ssl_unix.c

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/* ========================================================================
 * Copyright 1988-2008 University of Washington
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * 
 * ========================================================================
 */

/*
 * Program:	SSL authentication/encryption module
 *
 * Author:	Mark Crispin
 *		Networks and Distributed Computing
 *		Computing & Communications
 *		University of Washington
 *		Administration Building, AG-44
 *		Seattle, WA  98195
 *		Internet: [e-mail]
 *
 * Date:	22 September 1998
 * Last Edited:	13 January 2007
 */

#define crypt ssl_private_crypt
#include <x509v3.h>
#include <ssl.h>
#include <err.h>
#include <pem.h>
#include <buffer.h>
#include <bio.h>
#include <crypto.h>
#include <rand.h>
#undef crypt

#define SSLBUFLEN 8192
#define SSLCIPHERLIST "ALL:!LOW"


/* SSL I/O stream */

typedef struct ssl_stream {
  TCPSTREAM *tcpstream;		/* TCP stream */
  SSL_CTX *context;		/* SSL context */
  SSL *con;			/* SSL connection */
  int ictr;			/* input counter */
  char *iptr;			/* input pointer */
  char ibuf[SSLBUFLEN];		/* input buffer */
} SSLSTREAM;

#include "sslio.h"

/* Function prototypes */

static SSLSTREAM *ssl_start(TCPSTREAM *tstream,char *host,unsigned long flags);
static char *ssl_start_work (SSLSTREAM *stream,char *host,unsigned long flags);
static int ssl_open_verify (int ok,X509_STORE_CTX *ctx);
static char *ssl_validate_cert (X509 *cert,char *host);
static long ssl_compare_hostnames (unsigned char *s,unsigned char *pat);
static char *ssl_getline_work (SSLSTREAM *stream,unsigned long *size,
			       long *contd);
static long ssl_abort (SSLSTREAM *stream);
static RSA *ssl_genkey (SSL *con,int export,int keylength);


/* Secure Sockets Layer network driver dispatch */

static struct ssl_driver ssldriver = {
  ssl_open,			/* open connection */
  ssl_aopen,			/* open preauthenticated connection */
  ssl_getline,			/* get a line */
  ssl_getbuffer,		/* get a buffer */
  ssl_soutr,			/* output pushed data */
  ssl_sout,			/* output string */
  ssl_close,			/* close connection */
  ssl_host,			/* return host name */
  ssl_remotehost,		/* return remote host name */
  ssl_port,			/* return port number */
  ssl_localhost			/* return local host name */
};
				/* non-NIL if doing SSL primary I/O */
static SSLSTDIOSTREAM *sslstdio = NIL;
static char *start_tls = NIL;	/* non-NIL if start TLS requested */

/* One-time SSL initialization */

static int sslonceonly = 0;

void ssl_onceonlyinit (void)
{
  if (!sslonceonly++) {		/* only need to call it once */
    int fd;
    char tmp[MAILTMPLEN];
    struct stat sbuf;
				/* if system doesn't have /dev/urandom */
    if (stat ("/dev/urandom",&sbuf)) {
      while ((fd = open (tmpnam (tmp),O_WRONLY|O_CREAT|O_EXCL,0600)) < 0)
	sleep (1);
      unlink (tmp);		/* don't need the file */
      fstat (fd,&sbuf);		/* get information about the file */
      close (fd);		/* flush descriptor */
				/* not great but it'll have to do */
      sprintf (tmp + strlen (tmp),"%.80s%lx%.80s%lx%lx%lx%lx%lx",
	       tcp_serveraddr (),(unsigned long) tcp_serverport (),
	       tcp_clientaddr (),(unsigned long) tcp_clientport (),
	       (unsigned long) sbuf.st_ino,(unsigned long) time (0),
	       (unsigned long) gethostid (),(unsigned long) getpid ());
      RAND_seed (tmp,strlen (tmp));
    }
				/* apply runtime linkage */
    mail_parameters (NIL,SET_SSLDRIVER,(void *) &ssldriver);
    mail_parameters (NIL,SET_SSLSTART,(void *) ssl_start);
    SSL_library_init ();	/* add all algorithms */
  }
}

/* SSL open
 * Accepts: host name
 *	    contact service name
 *	    contact port number
 * Returns: SSL stream if success else NIL
 */

SSLSTREAM *ssl_open (char *host,char *service,unsigned long port)
{
  TCPSTREAM *stream = tcp_open (host,service,port);
  return stream ? ssl_start (stream,host,port) : NIL;
}


/* SSL authenticated open
 * Accepts: host name
 *	    service name
 *	    returned user name buffer
 * Returns: SSL stream if success else NIL
 */

SSLSTREAM *ssl_aopen (NETMBX *mb,char *service,char *usrbuf)
{
  return NIL;			/* don't use this mechanism with SSL */
}

/* Start SSL/TLS negotiations
 * Accepts: open TCP stream of session
 *	    user's host name
 *	    flags
 * Returns: SSL stream if success else NIL
 */

static SSLSTREAM *ssl_start (TCPSTREAM *tstream,char *host,unsigned long flags)
{
  char *reason,tmp[MAILTMPLEN];
  sslfailure_t sf = (sslfailure_t) mail_parameters (NIL,GET_SSLFAILURE,NIL);
  blocknotify_t bn = (blocknotify_t) mail_parameters (NIL,GET_BLOCKNOTIFY,NIL);
  void *data = (*bn) (BLOCK_SENSITIVE,NIL);
  SSLSTREAM *stream = (SSLSTREAM *) memset (fs_get (sizeof (SSLSTREAM)),0,
					    sizeof (SSLSTREAM));
  stream->tcpstream = tstream;	/* bind TCP stream */
				/* do the work */
  reason = ssl_start_work (stream,host,flags);
  (*bn) (BLOCK_NONSENSITIVE,data);
  if (reason) {			/* failed? */
    ssl_close (stream);		/* failed to do SSL */
    stream = NIL;		/* no stream returned */
    switch (*reason) {		/* analyze reason */
    case '*':			/* certificate failure */
      ++reason;			/* skip over certificate failure indication */
				/* pass to error callback */
      if (sf) (*sf) (host,reason,flags);
      else {			/* no error callback, build error message */
	sprintf (tmp,"Certificate failure for %.80s: %.512s",host,reason);
	mm_log (tmp,ERROR);
      }
    case '\0':			/* user answered no to certificate callback */
      if (flags & NET_TRYSSL)	/* return dummy stream to stop tryssl */
	stream = (SSLSTREAM *) memset (fs_get (sizeof (SSLSTREAM)),0,
				       sizeof (SSLSTREAM));
      break;
    default:			/* non-certificate failure */
      if (flags & NET_TRYSSL);	/* no error output if tryssl */
				/* pass to error callback */
      else if (sf) (*sf) (host,reason,flags);
      else {			/* no error callback, build error message */
	sprintf (tmp,"TLS/SSL failure for %.80s: %.512s",host,reason);
	mm_log (tmp,ERROR);
      }
      break;
    }
  }
  return stream;
}

/* Start SSL/TLS negotiations worker routine
 * Accepts: SSL stream
 *	    user's host name
 *	    flags
 * Returns: NIL if success, else error reason
 */

				/* evil but I had no choice */
static char *ssl_last_error = NIL;
static char *ssl_last_host = NIL;

static char *ssl_start_work (SSLSTREAM *stream,char *host,unsigned long flags)
{
  BIO *bio;
  X509 *cert;
  unsigned long sl,tl;
  char *s,*t,*err,tmp[MAILTMPLEN];
  sslcertificatequery_t scq =
    (sslcertificatequery_t) mail_parameters (NIL,GET_SSLCERTIFICATEQUERY,NIL);
  sslclientcert_t scc =
    (sslclientcert_t) mail_parameters (NIL,GET_SSLCLIENTCERT,NIL);
  sslclientkey_t sck =
    (sslclientkey_t) mail_parameters (NIL,GET_SSLCLIENTKEY,NIL);
  if (ssl_last_error) fs_give ((void **) &ssl_last_error);
  ssl_last_host = host;
  if (!(stream->context = SSL_CTX_new ((flags & NET_TLSCLIENT) ?
				       TLSv1_client_method () :
				       SSLv23_client_method ())))
    return "SSL context failed";
  SSL_CTX_set_options (stream->context,0);
				/* disable certificate validation? */
  if (flags & NET_NOVALIDATECERT)
    SSL_CTX_set_verify (stream->context,SSL_VERIFY_NONE,NIL);
  else SSL_CTX_set_verify (stream->context,SSL_VERIFY_PEER,ssl_open_verify);
				/* set default paths to CAs... */
  SSL_CTX_set_default_verify_paths (stream->context);
				/* ...unless a non-standard path desired */
  if (s = (char *) mail_parameters (NIL,GET_SSLCAPATH,NIL))
    SSL_CTX_load_verify_locations (stream->context,NIL,s);
				/* want to send client certificate? */
  if (scc && (s = (*scc) ()) && (sl = strlen (s))) {
    if (cert = PEM_read_bio_X509 (bio = BIO_new_mem_buf (s,sl),NIL,NIL,NIL)) {
      SSL_CTX_use_certificate (stream->context,cert);
      X509_free (cert);
    }
    BIO_free (bio);
    if (!cert) return "SSL client certificate failed";
				/* want to supply private key? */
    if ((t = (sck ? (*sck) () : s)) && (tl = strlen (t))) {
      EVP_PKEY *key;
      if (key = PEM_read_bio_PrivateKey (bio = BIO_new_mem_buf (t,tl),
					 NIL,NIL,"")) {
	SSL_CTX_use_PrivateKey (stream->context,key);
	EVP_PKEY_free (key);
      }
      BIO_free (bio);
      memset (t,0,tl);		/* erase key */
    }
    if (s != t) memset (s,0,sl);/* erase certificate if different from key */
  }

				/* create connection */
  if (!(stream->con = (SSL *) SSL_new (stream->context)))
    return "SSL connection failed";
  bio = BIO_new_socket (stream->tcpstream->tcpsi,BIO_NOCLOSE);
  SSL_set_bio (stream->con,bio,bio);
  SSL_set_connect_state (stream->con);
  if (SSL_in_init (stream->con)) SSL_total_renegotiations (stream->con);
				/* now negotiate SSL */
  if (SSL_write (stream->con,"",0) < 0)
    return ssl_last_error ? ssl_last_error : "SSL negotiation failed";
				/* need to validate host names? */
  if (!(flags & NET_NOVALIDATECERT) &&
      (err = ssl_validate_cert (cert = SSL_get_peer_certificate (stream->con),
				host))) {
				/* application callback */
    if (scq) return (*scq) (err,host,cert ? cert->name : "???") ? NIL : "";
				/* error message to return via mm_log() */
    sprintf (tmp,"*%.128s: %.255s",err,cert ? cert->name : "???");
    return ssl_last_error = cpystr (tmp);
  }
  return NIL;
}

/* SSL certificate verification callback
 * Accepts: error flag
 *	    X509 context
 * Returns: error flag
 */

static int ssl_open_verify (int ok,X509_STORE_CTX *ctx)
{
  char *err,cert[256],tmp[MAILTMPLEN];
  sslcertificatequery_t scq =
    (sslcertificatequery_t) mail_parameters (NIL,GET_SSLCERTIFICATEQUERY,NIL);
  if (!ok) {			/* in case failure */
    err = (char *) X509_verify_cert_error_string
      (X509_STORE_CTX_get_error (ctx));
    X509_NAME_oneline (X509_get_subject_name
		       (X509_STORE_CTX_get_current_cert (ctx)),cert,255);
    if (!scq) {			/* mm_log() error message if no callback */
      sprintf (tmp,"*%.128s: %.255s",err,cert);
      ssl_last_error = cpystr (tmp);
    }
				/* ignore error if application says to */
    else if ((*scq) (err,ssl_last_host,cert)) ok = T;
				/* application wants punt */
    else ssl_last_error = cpystr ("");
  }
  return ok;
}


/* SSL validate certificate
 * Accepts: certificate
 *	    host to validate against
 * Returns: NIL if validated, else string of error message
 */

static char *ssl_validate_cert (X509 *cert,char *host)
{
  int i,n;
  char *s,*t,*ret;
  void *ext;
  GENERAL_NAME *name;
				/* make sure have a certificate */
  if (!cert) ret = "No certificate from server";
				/* and that it has a name */
  else if (!cert->name) ret = "No name in certificate";
				/* locate CN */
  else if (s = strstr (cert->name,"/CN=")) {
    if (t = strchr (s += 4,'/')) *t = '\0';
				/* host name matches pattern? */
    ret = ssl_compare_hostnames (host,s) ? NIL :
      "Server name does not match certificate";
    if (t) *t = '/';		/* restore smashed delimiter */
				/* if mismatch, see if in extensions */
    if (ret && (ext = X509_get_ext_d2i (cert,NID_subject_alt_name,NIL,NIL)) &&
	(n = sk_GENERAL_NAME_num (ext)))
      /* older versions of OpenSSL use "ia5" instead of dNSName */
      for (i = 0; ret && (i < n); i++)
	if ((name = sk_GENERAL_NAME_value (ext,i)) &&
	    (name->type = GEN_DNS) && (s = name->d.ia5->data) &&
	    ssl_compare_hostnames (host,s)) ret = NIL;
  }
  else ret = "Unable to locate common name in certificate";
  return ret;
}

/* Case-independent wildcard pattern match
 * Accepts: base string
 *	    pattern string
 * Returns: T if pattern matches base, else NIL
 */

static long ssl_compare_hostnames (unsigned char *s,unsigned char *pat)
{
  long ret = NIL;
  switch (*pat) {
  case '*':			/* wildcard */
    if (pat[1]) {		/* there must be a pattern suffix */
				/* there is, scan base against it */
      do if (ssl_compare_hostnames (s,pat+1)) ret = LONGT;
      while (!ret && (*s != '.') && *s++);
    }
    break;
  case '\0':			/* end of pattern */
    if (!*s) ret = LONGT;	/* success if base is also at end */
    break;
  default:			/* non-wildcard, recurse if match */
    if (!compare_uchar (*pat,*s)) ret = ssl_compare_hostnames (s+1,pat+1);
    break;
  }
  return ret;
}

/* SSL receive line
 * Accepts: SSL stream
 * Returns: text line string or NIL if failure
 */

char *ssl_getline (SSLSTREAM *stream)
{
  unsigned long n,contd;
  char *ret = ssl_getline_work (stream,&n,&contd);
  if (ret && contd) {		/* got a line needing continuation? */
    STRINGLIST *stl = mail_newstringlist ();
    STRINGLIST *stc = stl;
    do {			/* collect additional lines */
      stc->text.data = (unsigned char *) ret;
      stc->text.size = n;
      stc = stc->next = mail_newstringlist ();
      ret = ssl_getline_work (stream,&n,&contd);
    } while (ret && contd);
    if (ret) {			/* stash final part of line on list */
      stc->text.data = (unsigned char *) ret;
      stc->text.size = n;
				/* determine how large a buffer we need */
      for (n = 0, stc = stl; stc; stc = stc->next) n += stc->text.size;
      ret = fs_get (n + 1);	/* copy parts into buffer */
      for (n = 0, stc = stl; stc; n += stc->text.size, stc = stc->next)
	memcpy (ret + n,stc->text.data,stc->text.size);
      ret[n] = '\0';
    }
    mail_free_stringlist (&stl);/* either way, done with list */
  }
  return ret;
}

/* SSL receive line or partial line
 * Accepts: SSL stream
 *	    pointer to return size
 *	    pointer to return continuation flag
 * Returns: text line string, size and continuation flag, or NIL if failure
 */