Support the latest HTTP Digest authentication specification (Issue #4862)

[thirdparty/cups.git] / cups / auth.c

/*
 * Authentication functions for CUPS.
 *
 * Copyright 2007-2017 by Apple Inc.
 * Copyright 1997-2007 by Easy Software Products.
 *
 * This file contains Kerberos support code, copyright 2006 by
 * Jelmer Vernooij.
 *
 * These coded instructions, statements, and computer programs are the
 * property of Apple Inc. and are protected by Federal copyright
 * law.  Distribution and use rights are outlined in the file "LICENSE.txt"
 * which should have been included with this file.  If this file is
 * missing or damaged, see the license at "http://www.cups.org/".
 *
 * This file is subject to the Apple OS-Developed Software exception.
 */

/*
 * Include necessary headers...
 */

#include "cups-private.h"
#include <fcntl.h>
#include <sys/stat.h>
#if defined(WIN32) || defined(__EMX__)
#  include <io.h>
#else
#  include <unistd.h>
#endif /* WIN32 || __EMX__ */

#if HAVE_AUTHORIZATION_H
#  include <Security/Authorization.h>
#  ifdef HAVE_SECBASEPRIV_H
#    include <Security/SecBasePriv.h>
#  else
extern const char *cssmErrorString(int error);
#  endif /* HAVE_SECBASEPRIV_H */
#endif /* HAVE_AUTHORIZATION_H */

#if defined(SO_PEERCRED) && defined(AF_LOCAL)
#  include <pwd.h>
#endif /* SO_PEERCRED && AF_LOCAL */


/*
 * Local functions...
 */

static const char       *cups_auth_find(const char *www_authenticate, const char *scheme);
static const char       *cups_auth_param(const char *scheme, const char *name, char *value, size_t valsize);
static const char       *cups_auth_scheme(const char *www_authenticate, char *scheme, size_t schemesize);

#ifdef HAVE_GSSAPI
#  ifdef HAVE_GSS_ACQUIRE_CRED_EX_F
#    ifdef HAVE_GSS_GSSAPI_SPI_H
#      include <GSS/gssapi_spi.h>
#    else
#      define GSS_AUTH_IDENTITY_TYPE_1 1
#      define gss_acquire_cred_ex_f __ApplePrivate_gss_acquire_cred_ex_f
typedef struct gss_auth_identity /* @private@ */
{
  uint32_t type;
  uint32_t flags;
  char *username;
  char *realm;
  char *password;
  gss_buffer_t *credentialsRef;
} gss_auth_identity_desc;
extern OM_uint32 gss_acquire_cred_ex_f(gss_status_id_t, const gss_name_t,
                                       OM_uint32, OM_uint32, const gss_OID,
                                       gss_cred_usage_t, gss_auth_identity_t,
                                       void *, void (*)(void *, OM_uint32,
                                                        gss_status_id_t,
                                                        gss_cred_id_t,
                                                        gss_OID_set,
                                                        OM_uint32));
#    endif /* HAVE_GSS_GSSAPI_SPI_H */
#    include <dispatch/dispatch.h>
typedef struct _cups_gss_acquire_s      /* Acquire callback data */
{
  dispatch_semaphore_t  sem;            /* Synchronization semaphore */
  OM_uint32             major;          /* Returned status code */
  gss_cred_id_t         creds;          /* Returned credentials */
} _cups_gss_acquire_t;

static void     cups_gss_acquire(void *ctx, OM_uint32 major,
                                 gss_status_id_t status,
                                 gss_cred_id_t creds, gss_OID_set oids,
                                 OM_uint32 time_rec);
#  endif /* HAVE_GSS_ACQUIRE_CRED_EX_F */
static gss_name_t cups_gss_getname(http_t *http, const char *service_name);
#  ifdef DEBUG
static void     cups_gss_printf(OM_uint32 major_status, OM_uint32 minor_status,
                                const char *message);
#  else
#    define     cups_gss_printf(major, minor, message)
#  endif /* DEBUG */
#endif /* HAVE_GSSAPI */
static int      cups_local_auth(http_t *http);


/*
 * 'cupsDoAuthentication()' - Authenticate a request.
 *
 * This function should be called in response to a @code HTTP_STATUS_UNAUTHORIZED@
 * status, prior to resubmitting your request.
 *
 * @since CUPS 1.1.20/macOS 10.4@
 */

int                                     /* O - 0 on success, -1 on error */
cupsDoAuthentication(
    http_t     *http,                   /* I - Connection to server or @code CUPS_HTTP_DEFAULT@ */
    const char *method,                 /* I - Request method ("GET", "POST", "PUT") */
    const char *resource)               /* I - Resource path */
{
  const char    *password,              /* Password string */
                *www_auth,              /* WWW-Authenticate header */
                *schemedata;            /* Scheme-specific data */
  char          scheme[256],            /* Scheme name */
                prompt[1024],           /* Prompt for user */
                realm[HTTP_MAX_VALUE],  /* realm="xyz" string */
                nonce[HTTP_MAX_VALUE];  /* nonce="xyz" string */
  int           localauth;              /* Local authentication result */
  _cups_globals_t *cg;                  /* Global data */


  DEBUG_printf(("cupsDoAuthentication(http=%p, method=\"%s\", resource=\"%s\")", (void *)http, method, resource));

  if (!http)
    http = _cupsConnect();

  if (!http || !method || !resource)
    return (-1);

  DEBUG_printf(("2cupsDoAuthentication: digest_tries=%d, userpass=\"%s\"",
                http->digest_tries, http->userpass));
  DEBUG_printf(("2cupsDoAuthentication: WWW-Authenticate=\"%s\"",
                httpGetField(http, HTTP_FIELD_WWW_AUTHENTICATE)));

 /*
  * Clear the current authentication string...
  */

  httpSetAuthString(http, NULL, NULL);

 /*
  * See if we can do local authentication...
  */

  if (http->digest_tries < 3)
  {
    if ((localauth = cups_local_auth(http)) == 0)
    {
      DEBUG_printf(("2cupsDoAuthentication: authstring=\"%s\"",
                    http->authstring));

      if (http->status == HTTP_STATUS_UNAUTHORIZED)
        http->digest_tries ++;

      return (0);
    }
    else if (localauth == -1)
    {
      http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;
      return (-1);                      /* Error or canceled */
    }
  }

 /*
  * Nope, loop through the authentication schemes to find the first we support.
  */

  www_auth = httpGetField(http, HTTP_FIELD_WWW_AUTHENTICATE);

  for (schemedata = cups_auth_scheme(www_auth, scheme, sizeof(scheme)); schemedata; schemedata = cups_auth_scheme(schemedata + strlen(scheme), scheme, sizeof(scheme)))
  {
   /*
    * Check the scheme name...
    */

#ifdef HAVE_GSSAPI
    if (!_cups_strcasecmp(scheme, "Negotiate"))
    {
     /*
      * Kerberos authentication...
      */

      if (_cupsSetNegotiateAuthString(http, method, resource))
      {
        http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;
        return (-1);
      }

      break;
    }
    else
#endif /* HAVE_GSSAPI */
    if (_cups_strcasecmp(scheme, "Basic") && _cups_strcasecmp(scheme, "Digest"))
      continue;                         /* Not supported (yet) */

   /*
    * See if we should retry the current username:password...
    */

    if ((http->digest_tries > 1 || !http->userpass[0]) && (!_cups_strcasecmp(scheme, "Basic") || (!_cups_strcasecmp(scheme, "Digest"))))
    {
     /*
      * Nope - get a new password from the user...
      */

      char default_username[HTTP_MAX_VALUE];
                                        /* Default username */

      cg = _cupsGlobals();

      if (!cg->lang_default)
        cg->lang_default = cupsLangDefault();

      if (cups_auth_param(scheme, "username", default_username, sizeof(default_username)))
        cupsSetUser(default_username);

      snprintf(prompt, sizeof(prompt), _cupsLangString(cg->lang_default, _("Password for %s on %s? ")), cupsUser(), http->hostname[0] == '/' ? "localhost" : http->hostname);

      http->digest_tries  = _cups_strncasecmp(scheme, "Digest", 6) != 0;
      http->userpass[0]   = '\0';

      if ((password = cupsGetPassword2(prompt, http, method, resource)) == NULL)
      {
        http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;
        return (-1);
      }

      snprintf(http->userpass, sizeof(http->userpass), "%s:%s", cupsUser(), password);
    }
    else if (http->status == HTTP_STATUS_UNAUTHORIZED)
      http->digest_tries ++;

    if (http->status == HTTP_STATUS_UNAUTHORIZED && http->digest_tries >= 3)
    {
      DEBUG_printf(("1cupsDoAuthentication: Too many authentication tries (%d)", http->digest_tries));

      http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;
      return (-1);
    }

   /*
    * Got a password; encode it for the server...
    */

    if (!_cups_strcasecmp(scheme, "Basic"))
    {
     /*
      * Basic authentication...
      */

      char      encode[256];            /* Base64 buffer */

      httpEncode64_2(encode, sizeof(encode), http->userpass, (int)strlen(http->userpass));
      httpSetAuthString(http, "Basic", encode);
    }
    else if (!_cups_strcasecmp(scheme, "Digest"))
    {
     /*
      * Digest authentication...
      */

      int               i;              /* Looping var */
      char              algorithm[65],  /* Hashing algorithm */
                        opaque[HTTP_MAX_VALUE],
                                        /* Opaque data from server */
                        cnonce[65],     /* cnonce value */
                        kd[65],         /* Final MD5/SHA-256 digest */
                        ha1[65],        /* Hash of username:realm:password */
                        ha2[65],        /* Hash of method:request-uri */
                        hdata[65],      /* Hash of auth data */
                        temp[1024],     /* Temporary string */
                        digest[1024];   /* Digest auth data */
      unsigned char     hash[32];       /* Hash buffer */
      const char        *hashalg;       /* Hashing algorithm */
      size_t            hashsize;       /* Size of hash */

      if (strcmp(nonce, http->nonce))
      {
        strlcpy(http->nonce, nonce, sizeof(http->nonce));
        http->nonce_count = 1;
      }
      else
        http->nonce_count ++;

      cups_auth_param(schemedata, "opaque", opaque, sizeof(opaque));
      cups_auth_param(schemedata, "nonce", nonce, sizeof(nonce));
      cups_auth_param(schemedata, "realm", realm, sizeof(realm));

      for (i = 0; i < 64; i ++)
        cnonce[i] = "0123456789ABCDEF"[CUPS_RAND() & 15];
      cnonce[64] = '\0';

      if (cups_auth_param(schemedata, "algorithm", algorithm, sizeof(algorithm)))
      {
       /*
        * Follow RFC 2617/7616...
        */

        if (!_cups_strcasecmp(algorithm, "MD5"))
        {
         /*
          * RFC 2617 Digest with MD5
          */

          hashalg = "md5";
        }
        else if (!_cups_strcasecmp(algorithm, "SHA-256"))
        {
         /*
          * RFC 7616 Digest with SHA-256
          */

          hashalg = "sha2-256";
        }
        else
        {
         /*
          * Some other algorithm we don't support, skip this one...
          */

          continue;
        }

       /*
        * Calculate digest value...
        */

        /* H(A1) = H(username:realm:password) */
        snprintf(temp, sizeof(temp), "%s:%s:%s", cupsUser(), realm, strchr(http->userpass, ':') + 1);
        hashsize = (size_t)cupsHashData(hashalg, (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, ha1, sizeof(ha1));

        /* H(A2) = H(method:uri) */
        snprintf(temp, sizeof(temp), "%s:%s", method, resource);
        hashsize = (size_t)cupsHashData(hashalg, (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, ha2, sizeof(ha2));

        /* H(data) = H(nonce:nc:cnonce:qop:H(A2)) */
        snprintf(temp, sizeof(temp), "%s:%08x:%s:auth:%s", nonce, http->nonce_count, cnonce, ha2);
        hashsize = (size_t)cupsHashData(hashalg, (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, hdata, sizeof(hdata));

        /* KD = H(H(A1):H(data)) */
        snprintf(temp, sizeof(temp), "%s:%s", ha1, hdata);
        hashsize = (size_t)cupsHashData(hashalg, (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, kd, sizeof(kd));

        /* Pass the RFC 2617/7616 WWW-Authenticate header */
        if (opaque[0])
          snprintf(digest, sizeof(digest), "username=\"%s\", realm=\"%s\", nonce=\"%s\", algorithm=%s, qop=auth, opaque=\"%s\", cnonce=\"%s\", nc=%08x, uri=\"%s\", response=\"%s\"", cupsUser(), realm, nonce, algorithm, opaque, cnonce, http->nonce_count, resource, kd);
        else
          snprintf(digest, sizeof(digest), "username=\"%s\", realm=\"%s\", nonce=\"%s\", algorithm=%s, qop=auth, cnonce=\"%s\", nc=%08x, uri=\"%s\", response=\"%s\"", cupsUser(), realm, nonce, algorithm, cnonce, http->nonce_count, resource, kd);
      }
      else
      {
       /*
        * Use old RFC 2069 Digest method...
        */

        /* H(A1) = H(username:realm:password) */
        snprintf(temp, sizeof(temp), "%s:%s:%s", cupsUser(), realm, strchr(http->userpass, ':') + 1);
        hashsize = (size_t)cupsHashData("md5", (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, ha1, sizeof(ha1));

        /* H(A2) = H(method:uri) */
        snprintf(temp, sizeof(temp), "%s:%s", method, resource);
        hashsize = (size_t)cupsHashData("md5", (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, ha2, sizeof(ha2));

        /* KD = H(H(A1):nonce:H(A2)) */
        snprintf(temp, sizeof(temp), "%s:%s:%s", ha1, nonce, ha2);
        hashsize = (size_t)cupsHashData("md5", (unsigned char *)temp, strlen(temp), hash, sizeof(hash));
        cupsHashString(hash, hashsize, kd, sizeof(kd));

        /* Pass the RFC 2069 WWW-Authenticate header */
        snprintf(digest, sizeof(digest), "username=\"%s\", realm=\"%s\", nonce=\"%s\", uri=\"%s\", response=\"%s\"", cupsUser(), realm, nonce, resource, kd);
      }

      httpSetAuthString(http, "Digest", digest);
    }
  }

  if (http->authstring)
  {
    DEBUG_printf(("1cupsDoAuthentication: authstring=\"%s\"", http->authstring));

    return (0);
  }
  else
  {
    DEBUG_printf(("1cupsDoAuthentication: Unknown auth type: \"%s\"", www_auth));
    http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;

    return (-1);
  }
}


#ifdef HAVE_GSSAPI
/*
 * '_cupsSetNegotiateAuthString()' - Set the Kerberos authentication string.
 */

int                                     /* O - 0 on success, -1 on error */
_cupsSetNegotiateAuthString(
    http_t     *http,                   /* I - Connection to server */
    const char *method,                 /* I - Request method ("GET", "POST", "PUT") */
    const char *resource)               /* I - Resource path */
{
  OM_uint32     minor_status,           /* Minor status code */
                major_status;           /* Major status code */
  gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
                                        /* Output token */


  (void)method;
  (void)resource;

#  ifdef __APPLE__
 /*
  * If the weak-linked GSSAPI/Kerberos library is not present, don't try
  * to use it...
  */

  if (&gss_init_sec_context == NULL)
  {
    DEBUG_puts("1_cupsSetNegotiateAuthString: Weak-linked GSSAPI/Kerberos "
               "framework is not present");
    return (-1);
  }
#  endif /* __APPLE__ */

  if (http->gssname == GSS_C_NO_NAME)
  {
    http->gssname = cups_gss_getname(http, _cupsGSSServiceName());
  }

  if (http->gssctx != GSS_C_NO_CONTEXT)
  {
    gss_delete_sec_context(&minor_status, &http->gssctx, GSS_C_NO_BUFFER);
    http->gssctx = GSS_C_NO_CONTEXT;
  }

  major_status = gss_init_sec_context(&minor_status, GSS_C_NO_CREDENTIAL,
                                      &http->gssctx,
                                      http->gssname, http->gssmech,
                                      GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG,
                                      GSS_C_INDEFINITE,
                                      GSS_C_NO_CHANNEL_BINDINGS,
                                      GSS_C_NO_BUFFER, &http->gssmech,
                                      &output_token, NULL, NULL);

#ifdef HAVE_GSS_ACQUIRE_CRED_EX_F
  if (major_status == GSS_S_NO_CRED)
  {
   /*
    * Ask the user for credentials...
    */

    char                prompt[1024],   /* Prompt for user */
                        userbuf[256];   /* Kerberos username */
    const char          *username,      /* Username string */
                        *password;      /* Password string */
    _cups_gss_acquire_t data;           /* Callback data */
    gss_auth_identity_desc identity;    /* Kerberos user identity */
    _cups_globals_t     *cg = _cupsGlobals();
                                        /* Per-thread global data */

    if (!cg->lang_default)
      cg->lang_default = cupsLangDefault();

    snprintf(prompt, sizeof(prompt),
             _cupsLangString(cg->lang_default, _("Password for %s on %s? ")),
             cupsUser(), http->gsshost);

    if ((password = cupsGetPassword2(prompt, http, method, resource)) == NULL)
      return (-1);

   /*
    * Try to acquire credentials...
    */

    username = cupsUser();
    if (!strchr(username, '@'))
    {
      snprintf(userbuf, sizeof(userbuf), "%s@%s", username, http->gsshost);
      username = userbuf;
    }

    identity.type           = GSS_AUTH_IDENTITY_TYPE_1;
    identity.flags          = 0;
    identity.username       = (char *)username;
    identity.realm          = (char *)"";
    identity.password       = (char *)password;
    identity.credentialsRef = NULL;

    data.sem   = dispatch_semaphore_create(0);
    data.major = 0;
    data.creds = NULL;

    if (data.sem)
    {
      major_status = gss_acquire_cred_ex_f(NULL, GSS_C_NO_NAME, 0, GSS_C_INDEFINITE, GSS_KRB5_MECHANISM, GSS_C_INITIATE, (gss_auth_identity_t)&identity, &data, cups_gss_acquire);

      if (major_status == GSS_S_COMPLETE)
      {
        dispatch_semaphore_wait(data.sem, DISPATCH_TIME_FOREVER);
        major_status = data.major;
      }

      dispatch_release(data.sem);

      if (major_status == GSS_S_COMPLETE)
      {
        OM_uint32       release_minor;  /* Minor status from releasing creds */

        major_status = gss_init_sec_context(&minor_status, data.creds,
                                            &http->gssctx,
                                            http->gssname, http->gssmech,
                                            GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG,
                                            GSS_C_INDEFINITE,
                                            GSS_C_NO_CHANNEL_BINDINGS,
                                            GSS_C_NO_BUFFER, &http->gssmech,
                                            &output_token, NULL, NULL);
        gss_release_cred(&release_minor, &data.creds);
      }
    }
  }
#endif /* HAVE_GSS_ACQUIRED_CRED_EX_F */

  if (GSS_ERROR(major_status))
  {
    cups_gss_printf(major_status, minor_status,
                    "_cupsSetNegotiateAuthString: Unable to initialize "
                    "security context");
    return (-1);
  }

#ifdef DEBUG
  else if (major_status == GSS_S_CONTINUE_NEEDED)
    cups_gss_printf(major_status, minor_status,
                    "_cupsSetNegotiateAuthString: Continuation needed!");
#endif /* DEBUG */

  if (output_token.length > 0 && output_token.length <= 65536)
  {
   /*
    * Allocate the authorization string since Windows KDCs can have
    * arbitrarily large credentials...
    */

    int authsize = 10 +                 /* "Negotiate " */
                   (int)output_token.length * 4 / 3 + 1 + 1;
                                        /* Base64 + nul */

    httpSetAuthString(http, NULL, NULL);

    if ((http->authstring = malloc((size_t)authsize)) == NULL)
    {
      http->authstring = http->_authstring;
      authsize         = sizeof(http->_authstring);
    }

    strlcpy(http->authstring, "Negotiate ", (size_t)authsize);
    httpEncode64_2(http->authstring + 10, authsize - 10, output_token.value,
                   (int)output_token.length);

    gss_release_buffer(&minor_status, &output_token);
  }
  else
  {
    DEBUG_printf(("1_cupsSetNegotiateAuthString: Kerberos credentials too "
                  "large - %d bytes!", (int)output_token.length));
    gss_release_buffer(&minor_status, &output_token);

    return (-1);
  }

  return (0);
}


/*
 * 'cups_auth_find()' - Find the named WWW-Authenticate scheme.
 *
 * The "www_authenticate" parameter points to the current position in the header.
 *
 * Returns @code NULL@ if the auth scheme is not present.
 */

static const char *                             /* O - Start of matching scheme or @code NULL@ if not found */
cups_auth_find(const char *www_authenticate,    /* I - Pointer into WWW-Authenticate header */
               const char *scheme)              /* I - Authentication scheme */
{
  size_t        schemelen = strlen(scheme);     /* Length of scheme */


  while (*www_authenticate)
  {
   /*
    * Skip leading whitespace and commas...
    */

    while (isspace(*www_authenticate & 255) || *www_authenticate == ',')
      www_authenticate ++;

   /*
    * See if this is "Scheme" followed by whitespace or the end of the string.
    */

    if (!strncmp(www_authenticate, scheme, schemelen) && (isspace(www_authenticate[schemelen] & 255) || !www_authenticate[schemelen]))
    {
     /*
      * Yes, this is the start of the scheme-specific information...
      */

      return (www_authenticate);
    }

   /*
    * Skip the scheme name or param="value" string...
    */

    while (!isspace(*www_authenticate & 255) && *www_authenticate)
    {
      if (*www_authenticate == '\"')
      {
       /*
        * Skip quoted value...
        */

        while (www_authenticate[1] && www_authenticate[1] != '\"')
          www_authenticate ++;
      }

      www_authenticate ++;
    }
  }

  return (NULL);
}


/*
 * 'cups_auth_param()' - Copy the value for the named authentication parameter,
 *                       if present.
 */

static const char *                             /* O - Parameter value or @code NULL@ if not present */
cups_auth_param(const char *scheme,             /* I - Pointer to auth data */
                const char *name,               /* I - Name of parameter */
                char       *value,              /* I - Value buffer */
                size_t     valsize)             /* I - Size of value buffer */
{
  char          *valptr = value,                /* Pointer into value buffer */
                *valend = value + valsize - 1;  /* Pointer to end of buffer */
  size_t        namelen = strlen(name);         /* Name length */
  int           param;                          /* Is this a parameter? */


  while (!isspace(*scheme & 255) && *scheme)
    scheme ++;

  while (*scheme)
  {
    while (isspace(*scheme & 255) || *scheme == ',')
      scheme ++;

    if (!strncmp(scheme, name, namelen) && scheme[namelen] == '=')
    {
     /*
      * Found the parameter, copy the value...
      */

      scheme += namelen + 1;
      if (*scheme == '\"')
      {
        scheme ++;

        while (*scheme && *scheme != '\"')
        {
          if (valptr < valend)
            *valptr++ = *scheme;

          scheme ++;
        }
      }
      else
      {
        while (*scheme && strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~+/=", *scheme))
        {
          if (valptr < valend)
            *valptr++ = *scheme;

          scheme ++;
        }
      }

      *valptr = '\0';

      return (value);
    }

   /*
    * Skip the param=value string...
    */

    param = 0;

    while (!isspace(*scheme & 255) && *scheme)
    {
      if (*scheme == '=')
        param = 1;
      else if (*scheme == '\"')
      {
       /*
        * Skip quoted value...
        */

        while (scheme[1] && scheme[1] != '\"')
          scheme ++;
      }

      scheme ++;
    }

   /*
    * If this wasn't a parameter, we are at the end of this scheme's
    * parameters...
    */

    if (!param)
      break;
  }

  *value = '\0';

  return (NULL);
}


/*
 * 'cups_auth_scheme()' - Get the (next) WWW-Authenticate scheme.
 *
 * The "www_authenticate" parameter points to the current position in the header.
 *
 * Returns @code NULL@ if there are no (more) auth schemes present.
 */

static const char *                             /* O - Start of scheme or @code NULL@ if not found */
cups_auth_scheme(const char *www_authenticate,  /* I - Pointer into WWW-Authenticate header */
                 char       *scheme,            /* I - Scheme name buffer */
                 size_t     schemesize)         /* I - Size of buffer */
{
  const char    *start;                         /* Start of scheme data */
  char          *sptr = scheme,                 /* Pointer into scheme buffer */
                *send = scheme + schemesize - 1;/* End of scheme buffer */
  int           param;                          /* Is this a parameter? */


  while (*www_authenticate)
  {
   /*
    * Skip leading whitespace and commas...
    */

    while (isspace(*www_authenticate & 255) || *www_authenticate == ',')
      www_authenticate ++;

   /*
    * Parse the scheme name or param="value" string...
    */

    for (sptr = scheme, start = www_authenticate, param = 0; *www_authenticate && !isspace(*www_authenticate & 255); www_authenticate ++)
    {
      if (*www_authenticate == '=')
        param = 1;
      else if (!param && sptr < send)
        *sptr++ = *www_authenticate;
      else if (*www_authenticate == '\"')
      {
       /*
        * Skip quoted value...
        */

        while (www_authenticate[1] && www_authenticate[1] != '\"')
          www_authenticate ++;
      }
    }

    if (sptr > scheme && !param)
    {
      *sptr = '\0';
      return (start);
    }
  }

  *scheme = '\0';

  return (NULL);
}


#  ifdef HAVE_GSS_ACQUIRE_CRED_EX_F
/*
 * 'cups_gss_acquire()' - Kerberos credentials callback.
 */
static void
cups_gss_acquire(
    void            *ctx,               /* I - Caller context */
    OM_uint32       major,              /* I - Major error code */
    gss_status_id_t status,             /* I - Status (unused) */
    gss_cred_id_t   creds,              /* I - Credentials (if any) */
    gss_OID_set     oids,               /* I - Mechanism OIDs (unused) */
    OM_uint32       time_rec)           /* I - Timestamp (unused) */
{
  uint32_t              min;            /* Minor error code */
  _cups_gss_acquire_t   *data;          /* Callback data */


  (void)status;
  (void)time_rec;

  data        = (_cups_gss_acquire_t *)ctx;
  data->major = major;
  data->creds = creds;

  gss_release_oid_set(&min, &oids);
  dispatch_semaphore_signal(data->sem);
}
#  endif /* HAVE_GSS_ACQUIRE_CRED_EX_F */


/*
 * 'cups_gss_getname()' - Get CUPS service credentials for authentication.
 */

static gss_name_t                       /* O - Server name */
cups_gss_getname(
    http_t     *http,                   /* I - Connection to server */
    const char *service_name)           /* I - Service name */
{
  gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
                                        /* Service token */
  OM_uint32       major_status,         /* Major status code */
                  minor_status;         /* Minor status code */
  gss_name_t      server_name;          /* Server name */
  char            buf[1024];            /* Name buffer */


  DEBUG_printf(("7cups_gss_getname(http=%p, service_name=\"%s\")", http,
                service_name));


 /*
  * Get the hostname...
  */

  if (!http->gsshost[0])
  {
    httpGetHostname(http, http->gsshost, sizeof(http->gsshost));

    if (!strcmp(http->gsshost, "localhost"))
    {
      if (gethostname(http->gsshost, sizeof(http->gsshost)) < 0)
      {
        DEBUG_printf(("1cups_gss_getname: gethostname() failed: %s",
                      strerror(errno)));
        http->gsshost[0] = '\0';
        return (NULL);
      }

      if (!strchr(http->gsshost, '.'))
      {
       /*
        * The hostname is not a FQDN, so look it up...
        */

        struct hostent  *host;          /* Host entry to get FQDN */

        if ((host = gethostbyname(http->gsshost)) != NULL && host->h_name)
        {
         /*
          * Use the resolved hostname...
          */

          strlcpy(http->gsshost, host->h_name, sizeof(http->gsshost));
        }
        else
        {
          DEBUG_printf(("1cups_gss_getname: gethostbyname(\"%s\") failed.",
                        http->gsshost));
          http->gsshost[0] = '\0';
          return (NULL);
        }
      }
    }
  }

 /*
  * Get a service name we can use for authentication purposes...
  */

  snprintf(buf, sizeof(buf), "%s@%s", service_name, http->gsshost);

  DEBUG_printf(("8cups_gss_getname: Looking up \"%s\".", buf));

  token.value  = buf;
  token.length = strlen(buf);
  server_name  = GSS_C_NO_NAME;
  major_status = gss_import_name(&minor_status, &token,
                                 GSS_C_NT_HOSTBASED_SERVICE,
                                 &server_name);

  if (GSS_ERROR(major_status))
  {
    cups_gss_printf(major_status, minor_status,
                    "cups_gss_getname: gss_import_name() failed");
    return (NULL);
  }

  return (server_name);
}


#  ifdef DEBUG
/*
 * 'cups_gss_printf()' - Show debug error messages from GSSAPI.
 */

static void
cups_gss_printf(OM_uint32  major_status,/* I - Major status code */
                OM_uint32  minor_status,/* I - Minor status code */
                const char *message)    /* I - Prefix for error message */
{
  OM_uint32     err_major_status,       /* Major status code for display */
                err_minor_status;       /* Minor status code for display */
  OM_uint32     msg_ctx;                /* Message context */
  gss_buffer_desc major_status_string = GSS_C_EMPTY_BUFFER,
                                        /* Major status message */
                minor_status_string = GSS_C_EMPTY_BUFFER;
                                        /* Minor status message */


  msg_ctx          = 0;
  err_major_status = gss_display_status(&err_minor_status,
                                        major_status,
                                        GSS_C_GSS_CODE,
                                        GSS_C_NO_OID,
                                        &msg_ctx,
                                        &major_status_string);

  if (!GSS_ERROR(err_major_status))
    gss_display_status(&err_minor_status, minor_status, GSS_C_MECH_CODE,
                       GSS_C_NULL_OID, &msg_ctx, &minor_status_string);

  DEBUG_printf(("1%s: %s, %s", message, (char *)major_status_string.value,
                (char *)minor_status_string.value));

  gss_release_buffer(&err_minor_status, &major_status_string);
  gss_release_buffer(&err_minor_status, &minor_status_string);
}
#  endif /* DEBUG */
#endif /* HAVE_GSSAPI */


/*
 * 'cups_local_auth()' - Get the local authorization certificate if
 *                       available/applicable.
 */

static int                              /* O - 0 if available */
                                        /*     1 if not available */
                                        /*    -1 error */
cups_local_auth(http_t *http)           /* I - HTTP connection to server */
{
#if defined(WIN32) || defined(__EMX__)
 /*
  * Currently WIN32 and OS-2 do not support the CUPS server...
  */

  return (1);
#else
  int                   pid;            /* Current process ID */
  FILE                  *fp;            /* Certificate file */
  char                  trc[16],        /* Try Root Certificate parameter */
                        filename[1024]; /* Certificate filename */
  const char            *www_auth,      /* WWW-Authenticate header */
                        *schemedata;    /* Data for the named auth scheme */
  _cups_globals_t *cg = _cupsGlobals(); /* Global data */
#  if defined(HAVE_AUTHORIZATION_H)
  OSStatus              status;         /* Status */
  AuthorizationItem     auth_right;     /* Authorization right */
  AuthorizationRights   auth_rights;    /* Authorization rights */
  AuthorizationFlags    auth_flags;     /* Authorization flags */
  AuthorizationExternalForm auth_extrn; /* Authorization ref external */
  char                  auth_key[1024]; /* Buffer */
  char                  buffer[1024];   /* Buffer */
#  endif /* HAVE_AUTHORIZATION_H */


  DEBUG_printf(("7cups_local_auth(http=%p) hostaddr=%s, hostname=\"%s\"", (void *)http, httpAddrString(http->hostaddr, filename, sizeof(filename)), http->hostname));

 /*
  * See if we are accessing localhost...
  */

  if (!httpAddrLocalhost(http->hostaddr) && _cups_strcasecmp(http->hostname, "localhost") != 0)
  {
    DEBUG_puts("8cups_local_auth: Not a local connection!");
    return (1);
  }

#  if defined(HAVE_AUTHORIZATION_H)
 /*
  * Delete any previous authorization reference...
  */

  if (http->auth_ref)
  {
    AuthorizationFree(http->auth_ref, kAuthorizationFlagDefaults);
    http->auth_ref = NULL;
  }

  www_auth = httpGetField(http, HTTP_FIELD_WWW_AUTHENTICATE);

  if (!getenv("GATEWAY_INTERFACE") && (schemedata = cups_auth_find(www_auth, "AuthKey")) != NULL && cups_auth_param(schemedata, "key", auth_key, sizeof(auth_key)))
  {
    status = AuthorizationCreate(NULL, kAuthorizationEmptyEnvironment, kAuthorizationFlagDefaults, &http->auth_ref);
    if (status != errAuthorizationSuccess)
    {
      DEBUG_printf(("8cups_local_auth: AuthorizationCreate() returned %d (%s)",
                    (int)status, cssmErrorString(status)));
      return (-1);
    }

    auth_right.name        = auth_key;
    auth_right.valueLength = 0;
    auth_right.value       = NULL;
    auth_right.flags       = 0;

    auth_rights.count = 1;
    auth_rights.items = &auth_right;

    auth_flags = kAuthorizationFlagDefaults |
                 kAuthorizationFlagPreAuthorize |
                 kAuthorizationFlagInteractionAllowed |
                 kAuthorizationFlagExtendRights;

    status = AuthorizationCopyRights(http->auth_ref, &auth_rights,
                                     kAuthorizationEmptyEnvironment,
                                     auth_flags, NULL);
    if (status == errAuthorizationSuccess)
      status = AuthorizationMakeExternalForm(http->auth_ref, &auth_extrn);

    if (status == errAuthorizationSuccess)
    {
     /*
      * Set the authorization string and return...
      */

      httpEncode64_2(buffer, sizeof(buffer), (void *)&auth_extrn,
                     sizeof(auth_extrn));

      httpSetAuthString(http, "AuthRef", buffer);

      DEBUG_printf(("8cups_local_auth: Returning authstring=\"%s\"",
                    http->authstring));
      return (0);
    }
    else if (status == errAuthorizationCanceled)
      return (-1);

    DEBUG_printf(("9cups_local_auth: AuthorizationCopyRights() returned %d (%s)",
                  (int)status, cssmErrorString(status)));

  /*
   * Fall through to try certificates...
   */
  }
#  endif /* HAVE_AUTHORIZATION_H */

#  ifdef HAVE_GSSAPI
  if (cups_auth_find(www_auth, "Negotiate"))
    return (1);
#  endif /* HAVE_GSSAPI */
#  ifdef HAVE_AUTHORIZATION_H
  if (cups_auth_find(www_auth, "AuthKey"))
    return (1);
#  endif /* HAVE_AUTHORIZATION_H */

#  if defined(SO_PEERCRED) && defined(AF_LOCAL)
 /*
  * See if we can authenticate using the peer credentials provided over a
  * domain socket; if so, specify "PeerCred username" as the authentication
  * information...
  */

  if (http->hostaddr->addr.sa_family == AF_LOCAL &&
      !getenv("GATEWAY_INTERFACE") &&   /* Not via CGI programs... */
      cups_auth_find(www_auth, "PeerCred"))
  {
   /*
    * Verify that the current cupsUser() matches the current UID...
    */

    struct passwd       *pwd;           /* Password information */
    const char          *username;      /* Current username */

    username = cupsUser();

    if ((pwd = getpwnam(username)) != NULL && pwd->pw_uid == getuid())
    {
      httpSetAuthString(http, "PeerCred", username);

      DEBUG_printf(("8cups_local_auth: Returning authstring=\"%s\"",
                    http->authstring));

      return (0);
    }
  }
#  endif /* SO_PEERCRED && AF_LOCAL */

  if ((schemedata = cups_auth_find(www_auth, "Local")) == NULL)
    return (1);

 /*
  * Try opening a certificate file for this PID.  If that fails,
  * try the root certificate...
  */

  pid = getpid();
  snprintf(filename, sizeof(filename), "%s/certs/%d", cg->cups_statedir, pid);
  if ((fp = fopen(filename, "r")) == NULL && pid > 0)
  {
   /*
    * No certificate for this PID; see if we can get the root certificate...
    */

    DEBUG_printf(("9cups_local_auth: Unable to open file %s: %s", filename, strerror(errno)));

    if (!cups_auth_param(schemedata, "trc", trc, sizeof(trc)))
    {
     /*
      * Scheduler doesn't want us to use the root certificate...
      */

      return (1);
    }

    snprintf(filename, sizeof(filename), "%s/certs/0", cg->cups_statedir);
    fp = fopen(filename, "r");
  }

  if (fp)
  {
   /*
    * Read the certificate from the file...
    */

    char        certificate[33],        /* Certificate string */
                *certptr;               /* Pointer to certificate string */

    certptr = fgets(certificate, sizeof(certificate), fp);
    fclose(fp);

    if (certptr)
    {
     /*
      * Set the authorization string and return...
      */

      httpSetAuthString(http, "Local", certificate);

      DEBUG_printf(("8cups_local_auth: Returning authstring=\"%s\"",
                    http->authstring));

      return (0);
    }
  }

  return (1);
#endif /* WIN32 || __EMX__ */
}