssl_error_str(); + tls_out("rehandshake failed", err); die_read(); + } + + do { /* one iteration */ + X509 *peercert; + X509_NAME *subj; + stralloc email = {0}; + + int n = SSL_get_verify_result(ssl); + if (n != X509_V_OK) + { ssl_verify_err = X509_verify_cert_error_string(n); break; } + peercert = SSL_get_peer_certificate(ssl); + if (!peercert) break; + + subj = X509_get_subject_name(peercert); + n = X509_NAME_get_index_by_NID(subj, NID_pkcs9_emailAddress, -1); + if (n >= 0) { + const ASN1_STRING *s = X509_NAME_get_entry(subj, n)->value; + if (s) { email.len = s->length; email.s = s->data; } + } + + if (email.len <= 0) + ssl_verify_err = "contains no email address"; + else if (!constmap(&mapclients, email.s, email.len)) + ssl_verify_err = "email address not in my list of tlsclients"; + else { + /* add the cert email to the proto if it helped allow relaying */ + --proto.len; + if (!stralloc_cats(&proto, "\n (cert ") /* continuation line */ + || !stralloc_catb(&proto, email.s, email.len) + || !stralloc_cats(&proto, ")") + || !stralloc_0(&proto)) die_nomem(); + protocol = proto.s; + relayclient = ""; + /* also inform qmail-queue */ + if (!env_put("RELAYCLIENT=")) die_nomem(); + } + + X509_free(peercert); + } while (0); + constmap_free(&mapclients); alloc_free(clients.s); + + /* we are not going to need this anymore: free the memory */ + SSL_set_client_CA_list(ssl, NULL); + SSL_set_verify(ssl, SSL_VERIFY_NONE, NULL); + + return relayclient ? 1 : 0; +} + +void tls_init() +{ + SSL *myssl; + SSL_CTX *ctx; + const char *ciphers; + stralloc saciphers = {0}; + X509_STORE *store; + X509_LOOKUP *lookup; + + SSL_library_init(); + + /* a new SSL context with the bare minimum of options */ + ctx = SSL_CTX_new(SSLv23_server_method()); + if (!ctx) { tls_err("unable to initialize ctx"); return; } + + /* POODLE vulnerability */ + SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3); + + if (!SSL_CTX_use_certificate_chain_file(ctx, SERVERCERT)) + { SSL_CTX_free(ctx); tls_err("missing certificate"); return; } + SSL_CTX_load_verify_locations(ctx, CLIENTCA, NULL); + +#if OPENSSL_VERSION_NUMBER >= 0x00907000L + /* crl checking */ + store = SSL_CTX_get_cert_store(ctx); + if ((lookup = X509_STORE_add_lookup(store, X509_LOOKUP_file())) && + (X509_load_crl_file(lookup, CLIENTCRL, X509_FILETYPE_PEM) == 1)) + X509_STORE_set_flags(store, X509_V_FLAG_CRL_CHECK | + X509_V_FLAG_CRL_CHECK_ALL); +#endif + +#if OPENSSL_VERSION_NUMBER >= 0x10002000L + /* support ECDH */ + SSL_CTX_set_ecdh_auto(ctx,1); +#endif + + /* set the callback here; SSL_set_verify didn't work before 0.9.6c */ + SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, verify_cb); + + /* a new SSL object, with the rest added to it directly to avoid copying */ + myssl = SSL_new(ctx); + SSL_CTX_free(ctx); + if (!myssl) { tls_err("unable to initialize ssl"); return; } + + /* this will also check whether public and private keys match */ + if (!SSL_use_RSAPrivateKey_file(myssl, SERVERCERT, SSL_FILETYPE_PEM)) + { SSL_free(myssl); tls_err("no valid RSA private key"); return; } + + ciphers = env_get("TLSCIPHERS"); + if (!ciphers) { + if (control_readfile(&saciphers, "control/tlsserverciphers", 0) == -1) + { SSL_free(myssl); die_control(); } + if (saciphers.len) { /* convert all '\0's except the last one to ':' */ + int i; + for (i = 0; i < saciphers.len - 1; ++i) + if (!saciphers.s[i]) saciphers.s[i] = ':'; + ciphers = saciphers.s; + } + } + if (!ciphers || !*ciphers) ciphers = "DEFAULT"; + SSL_set_cipher_list(myssl, ciphers); + alloc_free(saciphers.s); + + SSL_set_tmp_rsa_callback(myssl, tmp_rsa_cb); + SSL_set_tmp_dh_callback(myssl, tmp_dh_cb); + SSL_set_rfd(myssl, ssl_rfd = substdio_fileno(&ssin)); + SSL_set_wfd(myssl, ssl_wfd = substdio_fileno(&ssout)); + + if (!smtps) { out("220 ready for tls\r\n"); flush(); } + + if (ssl_timeoutaccept(timeout, ssl_rfd, ssl_wfd, myssl) <= 0) { + /* neither cleartext nor any other response here is part of a standard */ + const char *err = ssl_error_str(); + ssl_free(myssl); tls_out("connection failed", err); die_read(); + } + ssl = myssl; + + /* populate the protocol string, used in Received */ + if (!stralloc_copys(&proto, "ESMTPS (") + || !stralloc_cats(&proto, SSL_get_cipher(ssl)) + || !stralloc_cats(&proto, " encrypted)")) die_nomem(); + if (!stralloc_0(&proto)) die_nomem(); + protocol = proto.s; + + /* have to discard the pre-STARTTLS HELO/EHLO argument, if any */ + dohelo(remotehost); +} + +# undef SERVERCERT +# undef CLIENTCA + +#endif + struct commands smtpcommands[] = { { "rcpt", smtp_rcpt, 0 } , { "mail", smtp_mail, 0 } @@ -669,6 +956,9 @@ struct commands smtpcommands[] = { , { "ehlo", smtp_ehlo, flush } , { "rset", smtp_rset, 0 } , { "help", smtp_help, flush } +#ifdef TLS +, { "starttls", smtp_tls, flush_io } +#endif , { "noop", err_noop, flush } , { "vrfy", err_vrfy, flush } , { 0, err_unimpl, flush } |