gnutls.c File Reference

Handling of GnuTLS encryption. More...

#include "config.h"
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <time.h>
#include "private.h"
#include "mutt/lib.h"
#include "config/lib.h"
#include "core/lib.h"
#include "lib.h"
#include "connaccount.h"
#include "connection.h"
#include "globals.h"
#include "muttlib.h"
#include "ssl.h"

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Data Structures
struct	TlsSockData
	TLS socket data -. More...

Macros
#define	CERTERR_VALID   0
#define	CERTERR_EXPIRED   (1 << 0)
#define	CERTERR_NOTYETVALID   (1 << 1)
#define	CERTERR_REVOKED   (1 << 2)
#define	CERTERR_NOTTRUSTED   (1 << 3)
#define	CERTERR_HOSTNAME   (1 << 4)
#define	CERTERR_SIGNERNOTCA   (1 << 5)
#define	CERTERR_INSECUREALG   (1 << 6)
#define	CERTERR_OTHER   (1 << 7)
#define	CERT_SEP   "-----BEGIN"

Functions
int	gnutls_protocol_set_priority (gnutls_session_t session, const int *list)
static int	tls_init (void)
	Set up Gnu TLS.
static int	tls_verify_peers (gnutls_session_t tlsstate, gnutls_certificate_status_t *certstat)
	Wrapper for gnutls_certificate_verify_peers()
static void	tls_fingerprint (gnutls_digest_algorithm_t algo, struct Buffer *buf, const gnutls_datum_t *data)
	Create a fingerprint of a TLS Certificate.
static bool	tls_check_stored_hostname (const gnutls_datum_t *cert, const char *hostname)
	Does the hostname match a stored certificate?
static int	tls_compare_certificates (const gnutls_datum_t *peercert)
	Compare certificates against $certificate_file
static int	tls_check_preauth (const gnutls_datum_t *certdata, gnutls_certificate_status_t certstat, const char *hostname, int chainidx, int *certerr, int *savedcert)
	Prepare a certificate for authentication.
static void	add_cert (const char *title, gnutls_x509_crt_t cert, bool issuer, struct CertArray *carr)
	Look up certificate info and save it to a list.
static int	tls_check_one_certificate (const gnutls_datum_t *certdata, gnutls_certificate_status_t certstat, const char *hostname, int idx, size_t len)
	Check a GnuTLS certificate.
static int	tls_check_certificate (struct Connection *conn)
	Check a connection's certificate.
static void	tls_get_client_cert (struct Connection *conn)
	Get the client certificate for a TLS connection.
static int	tls_set_priority (struct TlsSockData *data)
	Set the priority of various protocols.
static int	tls_negotiate (struct Connection *conn)
	Negotiate TLS connection.
static int	tls_socket_poll (struct Connection *conn, time_t wait_secs)
	Check if any data is waiting on a socket - Implements Connection::poll() -.
static int	tls_socket_close (struct Connection *conn)
	Close a TLS socket - Implements Connection::close() -.
static int	tls_socket_open (struct Connection *conn)
	Open a TLS socket - Implements Connection::open() -.
static int	tls_socket_read (struct Connection *conn, char *buf, size_t count)
	Read data from a TLS socket - Implements Connection::read() -.
static int	tls_socket_write (struct Connection *conn, const char *buf, size_t count)
	Write data to a TLS socket - Implements Connection::write() -.
static int	tls_starttls_close (struct Connection *conn)
	Close a TLS connection - Implements Connection::close() -.
int	mutt_ssl_socket_setup (struct Connection *conn)
	Set up SSL socket mulitplexor.
int	mutt_ssl_starttls (struct Connection *conn)
	Negotiate TLS over an already opened connection.

Variables
static int	ProtocolPriority [] = { GNUTLS_TLS1_2, GNUTLS_TLS1_1, GNUTLS_TLS1, GNUTLS_SSL3, 0 }
	This array needs to be large enough to hold all the possible values support by NeoMutt.

Detailed Description

Handling of GnuTLS encryption.

Authors

• Richard Russon
• Pietro Cerutti

Copyright

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Definition in file gnutls.c.

Macro Definition Documentation

CERTERR_VALID

#define CERTERR_VALID   0

Definition at line 53 of file gnutls.c.

CERTERR_EXPIRED

#define CERTERR_EXPIRED   (1 << 0)

Definition at line 54 of file gnutls.c.

CERTERR_NOTYETVALID

#define CERTERR_NOTYETVALID   (1 << 1)

Definition at line 55 of file gnutls.c.

CERTERR_REVOKED

#define CERTERR_REVOKED   (1 << 2)

Definition at line 56 of file gnutls.c.

CERTERR_NOTTRUSTED

#define CERTERR_NOTTRUSTED   (1 << 3)

Definition at line 57 of file gnutls.c.

CERTERR_HOSTNAME

#define CERTERR_HOSTNAME   (1 << 4)

Definition at line 58 of file gnutls.c.

CERTERR_SIGNERNOTCA

#define CERTERR_SIGNERNOTCA   (1 << 5)

Definition at line 59 of file gnutls.c.

CERTERR_INSECUREALG

#define CERTERR_INSECUREALG   (1 << 6)

Definition at line 60 of file gnutls.c.

CERTERR_OTHER

#define CERTERR_OTHER   (1 << 7)

Definition at line 61 of file gnutls.c.

CERT_SEP

#define CERT_SEP   "-----BEGIN"

Definition at line 64 of file gnutls.c.

Function Documentation

gnutls_protocol_set_priority()

int gnutls_protocol_set_priority	(	gnutls_session_t	session,
		const int *	list
	)

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tls_init()

static int tls_init ( void  )

static

Set up Gnu TLS.

Return values

0	Success
-1	Error

Definition at line 92 of file gnutls.c.

{
  static bool init_complete = false;
  int err;
 
  if (init_complete)
    return 0;
 
  err = gnutls_global_init();
  if (err < 0)
  {
    mutt_error("gnutls_global_init: %s", gnutls_strerror(err));
    return -1;
  }
 
  init_complete = true;
  return 0;
}

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tls_verify_peers()

static int tls_verify_peers ( gnutls_session_t  tlsstate, gnutls_certificate_status_t *  certstat  )

static

Wrapper for gnutls_certificate_verify_peers()

Parameters

tlsstate	TLS state
certstat	Certificate state, e.g. GNUTLS_CERT_INVALID

Return values

0	Success If certstat was set. note: this does not mean success
>0	Error

Wrapper with sanity-checking.

certstat is technically a bitwise-or of gnutls_certificate_status_t values.

Definition at line 122 of file gnutls.c.

{
  /* gnutls_certificate_verify_peers2() chains to
   * gnutls_x509_trust_list_verify_crt2().  That function's documentation says:
   *
   *   When a certificate chain of cert_list_size with more than one
   *   certificates is provided, the verification status will apply to
   *   the first certificate in the chain that failed
   *   verification. The verification process starts from the end of
   *   the chain(from CA to end certificate). The first certificate
   *   in the chain must be the end-certificate while the rest of the
   *   members may be sorted or not.
   *
   * This is why tls_check_certificate() loops from CA to host in that order,
   * calling the menu, and recalling tls_verify_peers() for each approved
   * cert in the chain.
   */
  int rc = gnutls_certificate_verify_peers2(tlsstate, certstat);
 
  /* certstat was set */
  if (rc == 0)
    return 0;
 
  if (rc == GNUTLS_E_NO_CERTIFICATE_FOUND)
    mutt_error(_("Unable to get certificate from peer"));
  else
    mutt_error(_("Certificate verification error (%s)"), gnutls_strerror(rc));
 
  return rc;
}

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tls_fingerprint()

static void tls_fingerprint ( gnutls_digest_algorithm_t  algo, struct Buffer *  buf, const gnutls_datum_t *  data  )

static

Create a fingerprint of a TLS Certificate.

Parameters

algo	Fingerprint algorithm, e.g. GNUTLS_MAC_SHA256
buf	Buffer for the fingerprint
data	Certificate

Definition at line 159 of file gnutls.c.

{
  unsigned char md[128] = { 0 };
  size_t n = 64;
 
  if (gnutls_fingerprint(algo, data, (char *) md, &n) < 0)
  {
    buf_strcpy(buf, _("[unable to calculate]"));
    return;
  }
 
  for (size_t i = 0; i < n; i++)
  {
    buf_add_printf(buf, "%02X", md[i]);
 
    // Put a space after a pair of bytes (except for the last one)
    if (((i % 2) == 1) && (i < (n - 1)))
      buf_addch(buf, ' ');
  }
}

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tls_check_stored_hostname()

static bool tls_check_stored_hostname ( const gnutls_datum_t *  cert, const char *  hostname  )

static

Does the hostname match a stored certificate?

Parameters

cert	Certificate
hostname	Hostname

Return values

true	Hostname match found
false	Error, or no match

Definition at line 188 of file gnutls.c.

{
  char *linestr = NULL;
  size_t linestrsize = 0;
 
  /* try checking against names stored in stored certs file */
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  FILE *fp = mutt_file_fopen(c_certificate_file, "r");
  if (!fp)
    return false;
 
  struct Buffer *buf = buf_pool_get();
 
  tls_fingerprint(GNUTLS_DIG_MD5, buf, cert);
  while ((linestr = mutt_file_read_line(linestr, &linestrsize, fp, NULL, MUTT_RL_NO_FLAGS)))
  {
    regmatch_t *match = mutt_prex_capture(PREX_GNUTLS_CERT_HOST_HASH, linestr);
    if (match)
    {
      regmatch_t *mhost = &match[PREX_GNUTLS_CERT_HOST_HASH_MATCH_HOST];
      regmatch_t *mhash = &match[PREX_GNUTLS_CERT_HOST_HASH_MATCH_HASH];
      linestr[mutt_regmatch_end(mhost)] = '\0';
      linestr[mutt_regmatch_end(mhash)] = '\0';
      if ((mutt_str_equal(linestr + mutt_regmatch_start(mhost), hostname)) &&
          (mutt_str_equal(linestr + mutt_regmatch_start(mhash), buf_string(buf))))
      {
        FREE(&linestr);
        mutt_file_fclose(&fp);
        buf_pool_release(&buf);
        return true;
      }
    }
  }
 
  mutt_file_fclose(&fp);
  buf_pool_release(&buf);
 
  /* not found a matching name */
  return false;
}

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tls_compare_certificates()

static int tls_compare_certificates ( const gnutls_datum_t *  peercert )

static

Compare certificates against $certificate_file

Parameters

peercert

Certificate

Return values

1	Certificate matches file
0	Error, or no match

Definition at line 235 of file gnutls.c.

{
  gnutls_datum_t cert = { 0 };
  unsigned char *ptr = NULL;
  gnutls_datum_t b64_data = { 0 };
  unsigned char *b64_data_data = NULL;
  struct stat st = { 0 };
 
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  if (stat(c_certificate_file, &st) == -1)
    return 0;
 
  b64_data.size = st.st_size;
  b64_data_data = mutt_mem_calloc(1, b64_data.size + 1);
  b64_data.data = b64_data_data;
 
  FILE *fp = mutt_file_fopen(c_certificate_file, "r");
  if (!fp)
    return 0;
 
  b64_data.size = fread(b64_data.data, 1, b64_data.size, fp);
  b64_data.data[b64_data.size] = '\0';
  mutt_file_fclose(&fp);
 
  do
  {
    const int rc = gnutls_pem_base64_decode_alloc(NULL, &b64_data, &cert);
    if (rc != 0)
    {
      FREE(&b64_data_data);
      return 0;
    }
 
    /* find start of cert, skipping junk */
    ptr = (unsigned char *) strstr((char *) b64_data.data, CERT_SEP);
    if (!ptr)
    {
      gnutls_free(cert.data);
      FREE(&b64_data_data);
      return 0;
    }
    /* find start of next cert */
    ptr = (unsigned char *) strstr((char *) ptr + 1, CERT_SEP);
 
    b64_data.size = b64_data.size - (ptr - b64_data.data);
    b64_data.data = ptr;
 
    if (cert.size == peercert->size)
    {
      if (memcmp(cert.data, peercert->data, cert.size) == 0)
      {
        /* match found */
        gnutls_free(cert.data);
        FREE(&b64_data_data);
        return 1;
      }
    }
 
    gnutls_free(cert.data);
  } while (ptr);
 
  /* no match found */
  FREE(&b64_data_data);
  return 0;
}

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tls_check_preauth()

static int tls_check_preauth ( const gnutls_datum_t *  certdata, gnutls_certificate_status_t  certstat, const char *  hostname, int  chainidx, int *  certerr, int *  savedcert  )

static

Prepare a certificate for authentication.

Parameters

[in]	certdata	List of GnuTLS certificates
[in]	certstat	GnuTLS certificate status
[in]	hostname	Hostname
[in]	chainidx	Index in the certificate chain
[out]	certerr	Result, e.g. CERTERR_VALID
[out]	savedcert	1 if certificate has been saved

Return values

0	Success
-1	Error

Definition at line 312 of file gnutls.c.

{
  gnutls_x509_crt_t cert;
 
  *certerr = CERTERR_VALID;
  *savedcert = 0;
 
  if (gnutls_x509_crt_init(&cert) < 0)
  {
    mutt_error(_("Error initialising gnutls certificate data"));
    return -1;
  }
 
  if (gnutls_x509_crt_import(cert, certdata, GNUTLS_X509_FMT_DER) < 0)
  {
    mutt_error(_("Error processing certificate data"));
    gnutls_x509_crt_deinit(cert);
    return -1;
  }
 
  /* Note: tls_negotiate() contains a call to
   * gnutls_certificate_set_verify_flags() with a flag disabling
   * GnuTLS checking of the dates.  So certstat shouldn't have the
   * GNUTLS_CERT_EXPIRED and GNUTLS_CERT_NOT_ACTIVATED bits set. */
  const bool c_ssl_verify_dates = cs_subset_bool(NeoMutt->sub, "ssl_verify_dates");
  if (c_ssl_verify_dates != MUTT_NO)
  {
    if (gnutls_x509_crt_get_expiration_time(cert) < mutt_date_now())
      *certerr |= CERTERR_EXPIRED;
    if (gnutls_x509_crt_get_activation_time(cert) > mutt_date_now())
      *certerr |= CERTERR_NOTYETVALID;
  }
 
  const bool c_ssl_verify_host = cs_subset_bool(NeoMutt->sub, "ssl_verify_host");
  if ((chainidx == 0) && (c_ssl_verify_host != MUTT_NO) &&
      !gnutls_x509_crt_check_hostname(cert, hostname) &&
      !tls_check_stored_hostname(certdata, hostname))
  {
    *certerr |= CERTERR_HOSTNAME;
  }
 
  if (certstat & GNUTLS_CERT_REVOKED)
  {
    *certerr |= CERTERR_REVOKED;
    certstat ^= GNUTLS_CERT_REVOKED;
  }
 
  /* see whether certificate is in our cache (certificates file) */
  if (tls_compare_certificates(certdata))
  {
    *savedcert = 1;
 
    /* We check above for certs with bad dates or that are revoked.
     * These must be accepted manually each time.  Otherwise, we
     * accept saved certificates as valid. */
    if (*certerr == CERTERR_VALID)
    {
      gnutls_x509_crt_deinit(cert);
      return 0;
    }
  }
 
  if (certstat & GNUTLS_CERT_INVALID)
  {
    *certerr |= CERTERR_NOTTRUSTED;
    certstat ^= GNUTLS_CERT_INVALID;
  }
 
  if (certstat & GNUTLS_CERT_SIGNER_NOT_FOUND)
  {
    /* NB: already cleared if cert in cache */
    *certerr |= CERTERR_NOTTRUSTED;
    certstat ^= GNUTLS_CERT_SIGNER_NOT_FOUND;
  }
 
  if (certstat & GNUTLS_CERT_SIGNER_NOT_CA)
  {
    /* NB: already cleared if cert in cache */
    *certerr |= CERTERR_SIGNERNOTCA;
    certstat ^= GNUTLS_CERT_SIGNER_NOT_CA;
  }
 
  if (certstat & GNUTLS_CERT_INSECURE_ALGORITHM)
  {
    /* NB: already cleared if cert in cache */
    *certerr |= CERTERR_INSECUREALG;
    certstat ^= GNUTLS_CERT_INSECURE_ALGORITHM;
  }
 
  /* we've been zeroing the interesting bits in certstat -
   * don't return OK if there are any unhandled bits we don't
   * understand */
  if (certstat != 0)
    *certerr |= CERTERR_OTHER;
 
  gnutls_x509_crt_deinit(cert);
 
  if (*certerr == CERTERR_VALID)
    return 0;
 
  return -1;
}

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add_cert()

static void add_cert ( const char *  title, gnutls_x509_crt_t  cert, bool  issuer, struct CertArray *  carr  )

static

Look up certificate info and save it to a list.

Parameters

title	Title for this block of certificate info
cert	Certificate
issuer	If true, look up the issuer rather than owner details
carr	Array to save info to

Definition at line 424 of file gnutls.c.

{
  static const char *part[] = {
    GNUTLS_OID_X520_COMMON_NAME,              // CN
    GNUTLS_OID_PKCS9_EMAIL,                   // Email
    GNUTLS_OID_X520_ORGANIZATION_NAME,        // O
    GNUTLS_OID_X520_ORGANIZATIONAL_UNIT_NAME, // OU
    GNUTLS_OID_X520_LOCALITY_NAME,            // L
    GNUTLS_OID_X520_STATE_OR_PROVINCE_NAME,   // ST
    GNUTLS_OID_X520_COUNTRY_NAME,             // C
  };
 
  char buf[128] = { 0 };
  int rc;
 
  // Allocate formatted strings and let the array take ownership
  ARRAY_ADD(carr, mutt_str_dup(title));
 
  for (size_t i = 0; i < mutt_array_size(part); i++)
  {
    size_t buflen = sizeof(buf);
    if (issuer)
      rc = gnutls_x509_crt_get_issuer_dn_by_oid(cert, part[i], 0, 0, buf, &buflen);
    else
      rc = gnutls_x509_crt_get_dn_by_oid(cert, part[i], 0, 0, buf, &buflen);
    if (rc != 0)
      continue;
 
    char *line = NULL;
    mutt_str_asprintf(&line, "   %s", buf);
    ARRAY_ADD(carr, line);
  }
}

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tls_check_one_certificate()

static int tls_check_one_certificate ( const gnutls_datum_t *  certdata, gnutls_certificate_status_t  certstat, const char *  hostname, int  idx, size_t  len  )

static

Check a GnuTLS certificate.

Parameters

certdata	List of GnuTLS certificates
certstat	GnuTLS certificate status
hostname	Hostname
idx	Index into certificate list
len	Length of certificate list

Return values

1	Success
0	Failure

Definition at line 469 of file gnutls.c.

{
  struct CertArray carr = ARRAY_HEAD_INITIALIZER;
  int certerr, savedcert;
  gnutls_x509_crt_t cert;
  struct Buffer *fpbuf = NULL;
  time_t t;
  char datestr[30] = { 0 };
  char title[256] = { 0 };
  gnutls_datum_t pemdata = { 0 };
 
  if (tls_check_preauth(certdata, certstat, hostname, idx, &certerr, &savedcert) == 0)
    return 1;
 
  if (OptNoCurses)
  {
    mutt_debug(LL_DEBUG1, "unable to prompt for certificate in batch mode\n");
    mutt_error(_("Untrusted server certificate"));
    return 0;
  }
 
  /* interactive check from user */
  if (gnutls_x509_crt_init(&cert) < 0)
  {
    mutt_error(_("Error initialising gnutls certificate data"));
    return 0;
  }
 
  if (gnutls_x509_crt_import(cert, certdata, GNUTLS_X509_FMT_DER) < 0)
  {
    mutt_error(_("Error processing certificate data"));
    gnutls_x509_crt_deinit(cert);
    return 0;
  }
 
  add_cert(_("This certificate belongs to:"), cert, false, &carr);
  ARRAY_ADD(&carr, NULL);
  add_cert(_("This certificate was issued by:"), cert, true, &carr);
 
  ARRAY_ADD(&carr, NULL);
  ARRAY_ADD(&carr, mutt_str_dup(_("This certificate is valid")));
 
  char *line = NULL;
  t = gnutls_x509_crt_get_activation_time(cert);
  mutt_date_make_tls(datestr, sizeof(datestr), t);
  mutt_str_asprintf(&line, _("   from %s"), datestr);
  ARRAY_ADD(&carr, line);
 
  t = gnutls_x509_crt_get_expiration_time(cert);
  mutt_date_make_tls(datestr, sizeof(datestr), t);
  mutt_str_asprintf(&line, _("     to %s"), datestr);
  ARRAY_ADD(&carr, line);
  ARRAY_ADD(&carr, NULL);
 
  fpbuf = buf_pool_get();
  tls_fingerprint(GNUTLS_DIG_SHA, fpbuf, certdata);
  mutt_str_asprintf(&line, _("SHA1 Fingerprint: %s"), buf_string(fpbuf));
  ARRAY_ADD(&carr, line);
 
  tls_fingerprint(GNUTLS_DIG_SHA256, fpbuf, certdata);
  fpbuf->data[39] = '\0'; // Divide into two lines of output
  mutt_str_asprintf(&line, "%s%s", _("SHA256 Fingerprint: "), buf_string(fpbuf));
  ARRAY_ADD(&carr, line);
  mutt_str_asprintf(&line, "%*s%s", (int) mutt_str_len(_("SHA256 Fingerprint: ")),
                    "", fpbuf->data + 40);
  ARRAY_ADD(&carr, line);
 
  if (certerr)
    ARRAY_ADD(&carr, NULL);
 
  if (certerr & CERTERR_NOTYETVALID)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("WARNING: Server certificate is not yet valid")));
  }
  if (certerr & CERTERR_EXPIRED)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("WARNING: Server certificate has expired")));
  }
  if (certerr & CERTERR_REVOKED)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("WARNING: Server certificate has been revoked")));
  }
  if (certerr & CERTERR_HOSTNAME)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("WARNING: Server hostname does not match certificate")));
  }
  if (certerr & CERTERR_SIGNERNOTCA)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("WARNING: Signer of server certificate is not a CA")));
  }
  if (certerr & CERTERR_INSECUREALG)
  {
    ARRAY_ADD(&carr, mutt_str_dup(_("Warning: Server certificate was signed using an insecure algorithm")));
  }
 
  snprintf(title, sizeof(title),
           _("SSL Certificate check (certificate %zu of %zu in chain)"), len - idx, len);
 
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  const bool allow_always = (c_certificate_file && !savedcert &&
                             !(certerr & (CERTERR_EXPIRED | CERTERR_NOTYETVALID | CERTERR_REVOKED)));
  int rc = dlg_certificate(title, &carr, allow_always, false);
  if (rc == 3) // Accept always
  {
    bool saved = false;
    FILE *fp = mutt_file_fopen(c_certificate_file, "a");
    if (fp)
    {
      if (certerr & CERTERR_HOSTNAME) // Save hostname if necessary
      {
        tls_fingerprint(GNUTLS_DIG_MD5, fpbuf, certdata);
        fprintf(fp, "#H %s %s\n", hostname, buf_string(fpbuf));
        saved = true;
      }
      if (certerr ^ CERTERR_HOSTNAME) // Save the cert for all other errors
      {
        int rc2 = gnutls_pem_base64_encode_alloc("CERTIFICATE", certdata, &pemdata);
        if (rc2 == 0)
        {
          if (fwrite(pemdata.data, pemdata.size, 1, fp) == 1)
          {
            saved = true;
          }
          gnutls_free(pemdata.data);
        }
      }
      mutt_file_fclose(&fp);
    }
    if (saved)
      mutt_message(_("Certificate saved"));
    else
      mutt_error(_("Warning: Couldn't save certificate"));
  }
 
  buf_pool_release(&fpbuf);
  cert_array_clear(&carr);
  ARRAY_FREE(&carr);
  gnutls_x509_crt_deinit(cert);
  return (rc > 1);
}

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tls_check_certificate()

static int tls_check_certificate ( struct Connection *  conn )

static

Check a connection's certificate.

Parameters

conn	Connection to a server

Return values

1	Certificate is valid
0	Error, or certificate is invalid

Definition at line 618 of file gnutls.c.

{
  struct TlsSockData *data = conn->sockdata;
  gnutls_session_t session = data->session;
  const gnutls_datum_t *cert_list = NULL;
  unsigned int cert_list_size = 0;
  gnutls_certificate_status_t certstat;
  int certerr, savedcert, rc = 0;
  int max_preauth_pass = -1;
 
  /* tls_verify_peers() calls gnutls_certificate_verify_peers2(),
   * which verifies the auth_type is GNUTLS_CRD_CERTIFICATE
   * and that get_certificate_type() for the server is GNUTLS_CRT_X509.
   * If it returns 0, certstat will be set with failure codes for the first
   * cert in the chain(from CA to host) with an error.
   */
  if (tls_verify_peers(session, &certstat) != 0)
    return 0;
 
  cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
  if (!cert_list)
  {
    mutt_error(_("Unable to get certificate from peer"));
    return 0;
  }
 
  /* tls_verify_peers doesn't check hostname or expiration, so walk
   * from most specific to least checking these. If we see a saved certificate,
   * its status short-circuits the remaining checks. */
  int preauthrc = 0;
  for (int i = 0; i < cert_list_size; i++)
  {
    rc = tls_check_preauth(&cert_list[i], certstat, conn->account.host, i,
                           &certerr, &savedcert);
    preauthrc += rc;
    if (!preauthrc)
      max_preauth_pass = i;
 
    if (savedcert)
    {
      if (preauthrc == 0)
        return 1;
      break;
    }
  }
 
  /* then check interactively, starting from chain root */
  for (int i = cert_list_size - 1; i >= 0; i--)
  {
    rc = tls_check_one_certificate(&cert_list[i], certstat, conn->account.host,
                                   i, cert_list_size);
 
    /* Stop checking if the menu cert is aborted or rejected. */
    if (rc == 0)
      break;
 
    /* add signers to trust set, then reverify */
    if (i)
    {
      int rcsettrust = gnutls_certificate_set_x509_trust_mem(data->xcred, &cert_list[i],
                                                             GNUTLS_X509_FMT_DER);
      if (rcsettrust != 1)
        mutt_debug(LL_DEBUG1, "error trusting certificate %d: %d\n", i, rcsettrust);
 
      if (tls_verify_peers(session, &certstat) != 0)
        return 0;
 
      /* If the cert chain now verifies, and all lower certs already
       * passed preauth, we are done. */
      if (!certstat && (max_preauth_pass >= (i - 1)))
        return 1;
    }
  }
 
  return rc;
}

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tls_get_client_cert()

static void tls_get_client_cert ( struct Connection *  conn )

static

Get the client certificate for a TLS connection.

Parameters

conn	Connection to a server

Note

This function grabs the CN out of the client cert but appears to do nothing with it.

Definition at line 702 of file gnutls.c.

{
  struct TlsSockData *data = conn->sockdata;
  gnutls_x509_crt_t clientcrt;
  char *cn = NULL;
  size_t cnlen = 0;
  int rc;
 
  /* get our cert CN if we have one */
  const gnutls_datum_t *crtdata = gnutls_certificate_get_ours(data->session);
  if (!crtdata)
    return;
 
  if (gnutls_x509_crt_init(&clientcrt) < 0)
  {
    mutt_debug(LL_DEBUG1, "Failed to init gnutls crt\n");
    return;
  }
 
  if (gnutls_x509_crt_import(clientcrt, crtdata, GNUTLS_X509_FMT_DER) < 0)
  {
    mutt_debug(LL_DEBUG1, "Failed to import gnutls client crt\n");
    goto err;
  }
 
  /* get length of CN, then grab it. */
  rc = gnutls_x509_crt_get_dn_by_oid(clientcrt, GNUTLS_OID_X520_COMMON_NAME, 0,
                                     0, NULL, &cnlen);
  if (((rc >= 0) || (rc == GNUTLS_E_SHORT_MEMORY_BUFFER)) && (cnlen > 0))
  {
    cn = mutt_mem_calloc(1, cnlen);
    if (gnutls_x509_crt_get_dn_by_oid(clientcrt, GNUTLS_OID_X520_COMMON_NAME, 0,
                                      0, cn, &cnlen) < 0)
    {
      goto err;
    }
    mutt_debug(LL_DEBUG2, "client certificate CN: %s\n", cn);
  }
 
err:
  FREE(&cn);
  gnutls_x509_crt_deinit(clientcrt);
}

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tls_set_priority()

static int tls_set_priority ( struct TlsSockData *  data )

static

Set the priority of various protocols.

Parameters

data	TLS socket data

Return values

0	Success
-1	Error

Definition at line 825 of file gnutls.c.

{
  size_t nproto = 0; /* number of tls/ssl protocols */
 
  const bool c_ssl_use_tlsv1_2 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1_2");
  if (c_ssl_use_tlsv1_2)
    ProtocolPriority[nproto++] = GNUTLS_TLS1_2;
  const bool c_ssl_use_tlsv1_1 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1_1");
  if (c_ssl_use_tlsv1_1)
    ProtocolPriority[nproto++] = GNUTLS_TLS1_1;
  const bool c_ssl_use_tlsv1 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1");
  if (c_ssl_use_tlsv1)
    ProtocolPriority[nproto++] = GNUTLS_TLS1;
  const bool c_ssl_use_sslv3 = cs_subset_bool(NeoMutt->sub, "ssl_use_sslv3");
  if (c_ssl_use_sslv3)
    ProtocolPriority[nproto++] = GNUTLS_SSL3;
  ProtocolPriority[nproto] = 0;
 
  if (nproto == 0)
  {
    mutt_error(_("All available protocols for TLS/SSL connection disabled"));
    return -1;
  }
 
  const char *const c_ssl_ciphers = cs_subset_string(NeoMutt->sub, "ssl_ciphers");
  if (c_ssl_ciphers)
  {
    mutt_error(_("Explicit ciphersuite selection via $ssl_ciphers not supported"));
  }
 
  /* We use default priorities (see gnutls documentation),
   * except for protocol version */
  gnutls_set_default_priority(data->session);
  gnutls_protocol_set_priority(data->session, ProtocolPriority);
  return 0;
}

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tls_negotiate()

static int tls_negotiate ( struct Connection *  conn )

static

Negotiate TLS connection.

Parameters

conn	Connection to a server

Return values

0	Success
-1	Error

After TLS session has been initialized, attempt to negotiate TLS over the wire, including certificate checks.

Definition at line 872 of file gnutls.c.

{
  struct TlsSockData *data = mutt_mem_calloc(1, sizeof(struct TlsSockData));
  conn->sockdata = data;
  int err = gnutls_certificate_allocate_credentials(&data->xcred);
  if (err < 0)
  {
    FREE(&conn->sockdata);
    mutt_error("gnutls_certificate_allocate_credentials: %s", gnutls_strerror(err));
    return -1;
  }
 
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  gnutls_certificate_set_x509_trust_file(data->xcred, c_certificate_file, GNUTLS_X509_FMT_PEM);
  /* ignore errors, maybe file doesn't exist yet */
 
  const char *const c_ssl_ca_certificates_file = cs_subset_path(NeoMutt->sub, "ssl_ca_certificates_file");
  if (c_ssl_ca_certificates_file)
  {
    gnutls_certificate_set_x509_trust_file(data->xcred, c_ssl_ca_certificates_file,
                                           GNUTLS_X509_FMT_PEM);
  }
 
  const char *const c_ssl_client_cert = cs_subset_path(NeoMutt->sub, "ssl_client_cert");
  if (c_ssl_client_cert)
  {
    mutt_debug(LL_DEBUG2, "Using client certificate %s\n", c_ssl_client_cert);
    gnutls_certificate_set_x509_key_file(data->xcred, c_ssl_client_cert,
                                         c_ssl_client_cert, GNUTLS_X509_FMT_PEM);
  }
 
#ifdef HAVE_DECL_GNUTLS_VERIFY_DISABLE_TIME_CHECKS
  /* disable checking certificate activation/expiration times
   * in gnutls, we do the checks ourselves */
  gnutls_certificate_set_verify_flags(data->xcred, GNUTLS_VERIFY_DISABLE_TIME_CHECKS);
#endif
 
  err = gnutls_init(&data->session, GNUTLS_CLIENT);
  if (err)
  {
    mutt_error("gnutls_init: %s", gnutls_strerror(err));
    goto fail;
  }
 
  /* set socket */
  gnutls_transport_set_ptr(data->session, (gnutls_transport_ptr_t) (long) conn->fd);
 
  if (gnutls_server_name_set(data->session, GNUTLS_NAME_DNS, conn->account.host,
                             mutt_str_len(conn->account.host)))
  {
    mutt_error(_("Warning: unable to set TLS SNI host name"));
  }
 
  if (tls_set_priority(data) < 0)
  {
    goto fail;
  }
 
  const short c_ssl_min_dh_prime_bits = cs_subset_number(NeoMutt->sub, "ssl_min_dh_prime_bits");
  if (c_ssl_min_dh_prime_bits > 0)
  {
    gnutls_dh_set_prime_bits(data->session, c_ssl_min_dh_prime_bits);
  }
 
  gnutls_credentials_set(data->session, GNUTLS_CRD_CERTIFICATE, data->xcred);
 
  do
  {
    err = gnutls_handshake(data->session);
  } while ((err == GNUTLS_E_AGAIN) || (err == GNUTLS_E_INTERRUPTED));
 
  if (err < 0)
  {
    if (err == GNUTLS_E_FATAL_ALERT_RECEIVED)
    {
      mutt_error("gnutls_handshake: %s(%s)", gnutls_strerror(err),
                 gnutls_alert_get_name(gnutls_alert_get(data->session)));
    }
    else
    {
      mutt_error("gnutls_handshake: %s", gnutls_strerror(err));
    }
    goto fail;
  }
 
  if (tls_check_certificate(conn) == 0)
    goto fail;
 
  /* set Security Strength Factor (SSF) for SASL */
  /* NB: gnutls_cipher_get_key_size() returns key length in bytes */
  conn->ssf = gnutls_cipher_get_key_size(gnutls_cipher_get(data->session)) * 8;
 
  tls_get_client_cert(conn);
 
  if (!OptNoCurses)
  {
    mutt_message(_("SSL/TLS connection using %s (%s/%s/%s)"),
                 gnutls_protocol_get_name(gnutls_protocol_get_version(data->session)),
                 gnutls_kx_get_name(gnutls_kx_get(data->session)),
                 gnutls_cipher_get_name(gnutls_cipher_get(data->session)),
                 gnutls_mac_get_name(gnutls_mac_get(data->session)));
    mutt_sleep(0);
  }
 
  return 0;
 
fail:
  gnutls_certificate_free_credentials(data->xcred);
  gnutls_deinit(data->session);
  FREE(&conn->sockdata);
  return -1;
}

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mutt_ssl_socket_setup()

int mutt_ssl_socket_setup

(

struct Connection *

conn

)

Set up SSL socket mulitplexor.

Parameters

conn	Connection to a server

Return values

0	Success
-1	Error

Definition at line 1125 of file gnutls.c.

{
  if (tls_init() < 0)
    return -1;
 
  conn->open = tls_socket_open;
  conn->read = tls_socket_read;
  conn->write = tls_socket_write;
  conn->close = tls_socket_close;
  conn->poll = tls_socket_poll;
 
  return 0;
}

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mutt_ssl_starttls()

int mutt_ssl_starttls

(

struct Connection *

conn

)

Negotiate TLS over an already opened connection.

Parameters

conn	Connection to a server

Return values

0	Success
-1	Error

Definition at line 1145 of file gnutls.c.

{
  if (tls_init() < 0)
    return -1;
 
  if (tls_negotiate(conn) < 0)
    return -1;
 
  conn->read = tls_socket_read;
  conn->write = tls_socket_write;
  conn->close = tls_starttls_close;
  conn->poll = tls_socket_poll;
 
  return 0;
}

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Variable Documentation

ProtocolPriority

int ProtocolPriority[] = { GNUTLS_TLS1_2, GNUTLS_TLS1_1, GNUTLS_TLS1, GNUTLS_SSL3, 0 }

static

This array needs to be large enough to hold all the possible values support by NeoMutt.

The initialized values are just placeholders–the array gets overwrriten in tls_negotiate() depending on the $ssl_use_* options.

Note: gnutls_protocol_set_priority() was removed in GnuTLS version 3.4 (2015-04). TLS 1.3 support wasn't added until version 3.6.5. Therefore, no attempt is made to support $ssl_use_tlsv1_3 in this code.

Definition at line 75 of file gnutls.c.