//

// Authentication functions for CUPS.

//

// Copyright © 2021-2023 by OpenPrinting.

// Copyright © 2007-2019 by Apple Inc.

// Copyright © 1997-2007 by Easy Software Products.

//

// Licensed under Apache License v2.0.  See the file "LICENSE" for more

// information.

//

#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 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);

static bool   cups_do_local_auth(http_t *http);

//

// 'cupsDoAuthentication()' - Authenticate a request.

//

// This function performs authentication for a request.  It should be called in

// response to a `HTTP_STATUS_UNAUTHORIZED` status, prior to resubmitting your

// request.

//

bool          // O - `true` on success, `false` on failure/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

  _cups_globals_t *cg = _cupsGlobals(); // Global data

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

  // Range check input...

  if (!http)

    http = _cupsConnect();

  if (!http || !method || !resource)

    return (false);

  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 (cups_do_local_auth(http))

    {

      DEBUG_printf("2cupsDoAuthentication: authstring=\"%s\"", http->authstring);

      if (http->status == HTTP_STATUS_UNAUTHORIZED)

  http->digest_tries ++;

      return (true);

    }

  }

  //

  // 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...

    DEBUG_printf("2cupsDoAuthentication: Trying scheme \"%s\"...", scheme);

    if (!_cups_strcasecmp(scheme, "Bearer"))

    {

      // OAuth 2.0 (Bearer) authentication...

      const char  *bearer = NULL; // Bearer token string, if any

      if (cg->oauth_cb)

      {

        // Try callback...

  char  scope[HTTP_MAX_VALUE];  // scope="xyz" string

  cups_auth_param(schemedata, "realm", http->realm, sizeof(http->realm));

  if (cups_auth_param(schemedata, "scope", scope, sizeof(scope)))

    bearer = (cg->oauth_cb)(http, http->realm, scope, resource, cg->oauth_data);

  else

    bearer = (cg->oauth_cb)(http, http->realm, NULL, resource, cg->oauth_data);

      }

      if (bearer)

      {

        // Use this access token...

        httpSetAuthString(http, "Bearer", bearer);

        break;

      }

      else

      {

        // No access token, try the next scheme...

        DEBUG_puts("2cupsDoAuthentication: No OAuth access token to provide.");

        continue;

      }

    }

    else if (_cups_strcasecmp(scheme, "Basic") && _cups_strcasecmp(scheme, "Digest") && _cups_strcasecmp(scheme, "Negotiate"))

    {

      // Other schemes not yet supported...

      DEBUG_printf("2cupsDoAuthentication: Scheme \"%s\" not yet supported.", scheme);

      continue;

    }

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

    if (http->digest_tries > 1 || !http->userpass[0])

    {

      // Nope - get a new password from the user...

      char default_username[HTTP_MAX_VALUE];

          // Default username

      if (!cg->lang_default)

  cg->lang_default = cupsLangDefault();

      if (cups_auth_param(schemedata, "username", default_username, sizeof(default_username)))

  cupsSetUser(default_username);

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

      http->digest_tries  = _cups_strncasecmp(scheme, "Digest", 6) != 0;

      http->userpass[0]   = '\0';

      if ((password = cupsGetPassword(prompt, http, method, resource)) == NULL)

      {

        DEBUG_puts("1cupsDoAuthentication: User canceled password request.");

  http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;

  return (false);

      }

      snprintf(http->userpass, sizeof(http->userpass), "%s:%s", cupsGetUser(), 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 (false);

    }

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

    if (!_cups_strcasecmp(scheme, "Basic"))

    {

      // Basic authentication...

      char  encode[256];    // Base64 buffer

      DEBUG_puts("2cupsDoAuthentication: Using Basic.");

      httpEncode64(encode, sizeof(encode), http->userpass, strlen(http->userpass), false);

      httpSetAuthString(http, "Basic", encode);

      break;

    }

    else if (!_cups_strcasecmp(scheme, "Digest"))

    {

      // Digest authentication...

      char nonce[HTTP_MAX_VALUE]; // nonce="xyz" string

      cups_auth_param(schemedata, "algorithm", http->algorithm, sizeof(http->algorithm));

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

      cups_auth_param(schemedata, "opaque", http->opaque, sizeof(http->opaque));

      cups_auth_param(schemedata, "qop", http->qop, sizeof(http->qop));

      cups_auth_param(schemedata, "realm", http->realm, sizeof(http->realm));

      if (_httpSetDigestAuthString(http, nonce, method, resource))

      {

  DEBUG_puts("2cupsDoAuthentication: Using Digest.");

        break;

      }

    }

  }

  if (http->authstring && http->authstring[0])

  {

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

    return (true);

  }

  else

  {

    DEBUG_puts("1cupsDoAuthentication: No supported schemes.");

    http->status = HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED;

    return (false);

  }

}

//

// 'cups_auth_find()' - Find the named WWW-Authenticate scheme.

//

// The "www_authenticate" parameter points to the current position in the header.

//

// Returns `NULL` if the auth scheme is not present.

//

static const char *       // O - Start of matching scheme or `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

  DEBUG_printf("8cups_auth_find(www_authenticate=\"%s\", scheme=\"%s\"(%d))", www_authenticate, scheme, (int)schemelen);

  while (*www_authenticate)

  {

    // Skip leading whitespace and commas...

    DEBUG_printf("9cups_auth_find: Before whitespace: \"%s\"", www_authenticate);

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

      www_authenticate ++;

    DEBUG_printf("9cups_auth_find: After whitespace: \"%s\"", 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] == ',' || !www_authenticate[schemelen]))

    {

      // Yes, this is the start of the scheme-specific information...

      DEBUG_printf("9cups_auth_find: Returning \"%s\".", www_authenticate);

      return (www_authenticate);

    }

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

    while (!isspace(*www_authenticate & 255) && *www_authenticate)

    {

      if (*www_authenticate == '\"')

      {

        // Skip quoted value...

        www_authenticate ++;

        while (*www_authenticate && *www_authenticate != '\"')

          www_authenticate ++;

        DEBUG_printf("9cups_auth_find: After quoted: \"%s\"", www_authenticate);

      }

      www_authenticate ++;

    }

    DEBUG_printf("9cups_auth_find: After skip: \"%s\"", www_authenticate);

  }

  DEBUG_puts("9cups_auth_find: Returning NULL.");

  return (NULL);

}

//

// 'cups_auth_param()' - Copy the value for the named authentication parameter,

//                       if present.

//

static const char *       // O - Parameter value or `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

  bool    param;        // Is this a parameter?

  DEBUG_printf("8cups_auth_param(scheme=\"%s\", name=\"%s\", value=%p, valsize=%d)", scheme, name, (void *)value, (int)valsize);

  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';

      DEBUG_printf("9cups_auth_param: Returning \"%s\".", value);

      return (value);

    }

    // Skip the param=value string...

    param = false;

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

    {

      if (*scheme == '=')

      {

        param = true;

      }

      else if (*scheme == '\"')

      {

        // Skip quoted value...

        scheme ++;

        while (*scheme && *scheme != '\"')

          scheme ++;

      }

      scheme ++;

    }

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

    if (!param)

      break;

  }

  *value = '\0';

  DEBUG_puts("9cups_auth_param: Returning NULL.");

  return (NULL);

}

//

// 'cups_auth_scheme()' - Get the (next) WWW-Authenticate scheme.

//

// The "www_authenticate" parameter points to the current position in the header.

//

// Returns `NULL` if there are no (more) auth schemes present.

//

static const char *       // O - Start of scheme or `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

  bool    param;        // Is this a parameter?

  DEBUG_printf("8cups_auth_scheme(www_authenticate=\"%s\", scheme=%p, schemesize=%d)", www_authenticate, (void *)scheme, (int)schemesize);

  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 = false; *www_authenticate && *www_authenticate != ',' && !isspace(*www_authenticate & 255); www_authenticate ++)

    {

      if (*www_authenticate == '=')

      {

        param = true;

      }

      else if (!param && sptr < send)

      {

        *sptr++ = *www_authenticate;

      }

      else if (*www_authenticate == '\"')

      {

        // Skip quoted value...

        do

        {

          www_authenticate ++;

        }

        while (*www_authenticate && *www_authenticate != '\"');

      }

    }

    if (sptr > scheme && !param)

    {

      *sptr = '\0';

      DEBUG_printf("9cups_auth_scheme: Returning \"%s\".", start);

      return (start);

    }

  }

  *scheme = '\0';

  DEBUG_puts("9cups_auth_scheme: Returning NULL.");

  return (NULL);

}

//

// 'cups_do_local_auth()' - Use local peer credentials if available/applicable.

//

static bool       // O - `true` if authorized, `false` otherwise

cups_do_local_auth(http_t *http)  // I - HTTP connection to server

{

#ifdef DEBUG

  char      hostaddr[256];  // Host address string

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

#endif // DEBUG

#if defined(SO_PEERCRED) && defined(AF_LOCAL)

  const char    *www_auth;  // WWW-Authenticate header

  struct passwd   pwd;    // Password information

  struct passwd   *result;  // Auxiliary pointer

  const char    *username;  // Current username

  _cups_globals_t *cg = _cupsGlobals(); // Global data

  // See if we can authenticate using the peer credentials provided over a

  // domain socket; if so, specify "PeerCred username" as the authentication

  // information...

  www_auth = httpGetField(http, HTTP_FIELD_WWW_AUTHENTICATE);

  if (http->hostaddr->addr.sa_family == AF_LOCAL && cups_auth_find(www_auth, "PeerCred"))

  {

    // Verify that the current cupsGetUser() matches the current UID...

    username = cupsGetUser();

    getpwnam_r(username, &pwd, cg->pw_buf, PW_BUF_SIZE, &result);

    if (result && pwd.pw_uid == getuid())

    {

      httpSetAuthString(http, "PeerCred", username);

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

      return (true);

    }

  }

#endif // SO_PEERCRED && AF_LOCAL

  DEBUG_puts("8cups_do_local_auth: Returning false.");

  return (false);

}