curl_sasl.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 2012 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * RFC2195 CRAM-MD5 authentication
 * RFC2617 Basic and Digest Access Authentication
 * RFC2831 DIGEST-MD5 authentication
 * RFC4422 Simple Authentication and Security Layer (SASL)
 * RFC4616 PLAIN authentication
 * RFC6749 OAuth 2.0 Authorization Framework
 * Draft   LOGIN SASL Mechanism <draft-murchison-sasl-login-00.txt>
 *
 ***************************************************************************/

#include "curl_setup.h"

#include <curl/curl.h>
#include "urldata.h"

#include "curl_base64.h"
#include "curl_md5.h"
#include "vtls/vtls.h"
#include "curl_hmac.h"
#include "curl_ntlm_msgs.h"
#include "curl_sasl.h"
#include "warnless.h"
#include "curl_memory.h"
#include "strtok.h"
#include "rawstr.h"
#include "non-ascii.h" /* included for Curl_convert_... prototypes */

#ifdef USE_NSS
#include "vtls/nssg.h" /* for Curl_nss_force_init() */
#endif

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>

/* The last #include file should be: */
#include "memdebug.h"

#if defined(USE_KRB5)
extern void Curl_sasl_gssapi_cleanup(struct kerberos5data *krb5);
#endif

#if !defined(CURL_DISABLE_CRYPTO_AUTH)

#if !defined(USE_WINDOWS_SSPI)
#define DIGEST_QOP_VALUE_AUTH             (1 << 0)
#define DIGEST_QOP_VALUE_AUTH_INT         (1 << 1)
#define DIGEST_QOP_VALUE_AUTH_CONF        (1 << 2)
#endif /* !USE_WINDOWS_SSPI */

#define DIGEST_QOP_VALUE_STRING_AUTH      "auth"
#define DIGEST_QOP_VALUE_STRING_AUTH_INT  "auth-int"
#define DIGEST_QOP_VALUE_STRING_AUTH_CONF "auth-conf"

#define DIGEST_MAX_VALUE_LENGTH           256
#define DIGEST_MAX_CONTENT_LENGTH         1024

/* The CURL_OUTPUT_DIGEST_CONV macro below is for non-ASCII machines.
   It converts digest text to ASCII so the MD5 will be correct for
   what ultimately goes over the network.
*/
#define CURL_OUTPUT_DIGEST_CONV(a, b) \
  result = Curl_convert_to_network(a, (char *)b, strlen((const char*)b)); \
  if(result) { \
    free(b); \
    return result; \
  }

/*
 * Return 0 on success and then the buffers are filled in fine.
 *
 * Non-zero means failure to parse.
 */
static int sasl_digest_get_pair(const char *str, char *value, char *content,
                                const char **endptr)
{
  int c;
  bool starts_with_quote = FALSE;
  bool escape = FALSE;

  for(c = DIGEST_MAX_VALUE_LENGTH - 1; (*str && (*str != '=') && c--); )
    *value++ = *str++;
  *value=0;

  if('=' != *str++)
    /* eek, no match */
    return 1;

  if('\"' == *str) {
    /* this starts with a quote so it must end with one as well! */
    str++;
    starts_with_quote = TRUE;
  }

  for(c = DIGEST_MAX_CONTENT_LENGTH - 1; *str && c--; str++) {
    switch(*str) {
    case '\\':
      if(!escape) {
        /* possibly the start of an escaped quote */
        escape = TRUE;
        *content++ = '\\'; /* even though this is an escape character, we still
                              store it as-is in the target buffer */
        continue;
      }
      break;
    case ',':
      if(!starts_with_quote) {
        /* this signals the end of the content if we didn't get a starting
           quote and then we do "sloppy" parsing */
        c=0; /* the end */
        continue;
      }
      break;
    case '\r':
    case '\n':
      /* end of string */
      c=0;
      continue;
    case '\"':
      if(!escape && starts_with_quote) {
        /* end of string */
        c=0;
        continue;
      }
      break;
    }
    escape = FALSE;
    *content++ = *str;
  }
  *content=0;

  *endptr = str;

  return 0; /* all is fine! */
}

/* Convert md5 chunk to RFC2617 (section 3.1.3) -suitable ascii string*/
static void sasl_digest_md5_to_ascii(unsigned char *source, /* 16 bytes */
                                     unsigned char *dest) /* 33 bytes */
{
  int i;
  for(i = 0; i < 16; i++)
    snprintf((char *)&dest[i*2], 3, "%02x", source[i]);
}

/* Perform quoted-string escaping as described in RFC2616 and its errata */
static char *sasl_digest_string_quoted(const char *source)
{
  char *dest, *d;
  const char *s = source;
  size_t n = 1; /* null terminator */

  /* Calculate size needed */
  while(*s) {
    ++n;
    if(*s == '"' || *s == '\\') {
      ++n;
    }
    ++s;
  }

  dest = malloc(n);
  if(dest) {
    s = source;
    d = dest;
    while(*s) {
      if(*s == '"' || *s == '\\') {
        *d++ = '\\';
      }
      *d++ = *s++;
    }
    *d = 0;
  }

  return dest;
}

#if !defined(USE_WINDOWS_SSPI)
/* Retrieves the value for a corresponding key from the challenge string
 * returns TRUE if the key could be found, FALSE if it does not exists
 */
static bool sasl_digest_get_key_value(const char *chlg,
                                      const char *key,
                                      char *value,
                                      size_t max_val_len,
                                      char end_char)
{
  char *find_pos;
  size_t i;

  find_pos = strstr(chlg, key);
  if(!find_pos)
    return FALSE;

  find_pos += strlen(key);

  for(i = 0; *find_pos && *find_pos != end_char && i < max_val_len - 1; ++i)
    value[i] = *find_pos++;
  value[i] = '\0';

  return TRUE;
}

static CURLcode sasl_digest_get_qop_values(const char *options, int *value)
{
  char *tmp;
  char *token;
  char *tok_buf;

  /* Initialise the output */
  *value = 0;

  /* Tokenise the list of qop values. Use a temporary clone of the buffer since
     strtok_r() ruins it. */
  tmp = strdup(options);
  if(!tmp)
    return CURLE_OUT_OF_MEMORY;

  token = strtok_r(tmp, ",", &tok_buf);
  while(token != NULL) {
    if(Curl_raw_equal(token, DIGEST_QOP_VALUE_STRING_AUTH))
      *value |= DIGEST_QOP_VALUE_AUTH;
    else if(Curl_raw_equal(token, DIGEST_QOP_VALUE_STRING_AUTH_INT))
      *value |= DIGEST_QOP_VALUE_AUTH_INT;
    else if(Curl_raw_equal(token, DIGEST_QOP_VALUE_STRING_AUTH_CONF))
      *value |= DIGEST_QOP_VALUE_AUTH_CONF;

    token = strtok_r(NULL, ",", &tok_buf);
  }

  Curl_safefree(tmp);

  return CURLE_OK;
}
#endif /* !USE_WINDOWS_SSPI */

#endif /* !CURL_DISABLE_CRYPTO_AUTH */

#if !defined(USE_WINDOWS_SSPI)
/*
 * Curl_sasl_build_spn()
 *
 * This is used to build a SPN string in the format service/host.
 *
 * Parameters:
 *
 * serivce  [in] - The service type such as www, smtp, pop or imap.
 * instance [in] - The instance name such as the host nme or realm.
 *
 * Returns a pointer to the newly allocated SPN.
 */
char *Curl_sasl_build_spn(const char *service, const char *host)
{
  /* Generate and return our SPN */
  return aprintf("%s/%s", service, host);
}
#endif

/*
 * Curl_sasl_create_plain_message()
 *
 * This is used to generate an already encoded PLAIN message ready
 * for sending to the recipient.
 *
 * Parameters:
 *
 * data    [in]     - The session handle.
 * userp   [in]     - The user name.
 * passdwp [in]     - The user's password.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_create_plain_message(struct SessionHandle *data,
                                        const char *userp,
                                        const char *passwdp,
                                        char **outptr, size_t *outlen)
{
  CURLcode result;
  char *plainauth;
  size_t ulen;
  size_t plen;

  ulen = strlen(userp);
  plen = strlen(passwdp);

  plainauth = malloc(2 * ulen + plen + 2);
  if(!plainauth) {
    *outlen = 0;
    *outptr = NULL;
    return CURLE_OUT_OF_MEMORY;
  }

  /* Calculate the reply */
  memcpy(plainauth, userp, ulen);
  plainauth[ulen] = '\0';
  memcpy(plainauth + ulen + 1, userp, ulen);
  plainauth[2 * ulen + 1] = '\0';
  memcpy(plainauth + 2 * ulen + 2, passwdp, plen);

  /* Base64 encode the reply */
  result = Curl_base64_encode(data, plainauth, 2 * ulen + plen + 2, outptr,
                              outlen);
  Curl_safefree(plainauth);
  return result;
}

/*
 * Curl_sasl_create_login_message()
 *
 * This is used to generate an already encoded LOGIN message containing the
 * user name or password ready for sending to the recipient.
 *
 * Parameters:
 *
 * data    [in]     - The session handle.
 * valuep  [in]     - The user name or user's password.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_create_login_message(struct SessionHandle *data,
                                        const char *valuep, char **outptr,
                                        size_t *outlen)
{
  size_t vlen = strlen(valuep);

  if(!vlen) {
    /* Calculate an empty reply */
    *outptr = strdup("=");
    if(*outptr) {
      *outlen = (size_t) 1;
      return CURLE_OK;
    }

    *outlen = 0;
    return CURLE_OUT_OF_MEMORY;
  }

  /* Base64 encode the value */
  return Curl_base64_encode(data, valuep, vlen, outptr, outlen);
}

#ifndef CURL_DISABLE_CRYPTO_AUTH
 /*
 * Curl_sasl_decode_cram_md5_message()
 *
 * This is used to decode an already encoded CRAM-MD5 challenge message.
 *
 * Parameters:
 *
 * chlg64  [in]     - Pointer to the base64 encoded challenge message.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_decode_cram_md5_message(const char *chlg64, char **outptr,
                                           size_t *outlen)
{
  CURLcode result = CURLE_OK;
  size_t chlg64len = strlen(chlg64);

  *outptr = NULL;
  *outlen = 0;

  /* Decode the challenge if necessary */
  if(chlg64len && *chlg64 != '=')
    result = Curl_base64_decode(chlg64, (unsigned char **) outptr, outlen);

    return result;
 }

 /*
 * Curl_sasl_create_cram_md5_message()
 *
 * This is used to generate an already encoded CRAM-MD5 response message ready
 * for sending to the recipient.
 *
 * Parameters:
 *
 * data    [in]     - The session handle.
 * chlg    [in]     - The challenge.
 * userp   [in]     - The user name.
 * passdwp [in]     - The user's password.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_create_cram_md5_message(struct SessionHandle *data,
                                           const char *chlg,
                                           const char *userp,
                                           const char *passwdp,
                                           char **outptr, size_t *outlen)
{
  CURLcode result = CURLE_OK;
  size_t chlglen = 0;
  HMAC_context *ctxt;
  unsigned char digest[MD5_DIGEST_LEN];
  char *response;

  if(chlg)
    chlglen = strlen(chlg);

  /* Compute the digest using the password as the key */
  ctxt = Curl_HMAC_init(Curl_HMAC_MD5,
                        (const unsigned char *) passwdp,
                        curlx_uztoui(strlen(passwdp)));
  if(!ctxt)
    return CURLE_OUT_OF_MEMORY;

  /* Update the digest with the given challenge */
  if(chlglen > 0)
    Curl_HMAC_update(ctxt, (const unsigned char *) chlg,
                     curlx_uztoui(chlglen));

  /* Finalise the digest */
  Curl_HMAC_final(ctxt, digest);

  /* Generate the response */
  response = aprintf(
      "%s %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
           userp, digest[0], digest[1], digest[2], digest[3], digest[4],
           digest[5], digest[6], digest[7], digest[8], digest[9], digest[10],
           digest[11], digest[12], digest[13], digest[14], digest[15]);
  if(!response)
    return CURLE_OUT_OF_MEMORY;

  /* Base64 encode the response */
  result = Curl_base64_encode(data, response, 0, outptr, outlen);

  Curl_safefree(response);

  return result;
}

#ifndef USE_WINDOWS_SSPI
/*
 * sasl_decode_digest_md5_message()
 *
 * This is used internally to decode an already encoded DIGEST-MD5 challenge
 * message into the seperate attributes.
 *
 * Parameters:
 *
 * chlg64  [in]     - Pointer to the base64 encoded challenge message.
 * nonce   [in/out] - The buffer where the nonce will be stored.
 * nlen    [in]     - The length of the nonce buffer.
 * realm   [in/out] - The buffer where the realm will be stored.
 * rlen    [in]     - The length of the realm buffer.
 * alg     [in/out] - The buffer where the algorithm will be stored.
 * alen    [in]     - The length of the algorithm buffer.
 * qop     [in/out] - The buffer where the qop-options will be stored.
 * qlen    [in]     - The length of the qop buffer.
 *
 * Returns CURLE_OK on success.
 */
static CURLcode sasl_decode_digest_md5_message(const char *chlg64,
                                               char *nonce, size_t nlen,
                                               char *realm, size_t rlen,
                                               char *alg, size_t alen,
                                               char *qop, size_t qlen)
{
  CURLcode result = CURLE_OK;
  unsigned char *chlg = NULL;
  size_t chlglen = 0;
  size_t chlg64len = strlen(chlg64);

  /* Decode the base-64 encoded challenge message */
  if(chlg64len && *chlg64 != '=') {
    result = Curl_base64_decode(chlg64, &chlg, &chlglen);
    if(result)
      return result;
  }

  /* Ensure we have a valid challenge message */
  if(!chlg)
    return CURLE_BAD_CONTENT_ENCODING;

  /* Retrieve nonce string from the challenge */
  if(!sasl_digest_get_key_value((char *)chlg, "nonce=\"", nonce, nlen, '\"')) {
    Curl_safefree(chlg);
    return CURLE_BAD_CONTENT_ENCODING;
  }

  /* Retrieve realm string from the challenge */
  if(!sasl_digest_get_key_value((char *)chlg, "realm=\"", realm, rlen, '\"')) {
    /* Challenge does not have a realm, set empty string [RFC2831] page 6 */
    strcpy(realm, "");
  }

  /* Retrieve algorithm string from the challenge */
  if(!sasl_digest_get_key_value((char *)chlg, "algorithm=", alg, alen, ',')) {
    Curl_safefree(chlg);
    return CURLE_BAD_CONTENT_ENCODING;
  }

  /* Retrieve qop-options string from the challenge */
  if(!sasl_digest_get_key_value((char *)chlg, "qop=\"", qop, qlen, '\"')) {
    Curl_safefree(chlg);
    return CURLE_BAD_CONTENT_ENCODING;
  }

  Curl_safefree(chlg);

  return CURLE_OK;
}

/*
 * Curl_sasl_create_digest_md5_message()
 *
 * This is used to generate an already encoded DIGEST-MD5 response message
 * ready for sending to the recipient.
 *
 * Parameters:
 *
 * data    [in]     - The session handle.
 * chlg64  [in]     - Pointer to the base64 encoded challenge message.
 * userp   [in]     - The user name.
 * passdwp [in]     - The user's password.
 * service [in]     - The service type such as www, smtp, pop or imap.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
                                             const char *chlg64,
                                             const char *userp,
                                             const char *passwdp,
                                             const char *service,
                                             char **outptr, size_t *outlen)
{
  CURLcode result = CURLE_OK;
  size_t i;
  MD5_context *ctxt;
  char *response = NULL;
  unsigned char digest[MD5_DIGEST_LEN];
  char HA1_hex[2 * MD5_DIGEST_LEN + 1];
  char HA2_hex[2 * MD5_DIGEST_LEN + 1];
  char resp_hash_hex[2 * MD5_DIGEST_LEN + 1];
  char nonce[64];
  char realm[128];
  char algorithm[64];
  char qop_options[64];
  int qop_values;
  char cnonce[33];
  unsigned int entropy[4];
  char nonceCount[] = "00000001";
  char method[]     = "AUTHENTICATE";
  char qop[]        = DIGEST_QOP_VALUE_STRING_AUTH;
  char *spn         = NULL;

  /* Decode the challange message */
  result = sasl_decode_digest_md5_message(chlg64, nonce, sizeof(nonce),
                                          realm, sizeof(realm),
                                          algorithm, sizeof(algorithm),
                                          qop_options, sizeof(qop_options));
  if(result)
    return result;

  /* We only support md5 sessions */
  if(strcmp(algorithm, "md5-sess") != 0)
    return CURLE_BAD_CONTENT_ENCODING;

  /* Get the qop-values from the qop-options */
  result = sasl_digest_get_qop_values(qop_options, &qop_values);
  if(result)
    return result;

  /* We only support auth quality-of-protection */
  if(!(qop_values & DIGEST_QOP_VALUE_AUTH))
    return CURLE_BAD_CONTENT_ENCODING;

  /* Generate 16 bytes of random data */
  entropy[0] = Curl_rand(data);
  entropy[1] = Curl_rand(data);
  entropy[2] = Curl_rand(data);
  entropy[3] = Curl_rand(data);

  /* Convert the random data into a 32 byte hex string */
  snprintf(cnonce, sizeof(cnonce), "%08x%08x%08x%08x",
           entropy[0], entropy[1], entropy[2], entropy[3]);

  /* So far so good, now calculate A1 and H(A1) according to RFC 2831 */
  ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
  if(!ctxt)
    return CURLE_OUT_OF_MEMORY;

  Curl_MD5_update(ctxt, (const unsigned char *) userp,
                  curlx_uztoui(strlen(userp)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) realm,
                  curlx_uztoui(strlen(realm)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) passwdp,
                  curlx_uztoui(strlen(passwdp)));
  Curl_MD5_final(ctxt, digest);

  ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
  if(!ctxt)
    return CURLE_OUT_OF_MEMORY;

  Curl_MD5_update(ctxt, (const unsigned char *) digest, MD5_DIGEST_LEN);
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) nonce,
                  curlx_uztoui(strlen(nonce)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) cnonce,
                  curlx_uztoui(strlen(cnonce)));
  Curl_MD5_final(ctxt, digest);

  /* Convert calculated 16 octet hex into 32 bytes string */
  for(i = 0; i < MD5_DIGEST_LEN; i++)
    snprintf(&HA1_hex[2 * i], 3, "%02x", digest[i]);

  /* Generate our SPN */
  spn = Curl_sasl_build_spn(service, realm);
  if(!spn)
    return CURLE_OUT_OF_MEMORY;

  /* Calculate H(A2) */
  ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
  if(!ctxt) {
    Curl_safefree(spn);

    return CURLE_OUT_OF_MEMORY;
  }

  Curl_MD5_update(ctxt, (const unsigned char *) method,
                  curlx_uztoui(strlen(method)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) spn,
                  curlx_uztoui(strlen(spn)));
  Curl_MD5_final(ctxt, digest);

  for(i = 0; i < MD5_DIGEST_LEN; i++)
    snprintf(&HA2_hex[2 * i], 3, "%02x", digest[i]);

  /* Now calculate the response hash */
  ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
  if(!ctxt) {
    Curl_safefree(spn);

    return CURLE_OUT_OF_MEMORY;
  }

  Curl_MD5_update(ctxt, (const unsigned char *) HA1_hex, 2 * MD5_DIGEST_LEN);
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) nonce,
                  curlx_uztoui(strlen(nonce)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);

  Curl_MD5_update(ctxt, (const unsigned char *) nonceCount,
                  curlx_uztoui(strlen(nonceCount)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) cnonce,
                  curlx_uztoui(strlen(cnonce)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);
  Curl_MD5_update(ctxt, (const unsigned char *) qop,
                  curlx_uztoui(strlen(qop)));
  Curl_MD5_update(ctxt, (const unsigned char *) ":", 1);

  Curl_MD5_update(ctxt, (const unsigned char *) HA2_hex, 2 * MD5_DIGEST_LEN);
  Curl_MD5_final(ctxt, digest);

  for(i = 0; i < MD5_DIGEST_LEN; i++)
    snprintf(&resp_hash_hex[2 * i], 3, "%02x", digest[i]);

  /* Generate the response */
  response = aprintf("username=\"%s\",realm=\"%s\",nonce=\"%s\","
                     "cnonce=\"%s\",nc=\"%s\",digest-uri=\"%s\",response=%s,"
                     "qop=%s",
                     userp, realm, nonce,
                     cnonce, nonceCount, spn, resp_hash_hex, qop);
  Curl_safefree(spn);
  if(!response)
    return CURLE_OUT_OF_MEMORY;

  /* Base64 encode the response */
  result = Curl_base64_encode(data, response, 0, outptr, outlen);

  Curl_safefree(response);

  return result;
}

/*
 * Curl_sasl_decode_digest_http_message()
 *
 * This is used to decode a HTTP DIGEST challenge message into the seperate
 * attributes.
 *
 * Parameters:
 *
 * chlg    [in]     - Pointer to the challenge message.
 * digest  [in/out] - The digest data struct being used and modified.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_decode_digest_http_message(const char *chlg,
                                              struct digestdata *digest)
{
  bool before = FALSE; /* got a nonce before */
  bool foundAuth = FALSE;
  bool foundAuthInt = FALSE;
  char *token = NULL;
  char *tmp = NULL;

  /* If we already have received a nonce, keep that in mind */
  if(digest->nonce)
    before = TRUE;

  /* Clean up any former leftovers and initialise to defaults */
  Curl_sasl_digest_cleanup(digest);

  for(;;) {
    char value[DIGEST_MAX_VALUE_LENGTH];
    char content[DIGEST_MAX_CONTENT_LENGTH];

    /* Pass all additional spaces here */
    while(*chlg && ISSPACE(*chlg))
      chlg++;

    /* Extract a value=content pair */
    if(!sasl_digest_get_pair(chlg, value, content, &chlg)) {
      if(Curl_raw_equal(value, "nonce")) {
        digest->nonce = strdup(content);
        if(!digest->nonce)
          return CURLE_OUT_OF_MEMORY;
      }
      else if(Curl_raw_equal(value, "stale")) {
        if(Curl_raw_equal(content, "true")) {
          digest->stale = TRUE;
          digest->nc = 1; /* we make a new nonce now */
        }
      }
      else if(Curl_raw_equal(value, "realm")) {
        digest->realm = strdup(content);
        if(!digest->realm)
          return CURLE_OUT_OF_MEMORY;
      }
      else if(Curl_raw_equal(value, "opaque")) {
        digest->opaque = strdup(content);
        if(!digest->opaque)
          return CURLE_OUT_OF_MEMORY;
      }
      else if(Curl_raw_equal(value, "qop")) {
        char *tok_buf;
        /* Tokenize the list and choose auth if possible, use a temporary
            clone of the buffer since strtok_r() ruins it */
        tmp = strdup(content);
        if(!tmp)
          return CURLE_OUT_OF_MEMORY;

        token = strtok_r(tmp, ",", &tok_buf);
        while(token != NULL) {
          if(Curl_raw_equal(token, DIGEST_QOP_VALUE_STRING_AUTH)) {
            foundAuth = TRUE;
          }
          else if(Curl_raw_equal(token, DIGEST_QOP_VALUE_STRING_AUTH_INT)) {
            foundAuthInt = TRUE;
          }
          token = strtok_r(NULL, ",", &tok_buf);
        }

        free(tmp);

        /* Select only auth o auth-int. Otherwise, ignore */
        if(foundAuth) {
          digest->qop = strdup(DIGEST_QOP_VALUE_STRING_AUTH);
          if(!digest->qop)
            return CURLE_OUT_OF_MEMORY;
        }
        else if(foundAuthInt) {
          digest->qop = strdup(DIGEST_QOP_VALUE_STRING_AUTH_INT);
          if(!digest->qop)
            return CURLE_OUT_OF_MEMORY;
        }
      }
      else if(Curl_raw_equal(value, "algorithm")) {
        digest->algorithm = strdup(content);
        if(!digest->algorithm)
          return CURLE_OUT_OF_MEMORY;

        if(Curl_raw_equal(content, "MD5-sess"))
          digest->algo = CURLDIGESTALGO_MD5SESS;
        else if(Curl_raw_equal(content, "MD5"))
          digest->algo = CURLDIGESTALGO_MD5;
        else
          return CURLE_BAD_CONTENT_ENCODING;
      }
      else {
        /* unknown specifier, ignore it! */
      }
    }
    else
      break; /* we're done here */

    /* Pass all additional spaces here */
    while(*chlg && ISSPACE(*chlg))
      chlg++;

    /* Allow the list to be comma-separated */
    if(',' == *chlg)
      chlg++;
  }

  /* We had a nonce since before, and we got another one now without
     'stale=true'. This means we provided bad credentials in the previous
     request */
  if(before && !digest->stale)
    return CURLE_BAD_CONTENT_ENCODING;

  /* We got this header without a nonce, that's a bad Digest line! */
  if(!digest->nonce)
    return CURLE_BAD_CONTENT_ENCODING;

  return CURLE_OK;
}

/*
 * Curl_sasl_create_digest_http_message()
 *
 * This is used to generate a HTTP DIGEST response message ready for sending
 * to the recipient.
 *
 * Parameters:
 *
 * data    [in]     - The session handle.
 * userp   [in]     - The user name.
 * passdwp [in]     - The user's password.
 * request [in]     - The HTTP request.
 * uripath [in]     - The path of the HTTP uri.
 * digest  [in/out] - The digest data struct being used and modified.
 * outptr  [in/out] - The address where a pointer to newly allocated memory
 *                    holding the result will be stored upon completion.
 * outlen  [out]    - The length of the output message.
 *
 * Returns CURLE_OK on success.
 */
CURLcode Curl_sasl_create_digest_http_message(struct SessionHandle *data,
                                              const char *userp,
                                              const char *passwdp,
                                              const unsigned char *request,
                                              const unsigned char *uripath,
                                              struct digestdata *digest,
                                              char **outptr, size_t *outlen)
{
  CURLcode result;
  unsigned char md5buf[16]; /* 16 bytes/128 bits */
  unsigned char request_digest[33];
  unsigned char *md5this;
  unsigned char ha1[33];/* 32 digits and 1 zero byte */
  unsigned char ha2[33];/* 32 digits and 1 zero byte */
  char cnoncebuf[33];
  char *cnonce = NULL;
  size_t cnonce_sz = 0;
  char *userp_quoted;
  char *response = NULL;
  char *tmp = NULL;

  if(!digest->nc)
    digest->nc = 1;

  if(!digest->cnonce) {
    snprintf(cnoncebuf, sizeof(cnoncebuf), "%08x%08x%08x%08x",
             Curl_rand(data), Curl_rand(data),
             Curl_rand(data), Curl_rand(data));

    result = Curl_base64_encode(data, cnoncebuf, strlen(cnoncebuf),
                                &cnonce, &cnonce_sz);
    if(result)
      return result;

    digest->cnonce = cnonce;
  }

  /*
    if the algorithm is "MD5" or unspecified (which then defaults to MD5):

    A1 = unq(username-value) ":" unq(realm-value) ":" passwd

    if the algorithm is "MD5-sess" then:

    A1 = H( unq(username-value) ":" unq(realm-value) ":" passwd )
         ":" unq(nonce-value) ":" unq(cnonce-value)
  */

  md5this = (unsigned char *)
    aprintf("%s:%s:%s", userp, digest->realm, passwdp);
  if(!md5this)
    return CURLE_OUT_OF_MEMORY;

  CURL_OUTPUT_DIGEST_CONV(data, md5this); /* convert on non-ASCII machines */
  Curl_md5it(md5buf, md5this);
  Curl_safefree(md5this);
  sasl_digest_md5_to_ascii(md5buf, ha1);

  if(digest->algo == CURLDIGESTALGO_MD5SESS) {
    /* nonce and cnonce are OUTSIDE the hash */
    tmp = aprintf("%s:%s:%s", ha1, digest->nonce, digest->cnonce);
    if(!tmp)
      return CURLE_OUT_OF_MEMORY;

    CURL_OUTPUT_DIGEST_CONV(data, tmp); /* convert on non-ASCII machines */
    Curl_md5it(md5buf, (unsigned char *)tmp);
    Curl_safefree(tmp);
    sasl_digest_md5_to_ascii(md5buf, ha1);
  }

  /*
    If the "qop" directive's value is "auth" or is unspecified, then A2 is:

      A2       = Method ":" digest-uri-value

          If the "qop" value is "auth-int", then A2 is:

      A2       = Method ":" digest-uri-value ":" H(entity-body)

    (The "Method" value is the HTTP request method as specified in section
    5.1.1 of RFC 2616)
  */

  md5this = (unsigned char *)aprintf("%s:%s", request, uripath);

  if(digest->qop && Curl_raw_equal(digest->qop, "auth-int")) {
    /* We don't support auth-int for PUT or POST at the moment.
       TODO: replace md5 of empty string with entity-body for PUT/POST */
    unsigned char *md5this2 = (unsigned char *)
      aprintf("%s:%s", md5this, "d41d8cd98f00b204e9800998ecf8427e");
    Curl_safefree(md5this);
    md5this = md5this2;
  }

  if(!md5this)
    return CURLE_OUT_OF_MEMORY;

  CURL_OUTPUT_DIGEST_CONV(data, md5this); /* convert on non-ASCII machines */
  Curl_md5it(md5buf, md5this);
  Curl_safefree(md5this);
  sasl_digest_md5_to_ascii(md5buf, ha2);

  if(digest->qop) {
    md5this = (unsigned char *)aprintf("%s:%s:%08x:%s:%s:%s",
                                       ha1,
                                       digest->nonce,
                                       digest->nc,
                                       digest->cnonce,
                                       digest->qop,
                                       ha2);
  }
  else {
    md5this = (unsigned char *)aprintf("%s:%s:%s",
                                       ha1,
                                       digest->nonce,
                                       ha2);
  }

  if(!md5this)
    return CURLE_OUT_OF_MEMORY;

  CURL_OUTPUT_DIGEST_CONV(data, md5this); /* convert on non-ASCII machines */
  Curl_md5it(md5buf, md5this);
  Curl_safefree(md5this);
  sasl_digest_md5_to_ascii(md5buf, request_digest);

  /* for test case 64 (snooped from a Mozilla 1.3a request)

    Authorization: Digest username="testuser", realm="testrealm", \
    nonce="1053604145", uri="/64", response="c55f7f30d83d774a3d2dcacf725abaca"

    Digest parameters are all quoted strings.  Username which is provided by