/src/plan9port/src/libsec/port/x509.c

Source (jump to first uncovered line)
#include <u.h>
#include <libc.h>
#include <mp.h>
#include <libsec.h>

typedef DigestState*(*DigestFun)(uchar*,ulong,uchar*,DigestState*);

/* ANSI offsetof, backwards. */
#define OFFSETOF(a, b)  offsetof(b, a)

/*=============================================================*/
/*  general ASN1 declarations and parsing
 *
 *  For now, this is used only for extracting the key from an
 *  X509 certificate, so the entire collection is hidden.  But
 *  someday we should probably make the functions visible and
 *  give them their own man page.
 */
typedef struct Elem Elem;
typedef struct Tag Tag;
typedef struct Value Value;
typedef struct Bytes Bytes;
typedef struct Ints Ints;
typedef struct Bits Bits;
typedef struct Elist Elist;

/* tag classes */
#define Universal 0
#define Context 0x80

/* universal tags */
#define BOOLEAN 1
#define INTEGER 2
#define BIT_STRING 3
#define OCTET_STRING 4
#define NULLTAG 5
#define OBJECT_ID 6
#define ObjectDescriptor 7
#define EXTERNAL 8
#define REAL 9
#define ENUMERATED 10
#define EMBEDDED_PDV 11
#define SEQUENCE 16    /* also SEQUENCE OF */
#define SETOF 17        /* also SETOF OF */
#define NumericString 18
#define PrintableString 19
#define TeletexString 20
#define VideotexString 21
#define IA5String 22
#define UTCTime 23
#define GeneralizedTime 24
#define GraphicString 25
#define VisibleString 26
#define GeneralString 27
#define UniversalString 28
#define BMPString 30

struct Bytes {
  int len;
  uchar data[1];
};

struct Ints {
  int len;
  int data[1];
};

struct Bits {
  int len;    /* number of bytes */
  int unusedbits; /* unused bits in last byte */
  uchar data[1];  /* most-significant bit first */
};

struct Tag {
  int class;
  int num;
};

enum { VBool, VInt, VOctets, VBigInt, VReal, VOther,
  VBitString, VNull, VEOC, VObjId, VString, VSeq, VSet };
struct Value {
  int tag;    /* VBool, etc. */
  union {
    int boolval;
    int intval;
    Bytes*  octetsval;
    Bytes*  bigintval;
    Bytes*  realval;  /* undecoded; hardly ever used */
    Bytes*  otherval;
    Bits* bitstringval;
    Ints* objidval;
    char* stringval;
    Elist*  seqval;
    Elist*  setval;
  } u;  /* (Don't use anonymous unions, for ease of porting) */
};

struct Elem {
  Tag tag;
  Value val;
};

struct Elist {
  Elist*  tl;
  Elem  hd;
};

/* decoding errors */
enum { ASN_OK, ASN_ESHORT, ASN_ETOOBIG, ASN_EVALLEN,
    ASN_ECONSTR, ASN_EPRIM, ASN_EINVAL, ASN_EUNIMPL };


/* here are the functions to consider making extern someday */
static Bytes* newbytes(int len);
static Bytes* makebytes(uchar* buf, int len);
static void freebytes(Bytes* b);
static Bytes* catbytes(Bytes* b1, Bytes* b2);
static Ints*  newints(int len);
static Ints*  makeints(int* buf, int len);
static void freeints(Ints* b);
static Bits*  newbits(int len);
static Bits*  makebits(uchar* buf, int len, int unusedbits);
static void freebits(Bits* b);
static Elist* mkel(Elem e, Elist* tail);
static void freeelist(Elist* el);
static int  elistlen(Elist* el);
static int  is_seq(Elem* pe, Elist** pseq);
static int  is_set(Elem* pe, Elist** pset);
static int  is_int(Elem* pe, int* pint);
static int  is_bigint(Elem* pe, Bytes** pbigint);
static int  is_bitstring(Elem* pe, Bits** pbits);
static int  is_octetstring(Elem* pe, Bytes** poctets);
static int  is_oid(Elem* pe, Ints** poid);
static int  is_string(Elem* pe, char** pstring);
static int  is_time(Elem* pe, char** ptime);
static int  decode(uchar* a, int alen, Elem* pelem);
/*
static int  decode_seq(uchar* a, int alen, Elist** pelist);
static int  decode_value(uchar* a, int alen, int kind, int isconstr, Value* pval);
*/
static int  encode(Elem e, Bytes** pbytes);
static int  oid_lookup(Ints* o, Ints** tab);
static void freevalfields(Value* v);
static mpint  *asn1mpint(Elem *e);



#define TAG_MASK 0x1F
#define CONSTR_MASK 0x20
#define CLASS_MASK 0xC0
#define MAXOBJIDLEN 20

static int ber_decode(uchar** pp, uchar* pend, Elem* pelem);
static int tag_decode(uchar** pp, uchar* pend, Tag* ptag, int* pisconstr);
static int length_decode(uchar** pp, uchar* pend, int* plength);
static int value_decode(uchar** pp, uchar* pend, int length, int kind, int isconstr, Value* pval);
static int int_decode(uchar** pp, uchar* pend, int count, int unsgned, int* pint);
static int uint7_decode(uchar** pp, uchar* pend, int* pint);
static int octet_decode(uchar** pp, uchar* pend, int length, int isconstr, Bytes** pbytes);
static int seq_decode(uchar** pp, uchar* pend, int length, int isconstr, Elist** pelist);
static int enc(uchar** pp, Elem e, int lenonly);
static int val_enc(uchar** pp, Elem e, int *pconstr, int lenonly);
static void uint7_enc(uchar** pp, int num, int lenonly);
static void int_enc(uchar** pp, int num, int unsgned, int lenonly);

static void *
emalloc(int n)
{
  void *p;
  if(n==0)
    n=1;
  p = malloc(n);
  if(p == nil){
    exits("out of memory");
  }
  memset(p, 0, n);
  return p;
}

static char*
estrdup(char *s)
{
  char *d, *d0;

  if(!s)
    return 0;
  d = d0 = emalloc(strlen(s)+1);
  while(*d++ = *s++)
    ;
  return d0;
}


/*
 * Decode a[0..len] as a BER encoding of an ASN1 type.
 * The return value is one of ASN_OK, etc.
 * Depending on the error, the returned elem may or may not
 * be nil.
 */
static int
decode(uchar* a, int alen, Elem* pelem)
{
  uchar* p = a;

  return  ber_decode(&p, &a[alen], pelem);
}

/*
 * Like decode, but continue decoding after first element
 * of array ends.
 *
static int
decode_seq(uchar* a, int alen, Elist** pelist)
{
  uchar* p = a;

  return seq_decode(&p, &a[alen], -1, 1, pelist);
}
*/

/*
 * Decode the whole array as a BER encoding of an ASN1 value,
 * (i.e., the part after the tag and length).
 * Assume the value is encoded as universal tag "kind".
 * The constr arg is 1 if the value is constructed, 0 if primitive.
 * If there's an error, the return string will contain the error.
 * Depending on the error, the returned value may or may not
 * be nil.
 *
static int
decode_value(uchar* a, int alen, int kind, int isconstr, Value* pval)
{
  uchar* p = a;

  return value_decode(&p, &a[alen], alen, kind, isconstr, pval);
}
*/

/*
 * All of the following decoding routines take arguments:
 *  uchar **pp;
 *  uchar *pend;
 * Where parsing is supposed to start at **pp, and when parsing
 * is done, *pp is updated to point at next char to be parsed.
 * The pend pointer is just past end of string; an error should
 * be returned parsing hasn't finished by then.
 *
 * The returned int is ASN_OK if all went fine, else ASN_ESHORT, etc.
 * The remaining argument(s) are pointers to where parsed entity goes.
 */

/* Decode an ASN1 'Elem' (tag, length, value) */
static int
ber_decode(uchar** pp, uchar* pend, Elem* pelem)
{
  int err;
  int isconstr;
  int length;
  Tag tag;
  Value val;

  err = tag_decode(pp, pend, &tag, &isconstr);
  if(err == ASN_OK) {
    err = length_decode(pp, pend, &length);
    if(err == ASN_OK) {
      if(tag.class == Universal)
        err = value_decode(pp, pend, length, tag.num, isconstr, &val);
      else
        err = value_decode(pp, pend, length, OCTET_STRING, 0, &val);
      if(err == ASN_OK) {
        pelem->tag = tag;
        pelem->val = val;
      }
    }
  }
  return err;
}

/* Decode a tag field */
static int
tag_decode(uchar** pp, uchar* pend, Tag* ptag, int* pisconstr)
{
  int err;
  int v;
  uchar* p;

  err = ASN_OK;
  p = *pp;
  if(pend-p >= 2) {
    v = *p++;
    ptag->class = v&CLASS_MASK;
    if(v&CONSTR_MASK)
      *pisconstr = 1;
    else
      *pisconstr = 0;
    v &= TAG_MASK;
    if(v == TAG_MASK)
      err = uint7_decode(&p, pend, &v);
    ptag->num = v;
  }
  else
    err = ASN_ESHORT;
  *pp = p;
  return err;
}

/* Decode a length field */
static int
length_decode(uchar** pp, uchar* pend, int* plength)
{
  int err;
  int num;
  int v;
  uchar* p;

  err = ASN_OK;
  num = 0;
  p = *pp;
  if(p < pend) {
    v = *p++;
    if(v&0x80)
      err = int_decode(&p, pend, v&0x7F, 1, &num);
    else
      num = v;
  }
  else
    err = ASN_ESHORT;
  *pp = p;
  *plength = num;
  return err;
}

/* Decode a value field  */
static int
value_decode(uchar** pp, uchar* pend, int length, int kind, int isconstr, Value* pval)
{
  int err;
  Bytes* va;
  int num;
  int bitsunused;
  int subids[MAXOBJIDLEN];
  int isubid;
  Elist*  vl;
  uchar* p;
  uchar* pe;

  err = ASN_OK;
  p = *pp;
  if(length == -1) { /* "indefinite" length spec */
    if(!isconstr)
      err = ASN_EINVAL;
  }
  else if(p + length > pend)
    err = ASN_EVALLEN;
  if(err != ASN_OK)
    return err;

  switch(kind) {
  case 0:
    /* marker for end of indefinite constructions */
    if(length == 0)
      pval->tag = VNull;
    else
      err = ASN_EINVAL;
    break;

  case BOOLEAN:
    if(isconstr)
      err = ASN_ECONSTR;
    else if(length != 1)
      err = ASN_EVALLEN;
    else {
      pval->tag = VBool;
      pval->u.boolval = (*p++ != 0);
    }
    break;

  case INTEGER:
  case ENUMERATED:
    if(isconstr)
      err = ASN_ECONSTR;
    else if(length <= 4) {
      err = int_decode(&p, pend, length, 0, &num);
      if(err == ASN_OK) {
        pval->tag = VInt;
        pval->u.intval = num;
      }
    }
    else {
      pval->tag = VBigInt;
      pval->u.bigintval = makebytes(p, length);
      p += length;
    }
    break;

  case BIT_STRING:
    pval->tag = VBitString;
    if(isconstr) {
      if(length == -1 && p + 2 <= pend && *p == 0 && *(p+1) ==0) {
        pval->u.bitstringval = makebits(0, 0, 0);
        p += 2;
      }
      else
        /* TODO: recurse and concat results */
        err = ASN_EUNIMPL;
    }
    else {
      if(length < 2) {
        if(length == 1 && *p == 0) {
          pval->u.bitstringval = makebits(0, 0, 0);
          p++;
        }
        else
          err = ASN_EINVAL;
      }
      else {
        bitsunused = *p;
        if(bitsunused > 7)
          err = ASN_EINVAL;
        else if(length > 0x0FFFFFFF)
          err = ASN_ETOOBIG;
        else {
          pval->u.bitstringval = makebits(p+1, length-1, bitsunused);
          p += length;
        }
      }
    }
    break;

  case OCTET_STRING:
  case ObjectDescriptor:
    err = octet_decode(&p, pend, length, isconstr, &va);
    if(err == ASN_OK) {
      pval->tag = VOctets;
      pval->u.octetsval = va;
    }
    break;

  case NULLTAG:
    if(isconstr)
      err = ASN_ECONSTR;
    else if(length != 0)
      err = ASN_EVALLEN;
    else
      pval->tag = VNull;
    break;

  case OBJECT_ID:
    if(isconstr)
      err = ASN_ECONSTR;
    else if(length == 0)
      err = ASN_EVALLEN;
    else {
      isubid = 0;
      pe = p+length;
      while(p < pe && isubid < MAXOBJIDLEN) {
        err = uint7_decode(&p, pend, &num);
        if(err != ASN_OK)
          break;
        if(isubid == 0) {
          subids[isubid++] = num / 40;
          subids[isubid++] = num % 40;
        }
        else
          subids[isubid++] = num;
      }
      if(err == ASN_OK) {
        if(p != pe)
          err = ASN_EVALLEN;
        else {
          pval->tag = VObjId;
          pval->u.objidval = makeints(subids, isubid);
        }
      }
    }
    break;

  case EXTERNAL:
  case EMBEDDED_PDV:
    /* TODO: parse this internally */
    if(p+length > pend)
      err = ASN_EVALLEN;
    else {
      pval->tag = VOther;
      pval->u.otherval = makebytes(p, length);
      p += length;
    }
    break;

  case REAL:
    /* Let the application decode */
    if(isconstr)
      err = ASN_ECONSTR;
    else if(p+length > pend)
      err = ASN_EVALLEN;
    else {
      pval->tag = VReal;
      pval->u.realval = makebytes(p, length);
      p += length;
    }
    break;

  case SEQUENCE:
    err = seq_decode(&p, pend, length, isconstr, &vl);
    if(err == ASN_OK) {
      pval->tag = VSeq ;
      pval->u.seqval = vl;
    }
    break;

  case SETOF:
    err = seq_decode(&p, pend, length, isconstr, &vl);
    if(err == ASN_OK) {
      pval->tag = VSet;
      pval->u.setval = vl;
    }
    break;

  case NumericString:
  case PrintableString:
  case TeletexString:
  case VideotexString:
  case IA5String:
  case UTCTime:
  case GeneralizedTime:
  case GraphicString:
  case VisibleString:
  case GeneralString:
  case UniversalString:
  case BMPString:
    /* TODO: figure out when character set conversion is necessary */
    err = octet_decode(&p, pend, length, isconstr, &va);
    if(err == ASN_OK) {
      pval->tag = VString;
      pval->u.stringval = (char*)emalloc(va->len+1);
      memmove(pval->u.stringval, va->data, va->len);
      pval->u.stringval[va->len] = 0;
      free(va);
    }
    break;

  default:
    if(p+length > pend)
      err = ASN_EVALLEN;
    else {
      pval->tag = VOther;
      pval->u.otherval = makebytes(p, length);
      p += length;
    }
    break;
  }
  *pp = p;
  return err;
}

/*
 * Decode an int in format where count bytes are
 * concatenated to form value.
 * Although ASN1 allows any size integer, we return
 * an error if the result doesn't fit in a 32-bit int.
 * If unsgned is not set, make sure to propagate sign bit.
 */
static int
int_decode(uchar** pp, uchar* pend, int count, int unsgned, int* pint)
{
  int err;
  int num;
  uchar* p;

  p = *pp;
  err = ASN_OK;
  num = 0;
  if(p+count <= pend) {
    if((count > 4) || (unsgned && count == 4 && (*p&0x80)))
      err = ASN_ETOOBIG;
    else {
      if(!unsgned && count > 0 && count < 4 && (*p&0x80))
        num = -1;   /* set all bits, initially */
      while(count--)
        num = (num << 8)|(*p++);
    }
  }
  else
    err = ASN_ESHORT;
  *pint = num;
  *pp = p;
  return err;
}

/*
 * Decode an unsigned int in format where each
 * byte except last has high bit set, and remaining
 * seven bits of each byte are concatenated to form value.
 * Although ASN1 allows any size integer, we return
 * an error if the result doesn't fit in a 32 bit int.
 */
static int
uint7_decode(uchar** pp, uchar* pend, int* pint)
{
  int err;
  int num;
  int more;
  int v;
  uchar* p;

  p = *pp;
  err = ASN_OK;
  num = 0;
  more = 1;
  while(more && p < pend) {
    v = *p++;
    if(num&0x7F000000) {
      err = ASN_ETOOBIG;
      break;
    }
    num <<= 7;
    more = v&0x80;
    num |= (v&0x7F);
  }
  if(p == pend)
    err = ASN_ESHORT;
  *pint = num;
  *pp = p;
  return err;
}

/*
 * Decode an octet string, recursively if isconstr.
 * We've already checked that length==-1 implies isconstr==1,
 * and otherwise that specified length fits within (*pp..pend)
 */
static int
octet_decode(uchar** pp, uchar* pend, int length, int isconstr, Bytes** pbytes)
{
  int err;
  uchar* p;
  Bytes* ans;
  Bytes* newans;
  uchar* pstart;
  uchar* pold;
  Elem  elem;

  err = ASN_OK;
  p = *pp;
  ans = nil;
  if(length >= 0 && !isconstr) {
    ans = makebytes(p, length);
    p += length;
  }
  else {
    /* constructed, either definite or indefinite length */
    pstart = p;
    for(;;) {
      if(length >= 0 && p >= pstart + length) {
        if(p != pstart + length)
          err = ASN_EVALLEN;
        break;
      }
      pold = p;
      err = ber_decode(&p, pend, &elem);
      if(err != ASN_OK)
        break;
      switch(elem.val.tag) {
      case VOctets:
        newans = catbytes(ans, elem.val.u.octetsval);
        freebytes(ans);
        ans = newans;
        break;

      case VEOC:
        if(length != -1) {
          p = pold;
          err = ASN_EINVAL;
        }
        goto cloop_done;

      default:
        p = pold;
        err = ASN_EINVAL;
        goto cloop_done;
      }
    }
cloop_done:
    ;
  }
  *pp = p;
  *pbytes = ans;
  return err;
}

/*
 * Decode a sequence or set.
 * We've already checked that length==-1 implies isconstr==1,
 * and otherwise that specified length fits within (*p..pend)
 */
static int
seq_decode(uchar** pp, uchar* pend, int length, int isconstr, Elist** pelist)
{
  int err;
  uchar* p;
  uchar* pstart;
  uchar* pold;
  Elist* ans;
  Elem elem;
  Elist* lve;
  Elist* lveold;

  err = ASN_OK;
  ans = nil;
  p = *pp;
  if(!isconstr)
    err = ASN_EPRIM;
  else {
    /* constructed, either definite or indefinite length */
    lve = nil;
    pstart = p;
    for(;;) {
      if(length >= 0 && p >= pstart + length) {
        if(p != pstart + length)
          err = ASN_EVALLEN;
        break;
      }
      pold = p;
      err = ber_decode(&p, pend, &elem);
      if(err != ASN_OK)
        break;
      if(elem.val.tag == VEOC) {
        if(length != -1) {
          p = pold;
          err = ASN_EINVAL;
        }
        break;
      }
      else
        lve = mkel(elem, lve);
    }
    if(err == ASN_OK) {
      /* reverse back to original order */
      while(lve != nil) {
        lveold = lve;
        lve = lve->tl;
        lveold->tl = ans;
        ans = lveold;
      }
    }
  }
  *pp = p;
  *pelist = ans;
  return err;
}

/*
 * Encode e by BER rules, putting answer in *pbytes.
 * This is done by first calling enc with lenonly==1
 * to get the length of the needed buffer,
 * then allocating the buffer and using enc again to fill it up.
 */
static int
encode(Elem e, Bytes** pbytes)
{
  uchar* p;
  Bytes* ans;
  int err;
  uchar uc;

  p = &uc;
  err = enc(&p, e, 1);
  if(err == ASN_OK) {
    ans = newbytes(p-&uc);
    p = ans->data;
    err = enc(&p, e, 0);
    *pbytes = ans;
  }
  return err;
}

/*
 * The various enc functions take a pointer to a pointer
 * into a buffer, and encode their entity starting there,
 * updating the pointer afterwards.
 * If lenonly is 1, only the pointer update is done,
 * allowing enc to be called first to calculate the needed
 * buffer length.
 * If lenonly is 0, it is assumed that the answer will fit.
 */

static int
enc(uchar** pp, Elem e, int lenonly)
{
  int err;
  int vlen;
  int constr;
  Tag tag;
  int v;
  int ilen;
  uchar* p;
  uchar* psave;

  p = *pp;
  err = val_enc(&p, e, &constr, 1);
  if(err != ASN_OK)
    return err;
  vlen = p - *pp;
  p = *pp;
  tag = e.tag;
  v = tag.class|constr;
  if(tag.num < 31) {
    if(!lenonly)
      *p = (v|tag.num);
    p++;
  }
  else {
    if(!lenonly)
      *p = (v|31);
    p++;
    if(tag.num < 0)
      return ASN_EINVAL;
    uint7_enc(&p, tag.num, lenonly);
  }
  if(vlen < 0x80) {
    if(!lenonly)
      *p = vlen;
    p++;
  }
  else {
    psave = p;
    int_enc(&p, vlen, 1, 1);
    ilen = p-psave;
    p = psave;
    if(!lenonly) {
      *p++ = (0x80 | ilen);
      int_enc(&p, vlen, 1, 0);
    }
    else
      p += 1 + ilen;
  }
  if(!lenonly)
    val_enc(&p, e, &constr, 0);
  else
    p += vlen;
  *pp = p;
  return err;
}

static int
val_enc(uchar** pp, Elem e, int *pconstr, int lenonly)
{
  int err;
  uchar* p;
  int kind;
  int cl;
  int v;
  Bytes* bb = nil;
  Bits* bits;
  Ints* oid;
  int k;
  Elist* el;
  char* s;

  p = *pp;
  err = ASN_OK;
  kind = e.tag.num;
  cl = e.tag.class;
  *pconstr = 0;
  if(cl != Universal) {
    switch(e.val.tag) {
    case VBool:
      kind = BOOLEAN;
      break;
    case VInt:
      kind = INTEGER;
      break;
    case VBigInt:
      kind = INTEGER;
      break;
    case VOctets:
      kind = OCTET_STRING;
      break;
    case VReal:
      kind = REAL;
      break;
    case VOther:
      kind = OCTET_STRING;
      break;
    case VBitString:
      kind = BIT_STRING;
      break;
    case VNull:
      kind = NULLTAG;
      break;
    case VObjId:
      kind = OBJECT_ID;
      break;
    case VString:
      kind = UniversalString;
      break;
    case VSeq:
      kind = SEQUENCE;
      break;
    case VSet:
      kind = SETOF;
      break;
    }
  }
  switch(kind) {
  case BOOLEAN:
    if(is_int(&e, &v)) {
      if(v != 0)
        v = 255;
       int_enc(&p, v, 1, lenonly);
    }
    else
      err = ASN_EINVAL;
    break;

  case INTEGER:
  case ENUMERATED:
    if(is_int(&e, &v))
      int_enc(&p, v, 0, lenonly);
    else {
      if(is_bigint(&e, &bb)) {
        if(!lenonly)
          memmove(p, bb->data, bb->len);
        p += bb->len;
      }
      else
        err = ASN_EINVAL;
    }
    break;

  case BIT_STRING:
    if(is_bitstring(&e, &bits)) {
      if(bits->len == 0) {
        if(!lenonly)
          *p = 0;
        p++;
      }
      else {
        v = bits->unusedbits;
        if(v < 0 || v > 7)
          err = ASN_EINVAL;
        else {
          if(!lenonly) {
            *p = v;
            memmove(p+1, bits->data, bits->len);
          }
          p += 1 + bits->len;
        }
      }
    }
    else
      err = ASN_EINVAL;
    break;

  case OCTET_STRING:
  case ObjectDescriptor:
  case EXTERNAL:
  case REAL:
  case EMBEDDED_PDV:
    bb = nil;
    switch(e.val.tag) {
    case VOctets:
      bb = e.val.u.octetsval;
      break;
    case VReal:
      bb = e.val.u.realval;
      break;
    case VOther:
      bb = e.val.u.otherval;
      break;
    }
    if(bb != nil) {
      if(!lenonly)
        memmove(p, bb->data, bb->len);
      p += bb->len;
    }
      else
        err = ASN_EINVAL;
    break;

  case NULLTAG:
    break;

  case OBJECT_ID:
    if(is_oid(&e, &oid)) {
      for(k = 0; k < oid->len; k++) {
        v = oid->data[k];
        if(k == 0) {
          v *= 40;
          if(oid->len > 1)
            v += oid->data[++k];
        }
        uint7_enc(&p, v, lenonly);
      }
    }
    else
      err = ASN_EINVAL;
    break;

  case SEQUENCE:
  case SETOF:
    el = nil;
    if(e.val.tag == VSeq)
      el = e.val.u.seqval;
    else if(e.val.tag == VSet)
      el = e.val.u.setval;
    else
      err = ASN_EINVAL;
    if(el != nil) {
      *pconstr = CONSTR_MASK;
      for(; el != nil; el = el->tl) {
        err = enc(&p, el->hd, lenonly);
        if(err != ASN_OK)
          break;
      }
    }
    break;

  case NumericString:
  case PrintableString:
  case TeletexString:
  case VideotexString:
  case IA5String:
  case UTCTime:
  case GeneralizedTime:
  case GraphicString:
  case VisibleString:
  case GeneralString:
  case UniversalString:
  case BMPString:
    if(e.val.tag == VString) {
      s = e.val.u.stringval;
      if(s != nil) {
        v = strlen(s);
        if(!lenonly)
          memmove(p, s, v);
        p += v;
      }
    }
    else
      err = ASN_EINVAL;
    break;

  default:
    err = ASN_EINVAL;
  }
  *pp = p;
  return err;
}

/*
 * Encode num as unsigned 7 bit values with top bit 1 on all bytes
 * except last, only putting in bytes if !lenonly.
 */
static void
uint7_enc(uchar** pp, int num, int lenonly)
{
  int n;
  int v;
  int k;
  uchar* p;

  p = *pp;
  n = 1;
  v = num >> 7;
  while(v > 0) {
    v >>= 7;
    n++;
  }
  if(lenonly)
    p += n;
  else {
    for(k = (n - 1)*7; k > 0; k -= 7)
      *p++= ((num >> k)|0x80);
    *p++ = (num&0x7F);
  }
  *pp = p;
}

/*
 * Encode num as unsigned or signed integer,
 * only putting in bytes if !lenonly.
 * Encoding is length followed by bytes to concatenate.
 */
static void
int_enc(uchar** pp, int num, int unsgned, int lenonly)
{
  int v;
  int n;
  int prevv;
  int k;
  uchar* p;

  p = *pp;
  v = num;
  if(v < 0)
    v = -(v + 1);
  n = 1;
  prevv = v;
  v >>= 8;
  while(v > 0) {
    prevv = v;
    v >>= 8;
    n++;
  }
  if(!unsgned && (prevv&0x80))
    n++;
  if(lenonly)
    p += n;
  else {
    for(k = (n - 1)*8; k >= 0; k -= 8)
      *p++ = (num >> k);
  }
  *pp = p;
}

static int
ints_eq(Ints* a, Ints* b)
{
  int alen;
  int i;

  alen = a->len;
  if(alen != b->len)
    return 0;
  for(i = 0; i < alen; i++)
    if(a->data[i] != b->data[i])
      return 0;
  return 1;
}

/*
 * Look up o in tab (which must have nil entry to terminate).
 * Return index of matching entry, or -1 if none.
 */
static int
oid_lookup(Ints* o, Ints** tab)
{
  int i;

  for(i = 0; tab[i] != nil; i++)
    if(ints_eq(o, tab[i]))
      return  i;
  return -1;
}

/*
 * Return true if *pe is a SEQUENCE, and set *pseq to
 * the value of the sequence if so.
 */
static int
is_seq(Elem* pe, Elist** pseq)
{
  if(pe->tag.class == Universal && pe->tag.num == SEQUENCE && pe->val.tag == VSeq) {
    *pseq = pe->val.u.seqval;
    return 1;
  }
  return 0;
}

static int
is_set(Elem* pe, Elist** pset)
{
  if(pe->tag.class == Universal && pe->tag.num == SETOF && pe->val.tag == VSet) {
    *pset = pe->val.u.setval;
    return 1;
  }
  return 0;
}

static int
is_int(Elem* pe, int* pint)
{
  if(pe->tag.class == Universal) {
    if(pe->tag.num == INTEGER && pe->val.tag == VInt) {
      *pint = pe->val.u.intval;
      return 1;
    }
    else if(pe->tag.num == BOOLEAN && pe->val.tag == VBool) {
      *pint = pe->val.u.boolval;
      return 1;
    }
  }
  return 0;
}

/*
 * for convience, all VInt's are readable via this routine,
 * as well as all VBigInt's
 */
static int
is_bigint(Elem* pe, Bytes** pbigint)
{
  int v, n, i;

  if(pe->tag.class == Universal && pe->tag.num == INTEGER) {
    if(pe->val.tag == VBigInt)
      *pbigint = pe->val.u.bigintval;
    else if(pe->val.tag == VInt){
      v = pe->val.u.intval;
      for(n = 1; n < 4; n++)
        if((1 << (8 * n)) > v)
          break;
      *pbigint = newbytes(n);
      for(i = 0; i < n; i++)
        (*pbigint)->data[i] = (v >> ((n - 1 - i) * 8));
    }else
      return 0;
    return 1;
  }
  return 0;
}

static int
is_bitstring(Elem* pe, Bits** pbits)
{
  if(pe->tag.class == Universal && pe->tag.num == BIT_STRING && pe->val.tag == VBitString) {
    *pbits = pe->val.u.bitstringval;
    return 1;
  }
  return 0;
}

static int
is_octetstring(Elem* pe, Bytes** poctets)
{
  if(pe->tag.class == Universal && pe->tag.num == OCTET_STRING && pe->val.tag == VOctets) {
    *poctets = pe->val.u.octetsval;
    return 1;
  }
  return 0;
}

static int
is_oid(Elem* pe, Ints** poid)
{
  if(pe->tag.class == Universal && pe->tag.num == OBJECT_ID && pe->val.tag == VObjId) {
    *poid = pe->val.u.objidval;
    return 1;
  }
  return 0;
}

static int
is_string(Elem* pe, char** pstring)
{
  if(pe->tag.class == Universal) {
    switch(pe->tag.num) {
    case NumericString:
    case PrintableString:
    case TeletexString:
    case VideotexString:
    case IA5String:
    case GraphicString:
    case VisibleString:
    case GeneralString:
    case UniversalString:
    case BMPString:
      if(pe->val.tag == VString) {
        *pstring = pe->val.u.stringval;
        return 1;
      }
    }
  }
  return 0;
}

static int
is_time(Elem* pe, char** ptime)
{
  if(pe->tag.class == Universal
     && (pe->tag.num == UTCTime || pe->tag.num == GeneralizedTime)
     && pe->val.tag == VString) {
    *ptime = pe->val.u.stringval;
    return 1;
  }
  return 0;
}


/*
 * malloc and return a new Bytes structure capable of
 * holding len bytes. (len >= 0)
 */
static Bytes*
newbytes(int len)
{
  Bytes* ans;

  ans = (Bytes*)emalloc(OFFSETOF(data[0], Bytes) + len);
  ans->len = len;
  return ans;
}

/*
 * newbytes(len), with data initialized from buf
 */
static Bytes*
makebytes(uchar* buf, int len)
{
  Bytes* ans;

  ans = newbytes(len);
  memmove(ans->data, buf, len);
  return ans;
}

static void
freebytes(Bytes* b)
{
  if(b != nil)
    free(b);
}

/*
 * Make a new Bytes, containing bytes of b1 followed by those of b2.
 * Either b1 or b2 or both can be nil.
 */
static Bytes*
catbytes(Bytes* b1, Bytes* b2)
{
  Bytes* ans;
  int n;

  if(b1 == nil) {
    if(b2 == nil)
      ans = newbytes(0);
    else
      ans = makebytes(b2->data, b2->len);
  }
  else if(b2 == nil) {
    ans = makebytes(b1->data, b1->len);
  }
  else {
    n = b1->len + b2->len;
    ans = newbytes(n);
    ans->len = n;
    memmove(ans->data, b1->data, b1->len);
    memmove(ans->data+b1->len, b2->data, b2->len);
  }
  return ans;
}

/* len is number of ints */
static Ints*
newints(int len)
{
  Ints* ans;

  ans = (Ints*)emalloc(OFFSETOF(data[0], Ints) + len*sizeof(int));
  ans->len = len;
  return ans;
}

static Ints*
makeints(int* buf, int len)
{
  Ints* ans;

  ans = newints(len);
  if(len > 0)
    memmove(ans->data, buf, len*sizeof(int));
  return ans;
}

static void
freeints(Ints* b)
{
  if(b != nil)
    free(b);
}

/* len is number of bytes */
static Bits*
newbits(int len)
{
  Bits* ans;

  ans = (Bits*)emalloc(OFFSETOF(data[0], Bits) + len);
  ans->len = len;
  ans->unusedbits = 0;
  return ans;
}

static Bits*
makebits(uchar* buf, int len, int unusedbits)
{
  Bits* ans;

  ans = newbits(len);
  memmove(ans->data, buf, len);
  ans->unusedbits = unusedbits;
  return ans;
}

static void
freebits(Bits* b)
{
  if(b != nil)
    free(b);
}

static Elist*
mkel(Elem e, Elist* tail)
{
  Elist* el;

  el = (Elist*)emalloc(sizeof(Elist));
  el->hd = e;
  el->tl = tail;
  return el;
}

static int
elistlen(Elist* el)
{
  int ans = 0;
  while(el != nil) {
    ans++;
    el = el->tl;
  }
  return ans;
}

/* Frees elist, but not fields inside values of constituent elems */
static void
freeelist(Elist* el)
{
  Elist* next;

  while(el != nil) {
    next = el->tl;
    free(el);
    el = next;
  }
}

/* free any allocated structures inside v (recursively freeing Elists) */
static void
freevalfields(Value* v)
{
  Elist* el;
  Elist* l;
  if(v == nil)
    return;
  switch(v->tag) {
  case VOctets:
    freebytes(v->u.octetsval);
    break;
  case VBigInt:
    freebytes(v->u.bigintval);
    break;
  case VReal:
    freebytes(v->u.realval);
    break;
  case VOther:
    freebytes(v->u.otherval);
    break;
  case VBitString:
    freebits(v->u.bitstringval);
    break;
  case VObjId:
    freeints(v->u.objidval);
    break;
  case VString:
    if (v->u.stringval)
      free(v->u.stringval);
    break;
  case VSeq:
    el = v->u.seqval;
    for(l = el; l != nil; l = l->tl)
      freevalfields(&l->hd.val);
    if (el)
      freeelist(el);
    break;
  case VSet:
    el = v->u.setval;
    for(l = el; l != nil; l = l->tl)
      freevalfields(&l->hd.val);
    if (el)
      freeelist(el);
    break;
  }
}

/* end of general ASN1 functions */





/*=============================================================*/
/*
 * Decode and parse an X.509 Certificate, defined by this ASN1:
 *  Certificate ::= SEQUENCE {
 *    certificateInfo CertificateInfo,
 *    signatureAlgorithm AlgorithmIdentifier,
 *    signature BIT STRING }
 *
 *  CertificateInfo ::= SEQUENCE {
 *    version [0] INTEGER DEFAULT v1 (0),
 *    serialNumber INTEGER,
 *    signature AlgorithmIdentifier,
 *    issuer Name,
 *    validity Validity,
 *    subject Name,
 *    subjectPublicKeyInfo SubjectPublicKeyInfo }
 *  (version v2 has two more fields, optional unique identifiers for
 *  issuer and subject; since we ignore these anyway, we won't parse them)
 *
 *  Validity ::= SEQUENCE {
 *    notBefore UTCTime,
 *    notAfter UTCTime }
 *
 *  SubjectPublicKeyInfo ::= SEQUENCE {
 *    algorithm AlgorithmIdentifier,
 *    subjectPublicKey BIT STRING }
 *
 *  AlgorithmIdentifier ::= SEQUENCE {
 *    algorithm OBJECT IDENTIFER,
 *    parameters ANY DEFINED BY ALGORITHM OPTIONAL }
 *
 *  Name ::= SEQUENCE OF RelativeDistinguishedName
 *
 *  RelativeDistinguishedName ::= SETOF SIZE(1..MAX) OF AttributeTypeAndValue
 *
 *  AttributeTypeAndValue ::= SEQUENCE {
 *    type OBJECT IDENTIFER,
 *    value DirectoryString }
 *  (selected attributes have these Object Ids:
 *    commonName {2 5 4 3}
 *    countryName {2 5 4 6}
 *    localityName {2 5 4 7}
 *    stateOrProvinceName {2 5 4 8}
 *    organizationName {2 5 4 10}
 *    organizationalUnitName {2 5 4 11}
 *  )
 *
 *  DirectoryString ::= CHOICE {
 *    teletexString TeletexString,
 *    printableString PrintableString,
 *    universalString UniversalString }
 *
 *  See rfc1423, rfc2437 for AlgorithmIdentifier, subjectPublicKeyInfo, signature.
 *
 *  Not yet implemented:
 *   CertificateRevocationList ::= SIGNED SEQUENCE{
 *           signature       AlgorithmIdentifier,
 *           issuer          Name,
 *           lastUpdate      UTCTime,
 *           nextUpdate      UTCTime,
 *           revokedCertificates
 *                           SEQUENCE OF CRLEntry OPTIONAL}
 *   CRLEntry ::= SEQUENCE{
 *           userCertificate SerialNumber,
 *           revocationDate UTCTime}
 */

typedef struct CertX509 {
  int serial;
  char* issuer;
  char* validity_start;
  char* validity_end;
  char* subject;
  int publickey_alg;
  Bytes*  publickey;
  int signature_alg;
  Bytes*  signature;
} CertX509;

/* Algorithm object-ids */
enum {
  ALG_rsaEncryption,
  ALG_md2WithRSAEncryption,
  ALG_md4WithRSAEncryption,
  ALG_md5WithRSAEncryption,
  ALG_sha1WithRSAEncryption,
  ALG_md5,
  NUMALGS
};
typedef struct Ints7 {
  int   len;
  int   data[7];
} Ints7;
static Ints7 oid_rsaEncryption = {7, 1, 2, 840, 113549, 1, 1, 1 };
static Ints7 oid_md2WithRSAEncryption = {7, 1, 2, 840, 113549, 1, 1, 2 };
static Ints7 oid_md4WithRSAEncryption = {7, 1, 2, 840, 113549, 1, 1, 3 };
static Ints7 oid_md5WithRSAEncryption = {7, 1, 2, 840, 113549, 1, 1, 4 };
static Ints7 oid_sha1WithRSAEncryption ={7, 1, 2, 840, 113549, 1, 1, 5 };
static Ints7 oid_md5 ={6, 1, 2, 840, 113549, 2, 5, 0 };
static Ints *alg_oid_tab[NUMALGS+1] = {
  (Ints*)(void*)&oid_rsaEncryption,
  (Ints*)(void*)&oid_md2WithRSAEncryption,
  (Ints*)(void*)&oid_md4WithRSAEncryption,
  (Ints*)(void*)&oid_md5WithRSAEncryption,
  (Ints*)(void*)&oid_sha1WithRSAEncryption,
  (Ints*)(void*)&oid_md5,
  nil
};
static DigestFun digestalg[NUMALGS+1] = { md5, md5, md5, md5, sha1, md5, 0 };

static void
freecert(CertX509* c)
{
  if (!c) return;
  if(c->issuer != nil)
    free(c->issuer);
  if(c->validity_start != nil)
    free(c->validity_start);
  if(c->validity_end != nil)
    free(c->validity_end);
  if(c->subject != nil)
    free(c->subject);
  freebytes(c->publickey);
  freebytes(c->signature);
}

/*
 * Parse the Name ASN1 type.
 * The sequence of RelativeDistinguishedName's gives a sort of pathname,
 * from most general to most specific.  Each element of the path can be
 * one or more (but usually just one) attribute-value pair, such as
 * countryName="US".
 * We'll just form a "postal-style" address string by concatenating the elements
 * from most specific to least specific, separated by commas.
 * Return name-as-string (which must be freed by caller).
 */
static char*
parse_name(Elem* e)
{
  Elist* el;
  Elem* es;
  Elist* esetl;
  Elem* eat;
  Elist* eatl;
  char* s;
  enum { MAXPARTS = 100 };
  char* parts[MAXPARTS];
  int i;
  int plen;
  char* ans = nil;

  if(!is_seq(e, &el))
    goto errret;
  i = 0;
  plen = 0;
  while(el != nil) {
    es = &el->hd;
    if(!is_set(es, &esetl))
      goto errret;
    while(esetl != nil) {
      eat = &esetl->hd;
      if(!is_seq(eat, &eatl) || elistlen(eatl) != 2)
        goto errret;
      if(!is_string(&eatl->tl->hd, &s) || i>=MAXPARTS)
        goto errret;
      parts[i++] = s;
      plen += strlen(s) + 2;    /* room for ", " after */
      esetl = esetl->tl;
    }
    el = el->tl;
  }
  if(i > 0) {
    ans = (char*)emalloc(plen);
    *ans = '\0';
    while(--i >= 0) {
      s = parts[i];
      strcat(ans, s);
      if(i > 0)
        strcat(ans, ", ");
    }
  }

errret:
  return ans;
}

/*
 * Parse an AlgorithmIdentifer ASN1 type.
 * Look up the oid in oid_tab and return one of OID_rsaEncryption, etc..,
 * or -1 if not found.
 * For now, ignore parameters, since none of our algorithms need them.
 */
static int
parse_alg(Elem* e)
{
  Elist* el;
  Ints* oid;

  if(!is_seq(e, &el) || el == nil || !is_oid(&el->hd, &oid))
    return -1;
  return oid_lookup(oid, alg_oid_tab);
}

static CertX509*
decode_cert(Bytes* a)
{
  int ok = 0;
  int n;
  CertX509* c = nil;
  Elem  ecert;
  Elem* ecertinfo;
  Elem* esigalg;
  Elem* esig;
  Elem* eserial;
  Elem* eissuer;
  Elem* evalidity;
  Elem* esubj;
  Elem* epubkey;
  Elist* el;
  Elist* elcert = nil;
  Elist* elcertinfo = nil;
  Elist* elvalidity = nil;
  Elist* elpubkey = nil;
  Bits* bits = nil;
  Bytes* b;
  Elem* e;

  if(decode(a->data, a->len, &ecert) != ASN_OK)
    goto errret;

  c = (CertX509*)emalloc(sizeof(CertX509));
  c->serial = -1;
  c->issuer = nil;
  c->validity_start = nil;
  c->validity_end = nil;
  c->subject = nil;
  c->publickey_alg = -1;
  c->publickey = nil;
  c->signature_alg = -1;
  c->signature = nil;

  /* Certificate */
  if(!is_seq(&ecert, &elcert) || elistlen(elcert) !=3)
    goto errret;
  ecertinfo = &elcert->hd;
  el = elcert->tl;
  esigalg = &el->hd;
  c->signature_alg = parse_alg(esigalg);
  el = el->tl;
  esig = &el->hd;

  /* Certificate Info */
  if(!is_seq(ecertinfo, &elcertinfo))
    goto errret;
  n = elistlen(elcertinfo);
    if(n < 6)
    goto errret;
  eserial =&elcertinfo->hd;
  el = elcertinfo->tl;
  /* check for optional version, marked by explicit context tag 0 */
  if(eserial->tag.class == Context && eserial->tag.num == 0) {
    eserial = &el->hd;
    if(n < 7)
      goto errret;
    el = el->tl;
  }

  if(parse_alg(&el->hd) != c->signature_alg)
    goto errret;
  el = el->tl;
  eissuer = &el->hd;
  el = el->tl;
  evalidity = &el->hd;
  el = el->tl;
  esubj = &el->hd;
  el = el->tl;
  epubkey = &el->hd;
  if(!is_int(eserial, &c->serial)) {
    if(!is_bigint(eserial, &b))
      goto errret;
    c->serial = -1; /* else we have to change cert struct */
    }
  c->issuer = parse_name(eissuer);
  if(c->issuer == nil)
    goto errret;
  /* Validity */
    if(!is_seq(evalidity, &elvalidity))
    goto errret;
  if(elistlen(elvalidity) != 2)
    goto errret;
  e = &elvalidity->hd;
  if(!is_time(e, &c->validity_start))
    goto errret;
  e->val.u.stringval = nil; /* string ownership transfer */
  e = &elvalidity->tl->hd;
  if(!is_time(e, &c->validity_end))
    goto errret;
  e->val.u.stringval = nil; /* string ownership transfer */

  /* resume CertificateInfo */
  c->subject = parse_name(esubj);
  if(c->subject == nil)
    goto errret;

  /* SubjectPublicKeyInfo */
  if(!is_seq(epubkey, &elpubkey))
    goto errret;
  if(elistlen(elpubkey) != 2)
    goto errret;

  c->publickey_alg = parse_alg(&elpubkey->hd);
  if(c->publickey_alg < 0)
    goto errret;
    if(!is_bitstring(&elpubkey->tl->hd, &bits))
    goto errret;
  if(bits->unusedbits != 0)
    goto errret;
  c->publickey = makebytes(bits->data, bits->len);

  /*resume Certificate */
  if(c->signature_alg < 0)
    goto errret;
  if(!is_bitstring(esig, &bits))
    goto errret;
  c->signature = makebytes(bits->data, bits->len);
  ok = 1;

errret:
  freevalfields(&ecert.val);  /* recurses through lists, too */
  if(!ok){
    freecert(c);
    c = nil;
  }
  return c;
}

/*
 *  RSAPublickKey :: SEQUENCE {
 *    modulus INTEGER,
 *    publicExponent INTEGER
 *  }
 */
static RSApub*
decode_rsapubkey(Bytes* a)
{
  Elem e;
  Elist *el;
  mpint *mp;
  RSApub* key;

  key = rsapuballoc();
  if(decode(a->data, a->len, &e) != ASN_OK)
    goto errret;
  if(!is_seq(&e, &el) || elistlen(el) != 2)
    goto errret;

  key->n = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->ek = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;
  return key;
errret:
  rsapubfree(key);
  return nil;
}

/*
 *  RSAPrivateKey ::= SEQUENCE {
 *    version Version,
 *    modulus INTEGER, -- n
 *    publicExponent INTEGER, -- e
 *    privateExponent INTEGER, -- d
 *    prime1 INTEGER, -- p
 *    prime2 INTEGER, -- q
 *    exponent1 INTEGER, -- d mod (p-1)
 *    exponent2 INTEGER, -- d mod (q-1)
 *    coefficient INTEGER -- (inverse of q) mod p }
 */
static RSApriv*
decode_rsaprivkey(Bytes* a)
{
  int version;
  Elem e;
  Elist *el;
  mpint *mp;
  RSApriv* key;

  key = rsaprivalloc();
  if(decode(a->data, a->len, &e) != ASN_OK)
    goto errret;
  if(!is_seq(&e, &el) || elistlen(el) != 9)
    goto errret;
  if(!is_int(&el->hd, &version) || version != 0)
    goto errret;

  el = el->tl;
  key->pub.n = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->pub.ek = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->dk = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->q = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->p = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->kq = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->kp = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->c2 = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  return key;
errret:
  rsaprivfree(key);
  return nil;
}

/*
 *  DSAPrivateKey ::= SEQUENCE{
 *    version Version,
 *    p INTEGER,
 *    q INTEGER,
 *    g INTEGER, -- alpha
 *    pub_key INTEGER, -- key
 *    priv_key INTEGER, -- secret
 *  }
 */
static DSApriv*
decode_dsaprivkey(Bytes* a)
{
  int version;
  Elem e;
  Elist *el;
  mpint *mp;
  DSApriv* key;

  key = dsaprivalloc();
  if(decode(a->data, a->len, &e) != ASN_OK)
    goto errret;
  if(!is_seq(&e, &el) || elistlen(el) != 6)
    goto errret;
version=-1;
  if(!is_int(&el->hd, &version) || version != 0)
{
fprint(2, "version %d\n", version);
    goto errret;
  }

  el = el->tl;
  key->pub.p = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->pub.q = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->pub.alpha = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->pub.key = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  el = el->tl;
  key->secret = mp = asn1mpint(&el->hd);
  if(mp == nil)
    goto errret;

  return key;
errret:
  dsaprivfree(key);
  return nil;
}

static mpint*
asn1mpint(Elem *e)
{
  Bytes *b;
  mpint *mp;
  int v;

  if(is_int(e, &v))
    return itomp(v, nil);
  if(is_bigint(e, &b)) {
    mp = betomp(b->data, b->len, nil);
    freebytes(b);
    return mp;
  }
  return nil;
}

static mpint*
pkcs1pad(Bytes *b, mpint *modulus)
{
  int n = (mpsignif(modulus)+7)/8;
  int pm1, i;
  uchar *p;
  mpint *mp;

  pm1 = n - 1 - b->len;
  p = (uchar*)emalloc(n);
  p[0] = 0;
  p[1] = 1;
  for(i = 2; i < pm1; i++)
    p[i] = 0xFF;
  p[pm1] = 0;
  memcpy(&p[pm1+1], b->data, b->len);
  mp = betomp(p, n, nil);
  free(p);
  return mp;
}

RSApriv*
asn1toRSApriv(uchar *kd, int kn)
{
  Bytes *b;
  RSApriv *key;

  b = makebytes(kd, kn);
  key = decode_rsaprivkey(b);
  freebytes(b);
  return key;
}

DSApriv*
asn1toDSApriv(uchar *kd, int kn)
{
  Bytes *b;
  DSApriv *key;

  b = makebytes(kd, kn);
  key = decode_dsaprivkey(b);
  freebytes(b);
  return key;
}

/*
 * digest(CertificateInfo)
 * Our ASN.1 library doesn't return pointers into the original
 * data array, so we need to do a little hand decoding.
 */
static void
digest_certinfo(Bytes *cert, DigestFun digestfun, uchar *digest)
{
  uchar *info, *p, *pend;
  ulong infolen;
  int isconstr, length;
  Tag tag;
  Elem elem;

  p = cert->data;
  pend = cert->data + cert->len;
  if(tag_decode(&p, pend, &tag, &isconstr) != ASN_OK ||
     tag.class != Universal || tag.num != SEQUENCE ||
     length_decode(&p, pend, &length) != ASN_OK ||
     length > pend - p)
    return;
  info = p;
  if(ber_decode(&p, pend, &elem) != ASN_OK || elem.tag.num != SEQUENCE)
    return;
  infolen = p - info;
  (*digestfun)(info, infolen, digest, nil);
}

static char*
verify_signature(Bytes* signature, RSApub *pk, uchar *edigest, Elem **psigalg)
{
  Elem e;
  Elist *el;
  Bytes *digest;
  uchar *pkcs1buf, *buf;
  int buflen;
  mpint *pkcs1;
  int nlen;

  /* one less than the byte length of the modulus */
  nlen = (mpsignif(pk->n)-1)/8;

  /* see 9.2.1 of rfc2437 */
  pkcs1 = betomp(signature->data, signature->len, nil);
  mpexp(pkcs1, pk->ek, pk->n, pkcs1);
  pkcs1buf = nil;
  buflen = mptobe(pkcs1, nil, 0, &pkcs1buf);
  buf = pkcs1buf;
  if(buflen != nlen || buf[0] != 1)
    return "expected 1";
  buf++;
  while(buf[0] == 0xff)
    buf++;
  if(buf[0] != 0)
    return "expected 0";
  buf++;
  buflen -= buf-pkcs1buf;
  if(decode(buf, buflen, &e) != ASN_OK || !is_seq(&e, &el) || elistlen(el) != 2 ||
      !is_octetstring(&el->tl->hd, &digest))
    return "signature parse error";
  *psigalg = &el->hd;
  if(memcmp(digest->data, edigest, digest->len) == 0)
    return nil;
  return "digests did not match";
}

RSApub*
X509toRSApub(uchar *cert, int ncert, char *name, int nname)
{
  char *e;
  Bytes *b;
  CertX509 *c;
  RSApub *pk;

  b = makebytes(cert, ncert);
  c = decode_cert(b);
  freebytes(b);
  if(c == nil)
    return nil;
  if(name != nil && c->subject != nil){
    e = strchr(c->subject, ',');
    if(e != nil)
      *e = 0;  /* take just CN part of Distinguished Name */
    strncpy(name, c->subject, nname);
  }
  pk = decode_rsapubkey(c->publickey);
  freecert(c);
  return pk;
}

char*
X509verify(uchar *cert, int ncert, RSApub *pk)
{
  char *e;
  Bytes *b;
  CertX509 *c;
  uchar digest[SHA1dlen];
  Elem *sigalg;

  b = makebytes(cert, ncert);
  c = decode_cert(b);
  if(c != nil)
    digest_certinfo(b, digestalg[c->signature_alg], digest);
  freebytes(b);
  if(c == nil)
    return "cannot decode cert";
  e = verify_signature(c->signature, pk, digest, &sigalg);
  freecert(c);
  return e;
}

/* ------- Elem constructors ---------- */
static Elem
Null(void)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = NULLTAG;
  e.val.tag = VNull;
  return e;
}

static Elem
mkint(int j)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = INTEGER;
  e.val.tag = VInt;
  e.val.u.intval = j;
  return e;
}

static Elem
mkbigint(mpint *p)
{
  Elem e;
  uchar *buf;
  int buflen;

  e.tag.class = Universal;
  e.tag.num = INTEGER;
  e.val.tag = VBigInt;
  buflen = mptobe(p, nil, 0, &buf);
  e.val.u.bigintval = makebytes(buf, buflen);
  free(buf);
  return e;
}

static Elem
mkstring(char *s)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = IA5String;
  e.val.tag = VString;
  e.val.u.stringval = estrdup(s);
  return e;
}

static Elem
mkoctet(uchar *buf, int buflen)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = OCTET_STRING;
  e.val.tag = VOctets;
  e.val.u.octetsval = makebytes(buf, buflen);
  return e;
}

static Elem
mkbits(uchar *buf, int buflen)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = BIT_STRING;
  e.val.tag = VBitString;
  e.val.u.bitstringval = makebits(buf, buflen, 0);
  return e;
}

static Elem
mkutc(long t)
{
  Elem e;
  char utc[50];
  Tm *tm = gmtime(t);

  e.tag.class = Universal;
  e.tag.num = UTCTime;
  e.val.tag = VString;
  snprint(utc, 50, "%.2d%.2d%.2d%.2d%.2d%.2dZ",
    tm->year % 100, tm->mon+1, tm->mday, tm->hour, tm->min, tm->sec);
  e.val.u.stringval = estrdup(utc);
  return e;
}

static Elem
mkoid(Ints *oid)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = OBJECT_ID;
  e.val.tag = VObjId;
  e.val.u.objidval = makeints(oid->data, oid->len);
  return e;
}

static Elem
mkseq(Elist *el)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = SEQUENCE;
  e.val.tag = VSeq;
  e.val.u.seqval = el;
  return e;
}

static Elem
mkset(Elist *el)
{
  Elem e;

  e.tag.class = Universal;
  e.tag.num = SETOF;
  e.val.tag = VSet;
  e.val.u.setval = el;
  return e;
}

static Elem
mkalg(int alg)
{
  return mkseq(mkel(mkoid(alg_oid_tab[alg]), mkel(Null(), nil)));
}

typedef struct Ints7pref {
  int   len;
  int   data[7];
  char  prefix[4];
} Ints7pref;
Ints7pref DN_oid[] = {
  {4, 2, 5, 4, 6, 0, 0, 0,  "C="},
  {4, 2, 5, 4, 8, 0, 0, 0,  "ST="},
  {4, 2, 5, 4, 7, 0, 0, 0,  "L="},
  {4, 2, 5, 4, 10, 0, 0, 0, "O="},
  {4, 2, 5, 4, 11, 0, 0, 0, "OU="},
  {4, 2, 5, 4, 3, 0, 0, 0,  "CN="},
  {7, 1,2,840,113549,1,9,1, "E="},
};

static Elem
mkname(Ints7pref *oid, char *subj)
{
  return mkset(mkel(mkseq(mkel(mkoid((Ints*)oid), mkel(mkstring(subj), nil))), nil));
}

static Elem
mkDN(char *dn)
{
  int i, j, nf;
  char *f[20], *prefix, *d2 = estrdup(dn);
  Elist* el = nil;

  nf = tokenize(d2, f, nelem(f));
  for(i=nf-1; i>=0; i--){
    for(j=0; j<nelem(DN_oid); j++){
      prefix = DN_oid[j].prefix;
      if(strncmp(f[i],prefix,strlen(prefix))==0){
        el = mkel(mkname(&DN_oid[j],f[i]+strlen(prefix)), el);
        break;
      }
    }
  }
  free(d2);
  return mkseq(el);
}


uchar*
X509gen(RSApriv *priv, char *subj, ulong valid[2], int *certlen)
{
  int serial = 0;
  uchar *cert = nil;
  RSApub *pk = rsaprivtopub(priv);
  Bytes *certbytes, *pkbytes, *certinfobytes, *sigbytes;
  Elem e, certinfo, issuer, subject, pubkey, validity, sig;
  uchar digest[MD5dlen], *buf;
  int buflen;
  mpint *pkcs1;

  e.val.tag = VInt;  /* so freevalfields at errret is no-op */
  issuer = mkDN(subj);
  subject = mkDN(subj);
  pubkey = mkseq(mkel(mkbigint(pk->n),mkel(mkint(mptoi(pk->ek)),nil)));
  if(encode(pubkey, &pkbytes) != ASN_OK)
    goto errret;
  freevalfields(&pubkey.val);
  pubkey = mkseq(
    mkel(mkalg(ALG_rsaEncryption),
    mkel(mkbits(pkbytes->data, pkbytes->len),
    nil)));
  freebytes(pkbytes);
  validity = mkseq(
    mkel(mkutc(valid[0]),
    mkel(mkutc(valid[1]),
    nil)));
  certinfo = mkseq(
    mkel(mkint(serial),
    mkel(mkalg(ALG_md5WithRSAEncryption),
    mkel(issuer,
    mkel(validity,
    mkel(subject,
    mkel(pubkey,
    nil)))))));
  if(encode(certinfo, &certinfobytes) != ASN_OK)
    goto errret;
  md5(certinfobytes->data, certinfobytes->len, digest, 0);
  freebytes(certinfobytes);
  sig = mkseq(
    mkel(mkalg(ALG_md5),
    mkel(mkoctet(digest, MD5dlen),
    nil)));
  if(encode(sig, &sigbytes) != ASN_OK)
    goto errret;
  pkcs1 = pkcs1pad(sigbytes, pk->n);
  freebytes(sigbytes);
  rsadecrypt(priv, pkcs1, pkcs1);
  buflen = mptobe(pkcs1, nil, 0, &buf);
  mpfree(pkcs1);
  e = mkseq(
    mkel(certinfo,
    mkel(mkalg(ALG_md5WithRSAEncryption),
    mkel(mkbits(buf, buflen),
    nil))));
  free(buf);
  if(encode(e, &certbytes) != ASN_OK)
    goto errret;
  if(certlen)
    *certlen = certbytes->len;
  cert = certbytes->data;
errret:
  freevalfields(&e.val);
  return cert;
}

uchar*
X509req(RSApriv *priv, char *subj, int *certlen)
{
  /* RFC 2314, PKCS #10 Certification Request Syntax */
  int version = 0;
  uchar *cert = nil;
  RSApub *pk = rsaprivtopub(priv);
  Bytes *certbytes, *pkbytes, *certinfobytes, *sigbytes;
  Elem e, certinfo, subject, pubkey, sig;
  uchar digest[MD5dlen], *buf;
  int buflen;
  mpint *pkcs1;

  e.val.tag = VInt;  /* so freevalfields at errret is no-op */
  subject = mkDN(subj);
  pubkey = mkseq(mkel(mkbigint(pk->n),mkel(mkint(mptoi(pk->ek)),nil)));
  if(encode(pubkey, &pkbytes) != ASN_OK)
    goto errret;
  freevalfields(&pubkey.val);
  pubkey = mkseq(
    mkel(mkalg(ALG_rsaEncryption),
    mkel(mkbits(pkbytes->data, pkbytes->len),
    nil)));
  freebytes(pkbytes);
  certinfo = mkseq(
    mkel(mkint(version),
    mkel(subject,
    mkel(pubkey,
    nil))));
  if(encode(certinfo, &certinfobytes) != ASN_OK)
    goto errret;
  md5(certinfobytes->data, certinfobytes->len, digest, 0);
  freebytes(certinfobytes);
  sig = mkseq(
    mkel(mkalg(ALG_md5),
    mkel(mkoctet(digest, MD5dlen),
    nil)));
  if(encode(sig, &sigbytes) != ASN_OK)
    goto errret;
  pkcs1 = pkcs1pad(sigbytes, pk->n);
  freebytes(sigbytes);
  rsadecrypt(priv, pkcs1, pkcs1);
  buflen = mptobe(pkcs1, nil, 0, &buf);
  mpfree(pkcs1);
  e = mkseq(
    mkel(certinfo,
    mkel(mkalg(ALG_md5),
    mkel(mkbits(buf, buflen),
    nil))));
  free(buf);
  if(encode(e, &certbytes) != ASN_OK)
    goto errret;
  if(certlen)
    *certlen = certbytes->len;
  cert = certbytes->data;
errret:
  freevalfields(&e.val);
  return cert;
}

static char*
tagdump(Tag tag)
{
  if(tag.class != Universal)
    return smprint("class%d,num%d", tag.class, tag.num);
  switch(tag.num){
    case BOOLEAN: return "BOOLEAN"; break;
    case INTEGER: return "INTEGER"; break;
    case BIT_STRING: return "BIT STRING"; break;
    case OCTET_STRING: return "OCTET STRING"; break;
    case NULLTAG: return "NULLTAG"; break;
    case OBJECT_ID: return "OID"; break;
    case ObjectDescriptor: return "OBJECT_DES"; break;
    case EXTERNAL: return "EXTERNAL"; break;
    case REAL: return "REAL"; break;
    case ENUMERATED: return "ENUMERATED"; break;
    case EMBEDDED_PDV: return "EMBEDDED PDV"; break;
    case SEQUENCE: return "SEQUENCE"; break;
    case SETOF: return "SETOF"; break;
    case NumericString: return "NumericString"; break;
    case PrintableString: return "PrintableString"; break;
    case TeletexString: return "TeletexString"; break;
    case VideotexString: return "VideotexString"; break;
    case IA5String: return "IA5String"; break;
    case UTCTime: return "UTCTime"; break;
    case GeneralizedTime: return "GeneralizedTime"; break;
    case GraphicString: return "GraphicString"; break;
    case VisibleString: return "VisibleString"; break;
    case GeneralString: return "GeneralString"; break;
    case UniversalString: return "UniversalString"; break;
    case BMPString: return "BMPString"; break;
    default:
      return smprint("Universal,num%d", tag.num);
  }
}

static void
edump(Elem e)
{
  Value v;
  Elist *el;
  int i;

  print("%s{", tagdump(e.tag));
  v = e.val;
  switch(v.tag){
  case VBool: print("Bool %d",v.u.boolval); break;
  case VInt: print("Int %d",v.u.intval); break;
  case VOctets: print("Octets[%d] %.2x%.2x...",v.u.octetsval->len,v.u.octetsval->data[0],v.u.octetsval->data[1]); break;
  case VBigInt: print("BigInt[%d] %.2x%.2x...",v.u.bigintval->len,v.u.bigintval->data[0],v.u.bigintval->data[1]); break;
  case VReal: print("Real..."); break;
  case VOther: print("Other..."); break;
  case VBitString: print("BitString..."); break;
  case VNull: print("Null"); break;
  case VEOC: print("EOC..."); break;
  case VObjId: print("ObjId");
    for(i = 0; i<v.u.objidval->len; i++)
      print(" %d", v.u.objidval->data[i]);
    break;
  case VString: print("String \"%s\"",v.u.stringval); break;
  case VSeq: print("Seq\n");
    for(el = v.u.seqval; el!=nil; el = el->tl)
      edump(el->hd);
    break;
  case VSet: print("Set\n");
    for(el = v.u.setval; el!=nil; el = el->tl)
      edump(el->hd);
    break;
  }
  print("}\n");
}

void
asn1dump(uchar *der, int len)
{
  Elem e;

  if(decode(der, len, &e) != ASN_OK){
    //print("didn't parse\n");
    //exits("didn't parse");
    return;
  }
  edump(e);
}

void
X509dump(uchar *cert, int ncert)
{
  char *e;
  Bytes *b;
  CertX509 *c;
  RSApub *pk;
  uchar digest[SHA1dlen];
  Elem *sigalg;

  print("begin X509dump\n");
  b = makebytes(cert, ncert);
  c = decode_cert(b);
  if(c != nil)
    digest_certinfo(b, digestalg[c->signature_alg], digest);
  freebytes(b);
  if(c == nil){
    print("cannot decode cert");
    return;
  }

  print("serial %d\n", c->serial);
  print("issuer %s\n", c->issuer);
  print("validity %s %s\n", c->validity_start, c->validity_end);
  print("subject %s\n", c->subject);
  pk = decode_rsapubkey(c->publickey);
  print("pubkey e=%B n(%d)=%B\n", pk->ek, mpsignif(pk->n), pk->n);

  print("sigalg=%d digest=%.*H\n", c->signature_alg, MD5dlen, digest);
  e = verify_signature(c->signature, pk, digest, &sigalg);
  if(e==nil){
    e = "nil (meaning ok)";
    print("sigalg=\n");
    if(sigalg)
      edump(*sigalg);
  }
  print("self-signed verify_signature returns: %s\n", e);

  rsapubfree(pk);
  freecert(c);
  print("end X509dump\n");
}

Coverage Report

Created: 2024-02-27 06:14