[PATCH v2] mingw: avoid C99 "hh" scanf length modifier

From: Heiko Hund <[email protected]>

read_key_file() and parse_hexstring() parse hex bytes with sscanf()
using the C99 "hh" length modifier, storing directly into an octet.

This is not portable to the legacy MSVCRT runtime that Ubuntu
resolute's (26.04) mingw toolchain links against.

Scan into an unsigned int and cast to the octet instead. The field width
caps the value at 0xFF, so the narrowing cast cannot lose data.

Change-Id: I6595695ab6401047d498d530f8739686880bea3a
Signed-off-by: Heiko Hund <[email protected]>
Acked-by: Frank Lichtenheld <[email protected]>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1733
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1733
This mail reflects revision 2 of this Change.

Acked-by according to Gerrit (reflected above):
Frank Lichtenheld <[email protected]>

        
diff --git a/src/openvpn/crypto.c b/src/openvpn/crypto.c
index 3d79fe5..ee43d65 100644
--- a/src/openvpn/crypto.c
+++ b/src/openvpn/crypto.c
@@ -1473,9 +1473,9 @@
                     hex_byte[hb_index++] = c;
                     if (hb_index == 2)
                     {
-                        uint8_t u;
-                        ASSERT(sscanf((const char *)hex_byte, "%" SCNx8, &u) == 1);
-                        *out++ = u;
+                        unsigned int u;
+                        ASSERT(sscanf((const char *)hex_byte, "%2x", &u) == 1);
+                        *out++ = (uint8_t)u;
                         hb_index = 0;
                         if (++count == keylen)
                         {
diff --git a/src/openvpn/cryptoapi.c b/src/openvpn/cryptoapi.c
index bf80bbd..0f95ab7 100644
--- a/src/openvpn/cryptoapi.c
+++ b/src/openvpn/cryptoapi.c
@@ -169,10 +169,12 @@
             break;
         }
 
-        if (!isxdigit(p[0]) || !isxdigit(p[1]) || sscanf(p, "%2hhx", &arr[i++]) != 1)
+        unsigned int b;
+        if (!isxdigit(p[0]) || !isxdigit(p[1]) || sscanf(p, "%2x", &b) != 1)
         {
             return 0;
         }
+        arr[i++] = (unsigned char)b;
     }
     return i;
 }