Improve & test legacy mbedtls_pkcs12_pbe
* Prevent pkcs12_pbe encryption when PKCS7 padding has been
disabled since this not part of the specs.
* Allow decryption when PKCS7 padding is disabled for legacy
reasons, However, invalid padding is not checked.
* Document new behaviour, known limitations and possible
security concerns.
* Add tests to check these scenarios. Test data has been
generated by the below code using OpenSSL as a reference:
#include <openssl/pkcs12.h>
#include <openssl/evp.h>
#include <openssl/des.h>
#include <openssl/asn1.h>
#include "crypto/asn1.h"
#include <string.h>
int main()
{
char pass[] = "\xBB\xBB\xBB\xBB\xBB\xBB\xBB\xBB\xBB";
unsigned char salt[] = "\xCC\xCC\xCC\xCC\xCC\xCC\xCC\xCC\xCC";
unsigned char plaintext[] = "\xAA\xAA\xAA\xAA\xAA\xAA\xAA\xAA";
unsigned char *ciphertext = NULL;
int iter = 10;
X509_ALGOR *alg = X509_ALGOR_new();
int ciphertext_len = 0;
int alg_nid = NID_pbe_WithSHA1And3_Key_TripleDES_CBC;
alg->parameter = ASN1_TYPE_new();
struct asn1_object_st * aobj;
PKCS5_pbe_set0_algor(alg, alg_nid, iter,
salt, sizeof(salt)-1);
aobj = alg->algorithm;
printf("\"30%.2X", 2 + aobj->length + alg->parameter->value.asn1_string->length);
printf("06%.2X", aobj->length);
for (int i = 0; i < aobj->length; i++) {
printf("%.2X", aobj->data[i]);
}
for (int i = 0; i < alg->parameter->value.asn1_string->length; i++) {
printf("%.2X", alg->parameter->value.asn1_string->data[i]);
}
printf("\":\"");
for (int i = 0; i < sizeof(pass)-1; i++) {
printf("%.2X", pass[i] & 0xFF);
}
printf("\":\"");
for (int i = 0; i < sizeof(plaintext)-1; i++) {
printf("%.2X", plaintext[i]);
}
printf("\":");
printf("0");
printf(":\"");
unsigned char * res = PKCS12_pbe_crypt(alg, pass, sizeof(pass)-1, plaintext, sizeof(plaintext)-1, &ciphertext, &ciphertext_len, 1);
if (res == NULL)
printf("Encryption failed!\n");
for (int i = 0; i < ciphertext_len; i++) {
printf("%.2X", res[i]);
}
printf("\"\n");
return 0;
}
Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
#
diff --git a/library/pkcs12.c b/library/pkcs12.c
index db31722..6d52305 100644
--- a/library/pkcs12.c
+++ b/library/pkcs12.c
@@ -171,6 +171,25 @@
goto exit;
}
+#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
+ /* PKCS12 uses CBC with PKCS7 padding */
+
+ mbedtls_cipher_padding_t padding = MBEDTLS_PADDING_PKCS7;
+#if !defined(MBEDTLS_CIPHER_PADDING_PKCS7)
+ /* For historical reasons, when decrypting, this function works when
+ * decrypting even when support for PKCS7 padding is disabled. In this
+ * case, it ignores the padding, and so will never report a
+ * password mismatch.
+ */
+ if (mode == MBEDTLS_PKCS12_PBE_DECRYPT) {
+ padding = MBEDTLS_PADDING_NONE;
+ }
+#endif
+ if ((ret = mbedtls_cipher_set_padding_mode(&cipher_ctx, padding)) != 0) {
+ goto exit;
+ }
+#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
+
if ((ret =
mbedtls_cipher_set_iv(&cipher_ctx, iv,
mbedtls_cipher_info_get_iv_size(cipher_info))) != 0) {