openssl.c File Reference

Handling of OpenSSL encryption. More...

#include "config.h"
#include <errno.h>
#include <openssl/asn1.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/obj_mac.h>
#include <openssl/opensslv.h>
#include <openssl/ossl_typ.h>
#include <openssl/pem.h>
#include <openssl/rand.h>
#include <openssl/safestack.h>
#include <openssl/ssl.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <sys/stat.h>
#include <unistd.h>
#include "private.h"
#include "mutt/lib.h"
#include "address/lib.h"
#include "config/lib.h"
#include "core/lib.h"
#include "connaccount.h"
#include "connection.h"
#include "globals.h"
#include "mutt_logging.h"
#include "ssl.h"

Include dependency graph for openssl.c:

Go to the source code of this file.

Functions
static	STACK_OF (X509)
	Keep a handle on accepted certificates in case we want to open up another connection to the same server in this session.
static bool	ssl_load_certificates (SSL_CTX *ctx)
	Load certificates and filter out the expired ones.
static bool	ssl_set_verify_partial (SSL_CTX *ctx)
	Allow verification using partial chains (with no root)
static int	add_entropy (const char *file)
	Add a source of random numbers.
static void	ssl_err (struct SslSockData *data, int err)
	Display an SSL error message.
static void	ssl_dprint_err_stack (void)
	Dump the SSL error stack.
static int	ssl_passwd_cb (char *buf, int buflen, int rwflag, void *userdata)
	Callback to get a password.
static int	ssl_socket_open_err (struct Connection *conn)
	Error callback for opening an SSL connection - Implements Connection::open() -.
static char *	x509_get_part (X509_NAME *name, int nid)
	Retrieve from X509 data.
static void	x509_fingerprint (struct Buffer *buf, X509 *cert, const EVP_MD *(*hashfunc)(void))
	Generate a fingerprint for an X509 certificate.
static char *	asn1time_to_string (ASN1_UTCTIME *tm)
	Convert a time to a string.
static bool	certificates_equal (X509 *cert, X509 *peercert, unsigned char *peermd, unsigned int peermdlen)
	Compare two X509 certificated.
static bool	check_certificate_expiration (X509 *peercert, bool silent)
	Check if a certificate has expired.
static bool	hostname_match (const char *hostname, const char *certname)
	Does the hostname match the certificate.
static int	ssl_init (void)
	Initialise the SSL library.
static void	ssl_get_client_cert (struct SslSockData *ssldata, struct Connection *conn)
	Get the client certificate for an SSL connection.
static int	ssl_socket_close_and_restore (struct Connection *conn)
	Close an SSL Connection and restore Connection callbacks - Implements Connection::close() -.
static bool	check_certificate_cache (X509 *peercert)
	Is the X509 Certificate in the cache?
static bool	check_certificate_file (X509 *peercert)
	Read and check a certificate file.
static int	check_host (X509 *x509cert, const char *hostname, char *err, size_t errlen)
	Check the host on the certificate.
static bool	check_certificate_by_digest (X509 *peercert)
	Validate a certificate by its digest.
static int	ssl_cache_trusted_cert (X509 *c)
	Cache a trusted certificate.
static void	add_cert (const char *title, X509 *cert, bool issuer, struct CertArray *carr)
	Look up certificate info and save it to a list.
static bool	interactive_check_cert (X509 *cert, int idx, size_t len, SSL *ssl, bool allow_always)
	Ask the user if a certificate is valid.
static int	ssl_verify_callback (int preverify_ok, X509_STORE_CTX *ctx)
	Certificate verification callback.
static int	ssl_negotiate (struct Connection *conn, struct SslSockData *ssldata)
	Attempt to negotiate SSL over the wire.
static struct SslSockData *	sockdata (struct Connection *conn)
	Get a Connection's socket data.
static int	ssl_setup (struct Connection *conn)
	Set up SSL on the Connection.
static int	ssl_socket_poll (struct Connection *conn, time_t wait_secs)
	Check if any data is waiting on a socket - Implements Connection::poll() -.
static int	ssl_socket_open (struct Connection *conn)
	Open an SSL socket - Implements Connection::open() -.
static int	ssl_socket_read (struct Connection *conn, char *buf, size_t count)
	Read data from an SSL socket - Implements Connection::read() -.
static int	ssl_socket_write (struct Connection *conn, const char *buf, size_t count)
	Write data to an SSL socket - Implements Connection::write() -.
static int	ssl_socket_close (struct Connection *conn)
	Close an SSL connection - Implements Connection::close() -.
int	mutt_ssl_starttls (struct Connection *conn)
	Negotiate TLS over an already opened connection.
int	mutt_ssl_socket_setup (struct Connection *conn)
	Set up SSL socket mulitplexor.

Variables
static int	HostExDataIndex = -1
	index for storing hostname as application specific data in SSL structure
static int	SkipModeExDataIndex = -1
	Index for storing the "skip mode" state in SSL structure.

Detailed Description

Handling of OpenSSL encryption.

Authors

• Damien Riegel
• Pietro Cerutti
• Richard Russon
• Ian Zimmerman

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 openssl.c.

Function Documentation

STACK_OF()

static STACK_OF ( X509  )

static

Keep a handle on accepted certificates in case we want to open up another connection to the same server in this session.

SSL socket data -

Definition at line 93 of file openssl.c.

{
  SSL_CTX *sctx;
  SSL *ssl;
  unsigned char isopen;
};

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ssl_load_certificates()

static bool ssl_load_certificates ( SSL_CTX *  ctx )

static

Load certificates and filter out the expired ones.

Parameters

ctx	SSL context

Return values

1	Success
0	Error

ssl certificate verification can behave strangely if there are expired certs loaded into the trusted store. This function filters out expired certs.

Previously the code used this form: SSL_CTX_load_verify_locations (ssldata->ctx, $certificate_file, NULL);

Definition at line 119 of file openssl.c.

{
  bool rc = true;
 
  mutt_debug(LL_DEBUG2, "loading trusted certificates\n");
  X509_STORE *store = SSL_CTX_get_cert_store(ctx);
  if (!store)
  {
    store = X509_STORE_new();
    SSL_CTX_set_cert_store(ctx, store);
  }
 
  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 0;
 
  X509 *cert = NULL;
  while (NULL != PEM_read_X509(fp, &cert, NULL, NULL))
  {
    if ((X509_cmp_current_time(X509_get0_notBefore(cert)) >= 0) ||
        (X509_cmp_current_time(X509_get0_notAfter(cert)) <= 0))
    {
      char buf[256] = { 0 };
      mutt_debug(LL_DEBUG2, "filtering expired cert: %s\n",
                 X509_NAME_oneline(X509_get_subject_name(cert), buf, sizeof(buf)));
    }
    else
    {
      X509_STORE_add_cert(store, cert);
    }
  }
  /* PEM_read_X509 sets the error NO_START_LINE on eof */
  if (ERR_GET_REASON(ERR_peek_last_error()) != PEM_R_NO_START_LINE)
    rc = false;
  ERR_clear_error();
 
  X509_free(cert);
  mutt_file_fclose(&fp);
 
  return rc;
}

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ssl_set_verify_partial()

static bool ssl_set_verify_partial ( SSL_CTX *  ctx )

static

Allow verification using partial chains (with no root)

Parameters

ctx	SSL context

Return values

true	Success
false	Error

Definition at line 168 of file openssl.c.

{
  bool rc = true;
#ifdef HAVE_SSL_PARTIAL_CHAIN
  X509_VERIFY_PARAM *param = NULL;
 
  const bool c_ssl_verify_partial_chains = cs_subset_bool(NeoMutt->sub, "ssl_verify_partial_chains");
  if (c_ssl_verify_partial_chains)
  {
    param = X509_VERIFY_PARAM_new();
    if (param)
    {
      X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_PARTIAL_CHAIN);
      if (SSL_CTX_set1_param(ctx, param) == 0)
      {
        mutt_debug(LL_DEBUG2, "SSL_CTX_set1_param() failed\n");
        rc = false;
      }
      X509_VERIFY_PARAM_free(param);
    }
    else
    {
      mutt_debug(LL_DEBUG2, "X509_VERIFY_PARAM_new() failed\n");
      rc = false;
    }
  }
#endif
  return rc;
}

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add_entropy()

static int add_entropy ( const char *  file )

static

Add a source of random numbers.

Parameters

file	Random device

Return values

>0	Success, number of bytes read from the source
-1	Error

Definition at line 204 of file openssl.c.

{
  if (!file)
    return 0;
 
  struct stat st = { 0 };
  int n = -1;
 
  if (stat(file, &st) == -1)
    return (errno == ENOENT) ? 0 : -1;
 
  mutt_message(_("Filling entropy pool: %s..."), file);
 
  /* check that the file permissions are secure */
  if ((st.st_uid != getuid()) || ((st.st_mode & (S_IWGRP | S_IRGRP)) != 0) ||
      ((st.st_mode & (S_IWOTH | S_IROTH)) != 0))
  {
    mutt_error(_("%s has insecure permissions"), file);
    return -1;
  }
 
#ifdef HAVE_RAND_EGD
  n = RAND_egd(file);
#endif
  if (n <= 0)
    n = RAND_load_file(file, -1);
 
  return n;
}

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ssl_err()

static void ssl_err ( struct SslSockData *  data, int  err  )

static

Display an SSL error message.

Parameters

data	SSL socket data
err	SSL error code

Definition at line 239 of file openssl.c.

{
  int e = SSL_get_error(data->ssl, err);
  switch (e)
  {
    case SSL_ERROR_NONE:
      return;
    case SSL_ERROR_ZERO_RETURN:
      data->isopen = 0;
      break;
    case SSL_ERROR_SYSCALL:
      data->isopen = 0;
      break;
  }
 
  const char *errmsg = NULL;
  unsigned long sslerr;
 
  switch (e)
  {
    case SSL_ERROR_SYSCALL:
      errmsg = "I/O error";
      break;
    case SSL_ERROR_WANT_ACCEPT:
      errmsg = "retry accept";
      break;
    case SSL_ERROR_WANT_CONNECT:
      errmsg = "retry connect";
      break;
    case SSL_ERROR_WANT_READ:
      errmsg = "retry read";
      break;
    case SSL_ERROR_WANT_WRITE:
      errmsg = "retry write";
      break;
    case SSL_ERROR_WANT_X509_LOOKUP:
      errmsg = "retry x509 lookup";
      break;
    case SSL_ERROR_ZERO_RETURN:
      errmsg = "SSL connection closed";
      break;
    case SSL_ERROR_SSL:
      sslerr = ERR_get_error();
      switch (sslerr)
      {
        case 0:
          switch (err)
          {
            case 0:
              errmsg = "EOF";
              break;
            default:
              errmsg = strerror(errno);
          }
          break;
        default:
          errmsg = ERR_error_string(sslerr, NULL);
      }
      break;
    default:
      errmsg = "unknown error";
  }
 
  mutt_debug(LL_DEBUG1, "SSL error: %s\n", errmsg);
}

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ssl_dprint_err_stack()

static void ssl_dprint_err_stack ( void  )

static

Dump the SSL error stack.

Definition at line 308 of file openssl.c.

{
  BIO *bio = BIO_new(BIO_s_mem());
  if (!bio)
    return;
  ERR_print_errors(bio);
 
  char *buf = NULL;
  long buflen = BIO_get_mem_data(bio, &buf);
  if (buflen > 0)
  {
    char *output = MUTT_MEM_MALLOC(buflen + 1, char);
    memcpy(output, buf, buflen);
    output[buflen] = '\0';
    mutt_debug(LL_DEBUG1, "SSL error stack: %s\n", output);
    FREE(&output);
  }
  BIO_free(bio);
}

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ssl_passwd_cb()

static int ssl_passwd_cb ( char *  buf, int  buflen, int  rwflag, void *  userdata  )

static

Callback to get a password.

Parameters

buf	Buffer for the password
buflen	Length of the buffer
rwflag	0 if writing, 1 if reading (UNUSED)
userdata	ConnAccount whose password is requested

Return values

>0	Success, number of chars written to buf
0	Error

Definition at line 337 of file openssl.c.

{
  struct ConnAccount *cac = userdata;
 
  if (mutt_account_getuser(cac) < 0)
    return 0;
 
  mutt_debug(LL_DEBUG2, "getting password for %s@%s:%u\n", cac->user, cac->host, cac->port);
 
  if (mutt_account_getpass(cac) < 0)
    return 0;
 
  return snprintf(buf, buflen, "%s", cac->pass);
}

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x509_get_part()

static char * x509_get_part ( X509_NAME *  name, int  nid  )

static

Retrieve from X509 data.

Parameters

name	Name of data to retrieve
nid	ID of the item to retrieve

Return values

ptr	Retrieved data

The returned pointer is to a static buffer, so it must not be free()'d.

Definition at line 370 of file openssl.c.

{
  static char data[128];
 
  if (!name || (X509_NAME_get_text_by_NID(name, nid, data, sizeof(data)) < 0))
    return NULL;
 
  return data;
}

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x509_fingerprint()

static void x509_fingerprint ( struct Buffer *  buf, X509 *  cert, const EVP_MD *(*)(void)  hashfunc  )

static

Generate a fingerprint for an X509 certificate.

Parameters

buf	Buffer for fingerprint
cert	Certificate
hashfunc	Hashing function

Definition at line 386 of file openssl.c.

{
  unsigned char md[EVP_MAX_MD_SIZE];
  unsigned int n = 0;
 
  if (X509_digest(cert, hashfunc(), md, &n) == 0) // Failure
  {
    buf_strcpy(buf, _("[unable to calculate]"));
    return;
  }
 
  for (unsigned int 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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asn1time_to_string()

static char * asn1time_to_string ( ASN1_UTCTIME *  tm )

static

Convert a time to a string.

Parameters

tm	Time to convert

Return values

ptr	Time string

The returned pointer is to a static buffer, so it must not be free()'d.

Definition at line 414 of file openssl.c.

{
  static char buf[64];
  BIO *bio = NULL;
 
  mutt_str_copy(buf, _("[invalid date]"), sizeof(buf));
 
  bio = BIO_new(BIO_s_mem());
  if (bio)
  {
    if (ASN1_TIME_print(bio, tm))
      (void) BIO_read(bio, buf, sizeof(buf));
    BIO_free(bio);
  }
 
  return buf;
}

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certificates_equal()

static bool certificates_equal ( X509 *  cert, X509 *  peercert, unsigned char *  peermd, unsigned int  peermdlen  )

static

Compare two X509 certificated.

Parameters

cert	Certificate
peercert	Peer certificate
peermd	Peer certificate message digest
peermdlen	Length of peer certificate message digest

Return values

true	Certificates match
false	Certificates differ

Definition at line 441 of file openssl.c.

{
  unsigned char md[EVP_MAX_MD_SIZE];
  unsigned int mdlen;
 
  /* Avoid CPU-intensive digest calculation if the certificates are
   * not even remotely equal.  */
  if ((X509_subject_name_cmp(cert, peercert) != 0) ||
      (X509_issuer_name_cmp(cert, peercert) != 0))
  {
    return false;
  }
 
  if (!X509_digest(cert, EVP_sha256(), md, &mdlen) || (peermdlen != mdlen))
    return false;
 
  if (memcmp(peermd, md, mdlen) != 0)
    return false;
 
  return true;
}

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check_certificate_expiration()

static bool check_certificate_expiration ( X509 *  peercert, bool  silent  )

static

Check if a certificate has expired.

Parameters

peercert	Certificate to check
silent	If true, don't notify the user if the certificate has expired

Return values

true	Certificate is valid
false	Certificate has expired (or hasn't yet become valid)

Definition at line 471 of file openssl.c.

{
  const bool c_ssl_verify_dates = cs_subset_bool(NeoMutt->sub, "ssl_verify_dates");
  if (c_ssl_verify_dates == MUTT_NO)
    return true;
 
  if (X509_cmp_current_time(X509_get0_notBefore(peercert)) >= 0)
  {
    if (!silent)
    {
      mutt_debug(LL_DEBUG2, "Server certificate is not yet valid\n");
      mutt_error(_("Server certificate is not yet valid"));
    }
    return false;
  }
 
  if (X509_cmp_current_time(X509_get0_notAfter(peercert)) <= 0)
  {
    if (!silent)
    {
      mutt_debug(LL_DEBUG2, "Server certificate has expired\n");
      mutt_error(_("Server certificate has expired"));
    }
    return false;
  }
 
  return true;
}

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hostname_match()

static bool hostname_match ( const char *  hostname, const char *  certname  )

static

Does the hostname match the certificate.

Parameters

hostname	Hostname
certname	Certificate

Return values

true	Hostname matches the certificate

Definition at line 506 of file openssl.c.

{
  const char *cmp1 = NULL, *cmp2 = NULL;
 
  if (mutt_strn_equal(certname, "*.", 2))
  {
    cmp1 = certname + 2;
    cmp2 = strchr(hostname, '.');
    if (!cmp2)
      return false;
 
    cmp2++;
  }
  else
  {
    cmp1 = certname;
    cmp2 = hostname;
  }
 
  if ((*cmp1 == '\0') || (*cmp2 == '\0'))
  {
    return false;
  }
 
  if (strcasecmp(cmp1, cmp2) != 0)
  {
    return false;
  }
 
  return true;
}

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ssl_init()

static int ssl_init ( void  )

static

Initialise the SSL library.

Return values

0	Success
-1	Error

OpenSSL library needs to be fed with sufficient entropy. On systems with /dev/urandom, this is done transparently by the library itself, on other systems we need to fill the entropy pool ourselves.

Even though only OpenSSL 0.9.5 and later will complain about the lack of entropy, we try to our best and fill the pool with older versions also. (That's the reason for the ugly ifdefs and macros, otherwise I could have simply ifdef'd the whole ssl_init function)

Definition at line 552 of file openssl.c.

{
  static bool init_complete = false;
 
  if (init_complete)
    return 0;
 
  if (RAND_status() != 1)
  {
    /* load entropy from files */
    struct Buffer *path = buf_pool_get();
    const char *const c_entropy_file = cs_subset_path(NeoMutt->sub, "entropy_file");
    add_entropy(c_entropy_file);
    add_entropy(RAND_file_name(path->data, path->dsize));
 
/* load entropy from egd sockets */
#ifdef HAVE_RAND_EGD
    add_entropy(mutt_str_getenv("EGDSOCKET"));
    buf_printf(path, "%s/.entropy", NONULL(HomeDir));
    add_entropy(buf_string(path));
    add_entropy(TMPDIR "/entropy");
#endif
 
    /* shuffle $RANDFILE (or ~/.rnd if unset) */
    RAND_write_file(RAND_file_name(path->data, path->dsize));
    buf_pool_release(&path);
 
    mutt_clear_error();
    if (RAND_status() != 1)
    {
      mutt_error(_("Failed to find enough entropy on your system"));
      return -1;
    }
  }
 
/* OpenSSL performs automatic initialization as of 1.1.
 * However LibreSSL does not (as of 2.8.3). */
#if (defined(OPENSSL_VERSION_NUMBER) && (OPENSSL_VERSION_NUMBER < 0x10100000L)) || \
    (defined(LIBRESSL_VERSION_NUMBER))
  /* I don't think you can do this just before reading the error. The call
   * itself might clobber the last SSL error. */
  SSL_load_error_strings();
  SSL_library_init();
#endif
  init_complete = true;
  return 0;
}

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ssl_get_client_cert()

static void ssl_get_client_cert ( struct SslSockData *  ssldata, struct Connection *  conn  )

static

Get the client certificate for an SSL connection.

Parameters

ssldata	SSL socket data
conn	Connection to a server

Definition at line 605 of file openssl.c.

{
  const char *const c_ssl_client_cert = cs_subset_path(NeoMutt->sub, "ssl_client_cert");
  if (!c_ssl_client_cert)
    return;
 
  mutt_debug(LL_DEBUG2, "Using client certificate %s\n", c_ssl_client_cert);
  SSL_CTX_set_default_passwd_cb_userdata(ssldata->sctx, &conn->account);
  SSL_CTX_set_default_passwd_cb(ssldata->sctx, ssl_passwd_cb);
  SSL_CTX_use_certificate_file(ssldata->sctx, c_ssl_client_cert, SSL_FILETYPE_PEM);
  SSL_CTX_use_PrivateKey_file(ssldata->sctx, c_ssl_client_cert, SSL_FILETYPE_PEM);
}

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check_certificate_cache()

static bool check_certificate_cache ( X509 *  peercert )

static

Is the X509 Certificate in the cache?

Parameters

peercert

Certificate

Return values

true	Certificate is in the cache

Definition at line 637 of file openssl.c.

{
  unsigned char peermd[EVP_MAX_MD_SIZE];
  unsigned int peermdlen;
  X509 *cert = NULL;
 
  if (!X509_digest(peercert, EVP_sha256(), peermd, &peermdlen) || !SslSessionCerts)
  {
    return false;
  }
 
  for (int i = sk_X509_num(SslSessionCerts); i-- > 0;)
  {
    cert = sk_X509_value(SslSessionCerts, i);
    if (certificates_equal(cert, peercert, peermd, peermdlen))
    {
      return true;
    }
  }
 
  return false;
}

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check_certificate_file()

static bool check_certificate_file ( X509 *  peercert )

static

Read and check a certificate file.

Parameters

peercert

Certificate

Return values

true	Certificate is valid
false	Error, or certificate is invalid

Definition at line 666 of file openssl.c.

{
  unsigned char peermd[EVP_MAX_MD_SIZE];
  unsigned int peermdlen;
  X509 *cert = NULL;
  int pass = false;
  FILE *fp = NULL;
 
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  fp = mutt_file_fopen(c_certificate_file, "r");
  if (!fp)
    return false;
 
  if (!X509_digest(peercert, EVP_sha256(), peermd, &peermdlen))
  {
    mutt_file_fclose(&fp);
    return false;
  }
 
  while (PEM_read_X509(fp, &cert, NULL, NULL))
  {
    if (certificates_equal(cert, peercert, peermd, peermdlen) &&
        check_certificate_expiration(cert, true))
    {
      pass = true;
      break;
    }
  }
  /* PEM_read_X509 sets an error on eof */
  if (!pass)
    ERR_clear_error();
  X509_free(cert);
  mutt_file_fclose(&fp);
 
  return pass;
}

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check_host()

static int check_host ( X509 *  x509cert, const char *  hostname, char *  err, size_t  errlen  )

static

Check the host on the certificate.

Parameters

x509cert	Certificate
hostname	Hostname
err	Buffer for error message
errlen	Length of buffer

Return values

1	Hostname matches the certificate
0	Error

Definition at line 712 of file openssl.c.

{
  int rc = 0;
  /* hostname in ASCII format: */
  char *hostname_ascii = NULL;
  /* needed to get the common name: */
  X509_NAME *x509_subject = NULL;
  char *buf = NULL;
  int bufsize;
  /* needed to get the DNS subjectAltNames: */
  STACK_OF(GENERAL_NAME) * subj_alt_names;
  int subj_alt_names_count;
  GENERAL_NAME *subj_alt_name = NULL;
  /* did we find a name matching hostname? */
  bool match_found;
 
  /* Check if 'hostname' matches the one of the subjectAltName extensions of
   * type DNS or the Common Name (CN). */
 
#ifdef HAVE_LIBIDN
  if (mutt_idna_to_ascii_lz(hostname, &hostname_ascii, 0) != 0)
  {
    hostname_ascii = mutt_str_dup(hostname);
  }
#else
  hostname_ascii = mutt_str_dup(hostname);
#endif
 
  /* Try the DNS subjectAltNames. */
  match_found = false;
  subj_alt_names = X509_get_ext_d2i(x509cert, NID_subject_alt_name, NULL, NULL);
  if (subj_alt_names)
  {
    subj_alt_names_count = sk_GENERAL_NAME_num(subj_alt_names);
    for (int i = 0; i < subj_alt_names_count; i++)
    {
      subj_alt_name = sk_GENERAL_NAME_value(subj_alt_names, i);
      if (subj_alt_name->type == GEN_DNS)
      {
        if ((subj_alt_name->d.ia5->length >= 0) &&
            (mutt_str_len((char *) subj_alt_name->d.ia5->data) ==
             (size_t) subj_alt_name->d.ia5->length) &&
            (match_found = hostname_match(hostname_ascii,
                                          (char *) (subj_alt_name->d.ia5->data))))
        {
          break;
        }
      }
    }
    GENERAL_NAMES_free(subj_alt_names);
  }
 
  if (!match_found)
  {
    /* Try the common name */
    x509_subject = X509_get_subject_name(x509cert);
    if (!x509_subject)
    {
      if (err && errlen)
        mutt_str_copy(err, _("can't get certificate subject"), errlen);
      goto out;
    }
 
    /* first get the space requirements */
    bufsize = X509_NAME_get_text_by_NID(x509_subject, NID_commonName, NULL, 0);
    if (bufsize == -1)
    {
      if (err && errlen)
        mutt_str_copy(err, _("can't get certificate common name"), errlen);
      goto out;
    }
    bufsize++; /* space for the terminal nul char */
    buf = MUTT_MEM_MALLOC(bufsize, char);
    if (X509_NAME_get_text_by_NID(x509_subject, NID_commonName, buf, bufsize) == -1)
    {
      if (err && errlen)
        mutt_str_copy(err, _("can't get certificate common name"), errlen);
      goto out;
    }
    /* cast is safe since bufsize is incremented above, so bufsize-1 is always
     * zero or greater.  */
    if (mutt_str_len(buf) == (size_t) bufsize - 1)
    {
      match_found = hostname_match(hostname_ascii, buf);
    }
  }
 
  if (!match_found)
  {
    if (err && errlen)
      snprintf(err, errlen, _("certificate owner does not match hostname %s"), hostname);
    goto out;
  }
 
  rc = 1;
 
out:
  FREE(&buf);
  FREE(&hostname_ascii);
 
  return rc;
}

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check_certificate_by_digest()

static bool check_certificate_by_digest ( X509 *  peercert )

static

Validate a certificate by its digest.

Parameters

peercert

Certificate

Return values

true	Certificate is valid
false	Error

Definition at line 821 of file openssl.c.

{
  return check_certificate_expiration(peercert, false) && check_certificate_file(peercert);
}

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ssl_cache_trusted_cert()

static int ssl_cache_trusted_cert ( X509 *  c )

static

Cache a trusted certificate.

Parameters

c	Certificate

Return values

>0	Number of elements in the cache
0	Error

Definition at line 832 of file openssl.c.

{
  mutt_debug(LL_DEBUG1, "trusted\n");
  if (!SslSessionCerts)
    SslSessionCerts = sk_X509_new_null();
  return sk_X509_push(SslSessionCerts, X509_dup(c));
}

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add_cert()

static void add_cert ( const char *  title, X509 *  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 847 of file openssl.c.

{
  static const int part[] = {
    NID_commonName,             // CN
    NID_pkcs9_emailAddress,     // Email
    NID_organizationName,       // O
    NID_organizationalUnitName, // OU
    NID_localityName,           // L
    NID_stateOrProvinceName,    // ST
    NID_countryName,            // C
  };
 
  X509_NAME *x509 = NULL;
  if (issuer)
    x509 = X509_get_issuer_name(cert);
  else
    x509 = X509_get_subject_name(cert);
 
  // Allocate formatted strings and let the array take ownership
  ARRAY_ADD(carr, mutt_str_dup(title));
 
  char *line = NULL;
  char *text = NULL;
  for (size_t i = 0; i < mutt_array_size(part); i++)
  {
    text = x509_get_part(x509, part[i]);
    if (text)
    {
      mutt_str_asprintf(&line, "   %s", text);
      ARRAY_ADD(carr, line);
    }
  }
}

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interactive_check_cert()

static bool interactive_check_cert ( X509 *  cert, int  idx, size_t  len, SSL *  ssl, bool  allow_always  )

static

Ask the user if a certificate is valid.

Parameters

cert	Certificate
idx	Place of certificate in the chain
len	Length of the certificate chain
ssl	SSL state
allow_always	If certificate may be always allowed

Return values

true	User selected 'skip'
false	Otherwise

Definition at line 891 of file openssl.c.

{
  if (OptNoCurses)
  {
    mutt_debug(LL_DEBUG1, "unable to prompt for certificate in batch mode\n");
    mutt_error(_("Untrusted server certificate"));
    return 0;
  }
 
  struct CertArray carr = ARRAY_HEAD_INITIALIZER;
  struct Buffer *buf = buf_pool_get();
 
  add_cert(_("This certificate belongs to:"), cert, false, &carr);
  ARRAY_ADD(&carr, NULL);
  add_cert(_("This certificate was issued by:"), cert, true, &carr);
 
  char *line = NULL;
  ARRAY_ADD(&carr, NULL);
  ARRAY_ADD(&carr, mutt_str_dup(_("This certificate is valid")));
  mutt_str_asprintf(&line, _("   from %s"), asn1time_to_string(X509_getm_notBefore(cert)));
  ARRAY_ADD(&carr, line);
  mutt_str_asprintf(&line, _("     to %s"), asn1time_to_string(X509_getm_notAfter(cert)));
  ARRAY_ADD(&carr, line);
 
  ARRAY_ADD(&carr, NULL);
  x509_fingerprint(buf, cert, EVP_sha1);
  mutt_str_asprintf(&line, _("SHA1 Fingerprint: %s"), buf_string(buf));
  ARRAY_ADD(&carr, line);
  x509_fingerprint(buf, cert, EVP_sha256);
  buf->data[39] = '\0'; /* Divide into two lines of output */
  mutt_str_asprintf(&line, "%s%s", _("SHA256 Fingerprint: "), buf_string(buf));
  ARRAY_ADD(&carr, line);
  mutt_str_asprintf(&line, "%*s%s", (int) mutt_str_len(_("SHA256 Fingerprint: ")),
                    "", buf->data + 40);
  ARRAY_ADD(&carr, line);
 
  bool allow_skip = false;
/* The leaf/host certificate can't be skipped. */
#ifdef HAVE_SSL_PARTIAL_CHAIN
  const bool c_ssl_verify_partial_chains = cs_subset_bool(NeoMutt->sub, "ssl_verify_partial_chains");
  if ((idx != 0) && c_ssl_verify_partial_chains)
    allow_skip = true;
#endif
 
  char title[256] = { 0 };
  snprintf(title, sizeof(title),
           _("SSL Certificate check (certificate %zu of %zu in chain)"), len - idx, len);
 
  /* Inside ssl_verify_callback(), this function is guarded by a call to
   * check_certificate_by_digest().  This means if check_certificate_expiration() is
   * true, then check_certificate_file() must be false.  Therefore we don't need
   * to also scan the certificate file here.  */
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  allow_always = allow_always && c_certificate_file &&
                 check_certificate_expiration(cert, true);
 
  int rc = dlg_certificate(title, &carr, allow_always, allow_skip);
  if ((rc == 3) && !allow_always)
    rc = 4;
 
  switch (rc)
  {
    case 1: // Reject
      break;
    case 2: // Once
      SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
      ssl_cache_trusted_cert(cert);
      break;
    case 3: // Always
    {
      bool saved = false;
      FILE *fp = mutt_file_fopen(c_certificate_file, "a");
      if (fp)
      {
        if (PEM_write_X509(fp, cert))
          saved = true;
        mutt_file_fclose(&fp);
      }
 
      if (saved)
        mutt_message(_("Certificate saved"));
      else
        mutt_error(_("Warning: Couldn't save certificate"));
 
      SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
      ssl_cache_trusted_cert(cert);
      break;
    }
    case 4: // Skip
      SSL_set_ex_data(ssl, SkipModeExDataIndex, &SkipModeExDataIndex);
      break;
  }
 
  cert_array_clear(&carr);
  buf_pool_release(&buf);
 
  return (rc > 1);
}

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ssl_verify_callback()

static int ssl_verify_callback ( int  preverify_ok, X509_STORE_CTX *  ctx  )

static

Certificate verification callback.

Parameters

preverify_ok	If true, don't question the user if they skipped verification
ctx	X509 store context

Return values

true	Certificate is valid
false	Error, or Certificate is invalid

Called for each certificate in the chain sent by the peer, starting from the root; returning true means that the given certificate is trusted, returning false immediately aborts the SSL connection

Definition at line 1001 of file openssl.c.

{
  char buf[256] = { 0 };
 
  SSL *ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
  if (!ssl)
  {
    mutt_debug(LL_DEBUG1, "failed to retrieve SSL structure from X509_STORE_CTX\n");
    return false;
  }
  const char *host = SSL_get_ex_data(ssl, HostExDataIndex);
  if (!host)
  {
    mutt_debug(LL_DEBUG1, "failed to retrieve hostname from SSL structure\n");
    return false;
  }
 
  /* This is true when a previous entry in the certificate chain did
   * not verify and the user manually chose to skip it via the
   * $ssl_verify_partial_chains option.
   * In this case, all following certificates need to be treated as non-verified
   * until one is actually verified.  */
  bool skip_mode = (SSL_get_ex_data(ssl, SkipModeExDataIndex));
 
  X509 *cert = X509_STORE_CTX_get_current_cert(ctx);
  int pos = X509_STORE_CTX_get_error_depth(ctx);
  size_t len = sk_X509_num(X509_STORE_CTX_get0_chain(ctx));
 
  mutt_debug(LL_DEBUG1, "checking cert chain entry %s (preverify: %d skipmode: %d)\n",
             X509_NAME_oneline(X509_get_subject_name(cert), buf, sizeof(buf)),
             preverify_ok, skip_mode);
 
#ifdef HAVE_SSL_PARTIAL_CHAIN
  /* Sometimes, when a certificate is (s)kipped, OpenSSL will pass it
   * a second time with preverify_ok = 1.  Don't show it or the user
   * will think their "s" key is broken.  */
  const bool c_ssl_verify_partial_chains = cs_subset_bool(NeoMutt->sub, "ssl_verify_partial_chains");
  if (c_ssl_verify_partial_chains)
  {
    static int last_pos = 0;
    static X509 *last_cert = NULL;
    if (skip_mode && preverify_ok && (pos == last_pos) && last_cert)
    {
      unsigned char last_cert_md[EVP_MAX_MD_SIZE];
      unsigned int last_cert_mdlen;
      if (X509_digest(last_cert, EVP_sha256(), last_cert_md, &last_cert_mdlen) &&
          certificates_equal(cert, last_cert, last_cert_md, last_cert_mdlen))
      {
        mutt_debug(LL_DEBUG2, "ignoring duplicate skipped certificate\n");
        return true;
      }
    }
 
    last_pos = pos;
    if (last_cert)
      X509_free(last_cert);
    last_cert = X509_dup(cert);
  }
#endif
 
  /* check session cache first */
  if (check_certificate_cache(cert))
  {
    mutt_debug(LL_DEBUG2, "using cached certificate\n");
    SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
    return true;
  }
 
  /* check hostname only for the leaf certificate */
  buf[0] = '\0';
  const bool c_ssl_verify_host = cs_subset_bool(NeoMutt->sub, "ssl_verify_host");
  if ((pos == 0) && (c_ssl_verify_host != MUTT_NO))
  {
    if (check_host(cert, host, buf, sizeof(buf)) == 0)
    {
      mutt_error(_("Certificate host check failed: %s"), buf);
      /* we disallow (a)ccept always in the prompt, because it will have no effect
       * for hostname mismatches. */
      return interactive_check_cert(cert, pos, len, ssl, false);
    }
    mutt_debug(LL_DEBUG2, "hostname check passed\n");
  }
 
  if (!preverify_ok || skip_mode)
  {
    /* automatic check from user's database */
    const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
    if (c_certificate_file && check_certificate_by_digest(cert))
    {
      mutt_debug(LL_DEBUG2, "digest check passed\n");
      SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
      return true;
    }
 
    /* log verification error */
    int err = X509_STORE_CTX_get_error(ctx);
    snprintf(buf, sizeof(buf), "%s (%d)", X509_verify_cert_error_string(err), err);
    mutt_debug(LL_DEBUG2, "X509_verify_cert: %s\n", buf);
 
    /* prompt user */
    return interactive_check_cert(cert, pos, len, ssl, true);
  }
 
  return true;
}

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ssl_negotiate()

static int ssl_negotiate ( struct Connection *  conn, struct SslSockData *  ssldata  )

static

Attempt to negotiate SSL over the wire.

Parameters

conn	Connection to a server
ssldata	SSL socket data

Return values

0	Success
-1	Error

After SSL state has been initialized, attempt to negotiate SSL over the wire, including certificate checks.

Definition at line 1117 of file openssl.c.

{
  int err;
  const char *errmsg = NULL;
 
  HostExDataIndex = SSL_get_ex_new_index(0, "host", NULL, NULL, NULL);
  if (HostExDataIndex == -1)
  {
    mutt_debug(LL_DEBUG1, "#1 failed to get index for application specific data\n");
    return -1;
  }
 
  if (!SSL_set_ex_data(ssldata->ssl, HostExDataIndex, conn->account.host))
  {
    mutt_debug(LL_DEBUG1, "#2 failed to save hostname in SSL structure\n");
    return -1;
  }
 
  SkipModeExDataIndex = SSL_get_ex_new_index(0, "skip", NULL, NULL, NULL);
  if (SkipModeExDataIndex == -1)
  {
    mutt_debug(LL_DEBUG1, "#3 failed to get index for application specific data\n");
    return -1;
  }
 
  if (!SSL_set_ex_data(ssldata->ssl, SkipModeExDataIndex, NULL))
  {
    mutt_debug(LL_DEBUG1, "#4 failed to save skip mode in SSL structure\n");
    return -1;
  }
 
  SSL_set_verify(ssldata->ssl, SSL_VERIFY_PEER, ssl_verify_callback);
  SSL_set_mode(ssldata->ssl, SSL_MODE_AUTO_RETRY);
 
  if (!SSL_set_tlsext_host_name(ssldata->ssl, conn->account.host))
  {
    /* L10N: This is a warning when trying to set the host name for
       TLS Server Name Indication (SNI).  This allows the server to present
       the correct certificate if it supports multiple hosts. */
    mutt_error(_("Warning: unable to set TLS SNI host name"));
  }
 
  ERR_clear_error();
 
retry:
  err = SSL_connect(ssldata->ssl);
  if (err != 1)
  {
    // Temporary failure, e.g. signal received
    if (BIO_should_retry(SSL_get_rbio(ssldata->ssl)))
      goto retry;
 
    switch (SSL_get_error(ssldata->ssl, err))
    {
      case SSL_ERROR_SYSCALL:
        errmsg = _("I/O error");
        break;
      case SSL_ERROR_SSL:
        errmsg = ERR_error_string(ERR_get_error(), NULL);
        break;
      default:
        errmsg = _("unknown error");
    }
 
    mutt_error(_("SSL failed: %s"), errmsg);
 
    return -1;
  }
 
  return 0;
}

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sockdata()

static struct SslSockData * sockdata ( struct Connection *  conn )

inlinestatic

Get a Connection's socket data.

Parameters

conn	Connection

Return values

ptr	Socket data

Definition at line 1194 of file openssl.c.

{
  return conn->sockdata;
}

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ssl_setup()

static int ssl_setup ( struct Connection *  conn )

static

Set up SSL on the Connection.

Parameters

conn	Connection

Return values

0	Success
-1	Failure

Definition at line 1205 of file openssl.c.

{
  int maxbits = 0;
 
  conn->sockdata = MUTT_MEM_CALLOC(1, struct SslSockData);
 
  sockdata(conn)->sctx = SSL_CTX_new(SSLv23_client_method());
  if (!sockdata(conn)->sctx)
  {
    /* L10N: an SSL context is a data structure returned by the OpenSSL
       function SSL_CTX_new().  In this case it returned NULL: an
       error condition.  */
    mutt_error(_("Unable to create SSL context"));
    ssl_dprint_err_stack();
    goto free_ssldata;
  }
 
  /* disable SSL protocols as needed */
#ifdef SSL_OP_NO_TLSv1_3
  const bool c_ssl_use_tlsv1_3 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1_3");
  if (!c_ssl_use_tlsv1_3)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_TLSv1_3);
#endif
 
#ifdef SSL_OP_NO_TLSv1_2
  const bool c_ssl_use_tlsv1_2 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1_2");
  if (!c_ssl_use_tlsv1_2)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_TLSv1_2);
#endif
 
#ifdef SSL_OP_NO_TLSv1_1
  const bool c_ssl_use_tlsv1_1 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1_1");
  if (!c_ssl_use_tlsv1_1)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_TLSv1_1);
#endif
 
#ifdef SSL_OP_NO_TLSv1
  const bool c_ssl_use_tlsv1 = cs_subset_bool(NeoMutt->sub, "ssl_use_tlsv1");
  if (!c_ssl_use_tlsv1)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_TLSv1);
#endif
 
  const bool c_ssl_use_sslv3 = cs_subset_bool(NeoMutt->sub, "ssl_use_sslv3");
  if (!c_ssl_use_sslv3)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_SSLv3);
 
  const bool c_ssl_use_sslv2 = cs_subset_bool(NeoMutt->sub, "ssl_use_sslv2");
  if (!c_ssl_use_sslv2)
    SSL_CTX_set_options(sockdata(conn)->sctx, SSL_OP_NO_SSLv2);
 
  const bool c_ssl_use_system_certs = cs_subset_bool(NeoMutt->sub, "ssl_use_system_certs");
  if (c_ssl_use_system_certs)
  {
    if (!SSL_CTX_set_default_verify_paths(sockdata(conn)->sctx))
    {
      mutt_debug(LL_DEBUG1, "Error setting default verify paths\n");
      goto free_ctx;
    }
  }
 
  const char *const c_certificate_file = cs_subset_path(NeoMutt->sub, "certificate_file");
  if (c_certificate_file && !ssl_load_certificates(sockdata(conn)->sctx))
    mutt_debug(LL_DEBUG1, "Error loading trusted certificates\n");
 
  ssl_get_client_cert(sockdata(conn), conn);
 
  const char *const c_ssl_ciphers = cs_subset_string(NeoMutt->sub, "ssl_ciphers");
  if (c_ssl_ciphers)
  {
    SSL_CTX_set_cipher_list(sockdata(conn)->sctx, c_ssl_ciphers);
  }
 
  if (!ssl_set_verify_partial(sockdata(conn)->sctx))
  {
    mutt_error(_("Warning: error enabling ssl_verify_partial_chains"));
  }
 
  sockdata(conn)->ssl = SSL_new(sockdata(conn)->sctx);
  SSL_set_fd(sockdata(conn)->ssl, conn->fd);
 
  if (ssl_negotiate(conn, sockdata(conn)))
    goto free_ssl;
 
  sockdata(conn)->isopen = 1;
  conn->ssf = SSL_CIPHER_get_bits(SSL_get_current_cipher(sockdata(conn)->ssl), &maxbits);
 
  return 0;
 
free_ssl:
  SSL_free(sockdata(conn)->ssl);
  sockdata(conn)->ssl = NULL;
free_ctx:
  SSL_CTX_free(sockdata(conn)->sctx);
  sockdata(conn)->sctx = NULL;
free_ssldata:
  FREE(&conn->sockdata);
 
  return -1;
}

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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 1422 of file openssl.c.

{
  if (ssl_init())
    return -1;
 
  int rc = ssl_setup(conn);
 
  /* hmm. watch out if we're starting TLS over any method other than raw. */
  conn->read = ssl_socket_read;
  conn->write = ssl_socket_write;
  conn->close = ssl_socket_close_and_restore;
  conn->poll = ssl_socket_poll;
 
  return rc;
}

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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 1444 of file openssl.c.

{
  if (ssl_init() < 0)
  {
    conn->open = ssl_socket_open_err;
    return -1;
  }
 
  conn->open = ssl_socket_open;
  conn->read = ssl_socket_read;
  conn->write = ssl_socket_write;
  conn->poll = ssl_socket_poll;
  conn->close = ssl_socket_close;
 
  return 0;
}

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Variable Documentation

HostExDataIndex

int HostExDataIndex = -1

static

index for storing hostname as application specific data in SSL structure

Definition at line 85 of file openssl.c.

SkipModeExDataIndex

int SkipModeExDataIndex = -1

static

Index for storing the "skip mode" state in SSL structure.

When the user skips a certificate in the chain, the stored value will be non-null.

Definition at line 89 of file openssl.c.