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Add bounds check on KRB5KDF constant length to prevent buffer overflow #421

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Merged
padelsbach merged 1 commit into from
Jul 1, 2026
Merged

Add bounds check on KRB5KDF constant length to prevent buffer overflow #421

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3 changes: 3 additions & 0 deletions src/wp_krb5kdf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -479,6 +479,9 @@ static int wp_kdf_krb5kdf_derive(wp_Krb5kdfCtx* ctx, unsigned char* key,
if (ok && (ctx->constant == NULL || ctx->constantSz == 0)) {
ok = 0;
}
if (ok && (ctx->constantSz > AES_BLOCK_SIZE)) {
ok = 0;
}
if (ok) {
XMEMSET(key, 0, keyLen);

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15 changes: 15 additions & 0 deletions test/test_krb5kdf.c
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Expand Up @@ -90,6 +90,12 @@ static int test_krb5kdf_error_cases(OSSL_LIB_CTX* libCtx)
unsigned char constant[] = {
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88
};
/* Constant longer than the cipher block size. */
unsigned char constantLong[] = {
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
0x99
};

PRINT_MSG("Testing KRB5KDF error case - AES-128-CBC with 32-byte key");
/* This should fail since AES-128 key size is 16 bytes */
Expand Down Expand Up @@ -124,6 +130,15 @@ static int test_krb5kdf_error_cases(OSSL_LIB_CTX* libCtx)
}
PRINT_MSG("Negative test passed - KRB5KDF correctly rejected 0 length constant");

PRINT_MSG("Testing KRB5KDF error case - constant longer than block size");
err = test_krb5kdf_calc(libCtx, key, 16, "AES-128-CBC",
inKey16, sizeof(inKey16), constantLong, sizeof(constantLong));
if (err == 0) {
PRINT_MSG("FAILED: KRB5KDF accepted constant longer than block size");
return 1;
}
PRINT_MSG("Negative test passed - KRB5KDF correctly rejected oversized constant");

return 0;
}

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