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Defensive code additions for sanity checks on input arguments with Base64, PEM write, mp_read_unsigned_bin #10721

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Defensive code additions for sanity checks on input arguments with Base64, PEM write, mp_read_unsigned_bin #10721

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5e34dad
sanity check on read unsigned bin length argument
JacobBarthelmeh Jun 17, 2026
4d843ad
adjustment to sanity checks for avoiding potential overflow
JacobBarthelmeh Jun 17, 2026
a3e8bab
hardening against potential overflow cases
JacobBarthelmeh Jun 17, 2026
f869e94
adjustment to overflow check
JacobBarthelmeh Jul 7, 2026
5e1e423
adjust test case for updated sanity check with heap math
JacobBarthelmeh Jul 9, 2026
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8 changes: 7 additions & 1 deletion src/pk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6911,9 +6911,15 @@ static int pem_write_data(const char *name, const char *header,
int headerLen;
char* pem = NULL;
word32 pemLen;
word32 derLen = (word32)len;
word32 derLen;
byte* p;

/* Reject lengths that would wrap the PEM size calculation below. */
if ((len < 0) || ((word32)len >= (WOLFSSL_MAX_32BIT / 4))) {
return BAD_FUNC_ARG;
}
derLen = (word32)len;
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nameLen = (int)XSTRLEN(name);
headerLen = (int)XSTRLEN(header);

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8 changes: 4 additions & 4 deletions wolfcrypt/src/asn.c
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Expand Up @@ -2461,8 +2461,8 @@ int GetLength_ex(const byte* input, word32* inOutIdx, int* len, word32 maxIdx,
*len = 0;

/* Check there is at least one byte available containing length information.
*/
if ((idx + 1) > maxIdx) {
* Use >= to avoid a word32 wrap when idx is near UINT_MAX. */
if (idx >= maxIdx) {
WOLFSSL_MSG("GetLength - bad index on input");
return BUFFER_E;
}
Expand Down Expand Up @@ -2495,7 +2495,7 @@ int GetLength_ex(const byte* input, word32* inOutIdx, int* len, word32 maxIdx,
}

/* Check the number of bytes required are available. */
if ((idx + (word32)bytes) > maxIdx) {
if ((word32)bytes > (maxIdx - idx)) {
WOLFSSL_MSG("GetLength - bad long length");
return BUFFER_E;
}
Expand All @@ -2520,7 +2520,7 @@ int GetLength_ex(const byte* input, word32* inOutIdx, int* len, word32 maxIdx,
}

/* When requested, check the buffer has at least length bytes left. */
if (check && ((idx + length) > maxIdx)) {
if (check && (length > (maxIdx - idx))) {
WOLFSSL_MSG("GetLength - value exceeds buffer length");
return BUFFER_E;
}
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4 changes: 4 additions & 0 deletions wolfcrypt/src/coding.c
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Expand Up @@ -525,6 +525,10 @@ static int DoBase64_Encode(const byte* in, word32 inLen, byte* out,
if (in == NULL && inLen > 0)
return BAD_FUNC_ARG;

/* Reject lengths that would wrap the encoded-size calculation below. */
if (inLen >= (WOLFSSL_MAX_32BIT / 4))
return BAD_FUNC_ARG;

outSz = (inLen + 3 - 1) / 3 * 4;
addSz = (outSz + BASE64_LINE_SZ - 1) / BASE64_LINE_SZ; /* new lines */
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12 changes: 11 additions & 1 deletion wolfcrypt/src/integer.c
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Expand Up @@ -762,12 +762,22 @@ int mp_read_unsigned_bin (mp_int * a, const unsigned char *b, int c)
int res;
int digits_needed;

if (c < 0) {
return MP_VAL;
}

while (c > 0 && b[0] == 0) {
c--;
b++;
}

digits_needed = ((c * CHAR_BIT) + DIGIT_BIT - 1) / DIGIT_BIT;
/* reject sizes where the bit count would overflow, doing the math in
* word32 so c * CHAR_BIT can't overflow */
if ((word32)c > (WOLFSSL_MAX_32BIT - (DIGIT_BIT - 1)) / CHAR_BIT) {
return MP_VAL;
}

digits_needed = (int)(((word32)c * CHAR_BIT + DIGIT_BIT - 1) / DIGIT_BIT);

/* make sure there are enough digits available */
if (a->alloc < digits_needed) {
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6 changes: 2 additions & 4 deletions wolfcrypt/test/test.c
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Expand Up @@ -27262,11 +27262,9 @@ static wc_test_ret_t rsa_decode_test(RsaKey* keyPub)
ret = WC_TEST_RET_ENC_EC(ret);
goto done;
}
#if defined(USE_INTEGER_HEAP_MATH)
#define RSA_RAW_BADLEN_EXPECT 0
#else
/* All math backends now reject a negative/oversized length in
* mp_read_unsigned_bin, so a (word32)-1 length fails consistently. */
#define RSA_RAW_BADLEN_EXPECT WC_NO_ERR_TRACE(ASN_GETINT_E)
#endif
ret = wc_RsaPublicKeyDecodeRaw(n, (word32)-1, e, sizeof(e), keyPub);
if (ret != RSA_RAW_BADLEN_EXPECT) {
ret = WC_TEST_RET_ENC_EC(ret);
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