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asn1: Further IMPLICIT tagging fixes

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Commit 89389bc7a (asn1: Fix long-standing IMPLICIT tagging brokenness)
was incomplete.  Removing the hacks in lib/asn1/cms.asn1 revealed this.

Now the ASN.1 compiler generates enums to indicate what is the class and
tag of each type.  This is needed so the decoder functions generated by
the compiler can know what tag to restore.

Now, too, the compiler does handle IMPLICIT tags whose encoded length is
different from that of the underlying type.

However, we now don't handle indefinite BER and non-DER definite lengths
(DCE) following IMPLICIT tags.  This would affect only CMS in-tree.
This commit is contained in:
Nicolas Williams
2021-01-17 20:48:23 -06:00
parent 6d85ba384f
commit 81195acafa
12 changed files with 532 additions and 183 deletions
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128
lib/asn1/gen_decode.c
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@@ -362,6 +362,20 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
break;
}
case TSet: {
/*
* SET { ... } is the dumbest construct in ASN.1. It's semantically
* indistinguishable from SEQUENCE { ... } but in BER you can write the
* fields in any order you wish, and in DER you have to write them in
* lexicographic order. If you want a reason to hate ASN.1, this is
* certainly one, though the real reason to hate ASN.1 is BER/DER/CER,
* and, really, all tag-length-value (TLV) encodings ever invented,
* including Protocol Buffers. Fortunately not all ASN.1 encoding
* rules are TLV or otherwise self-describing. "Self-describing"
* encoding rules other than those meant to be [somewhat] readable by
* humans, such as XML and JSON, are simply dumb. But SET { ... } is a
* truly special sort of dumb. The only possible use of SET { ... }
* might well be for ASN.1 mappings of XML schemas(?).
*/
Member *m;
unsigned int memno;
@@ -391,6 +405,7 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
fprintf(codefile, "case MAKE_TAG(%s, %s, %s):\n",
classname(mst->tag.tagclass),
(mst->tag.tagclass == ASN1_C_UNIV || mst->tag.tagenv == TE_IMPLICIT) &&
is_primitive_type(mst->subtype) ? "PRIM" : "CONS",
valuename(mst->tag.tagclass, mst->tag.tagvalue));
@@ -506,17 +521,41 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
t->tag.tagenv == TE_EXPLICIT) &&
is_primitive_type(t->subtype);
/*
* XXX See the comments in gen_encode() about this.
*/
if (t->tag.tagenv == TE_IMPLICIT && !prim &&
t->subtype->type != TSequenceOf && t->subtype->type != TSetOf &&
t->subtype->type != TChoice) {
if (t->subtype->symbol &&
(t->subtype->type == TSequence ||
t->subtype->type == TSet))
replace_tag = 1;
else if (t->subtype->symbol && strcmp(t->subtype->symbol->name, "heim_any"))
replace_tag = 1;
} else if (t->tag.tagenv == TE_IMPLICIT && prim && t->subtype->symbol)
replace_tag = 1;
if (asprintf(&typestring, "%s_type", tmpstr) < 0 || typestring == NULL)
errx(1, "malloc");
fprintf(codefile,
"{\n"
"size_t %s_datalen, %s_oldlen;\n"
"size_t %s_datalen;\n"
"Der_type %s;\n",
tmpstr, tmpstr, typestring);
if(support_ber)
tmpstr, typestring);
if (replace_tag)
fprintf(codefile,
"const unsigned char *psave%u = p;\n"
"unsigned char *pcopy%u;\n"
"size_t lensave%u, lsave%u;\n",
depth, depth, depth, depth);
else if (support_ber)
fprintf(codefile,
"int is_indefinite%u;\n", depth);
if (!replace_tag)
fprintf(codefile,
"size_t %s_oldlen;\n", tmpstr);
fprintf(codefile, "e = der_match_tag_and_length(p, len, %s, &%s, %s, "
"&%s_datalen, &l);\n",
@@ -526,7 +565,7 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
tmpstr);
/* XXX hardcode for now */
if (support_ber && t->subtype->type == TOctetString) {
if (!replace_tag && support_ber && t->subtype->type == TOctetString) {
ide = typestring;
} else {
fprintf(codefile,
@@ -556,62 +595,50 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
} else {
fprintf(codefile, "if (e) %s;\n", forwstr);
}
fprintf (codefile,
"p += l; len -= l; ret += l;\n"
"%s_oldlen = len;\n",
tmpstr);
if(support_ber)
if (replace_tag)
fprintf(codefile,
"lsave%u = %s_datalen + l;\n"
"lensave%u = len;\n"
"e = der_replace_tag(p, len, &pcopy%u, &len, asn1_tag_class_%s, %s, asn1_tag_tag_%s);\n"
"if (e) %s;\n"
"p = pcopy%u;\n",
depth, tmpstr, depth, depth, t->subtype->symbol->gen_name,
prim ? "PRIM" : "CONS",
t->subtype->symbol->gen_name,
forwstr, depth);
else
fprintf(codefile,
"p += l; len -= l; ret += l;\n");
if (!replace_tag)
fprintf(codefile,
"%s_oldlen = len;\n",
tmpstr);
if (support_ber && !replace_tag)
fprintf (codefile,
"if((is_indefinite%u = _heim_fix_dce(%s_datalen, &len)) < 0)\n"
"{ e = ASN1_BAD_FORMAT; %s; }\n"
"if (is_indefinite%u) { if (len < 2) { e = ASN1_OVERRUN; %s; } len -= 2; }",
depth, tmpstr, forwstr, depth, forwstr);
else
else if (!replace_tag)
fprintf(codefile,
"if (%s_datalen > len) { e = ASN1_OVERRUN; %s; }\n"
"len = %s_datalen;\n", tmpstr, forwstr, tmpstr);
if (asprintf (&tname, "%s_Tag", tmpstr) < 0 || tname == NULL)
errx(1, "malloc");
/*
* XXX See the comments in gen_encode() about this.
* If `replace_tag' then here `p' and `len' will be the copy mutated by
* der_replace_tag().
*/
if (t->tag.tagenv == TE_IMPLICIT && !prim &&
t->subtype->type != TSequenceOf && t->subtype->type != TSetOf &&
t->subtype->type != TChoice) {
if (t->subtype->symbol &&
(t->subtype->type == TSequence ||
t->subtype->type == TSet))
replace_tag = 1;
else if (t->subtype->symbol && strcmp(t->subtype->symbol->name, "heim_any"))
replace_tag = 1;
} else if (t->tag.tagenv == TE_IMPLICIT && prim && t->subtype->symbol)
replace_tag = 1;
if (replace_tag) {
/*
* XXX We're assuming the IMPLICIT and original tags have the same
* length. This is one of the places that needs fixing if we want
* to properly support tags > 30.
*/
decode_type(name, t->subtype, 0, NULL, forwstr, tname, ide, depth + 1);
if (replace_tag)
fprintf(codefile,
"{ unsigned char *pcopy;\n"
"pcopy = calloc (1, len);\n"
"if (pcopy == 0) { e = ENOMEM; %s;}\n"
"memcpy (pcopy, p, len);\n"
"e = der_replace_tag (pcopy, len, %s, %s, %s);\n"
"if (e) %s;\n",
forwstr,
classname(t->subtype->tag.tagclass),
prim ? "PRIM" : "CONS",
valuename(t->subtype->tag.tagclass, t->subtype->tag.tagvalue),
forwstr);
decode_type(name, t->subtype, 0, NULL, forwstr, tname, ide, depth + 1);
fprintf(codefile,
"free(pcopy);"
"}\n");
} else {
decode_type(name, t->subtype, 0, NULL, forwstr, tname, ide, depth + 1);
}
if(support_ber)
"p = psave%u + lsave%u;\n"
"len = lensave%u - lsave%u;\n"
"ret += lsave%u - l;\n"
"free(pcopy%u);\n",
depth, depth, depth, depth, depth, depth);
else if(support_ber)
fprintf(codefile,
"if(is_indefinite%u){\n"
"len += 2;\n"
@@ -627,9 +654,10 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
tmpstr,
forwstr,
typestring, forwstr);
fprintf(codefile,
"len = %s_oldlen - %s_datalen;\n",
tmpstr, tmpstr);
if (!replace_tag)
fprintf(codefile,
"len = %s_oldlen - %s_datalen;\n",
tmpstr, tmpstr);
if (optional)
fprintf(codefile, "}\n");
else if (defval)