Add negative integer check when using ASN1_BIT_STRING

The negative integer check is done to prevent potential overflow.
Fixes #20719.

CLA: trivial

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20862)

diff --git a/crypto/asn1/a_bitstr.c b/crypto/asn1/a_bitstr.c
index 00a388a3a5734ffa0d46d5b159ca608a3b36b613..bd5fcaaa34fb4639096087bedb27d8990263f74c 100644 (file)
--- a/crypto/asn1/a_bitstr.c
+++ b/crypto/asn1/a_bitstr.c
@@ -145,6 +145,9 @@ int ASN1_BIT_STRING_set_bit(ASN1_BIT_STRING *a, int n, int value)
     int w, v, iv;
     unsigned char *c;
 
+    if (n < 0)
+        return 0;
+
     w = n / 8;
     v = 1 << (7 - (n & 0x07));
     iv = ~v;
@@ -177,6 +180,9 @@ int ASN1_BIT_STRING_get_bit(const ASN1_BIT_STRING *a, int n)
 {
     int w, v;
 
+    if (n < 0)
+        return 0;
+
     w = n / 8;
     v = 1 << (7 - (n & 0x07));
     if ((a == NULL) || (a->length < (w + 1)) || (a->data == NULL))