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support ASN ShortInts up to 4 bytes (2^32-1):

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* parameterize MAX_LENGTH_SZ using overrideable WOLFSSL_ASN_MAX_LENGTH_SZ, default value 5 (raised from 4).
* refactor other Misc_ASN constants to refer to MAX_LENGTH_SZ as appropriate.
* tweak BytePrecision() appropriately.
* refactor SetShortInt() to use BytePrecision() and include a length assert against MAX_SHORT_SZ to assure no buffer overruns with reduced WOLFSSL_ASN_MAX_LENGTH_SZ.
This commit is contained in:
Daniel Pouzzner
2023-12-11 12:07:07 -06:00
parent 03a82711aa
commit 9c17d5d2fa
2 changed files with 32 additions and 41 deletions
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49
wolfcrypt/src/asn.c
View File

@ -315,8 +315,6 @@ static const char* TagString(byte tag)
/* Calculates the minimum number of bytes required to encode the value.
*
* Only support up to 2^24-1.
*
* @param [in] value Value to be encoded.
* @return Number of bytes to encode value.
@ -324,7 +322,7 @@ static const char* TagString(byte tag)
static word32 BytePrecision(word32 value)
{
word32 i;
for (i = (word32)sizeof(value) - 1; i; --i)
for (i = (word32)sizeof(value); i; --i)
if (value >> ((i - 1) * WOLFSSL_BIT_SIZE))
break;
@ -3139,46 +3137,35 @@ int GetShortInt(const byte* input, word32* inOutIdx, int* number, word32 maxIdx)
defined(HAVE_PKCS12)
/* Set small integer, 32 bits or less. DER encoding with no leading 0s
* returns total amount written including ASN tag and length byte on success */
int SetShortInt(byte* input, word32* inOutIdx, word32 number, word32 maxIdx)
int SetShortInt(byte* output, word32* inOutIdx, word32 number, word32 maxIdx)
{
word32 idx = *inOutIdx;
int len = 0;
word32 len;
int i;
byte ar[MAX_LENGTH_SZ];
/* check for room for type and length bytes */
if ((idx + 2) > maxIdx)
if (number == 0)
len = 1;
else
len = BytePrecision(number);
/* check for room for type and length bytes. */
if ((idx + 2 + len) > maxIdx)
return BUFFER_E;
input[idx++] = ASN_INTEGER;
idx++; /* place holder for length byte */
if (MAX_LENGTH_SZ + idx > maxIdx)
/* check that MAX_SHORT_SZ allows this size of ShortInt. */
if (2 + len > MAX_SHORT_SZ)
return ASN_PARSE_E;
/* find first non zero byte */
XMEMSET(ar, 0, MAX_LENGTH_SZ);
c32toa(number, ar);
for (i = 0; i < MAX_LENGTH_SZ; i++) {
if (ar[i] != 0) {
break;
}
}
output[idx++] = ASN_INTEGER;
output[idx++] = (byte)len;
/* handle case of 0 */
if (i == MAX_LENGTH_SZ) {
input[idx++] = 0; len++;
}
for (i = (int)len - 1; i >= 0; --i)
output[idx++] = (byte)(number >> (i * WOLFSSL_BIT_SIZE));
for (; i < MAX_LENGTH_SZ && idx < maxIdx; i++) {
input[idx++] = ar[i]; len++;
}
/* jump back to beginning of input buffer using unaltered inOutIdx value
* and set number of bytes for integer, then update the index value */
input[*inOutIdx + 1] = (byte)len;
len = idx - *inOutIdx;
*inOutIdx = idx;
return len + 2; /* size of integer bytes plus ASN TAG and length byte */
return (int)len;
}
#endif /* !WOLFSSL_ASN_TEMPLATE || HAVE_PKCS8 || HAVE_PKCS12 */
#endif /* !NO_PWDBASED */

24
wolfssl/wolfcrypt/asn.h
View File

@ -901,6 +901,10 @@ enum ECC_TYPES
/* Maximum OID dotted form size. */
#define ASN1_OID_DOTTED_MAX_SZ 16
#ifndef WOLFSSL_ASN_MAX_LENGTH_SZ
#define WOLFSSL_ASN_MAX_LENGTH_SZ 5 /* 1 byte length + 4 bytes of number */
#endif
enum Misc_ASN {
MAX_SALT_SIZE = 64, /* MAX PKCS Salt length */
MAX_IV_SIZE = 64, /* MAX PKCS Iv length */
@ -943,18 +947,18 @@ enum Misc_ASN {
#endif
MAX_SIG_SZ = 256,
MAX_ALGO_SZ = 20,
MAX_SHORT_SZ = 6, /* asn int + byte len + 4 byte length */
MAX_LENGTH_SZ = 4, /* Max length size for DER encoding */
MAX_SEQ_SZ = 5, /* enum(seq | con) + length(4) */
MAX_SET_SZ = 5, /* enum(set | con) + length(4) */
MAX_OCTET_STR_SZ = 5, /* enum(set | con) + length(4) */
MAX_EXP_SZ = 5, /* enum(contextspec|con|exp) + length(4) */
MAX_PRSTR_SZ = 5, /* enum(prstr) + length(4) */
MAX_LENGTH_SZ = WOLFSSL_ASN_MAX_LENGTH_SZ, /* Max length size for DER encoding */
MAX_SHORT_SZ = (1 + MAX_LENGTH_SZ), /* asn int + byte len + 4 byte length */
MAX_SEQ_SZ = (1 + MAX_LENGTH_SZ), /* enum(seq | con) + length(5) */
MAX_SET_SZ = (1 + MAX_LENGTH_SZ), /* enum(set | con) + length(5) */
MAX_OCTET_STR_SZ = (1 + MAX_LENGTH_SZ), /* enum(set | con) + length(5) */
MAX_EXP_SZ = (1 + MAX_LENGTH_SZ), /* enum(contextspec|con|exp) + length(5) */
MAX_PRSTR_SZ = (1 + MAX_LENGTH_SZ), /* enum(prstr) + length(5) */
MAX_VERSION_SZ = 5, /* enum + id + version(byte) + (header(2))*/
MAX_ENCODED_DIG_ASN_SZ= 9, /* enum(bit or octet) + length(4) */
MAX_ENCODED_DIG_ASN_SZ = (5 + MAX_LENGTH_SZ), /* enum(bit or octet) + length(5) */
MAX_ENCODED_DIG_SZ = 64 + MAX_ENCODED_DIG_ASN_SZ, /* asn header + sha512 */
MAX_RSA_INT_SZ = 517, /* RSA raw sz 4096 for bits + tag + len(4) */
MAX_DSA_INT_SZ = 389, /* DSA raw sz 3072 for bits + tag + len(4) */
MAX_RSA_INT_SZ = (512 + 1 + MAX_LENGTH_SZ), /* RSA raw sz 4096 for bits + tag + len(5) */
MAX_DSA_INT_SZ = (384 + 1 + MAX_LENGTH_SZ), /* DSA raw sz 3072 for bits + tag + len(5) */
MAX_DSA_PUBKEY_SZ = (DSA_PUB_INTS * MAX_DSA_INT_SZ) + (2 * MAX_SEQ_SZ) +
2 + MAX_LENGTH_SZ, /* Maximum size of a DSA public
key taken from wc_SetDsaPublicKey. */