The encoding of negative ASN1 INTEGERs and the conversion of BNs to negative
authorDr. Stephen Henson <steve@openssl.org>
Fri, 14 May 1999 18:21:21 +0000 (18:21 +0000)
committerDr. Stephen Henson <steve@openssl.org>
Fri, 14 May 1999 18:21:21 +0000 (18:21 +0000)
integers was completely broken. Also added a NEG_PUBKEY_BUG compilation option
to compensate for public keys improperly encoded as negative integers.

CHANGES
crypto/asn1/a_enum.c
crypto/asn1/a_int.c
crypto/asn1/asn1.h
crypto/asn1/asn1_err.c
crypto/asn1/d2i_dsap.c
crypto/asn1/d2i_r_pu.c
crypto/asn1/d2i_s_pu.c
util/libeay.num

diff --git a/CHANGES b/CHANGES
index 1bd0fc2..b72f682 100644 (file)
--- a/CHANGES
+++ b/CHANGES
                                    [23-Dec-1998] down below; but in later
                                    versions, these hyphens are gone.]
 
+  *) Fix the encoding and decoding of negative ASN1 INTEGERS and conversion
+     to and from BNs: it was completely broken. New compilation option
+     NEG_PUBKEY_BUG to allow for some broken certificates that encode public
+     key elements as negative integers.
+     [Steve Henson]
+
   *) Reorganize and speed up MD5.
      [Andy Polyakov <appro@fy.chalmers.se>]
 
index 3654039..9239ecc 100644 (file)
 #include "cryptlib.h"
 #include <openssl/asn1.h>
 
-/* Support for ASN1 ENUMERATED type: based on a_int.c */
+/* 
+ * Code for ENUMERATED type: identical to INTEGER apart from a different tag.
+ * for comments on encoding see a_int.c
+ */
 
 int i2d_ASN1_ENUMERATED(ASN1_ENUMERATED *a, unsigned char **pp)
        {
        int pad=0,ret,r,i,t;
-       unsigned char *p,*pt,*n,pb=0;
+       unsigned char *p,*n,pb=0;
 
        if ((a == NULL) || (a->data == NULL)) return(0);
        t=a->type;
@@ -75,16 +78,21 @@ int i2d_ASN1_ENUMERATED(ASN1_ENUMERATED *a, unsigned char **pp)
                {
                ret=a->length;
                i=a->data[0];
-               if ((t == V_ASN1_ENUMERATED) && (i > 127))
-                       {
+               if ((t == V_ASN1_ENUMERATED) && (i > 127)) {
                        pad=1;
                        pb=0;
+               } else if(t == V_ASN1_NEG_ENUMERATED) {
+                       if(i>128) {
+                               pad=1;
+                               pb=0xFF;
+                       } else if(i == 128) {
+                               for(i = 1; i < a->length; i++) if(a->data[i]) {
+                                               pad=1;
+                                               pb=0xFF;
+                                               break;
+                               }
                        }
-               else if ((t == V_ASN1_NEG_ENUMERATED) && (i>128))
-                       {
-                       pad=1;
-                       pb=0xFF;
-                       }
+               }
                ret+=pad;
                }
        r=ASN1_object_size(0,ret,V_ASN1_ENUMERATED);
@@ -100,14 +108,24 @@ int i2d_ASN1_ENUMERATED(ASN1_ENUMERATED *a, unsigned char **pp)
                memcpy(p,a->data,(unsigned int)a->length);
                p+=a->length;
                }
-       else
-               {
-               n=a->data;
-               pt=p;
-               for (i=a->length; i>0; i--)
-                       *(p++)= (*(n++)^0xFF)+1;
-               if (!pad) *pt|=0x80;
+       else {
+               /* Begin at the end of the encoding */
+               n=a->data + a->length - 1;
+               p += a->length - 1;
+               i = a->length;
+               /* Copy zeros to destination as long as source is zero */
+               while(!*n) {
+                       *(p--) = 0;
+                       n--;
+                       i--;
                }
+               /* Complement and increment next octet */
+               *(p--) = ((*(n--)) ^ 0xff) + 1;
+               i--;
+               /* Complement any octets left */
+               for(;i > 0; i--) *(p--) = *(n--) ^ 0xff;
+               p += a->length;
+       }
 
        *pp=p;
        return(r);
@@ -156,16 +174,30 @@ ASN1_ENUMERATED *d2i_ASN1_ENUMERATED(ASN1_ENUMERATED **a, unsigned char **pp,
        if (*p & 0x80) /* a negative number */
                {
                ret->type=V_ASN1_NEG_ENUMERATED;
-               if (*p == 0xff)
-                       {
+               if ((*p == 0xff) && (len != 1)) {
                        p++;
                        len--;
-                       }
-               for (i=(int)len; i>0; i--)
-                       *(to++)= (*(p++)^0xFF)+1;
                }
-       else
-               {
+               i = len;
+               p += i - 1;
+               to += i - 1;
+               while((!*p) && i) {
+                       *(to--) = 0;
+                       i--;
+                       p--;
+               }
+               if(!i) {
+                       *s = 1;
+                       s[len] = 0;
+                       p += len;
+                       len++;
+               } else {
+                       *(to--) = (*(p--) ^ 0xff) + 1;
+                       i--;
+                       for(;i > 0; i--) *(to--) = *(p--) ^ 0xff;
+                       p += len;
+               }
+       } else {
                ret->type=V_ASN1_ENUMERATED;
                if ((*p == 0) && (len != 1))
                        {
@@ -174,7 +206,7 @@ ASN1_ENUMERATED *d2i_ASN1_ENUMERATED(ASN1_ENUMERATED **a, unsigned char **pp,
                        }
                memcpy(s,p,(int)len);
                p+=len;
-               }
+       }
 
        if (ret->data != NULL) Free((char *)ret->data);
        ret->data=s;
@@ -222,7 +254,6 @@ int ASN1_ENUMERATED_set(ASN1_ENUMERATED *a, long v)
                d>>=8;
                }
        j=0;
-       if (v < 0) a->data[j++]=0;
        for (k=i-1; k >=0; k--)
                a->data[j++]=buf[k];
        a->length=j;
@@ -272,7 +303,8 @@ ASN1_ENUMERATED *BN_to_ASN1_ENUMERATED(BIGNUM *bn, ASN1_ENUMERATED *ai)
                ASN1err(ASN1_F_BN_TO_ASN1_ENUMERATED,ERR_R_NESTED_ASN1_ERROR);
                goto err;
                }
-       ret->type=V_ASN1_ENUMERATED;
+       if(bn->neg) ret->type = V_ASN1_NEG_ENUMERATED;
+       else ret->type=V_ASN1_ENUMERATED;
        j=BN_num_bits(bn);
        len=((j == 0)?0:((j/8)+1));
        ret->data=(unsigned char *)Malloc(len+4);
@@ -289,5 +321,6 @@ BIGNUM *ASN1_ENUMERATED_to_BN(ASN1_ENUMERATED *ai, BIGNUM *bn)
 
        if ((ret=BN_bin2bn(ai->data,ai->length,bn)) == NULL)
                ASN1err(ASN1_F_ASN1_ENUMERATED_TO_BN,ASN1_R_BN_LIB);
+       if(ai->type == V_ASN1_NEG_ENUMERATED) bn->neg = 1;
        return(ret);
        }
index 6e8c7e5..768476a 100644 (file)
 #include "cryptlib.h"
 #include <openssl/asn1.h>
 
+/* 
+ * This converts an ASN1 INTEGER into its DER encoding.
+ * The internal representation is an ASN1_STRING whose data is a big endian
+ * representation of the value, ignoring the sign. The sign is determined by
+ * the type: V_ASN1_INTEGER for positive and V_ASN1_NEG_INTEGER for negative. 
+ *
+ * Positive integers are no problem: they are almost the same as the DER
+ * encoding, except if the first byte is >= 0x80 we need to add a zero pad.
+ *
+ * Negative integers are a bit trickier...
+ * The DER representation of negative integers is in 2s complement form.
+ * The internal form is converted by complementing each octet and finally 
+ * adding one to the result. This can be done less messily with a little trick.
+ * If the internal form has trailing zeroes then they will become FF by the
+ * complement and 0 by the add one (due to carry) so just copy as many trailing 
+ * zeros to the destination as there are in the source. The carry will add one
+ * to the last none zero octet: so complement this octet and add one and finally
+ * complement any left over until you get to the start of the string.
+ *
+ * Padding is a little trickier too. If the first bytes is > 0x80 then we pad
+ * with 0xff. However if the first byte is 0x80 and one of the following bytes
+ * is non-zero we pad with 0xff. The reason for this distinction is that 0x80
+ * followed by optional zeros isn't padded.
+ */
+
 int i2d_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
        {
        int pad=0,ret,r,i,t;
-       unsigned char *p,*pt,*n,pb=0;
+       unsigned char *p,*n,pb=0;
 
        if ((a == NULL) || (a->data == NULL)) return(0);
        t=a->type;
@@ -73,16 +98,25 @@ int i2d_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
                {
                ret=a->length;
                i=a->data[0];
-               if ((t == V_ASN1_INTEGER) && (i > 127))
-                       {
+               if ((t == V_ASN1_INTEGER) && (i > 127)) {
                        pad=1;
                        pb=0;
+               } else if(t == V_ASN1_NEG_INTEGER) {
+                       if(i>128) {
+                               pad=1;
+                               pb=0xFF;
+                       } else if(i == 128) {
+                       /*
+                        * Special case: if any other bytes non zero we pad:
+                        * otherwise we don't.
+                        */
+                               for(i = 1; i < a->length; i++) if(a->data[i]) {
+                                               pad=1;
+                                               pb=0xFF;
+                                               break;
+                               }
                        }
-               else if ((t == V_ASN1_NEG_INTEGER) && (i>128))
-                       {
-                       pad=1;
-                       pb=0xFF;
-                       }
+               }
                ret+=pad;
                }
        r=ASN1_object_size(0,ret,V_ASN1_INTEGER);
@@ -98,14 +132,24 @@ int i2d_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
                memcpy(p,a->data,(unsigned int)a->length);
                p+=a->length;
                }
-       else
-               {
-               n=a->data;
-               pt=p;
-               for (i=a->length; i>0; i--)
-                       *(p++)= (*(n++)^0xFF)+1;
-               if (!pad) *pt|=0x80;
+       else {
+               /* Begin at the end of the encoding */
+               n=a->data + a->length - 1;
+               p += a->length - 1;
+               i = a->length;
+               /* Copy zeros to destination as long as source is zero */
+               while(!*n) {
+                       *(p--) = 0;
+                       n--;
+                       i--;
                }
+               /* Complement and increment next octet */
+               *(p--) = ((*(n--)) ^ 0xff) + 1;
+               i--;
+               /* Complement any octets left */
+               for(;i > 0; i--) *(p--) = *(n--) ^ 0xff;
+               p += a->length;
+       }
 
        *pp=p;
        return(r);
@@ -154,16 +198,105 @@ ASN1_INTEGER *d2i_ASN1_INTEGER(ASN1_INTEGER **a, unsigned char **pp,
        if (*p & 0x80) /* a negative number */
                {
                ret->type=V_ASN1_NEG_INTEGER;
-               if (*p == 0xff)
+               if ((*p == 0xff) && (len != 1)) {
+                       p++;
+                       len--;
+               }
+               i = len;
+               p += i - 1;
+               to += i - 1;
+               while((!*p) && i) {
+                       *(to--) = 0;
+                       i--;
+                       p--;
+               }
+               /* Special case: if all zeros then the number will be of
+                * the form FF followed by n zero bytes: this corresponds to
+                * 1 followed by n zero bytes. We've already written n zeros
+                * so we just append an extra one and set the first byte to
+                * a 1. This is treated separately because it is the only case
+                * where the number of bytes is larger than len.
+                */
+               if(!i) {
+                       *s = 1;
+                       s[len] = 0;
+                       p += len;
+                       len++;
+               } else {
+                       *(to--) = (*(p--) ^ 0xff) + 1;
+                       i--;
+                       for(;i > 0; i--) *(to--) = *(p--) ^ 0xff;
+                       p += len;
+               }
+       } else {
+               ret->type=V_ASN1_INTEGER;
+               if ((*p == 0) && (len != 1))
                        {
                        p++;
                        len--;
                        }
-               for (i=(int)len; i>0; i--)
-                       *(to++)= (*(p++)^0xFF)+1;
+               memcpy(s,p,(int)len);
+               p+=len;
+       }
+
+       if (ret->data != NULL) Free((char *)ret->data);
+       ret->data=s;
+       ret->length=(int)len;
+       if (a != NULL) (*a)=ret;
+       *pp=p;
+       return(ret);
+err:
+       ASN1err(ASN1_F_D2I_ASN1_INTEGER,i);
+       if ((ret != NULL) && ((a == NULL) || (*a != ret)))
+               ASN1_INTEGER_free(ret);
+       return(NULL);
+       }
+
+/* This is a version of d2i_ASN1_INTEGER that ignores the sign bit of
+ * ASN1 integers: some broken software can encode a positive INTEGER
+ * with its MSB set as negative (it doesn't add a padding zero).
+ */
+
+ASN1_INTEGER *d2i_ASN1_UINTEGER(ASN1_INTEGER **a, unsigned char **pp,
+            long length)
+       {
+       ASN1_INTEGER *ret=NULL;
+       unsigned char *p,*to,*s;
+       long len;
+       int inf,tag,xclass;
+       int i;
+
+       if ((a == NULL) || ((*a) == NULL))
+               {
+               if ((ret=ASN1_INTEGER_new()) == NULL) return(NULL);
+               ret->type=V_ASN1_INTEGER;
                }
        else
+               ret=(*a);
+
+       p= *pp;
+       inf=ASN1_get_object(&p,&len,&tag,&xclass,length);
+       if (inf & 0x80)
+               {
+               i=ASN1_R_BAD_OBJECT_HEADER;
+               goto err;
+               }
+
+       if (tag != V_ASN1_INTEGER)
                {
+               i=ASN1_R_EXPECTING_AN_INTEGER;
+               goto err;
+               }
+
+       /* We must Malloc stuff, even for 0 bytes otherwise it
+        * signifies a missing NULL parameter. */
+       s=(unsigned char *)Malloc((int)len+1);
+       if (s == NULL)
+               {
+               i=ERR_R_MALLOC_FAILURE;
+               goto err;
+               }
+       to=s;
                ret->type=V_ASN1_INTEGER;
                if ((*p == 0) && (len != 1))
                        {
@@ -172,7 +305,6 @@ ASN1_INTEGER *d2i_ASN1_INTEGER(ASN1_INTEGER **a, unsigned char **pp,
                        }
                memcpy(s,p,(int)len);
                p+=len;
-               }
 
        if (ret->data != NULL) Free((char *)ret->data);
        ret->data=s;
@@ -181,7 +313,7 @@ ASN1_INTEGER *d2i_ASN1_INTEGER(ASN1_INTEGER **a, unsigned char **pp,
        *pp=p;
        return(ret);
 err:
-       ASN1err(ASN1_F_D2I_ASN1_INTEGER,i);
+       ASN1err(ASN1_F_D2I_ASN1_UINTEGER,i);
        if ((ret != NULL) && ((a == NULL) || (*a != ret)))
                ASN1_INTEGER_free(ret);
        return(NULL);
@@ -220,7 +352,6 @@ int ASN1_INTEGER_set(ASN1_INTEGER *a, long v)
                d>>=8;
                }
        j=0;
-       if (v < 0) a->data[j++]=0;
        for (k=i-1; k >=0; k--)
                a->data[j++]=buf[k];
        a->length=j;
@@ -270,7 +401,8 @@ ASN1_INTEGER *BN_to_ASN1_INTEGER(BIGNUM *bn, ASN1_INTEGER *ai)
                ASN1err(ASN1_F_BN_TO_ASN1_INTEGER,ERR_R_NESTED_ASN1_ERROR);
                goto err;
                }
-       ret->type=V_ASN1_INTEGER;
+       if(bn->neg) ret->type = V_ASN1_NEG_INTEGER;
+       else ret->type=V_ASN1_INTEGER;
        j=BN_num_bits(bn);
        len=((j == 0)?0:((j/8)+1));
        ret->data=(unsigned char *)Malloc(len+4);
@@ -287,5 +419,6 @@ BIGNUM *ASN1_INTEGER_to_BN(ASN1_INTEGER *ai, BIGNUM *bn)
 
        if ((ret=BN_bin2bn(ai->data,ai->length,bn)) == NULL)
                ASN1err(ASN1_F_ASN1_INTEGER_TO_BN,ASN1_R_BN_LIB);
+       if(ai->type == V_ASN1_NEG_INTEGER) bn->neg = 1;
        return(ret);
        }
index 8dc61e1..a0a3130 100644 (file)
@@ -518,6 +518,8 @@ int                 d2i_ASN1_BOOLEAN(int *a,unsigned char **pp,long length);
 int            i2d_ASN1_INTEGER(ASN1_INTEGER *a,unsigned char **pp);
 ASN1_INTEGER *d2i_ASN1_INTEGER(ASN1_INTEGER **a,unsigned char **pp,
                        long length);
+ASN1_INTEGER *d2i_ASN1_UINTEGER(ASN1_INTEGER **a,unsigned char **pp,
+                       long length);
 
 int            i2d_ASN1_ENUMERATED(ASN1_ENUMERATED *a,unsigned char **pp);
 ASN1_ENUMERATED *d2i_ASN1_ENUMERATED(ASN1_ENUMERATED **a,unsigned char **pp,
@@ -739,6 +741,7 @@ ASN1_STRING *ASN1_pack_string(char *obj, int (*i2d)(), ASN1_OCTET_STRING **oct);
 #define ASN1_F_D2I_ASN1_TIME                            224
 #define ASN1_F_D2I_ASN1_TYPE                            133
 #define ASN1_F_D2I_ASN1_TYPE_BYTES                      134
+#define ASN1_F_D2I_ASN1_UINTEGER                        280
 #define ASN1_F_D2I_ASN1_UTCTIME                                 135
 #define ASN1_F_D2I_ASN1_UTF8STRING                      266
 #define ASN1_F_D2I_ASN1_VISIBLESTRING                   267
index d3e0d0e..fbf73fb 100644 (file)
@@ -115,6 +115,7 @@ static ERR_STRING_DATA ASN1_str_functs[]=
 {ERR_PACK(0,ASN1_F_D2I_ASN1_TIME,0),   "d2i_ASN1_TIME"},
 {ERR_PACK(0,ASN1_F_D2I_ASN1_TYPE,0),   "d2i_ASN1_TYPE"},
 {ERR_PACK(0,ASN1_F_D2I_ASN1_TYPE_BYTES,0),     "d2i_ASN1_type_bytes"},
+{ERR_PACK(0,ASN1_F_D2I_ASN1_UINTEGER,0),       "d2i_ASN1_UINTEGER"},
 {ERR_PACK(0,ASN1_F_D2I_ASN1_UTCTIME,0),        "d2i_ASN1_UTCTIME"},
 {ERR_PACK(0,ASN1_F_D2I_ASN1_UTF8STRING,0),     "d2i_ASN1_UTF8STRING"},
 {ERR_PACK(0,ASN1_F_D2I_ASN1_VISIBLESTRING,0),  "d2i_ASN1_VISIBLESTRING"},
index 51863a8..cdd7136 100644 (file)
 #include <openssl/objects.h>
 #include <openssl/asn1_mac.h>
 
+#ifdef NEG_PUBKEY_BUG
+#define d2i_ASN1_INTEGER d2i_ASN1_UINTEGER
+#endif
+
 DSA *d2i_DSAparams(DSA **a, unsigned char **pp, long length)
        {
        int i=ERR_R_NESTED_ASN1_ERROR;
index 04cfe56..c4ae58b 100644 (file)
 #include <openssl/objects.h>
 #include <openssl/asn1_mac.h>
 
+#ifdef NEG_PUBKEY_BUG
+#define d2i_ASN1_INTEGER d2i_ASN1_UINTEGER
+#endif
+
 RSA *d2i_RSAPublicKey(RSA **a, unsigned char **pp, long length)
        {
        int i=ASN1_R_PARSING;
index 2b1bf63..94ea1c3 100644 (file)
 #include <openssl/objects.h>
 #include <openssl/asn1_mac.h>
 
+#ifdef NEG_PUBKEY_BUG
+#define d2i_ASN1_INTEGER d2i_ASN1_UINTEGER
+#endif
+
 DSA *d2i_DSAPublicKey(DSA **a, unsigned char **pp, long length)
        {
        int i=ASN1_R_PARSING;
index 01299b1..7be174a 100755 (executable)
@@ -1624,3 +1624,4 @@ X509V3_EXT_add_list                     1648
 EVP_CIPHER_type                         1649
 EVP_PBE_CipherInit                      1650
 X509V3_add_value_bool_nf                1651
+d2i_ASN1_UINTEGER                       1652