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Check that multi-strings/CHOICE types don't use implicit tagging 

It never makes sense for multi-string or CHOICE types to use implicit
tagging since the content would be ambiguous. It is an error in the
template if this ever happens. If we detect it we should stop parsing.

Thanks to David Benjamin from Google for reporting this issue.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
This commit is contained in:
Matt Caswell 2020-11-12 11:58:12 +00:00
parent b33c48b75a
commit 43a7033a01
4 changed files with 22 additions and 0 deletions
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1
crypto/asn1/asn1_err.c
View File

@ -21,6 +21,7 @@ static const ERR_STRING_DATA ASN1_str_reasons[] = {
"asn1 sig parse error"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_AUX_ERROR), "aux error"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_BAD_OBJECT_HEADER), "bad object header"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_BAD_TEMPLATE), "bad template"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_BMPSTRING_IS_WRONG_LENGTH),
"bmpstring is wrong length"},
{ERR_PACK(ERR_LIB_ASN1, 0, ASN1_R_BN_LIB), "bn lib"},

19
crypto/asn1/tasn_dec.c
View File

@ -183,6 +183,15 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
tag, aclass, opt, ctx);
case ASN1_ITYPE_MSTRING:
/*
* It never makes sense for multi-strings to have implicit tagging, so
* if tag != -1, then this looks like an error in the template.
*/
if (tag != -1) {
ERR_raise(ERR_LIB_ASN1, ASN1_R_BAD_TEMPLATE);
goto err;
}
p = *in;
/* Just read in tag and class */
ret = asn1_check_tlen(NULL, &otag, &oclass, NULL, NULL,
@ -200,6 +209,7 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
ERR_raise(ERR_LIB_ASN1, ASN1_R_MSTRING_NOT_UNIVERSAL);
goto err;
}
/* Check tag matches bit map */
if (!(ASN1_tag2bit(otag) & it->utype)) {
/* If OPTIONAL, assume this is OK */
@ -216,6 +226,15 @@ static int asn1_item_embed_d2i(ASN1_VALUE **pval, const unsigned char **in,
return ef->asn1_ex_d2i(pval, in, len, it, tag, aclass, opt, ctx);
case ASN1_ITYPE_CHOICE:
/*
* It never makes sense for CHOICE types to have implicit tagging, so
* if tag != -1, then this looks like an error in the template.
*/
if (tag != -1) {
ERR_raise(ERR_LIB_ASN1, ASN1_R_BAD_TEMPLATE);
goto err;
}
if (asn1_cb && !asn1_cb(ASN1_OP_D2I_PRE, pval, it, NULL))
goto auxerr;
if (*pval) {

1
crypto/err/openssl.txt
View File

@ -1901,6 +1901,7 @@ ASN1_R_ASN1_PARSE_ERROR:203:asn1 parse error
ASN1_R_ASN1_SIG_PARSE_ERROR:204:asn1 sig parse error
ASN1_R_AUX_ERROR:100:aux error
ASN1_R_BAD_OBJECT_HEADER:102:bad object header
ASN1_R_BAD_TEMPLATE:230:bad template
ASN1_R_BMPSTRING_IS_WRONG_LENGTH:214:bmpstring is wrong length
ASN1_R_BN_LIB:105:bn lib
ASN1_R_BOOLEAN_IS_WRONG_LENGTH:106:boolean is wrong length

1
include/openssl/asn1err.h
View File

@ -147,6 +147,7 @@
# define ASN1_R_ASN1_SIG_PARSE_ERROR 204
# define ASN1_R_AUX_ERROR 100
# define ASN1_R_BAD_OBJECT_HEADER 102
# define ASN1_R_BAD_TEMPLATE 230
# define ASN1_R_BMPSTRING_IS_WRONG_LENGTH 214
# define ASN1_R_BN_LIB 105
# define ASN1_R_BOOLEAN_IS_WRONG_LENGTH 106