text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2013, 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.
   *
   ***************************************************************************/
  
  #include "curl_setup.h"
  
  #if defined(USE_QSOSSL) || defined(USE_GSKIT) || defined(USE_NSS)
  
  #include <curl/curl.h>
  #include "urldata.h"
  #include "strequal.h"
  #include "hostcheck.h"
  #include "vtls/vtls.h"
  #include "sendf.h"
  #include "inet_pton.h"
  #include "curl_base64.h"
  #include "x509asn1.h"
  
  #define _MPRINTF_REPLACE /* use our functions only */
  #include <curl/mprintf.h>
  
  #include "curl_memory.h"
  /* The last #include file should be: */
  #include "memdebug.h"
  
  
  /* ASN.1 OIDs. */
  static const char       cnOID[] = "2.5.4.3";    /* Common name. */
  static const char       sanOID[] = "2.5.29.17"; /* Subject alternative name. */
  
  static const curl_OID   OIDtable[] = {
    { "1.2.840.10040.4.1",        "dsa" },
    { "1.2.840.10040.4.3",        "dsa-with-sha1" },
    { "1.2.840.10045.2.1",        "ecPublicKey" },
    { "1.2.840.10045.3.0.1",      "c2pnb163v1" },
    { "1.2.840.10045.4.1",        "ecdsa-with-SHA1" },
    { "1.2.840.10046.2.1",        "dhpublicnumber" },
    { "1.2.840.113549.1.1.1",     "rsaEncryption" },
    { "1.2.840.113549.1.1.2",     "md2WithRSAEncryption" },
    { "1.2.840.113549.1.1.4",     "md5WithRSAEncryption" },
    { "1.2.840.113549.1.1.5",     "sha1WithRSAEncryption" },
    { "1.2.840.113549.1.1.10",    "RSASSA-PSS" },
    { "1.2.840.113549.1.1.14",    "sha224WithRSAEncryption" },
    { "1.2.840.113549.1.1.11",    "sha256WithRSAEncryption" },
    { "1.2.840.113549.1.1.12",    "sha384WithRSAEncryption" },
    { "1.2.840.113549.1.1.13",    "sha512WithRSAEncryption" },
    { "1.2.840.113549.2.2",       "md2" },
    { "1.2.840.113549.2.5",       "md5" },
    { "1.3.14.3.2.26",            "sha1" },
    { cnOID,                      "CN" },
    { "2.5.4.4",                  "SN" },
    { "2.5.4.5",                  "serialNumber" },
    { "2.5.4.6",                  "C" },
    { "2.5.4.7",                  "L" },
    { "2.5.4.8",                  "ST" },
    { "2.5.4.9",                  "streetAddress" },
    { "2.5.4.10",                 "O" },
    { "2.5.4.11",                 "OU" },
    { "2.5.4.12",                 "title" },
    { "2.5.4.13",                 "description" },
    { "2.5.4.17",                 "postalCode" },
    { "2.5.4.41",                 "name" },
    { "2.5.4.42",                 "givenName" },
    { "2.5.4.43",                 "initials" },
    { "2.5.4.44",                 "generationQualifier" },
    { "2.5.4.45",                 "X500UniqueIdentifier" },
    { "2.5.4.46",                 "dnQualifier" },
    { "2.5.4.65",                 "pseudonym" },
    { "1.2.840.113549.1.9.1",     "emailAddress" },
    { "2.5.4.72",                 "role" },
    { sanOID,                     "subjectAltName" },
    { "2.5.29.18",                "issuerAltName" },
    { "2.5.29.19",                "basicConstraints" },
    { "2.16.840.1.101.3.4.2.4",   "sha224" },
    { "2.16.840.1.101.3.4.2.1",   "sha256" },
    { "2.16.840.1.101.3.4.2.2",   "sha384" },
    { "2.16.840.1.101.3.4.2.3",   "sha512" },
    { (const char *) NULL,        (const char *) NULL }
  };
  
  /*
   * Lightweight ASN.1 parser.
   * In particular, it does not check for syntactic/lexical errors.
   * It is intended to support certificate information gathering for SSL backends
   * that offer a mean to get certificates as a whole, but do not supply
   * entry points to get particular certificate sub-fields.
   * Please note there is no pretention here to rewrite a full SSL library.
   */
  
  
  const char * Curl_getASN1Element(curl_asn1Element * elem,
                                   const char * beg, const char * end)
  {
    unsigned char b;
    unsigned long len;
    curl_asn1Element lelem;
  
    /* Get a single ASN.1 element into `elem', parse ASN.1 string at `beg'
       ending at `end'.
       Returns a pointer in source string after the parsed element, or NULL
       if an error occurs. */
  
    if(beg >= end || !*beg)
      return (const char *) NULL;
  
    /* Process header byte. */
    b = (unsigned char) *beg++;
    elem->constructed = (b & 0x20) != 0;
    elem->class = (b >> 6) & 3;
    b &= 0x1F;
    if(b == 0x1F)
      return (const char *) NULL; /* Long tag values not supported here. */
    elem->tag = b;
  
    /* Process length. */
    if(beg >= end)
      return (const char *) NULL;
    b = (unsigned char) *beg++;
    if(!(b & 0x80))
      len = b;
    else if(!(b &= 0x7F)) {
      /* Unspecified length. Since we have all the data, we can determine the
         effective length by skipping element until an end element is found. */
      if(!elem->constructed)
        return (const char *) NULL;
      elem->beg = beg;
      while(beg < end && *beg) {
        beg = Curl_getASN1Element(&lelem, beg, end);
        if(!beg)
          return (const char *) NULL;
      }
      if(beg >= end)
        return (const char *) NULL;
      elem->end = beg;
      return beg + 1;
    }
    else if(beg + b > end)
      return (const char *) NULL; /* Does not fit in source. */
    else {
      /* Get long length. */
      len = 0;
      do {
        if(len & 0xFF000000L)
          return (const char *) NULL;  /* Lengths > 32 bits are not supported. */
        len = (len << 8) | (unsigned char) *beg++;
      } while(--b);
    }
    if((unsigned long) (end - beg) < len)
      return (const char *) NULL;  /* Element data does not fit in source. */
    elem->beg = beg;
    elem->end = beg + len;
    return elem->end;
  }
  
  static const curl_OID * searchOID(const char * oid)
  {
    const curl_OID * op;
  
    /* Search the null terminated OID or OID identifier in local table.
       Return the table entry pointer or NULL if not found. */
  
    for(op = OIDtable; op->numoid; op++)
      if(!strcmp(op->numoid, oid) || curl_strequal(op->textoid, oid))
        return op;
  
    return (const curl_OID *) NULL;
  }
  
  static const char * bool2str(const char * beg, const char * end)
  {
    /* Convert an ASN.1 Boolean value into its string representation.
       Return the dynamically allocated string, or NULL if source is not an
       ASN.1 Boolean value. */
  
    if(end - beg != 1)
      return (const char *) NULL;
    return strdup(*beg? "TRUE": "FALSE");
  }
  
  static const char * octet2str(const char * beg, const char * end)
  {
    size_t n = end - beg;
    char * buf;
  
    /* Convert an ASN.1 octet string to a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    buf = malloc(3 * n + 1);
    if(buf)
      for(n = 0; beg < end; n += 3)
        snprintf(buf + n, 4, "%02x:", *(const unsigned char *) beg++);
    return buf;
  }
  
  static const char * bit2str(const char * beg, const char * end)
  
  {
    /* Convert an ASN.1 bit string to a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    if(++beg > end)
      return (const char *) NULL;
    return octet2str(beg, end);
  }
  
  static const char * int2str(const char * beg, const char * end)
  {
    long val = 0;
    size_t n = end - beg;
  
    /* Convert an ASN.1 integer value into its string representation.
       Return the dynamically allocated string, or NULL if source is not an
       ASN.1 integer value. */
  
    if(!n)
      return (const char *) NULL;
  
    if(n > 4)
      return octet2str(beg, end);
  
    /* Represent integers <= 32-bit as a single value. */
    if(*beg & 0x80)
      val = ~val;
  
    do
      val = (val << 8) | *(const unsigned char *) beg++;
    while(beg < end);
    return curl_maprintf("%s%lx", (val < 0 || val >= 10)? "0x": "", val);
  }
  
  static ssize_t
  utf8asn1str(char * * to, int type, const char * from, const char * end)
  {
    size_t inlength = end - from;
    int size = 1;
    size_t outlength;
    int charsize;
    unsigned int wc;
    char * buf;
  
    /* Perform a lazy conversion from an ASN.1 typed string to UTF8. Allocate the
       destination buffer dynamically. The allocation size will normally be too
       large: this is to avoid buffer overflows.
       Terminate the string with a nul byte and return the converted
       string length. */
  
    *to = (char *) NULL;
    switch (type) {
    case CURL_ASN1_BMP_STRING:
      size = 2;
      break;
    case CURL_ASN1_UNIVERSAL_STRING:
      size = 4;
      break;
    case CURL_ASN1_NUMERIC_STRING:
    case CURL_ASN1_PRINTABLE_STRING:
    case CURL_ASN1_TELETEX_STRING:
    case CURL_ASN1_IA5_STRING:
    case CURL_ASN1_VISIBLE_STRING:
    case CURL_ASN1_UTF8_STRING:
      break;
    default:
      return -1;  /* Conversion not supported. */
    }
  
    if(inlength % size)
      return -1;  /* Length inconsistent with character size. */
    buf = malloc(4 * (inlength / size) + 1);
    if(!buf)
      return -1;  /* Not enough memory. */
  
    if(type == CURL_ASN1_UTF8_STRING) {
      /* Just copy. */
      outlength = inlength;
      if(outlength)
        memcpy(buf, from, outlength);
    }
    else {
      for(outlength = 0; from < end;) {
        wc = 0;
        switch (size) {
        case 4:
          wc = (wc << 8) | *(const unsigned char *) from++;
          wc = (wc << 8) | *(const unsigned char *) from++;
        case 2:
          wc = (wc << 8) | *(const unsigned char *) from++;
        default: /* case 1: */
          wc = (wc << 8) | *(const unsigned char *) from++;
        }
        charsize = 1;
        if(wc >= 0x00000080) {
          if(wc >= 0x00000800) {
            if(wc >= 0x00010000) {
              if(wc >= 0x00200000) {
                free(buf);
                return -1;        /* Invalid char. size for target encoding. */
              }
              buf[outlength + 3] = (char) (0x80 | (wc & 0x3F));
              wc = (wc >> 6) | 0x00010000;
              charsize++;
            }
            buf[outlength + 2] = (char) (0x80 | (wc & 0x3F));
            wc = (wc >> 6) | 0x00000800;
            charsize++;
          }
          buf[outlength + 1] = (char) (0x80 | (wc & 0x3F));
          wc = (wc >> 6) | 0x000000C0;
          charsize++;
        }
        buf[outlength] = (char) wc;
        outlength += charsize;
      }
    }
    buf[outlength] = '\0';
    *to = buf;
    return outlength;
  }
  
  static const char * string2str(int type, const char * beg, const char * end)
  {
    char * buf;
  
    /* Convert an ASN.1 String into its UTF-8 string representation.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    if(utf8asn1str(&buf, type, beg, end) < 0)
      return (const char *) NULL;
    return buf;
  }
  
  static int encodeUint(char * buf, int n, unsigned int x)
  {
    int i = 0;
    unsigned int y = x / 10;
  
    /* Decimal ASCII encode unsigned integer `x' in the `n'-byte buffer at `buf'.
       Return the total number of encoded digits, even if larger than `n'. */
  
    if(y) {
      i += encodeUint(buf, n, y);
      x -= y * 10;
    }
    if(i < n)
      buf[i] = (char) ('0' + x);
    i++;
    if(i < n)
      buf[i] = '\0';      /* Store a terminator if possible. */
    return i;
  }
  
  static int encodeOID(char * buf, int n, const char * beg, const char * end)
  {
    int i = 0;
    unsigned int x;
    unsigned int y;
  
    /* Convert an ASN.1 OID into its dotted string representation.
       Store the result in th `n'-byte buffer at `buf'.
       Return the converted string length, or -1 if an error occurs. */
  
    /* Process the first two numbers. */
    y = *(const unsigned char *) beg++;
    x = y / 40;
    y -= x * 40;
    i += encodeUint(buf + i, n - i, x);
    if(i < n)
      buf[i] = '.';
    i++;
    i += encodeUint(buf + i, n - i, y);
  
    /* Process the trailing numbers. */
    while(beg < end) {
      if(i < n)
        buf[i] = '.';
      i++;
      x = 0;
      do {
        if(x & 0xFF000000)
          return -1;
        y = *(const unsigned char *) beg++;
        x = (x << 7) | (y & 0x7F);
      } while(y & 0x80);
      i += encodeUint(buf + i, n - i, x);
    }
    if(i < n)
      buf[i] = '\0';
    return i;
  }
  
  static const char * OID2str(const char * beg, const char * end, bool symbolic)
  {
    char * buf = (char *) NULL;
    const curl_OID * op;
    int n;
  
    /* Convert an ASN.1 OID into its dotted or symbolic string representation.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    if(beg < end) {
      n = encodeOID((char *) NULL, -1, beg, end);
      if(n >= 0) {
        buf = malloc(n + 1);
        if(buf) {
          encodeOID(buf, n, beg, end);
          buf[n] = '\0';
  
          if(symbolic) {
            op = searchOID(buf);
            if(op) {
              free(buf);
              buf = strdup(op->textoid);
            }
          }
        }
      }
    }
    return buf;
  }
  
  static const char * GTime2str(const char * beg, const char * end)
  {
    const char * tzp;
    const char * fracp;
    char sec1, sec2;
    size_t fracl;
    size_t tzl;
    const char * sep = "";
  
    /* Convert an ASN.1 Generalized time to a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    for(fracp = beg; fracp < end && *fracp >= '0' && *fracp <= '9'; fracp++)
      ;
  
    /* Get seconds digits. */
    sec1 = '0';
    switch (fracp - beg - 12) {
    case 0:
      sec2 = '0';
      break;
    case 2:
      sec1 = fracp[-2];
    case 1:
      sec2 = fracp[-1];
      break;
    default:
      return (const char *) NULL;
    }
  
    /* Scan for timezone, measure fractional seconds. */
    tzp = fracp;
    fracl = 0;
    if(fracp < end && (*fracp == '.' || *fracp == ',')) {
      fracp++;
      do
        tzp++;
      while(tzp < end && *tzp >= '0' && *tzp <= '9');
      /* Strip leading zeroes in fractional seconds. */
      for(fracl = tzp - fracp - 1; fracl && fracp[fracl - 1] == '0'; fracl--)
        ;
    }
  
    /* Process timezone. */
    if(tzp >= end)
      ;           /* Nothing to do. */
    else if(*tzp == 'Z') {
      tzp = " GMT";
      end = tzp + 4;
    }
    else {
      sep = " ";
      tzp++;
    }
  
    tzl = end - tzp;
    return curl_maprintf("%.4s-%.2s-%.2s %.2s:%.2s:%c%c%s%.*s%s%.*s",
                         beg, beg + 4, beg + 6,
                         beg + 8, beg + 10, sec1, sec2,
                         fracl? ".": "", fracl, fracp,
                         sep, tzl, tzp);
  }
  
  static const char * UTime2str(const char * beg, const char * end)
  {
    const char * tzp;
    size_t tzl;
    const char * sec;
  
    /* Convert an ASN.1 UTC time to a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    for(tzp = beg; tzp < end && *tzp >= '0' && *tzp <= '9'; tzp++)
      ;
    /* Get the seconds. */
    sec = beg + 10;
    switch (tzp - sec) {
    case 0:
      sec = "00";
    case 2:
      break;
    default:
      return (const char *) NULL;
    }
  
    /* Process timezone. */
    if(tzp >= end)
      return (const char *) NULL;
    if(*tzp == 'Z') {
      tzp = "GMT";
      end = tzp + 3;
    }
    else
      tzp++;
  
    tzl = end - tzp;
    return curl_maprintf("%u%.2s-%.2s-%.2s %.2s:%.2s:%.2s %.*s",
                         20 - (*beg >= '5'), beg, beg + 2, beg + 4,
                         beg + 6, beg + 8, sec,
                         tzl, tzp);
  }
  
  const char * Curl_ASN1tostr(curl_asn1Element * elem, int type)
  {
    static const char zero = '\0';
  
    /* Convert an ASN.1 element to a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    if(elem->constructed)
      return (const char *) NULL; /* No conversion of structured elements. */
  
    if(!type)
      type = elem->tag;   /* Type not forced: use element tag as type. */
  
    switch (type) {
    case CURL_ASN1_BOOLEAN:
      return bool2str(elem->beg, elem->end);
    case CURL_ASN1_INTEGER:
    case CURL_ASN1_ENUMERATED:
      return int2str(elem->beg, elem->end);
    case CURL_ASN1_BIT_STRING:
      return bit2str(elem->beg, elem->end);
    case CURL_ASN1_OCTET_STRING:
      return octet2str(elem->beg, elem->end);
    case CURL_ASN1_NULL:
      return strdup(&zero);
    case CURL_ASN1_OBJECT_IDENTIFIER:
      return OID2str(elem->beg, elem->end, TRUE);
    case CURL_ASN1_UTC_TIME:
      return UTime2str(elem->beg, elem->end);
    case CURL_ASN1_GENERALIZED_TIME:
      return GTime2str(elem->beg, elem->end);
    case CURL_ASN1_UTF8_STRING:
    case CURL_ASN1_NUMERIC_STRING:
    case CURL_ASN1_PRINTABLE_STRING:
    case CURL_ASN1_TELETEX_STRING:
    case CURL_ASN1_IA5_STRING:
    case CURL_ASN1_VISIBLE_STRING:
    case CURL_ASN1_UNIVERSAL_STRING:
    case CURL_ASN1_BMP_STRING:
      return string2str(type, elem->beg, elem->end);
    }
  
    return (const char *) NULL;   /* Unsupported. */
  }
  
  static ssize_t encodeDN(char * buf, size_t n, curl_asn1Element * dn)
  {
    curl_asn1Element rdn;
    curl_asn1Element atv;
    curl_asn1Element oid;
    curl_asn1Element value;
    size_t l = 0;
    const char * p1;
    const char * p2;
    const char * p3;
    const char * str;
  
    /* ASCII encode distinguished name at `dn' into the `n'-byte buffer at `buf'.
       Return the total string length, even if larger than `n'. */
  
    for(p1 = dn->beg; p1 < dn->end;) {
      p1 = Curl_getASN1Element(&rdn, p1, dn->end);
      for(p2 = rdn.beg; p2 < rdn.end;) {
        p2 = Curl_getASN1Element(&atv, p2, rdn.end);
        p3 = Curl_getASN1Element(&oid, atv.beg, atv.end);
        Curl_getASN1Element(&value, p3, atv.end);
        str = Curl_ASN1tostr(&oid, 0);
        if(!str)
          return -1;
  
        /* Encode delimiter.
           If attribute has a short uppercase name, delimiter is ", ". */
        if(l) {
          for(p3 = str; isupper(*p3); p3++)
            ;
          for(p3 = (*p3 || p3 - str > 2)? "/": ", "; *p3; p3++) {
            if(l < n)
              buf[l] = *p3;
            l++;
          }
        }
  
        /* Encode attribute name. */
        for(p3 = str; *p3; p3++) {
          if(l < n)
            buf[l] = *p3;
          l++;
        }
        free((char *) str);
  
        /* Generate equal sign. */
        if(l < n)
          buf[l] = '=';
        l++;
  
        /* Generate value. */
        str = Curl_ASN1tostr(&value, 0);
        if(!str)
          return -1;
        for(p3 = str; *p3; p3++) {
          if(l < n)
            buf[l] = *p3;
          l++;
        }
        free((char *) str);
      }
    }
  
    return l;
  }
  
  const char * Curl_DNtostr(curl_asn1Element * dn)
  {
    char * buf = (char *) NULL;
    ssize_t n = encodeDN(buf, 0, dn);
  
    /* Convert an ASN.1 distinguished name into a printable string.
       Return the dynamically allocated string, or NULL if an error occurs. */
  
    if(n >= 0) {
      buf = malloc(n + 1);
      if(buf) {
        encodeDN(buf, n + 1, dn);
        buf[n] = '\0';
      }
    }
    return (const char *) buf;
  }
  
  static const char * checkOID(const char * beg, const char * end,
                               const char * oid)
  {
    curl_asn1Element e;
    const char * ccp;
    const char * p;
    bool matched;
  
    /* Check if first ASN.1 element at `beg' is the given OID.
       Return a pointer in the source after the OID if found, else NULL. */
  
    ccp = Curl_getASN1Element(&e, beg, end);
    if(!ccp || e.tag != CURL_ASN1_OBJECT_IDENTIFIER)
      return (const char *) NULL;
  
    p = OID2str(e.beg, e.end, FALSE);
    if(!p)
      return (const char *) NULL;
  
    matched = !strcmp(p, oid);
    free((char *) p);
    return matched? ccp: (const char *) NULL;
  }
  
  
  /*
   * X509 parser.
   */
  
  void Curl_parseX509(curl_X509certificate * cert,
                      const char * beg, const char * end)
  {
    curl_asn1Element elem;
    curl_asn1Element tbsCertificate;
    const char * ccp;
    static const char defaultVersion = 0;  /* v1. */
  
    /* ASN.1 parse an X509 certificate into structure subfields.
       Syntax is assumed to have already been checked by the SSL backend.
       See RFC 5280. */
  
    cert->certificate.beg = beg;
    cert->certificate.end = end;
  
    /* Get the sequence content. */
    Curl_getASN1Element(&elem, beg, end);
    beg = elem.beg;
    end = elem.end;
  
    /* Get tbsCertificate. */
    beg = Curl_getASN1Element(&tbsCertificate, beg, end);
    /* Skip the signatureAlgorithm. */
    beg = Curl_getASN1Element(&cert->signatureAlgorithm, beg, end);
    /* Get the signatureValue. */
    Curl_getASN1Element(&cert->signature, beg, end);
  
    /* Parse TBSCertificate. */
    beg = tbsCertificate.beg;
    end = tbsCertificate.end;
    /* Get optional version, get serialNumber. */
    cert->version.beg = &defaultVersion;
    cert->version.end = &defaultVersion + sizeof defaultVersion;;
    beg = Curl_getASN1Element(&elem, beg, end);
    if(elem.tag == 0) {
      Curl_getASN1Element(&cert->version, elem.beg, elem.end);
      beg = Curl_getASN1Element(&elem, beg, end);
    }
    cert->serialNumber = elem;
    /* Get signature algorithm. */
    beg = Curl_getASN1Element(&cert->signatureAlgorithm, beg, end);
    /* Get issuer. */
    beg = Curl_getASN1Element(&cert->issuer, beg, end);
    /* Get notBefore and notAfter. */
    beg = Curl_getASN1Element(&elem, beg, end);
    ccp = Curl_getASN1Element(&cert->notBefore, elem.beg, elem.end);
    Curl_getASN1Element(&cert->notAfter, ccp, elem.end);
    /* Get subject. */
    beg = Curl_getASN1Element(&cert->subject, beg, end);
    /* Get subjectPublicKeyAlgorithm and subjectPublicKey. */
    beg = Curl_getASN1Element(&elem, beg, end);
    ccp = Curl_getASN1Element(&cert->subjectPublicKeyAlgorithm,
                              elem.beg, elem.end);
    Curl_getASN1Element(&cert->subjectPublicKey, ccp, elem.end);
    /* Get optional issuerUiqueID, subjectUniqueID and extensions. */
    cert->issuerUniqueID.tag = cert->subjectUniqueID.tag = 0;
    cert->extensions.tag = elem.tag = 0;
    cert->issuerUniqueID.beg = cert->issuerUniqueID.end = "";
    cert->subjectUniqueID.beg = cert->subjectUniqueID.end = "";
    cert->extensions.beg = cert->extensions.end = "";
    if(beg < end)
      beg = Curl_getASN1Element(&elem, beg, end);
    if(elem.tag == 1) {
      cert->issuerUniqueID = elem;
      if(beg < end)
        beg = Curl_getASN1Element(&elem, beg, end);
    }
    if(elem.tag == 2) {
      cert->subjectUniqueID = elem;
      if(beg < end)
        beg = Curl_getASN1Element(&elem, beg, end);
    }
    if(elem.tag == 3)
      Curl_getASN1Element(&cert->extensions, elem.beg, elem.end);
  }
  
  static size_t copySubstring(char * to, const char * from)
  {
    size_t i;
  
    /* Copy at most 64-characters, terminate with a newline and returns the
       effective number of stored characters. */
  
    for(i = 0; i < 64; i++) {
      to[i] = *from;
      if(!*from++)
        break;
    }
  
    to[i++] = '\n';
    return i;
  }
  
  static const char * dumpAlgo(curl_asn1Element * param,
                               const char * beg, const char * end)
  {
    curl_asn1Element oid;
  
    /* Get algorithm parameters and return algorithm name. */
  
    beg = Curl_getASN1Element(&oid, beg, end);
    param->tag = 0;
    param->beg = param->end = end;
    if(beg < end)
      Curl_getASN1Element(param, beg, end);
    return OID2str(oid.beg, oid.end, TRUE);
  }
  
  static void do_pubkey_field(struct SessionHandle * data, int certnum,
                              const char * label, curl_asn1Element * elem)
  {
    const char * output;
  
    /* Generate a certificate information record for the public key. */
  
    output = Curl_ASN1tostr(elem, 0);
    if(output) {
      if(data->set.ssl.certinfo)
        Curl_ssl_push_certinfo(data, certnum, label, output);
      if(!certnum)
        infof(data, "   %s: %s\n", label, output);
      free((char *) output);
    }
  }
  
  static void do_pubkey(struct SessionHandle * data, int certnum,
                        const char * algo, curl_asn1Element * param,
                        curl_asn1Element * pubkey)
  {
    curl_asn1Element elem;
    curl_asn1Element pk;
    const char * p;
    const char * q;
    unsigned long len;
    unsigned int i;
  
    /* Generate all information records for the public key. */
  
    /* Get the public key (single element). */
    Curl_getASN1Element(&pk, pubkey->beg + 1, pubkey->end);
  
    if(curl_strequal(algo, "rsaEncryption")) {
      p = Curl_getASN1Element(&elem, pk.beg, pk.end);
      /* Compute key length. */
      for(q = elem.beg; !*q && q < elem.end; q++)
        ;
      len = (elem.end - q) * 8;
      if(len)
        for(i = *(unsigned char *) q; !(i & 0x80); i <<= 1)
          len--;
      if(len > 32)
        elem.beg = q;     /* Strip leading zero bytes. */
      if(!certnum)
        infof(data, "   RSA Public Key (%lu bits)\n", len);
      if(data->set.ssl.certinfo) {
        q = curl_maprintf("%lu", len);
        if(q) {
          Curl_ssl_push_certinfo(data, certnum, "RSA Public Key", q);
          free((char *) q);
        }
      }
      /* Generate coefficients. */
      do_pubkey_field(data, certnum, "rsa(n)", &elem);
      Curl_getASN1Element(&elem, p, pk.end);
      do_pubkey_field(data, certnum, "rsa(e)", &elem);
    }
    else if(curl_strequal(algo, "dsa")) {
      p = Curl_getASN1Element(&elem, param->beg, param->end);
      do_pubkey_field(data, certnum, "dsa(p)", &elem);
      p = Curl_getASN1Element(&elem, p, param->end);
      do_pubkey_field(data, certnum, "dsa(q)", &elem);
      Curl_getASN1Element(&elem, p, param->end);
      do_pubkey_field(data, certnum, "dsa(g)", &elem);
      do_pubkey_field(data, certnum, "dsa(pub_key)", &pk);
    }
    else if(curl_strequal(algo, "dhpublicnumber")) {
      p = Curl_getASN1Element(&elem, param->beg, param->end);
      do_pubkey_field(data, certnum, "dh(p)", &elem);
      Curl_getASN1Element(&elem, param->beg, param->end);
      do_pubkey_field(data, certnum, "dh(g)", &elem);
      do_pubkey_field(data, certnum, "dh(pub_key)", &pk);
    }
  #if 0 /* Patent-encumbered. */
    else if(curl_strequal(algo, "ecPublicKey")) {
      /* Left TODO. */
    }
  #endif
  }
  
  CURLcode Curl_extract_certinfo(struct connectdata * conn,
                                 int certnum,
                                 const char * beg,
                                 const char * end)
  {
    curl_X509certificate cert;
    struct SessionHandle * data = conn->data;
    curl_asn1Element param;
    const char * ccp;
    char * cp1;
    size_t cl1;
    char * cp2;
    CURLcode cc;
    unsigned long version;
    size_t i;
    size_t j;
  
    if(!data->set.ssl.certinfo)
      if(certnum)
        return CURLE_OK;
  
    /* Prepare the certificate information for curl_easy_getinfo(). */
  
    /* Extract the certificate ASN.1 elements. */
    Curl_parseX509(&cert, beg, end);
  
    /* Subject. */
    ccp = Curl_DNtostr(&cert.subject);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Subject", ccp);
    if(!certnum)
      infof(data, "%2d Subject: %s\n", certnum, ccp);
    free((char *) ccp);
  
    /* Issuer. */
    ccp = Curl_DNtostr(&cert.issuer);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Issuer", ccp);
    if(!certnum)
      infof(data, "   Issuer: %s\n", ccp);
    free((char *) ccp);
  
    /* Version (always fits in less than 32 bits). */
    version = 0;
    for(ccp = cert.version.beg; ccp < cert.version.end; ccp++)
      version = (version << 8) | *(const unsigned char *) ccp;
    if(data->set.ssl.certinfo) {
      ccp = curl_maprintf("%lx", version);
      if(!ccp)
        return CURLE_OUT_OF_MEMORY;
      Curl_ssl_push_certinfo(data, certnum, "Version", ccp);
      free((char *) ccp);
    }
    if(!certnum)
      infof(data, "   Version: %lu (0x%lx)\n", version + 1, version);
  
    /* Serial number. */
    ccp = Curl_ASN1tostr(&cert.serialNumber, 0);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Serial Number", ccp);
    if(!certnum)
      infof(data, "   Serial Number: %s\n", ccp);
    free((char *) ccp);
  
    /* Signature algorithm .*/
    ccp = dumpAlgo(&param, cert.signatureAlgorithm.beg,
                   cert.signatureAlgorithm.end);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Signature Algorithm", ccp);
    if(!certnum)
      infof(data, "   Signature Algorithm: %s\n", ccp);
    free((char *) ccp);
  
    /* Start Date. */
    ccp = Curl_ASN1tostr(&cert.notBefore, 0);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Start Date", ccp);
    if(!certnum)
      infof(data, "   Start Date: %s\n", ccp);
    free((char *) ccp);
  
    /* Expire Date. */
    ccp = Curl_ASN1tostr(&cert.notAfter, 0);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Expire Date", ccp);
    if(!certnum)
      infof(data, "   Expire Date: %s\n", ccp);
    free((char *) ccp);
  
    /* Public Key Algorithm. */
    ccp = dumpAlgo(&param, cert.subjectPublicKeyAlgorithm.beg,
                   cert.subjectPublicKeyAlgorithm.end);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Public Key Algorithm", ccp);
    if(!certnum)
      infof(data, "   Public Key Algorithm: %s\n", ccp);
    do_pubkey(data, certnum, ccp, &param, &cert.subjectPublicKey);
    free((char *) ccp);
  
  /* TODO: extensions. */
  
    /* Signature. */
    ccp = Curl_ASN1tostr(&cert.signature, 0);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Signature", ccp);
    if(!certnum)
      infof(data, "   Signature: %s\n", ccp);
    free((char *) ccp);
  
    /* Generate PEM certificate. */
    cc = Curl_base64_encode(data, cert.certificate.beg,
                            cert.certificate.end - cert.certificate.beg,
                            &cp1, &cl1);
    if(cc != CURLE_OK)
      return cc;
    /* Compute the number of characters in final certificate string. Format is:
       -----BEGIN CERTIFICATE-----\n
       <max 64 base64 characters>\n
       .
       .
       .
       -----END CERTIFICATE-----\n
     */
    i = 28 + cl1 + (cl1 + 64 - 1) / 64 + 26;
    cp2 = malloc(i + 1);
    if(!cp2) {
      free(cp1);
      return CURLE_OUT_OF_MEMORY;
    }
    /* Build the certificate string. */
    i = copySubstring(cp2, "-----BEGIN CERTIFICATE-----");
    for(j = 0; j < cl1; j += 64)
      i += copySubstring(cp2 + i, cp1 + j);
    i += copySubstring(cp2 + i, "-----END CERTIFICATE-----");
    cp2[i] = '\0';
    free(cp1);
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, "Cert", cp2);
    if(!certnum)
      infof(data, "%s\n", cp2);
    free(cp2);
    return CURLE_OK;
  }
  
  
  CURLcode Curl_verifyhost(struct connectdata * conn,
                           const char * beg, const char * end)
  {
    struct SessionHandle * data = conn->data;
    curl_X509certificate cert;
    curl_asn1Element dn;
    curl_asn1Element elem;
    curl_asn1Element ext;
    curl_asn1Element name;
    int i;
    const char * p;
    const char * q;
    char * dnsname;
    int matched = -1;
    size_t addrlen = (size_t) -1;
    ssize_t len;
  #ifdef ENABLE_IPV6
    struct in6_addr addr;
  #else
    struct in_addr addr;
  #endif
  
    /* Verify that connection server matches info in X509 certificate at
       `beg'..`end'. */
  
    if(!data->set.ssl.verifyhost)
      return CURLE_OK;
  
    if(!beg)
      return CURLE_PEER_FAILED_VERIFICATION;
    Curl_parseX509(&cert, beg, end);
  
    /* Get the server IP address. */
  #ifdef ENABLE_IPV6
    if(conn->bits.ipv6_ip && Curl_inet_pton(AF_INET6, conn->host.name, &addr))
      addrlen = sizeof(struct in6_addr);
    else
  #endif
    if(Curl_inet_pton(AF_INET, conn->host.name, &addr))
      addrlen = sizeof(struct in_addr);
  
    /* Process extensions. */
    for(p = cert.extensions.beg; p < cert.extensions.end && matched != 1;) {
      p = Curl_getASN1Element(&ext, p, cert.extensions.end);
      /* Check if extension is a subjectAlternativeName. */
      ext.beg = checkOID(ext.beg, ext.end, sanOID);
      if(ext.beg) {
        ext.beg = Curl_getASN1Element(&elem, ext.beg, ext.end);
        /* Skip critical if present. */
        if(elem.tag == CURL_ASN1_BOOLEAN)
          ext.beg = Curl_getASN1Element(&elem, ext.beg, ext.end);
        /* Parse the octet string contents: is a single sequence. */
        Curl_getASN1Element(&elem, elem.beg, elem.end);
        /* Check all GeneralNames. */
        for(q = elem.beg; matched != 1 && q < elem.end;) {
          q = Curl_getASN1Element(&name, q, elem.end);
          switch (name.tag) {
          case 2: /* DNS name. */
            i = 0;
            len = utf8asn1str(&dnsname, CURL_ASN1_IA5_STRING,
                              name.beg, name.end);
            if(len > 0)
              if(strlen(dnsname) == (size_t) len)
                i = Curl_cert_hostcheck((const char *) dnsname, conn->host.name);
            if(dnsname)
              free(dnsname);
            if(!i)
              return CURLE_PEER_FAILED_VERIFICATION;
            matched = i;
            break;
  
          case 7: /* IP address. */
            matched = (size_t) (name.end - q) == addrlen &&
                      !memcmp(&addr, q, addrlen);
            break;
          }
        }
      }
    }
  
    switch (matched) {
    case 1:
      /* an alternative name matched the server hostname */
      infof(data, "\t subjectAltName: %s matched\n", conn->host.dispname);
      return CURLE_OK;
    case 0:
      /* an alternative name field existed, but didn't match and then
         we MUST fail */
      infof(data, "\t subjectAltName does not match %s\n", conn->host.dispname);
      return CURLE_PEER_FAILED_VERIFICATION;
    }
  
    /* Process subject. */
    name.beg = name.end = "";
    q = cert.subject.beg;
    /* we have to look to the last occurrence of a commonName in the
       distinguished one to get the most significant one. */
    while(q < cert.subject.end) {
      q = Curl_getASN1Element(&dn, q, cert.subject.end);
      for(p = dn.beg; p < dn.end;) {
        p = Curl_getASN1Element(&elem, p, dn.end);
        /* We have a DN's AttributeTypeAndValue: check it in case it's a CN. */
        elem.beg = checkOID(elem.beg, elem.end, cnOID);
        if(elem.beg)
          name = elem;    /* Latch CN. */
      }
    }
  
    /* Check the CN if found. */
    if(!Curl_getASN1Element(&elem, name.beg, name.end))
      failf(data, "SSL: unable to obtain common name from peer certificate");
    else {
      len = utf8asn1str(&dnsname, elem.tag, elem.beg, elem.end);
      if(len < 0) {
        free(dnsname);
        return CURLE_OUT_OF_MEMORY;
      }
      if(strlen(dnsname) != (size_t) len)         /* Nul byte in string ? */
        failf(data, "SSL: illegal cert name field");
      else if(Curl_cert_hostcheck((const char *) dnsname, conn->host.name)) {
        infof(data, "\t common name: %s (matched)\n", dnsname);
        free(dnsname);
        return CURLE_OK;
      }
      else
        failf(data, "SSL: certificate subject name '%s' does not match "
              "target host name '%s'", dnsname, conn->host.dispname);
      free(dnsname);
    }
  
    return CURLE_PEER_FAILED_VERIFICATION;
  }
  
  #endif /* USE_QSOSSL or USE_GSKIT or USE_NSS */
  