An example is the encoding of ECC signatures used by the ECDSA
signature verification code. A user is the new SPDM support where
raw signatures are returned by the responder. These can then
be encoded so that we can pass them to signature_verify()
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
Needs considerably more testing with crafted examples to hit the corner
cases. For now it's enough to show how this 'might' fit together.
include/linux/asn1_encoder.h | 3 ++
lib/asn1_encoder.c | 54 ++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
diff --git a/include/linux/asn1_encoder.h b/include/linux/asn1_encoder.h
index 08cd0c2ad34f..30c3ebacd46c 100644
--- a/include/linux/asn1_encoder.h
+++ b/include/linux/asn1_encoder.h
@@ -19,6 +19,9 @@ unsigned char *
asn1_encode_tag(unsigned char *data, const unsigned char *end_data,
u32 tag, const unsigned char *string, int len);
unsigned char *
+asn1_encode_integer_large_positive(unsigned char *data, const unsigned char *end_data,
+ u32 tag, const unsigned char *integer, int len);
+unsigned char *
asn1_encode_octet_string(unsigned char *data,
const unsigned char *end_data,
const unsigned char *string, u32 len);
diff --git a/lib/asn1_encoder.c b/lib/asn1_encoder.c
index 41e71aae3ef6..135c5cf2d77e 100644
--- a/lib/asn1_encoder.c
+++ b/lib/asn1_encoder.c
@@ -317,6 +317,60 @@ asn1_encode_tag(unsigned char *data, const unsigned char *end_data,
}
EXPORT_SYMBOL_GPL(asn1_encode_tag);
+unsigned char *
+asn1_encode_integer_large_positive(unsigned char *data, const unsigned char *end_data,
+ u32 tag, const unsigned char *integer, int len)
+{
+ int data_len = end_data - data;
+ unsigned char *d = &data[2];
+ bool found = false;
+ int i;
+
+ if (WARN(tag > 30, "ASN.1 tag can't be > 30"))
+ return ERR_PTR(-EINVAL);
+
+ if (!integer && WARN(len > 127,
+ "BUG: recode tag is too big (>127)"))
+ return ERR_PTR(-EINVAL);
+
+ if (IS_ERR(data))
+ return data;
+
+ if (data_len < 3)
+ return ERR_PTR(-EINVAL);
+
+
+ data[0] = _tagn(UNIV, PRIM, tag);
+ /* Leave space for length */
+ data_len -= 2;
+
+ for (i = 0; i < len; i++) {
+ int byte = integer[i];
+
+ if (!found && byte == 0)
+ continue;
+
+ /*
+ * as per encode_integer
+ */
+ if (!found && (byte & 0x80)) {
+ *d++ = 0;
+ data_len--;
+ }
+ found = true;
+ if (data_len == 0)
+ return ERR_PTR(-EINVAL);
+
+ *d++ = byte;
+ data_len--;
+ }
+
+ data[1] = d - data - 2;
+
+ return d;
+}
+EXPORT_SYMBOL_GPL(asn1_encode_integer_large_positive);
+
/**
* asn1_encode_octet_string() - encode an ASN.1 OCTET STRING
* @data: pointer to encode at
--
2.19.1
