From e6a7ae7612b1d8f6b46bc70a21493265dbfcc20b Mon Sep 17 00:00:00 2001
From: Ilia Mirkin <imirkin@alum.mit.edu>
Date: Thu, 1 Feb 2024 10:20:27 -0500
Subject: [PATCH] Add ES256K support (#90)

---
 README.md           |  1 +
 lib/openssl/ec.c    |  3 ++-
 lib/openssl/ecdsa.c | 29 +++++++++++++++++++++++++----
 lib/openssl/jwk.c   |  4 +++-
 tests/jose-jwk-gen  |  1 +
 5 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index a3805585..b8f45c92 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@ José is extensively tested against the RFC test vectors.
 | ES256              |    YES    |   Signature    |     EC   |
 | ES384              |    YES    |   Signature    |     EC   |
 | ES512              |    YES    |   Signature    |     EC   |
+| ES256K             |    YES    |   Signature    |     EC   |
 | PS256              |    YES    |   Signature    |    RSA   |
 | PS384              |    YES    |   Signature    |    RSA   |
 | PS512              |    YES    |   Signature    |    RSA   |
diff --git a/lib/openssl/ec.c b/lib/openssl/ec.c
index 46433a30..0301f063 100644
--- a/lib/openssl/ec.c
+++ b/lib/openssl/ec.c
@@ -48,10 +48,11 @@ jwk_make_execute(jose_cfg_t *cfg, json_t *jwk)
     if (json_unpack(jwk, "{s?s}", "crv", &crv) < 0)
         return false;
 
-    switch (str2enum(crv, "P-256", "P-384", "P-521", NULL)) {
+    switch (str2enum(crv, "P-256", "P-384", "P-521", "secp256k1", NULL)) {
     case 0: nid = NID_X9_62_prime256v1; break;
     case 1: nid = NID_secp384r1; break;
     case 2: nid = NID_secp521r1; break;
+    case 3: nid = NID_secp256k1; break;
     default: return false;
     }
 
diff --git a/lib/openssl/ecdsa.c b/lib/openssl/ecdsa.c
index 263e931f..df887d6b 100644
--- a/lib/openssl/ecdsa.c
+++ b/lib/openssl/ecdsa.c
@@ -22,7 +22,7 @@
 
 #include <string.h>
 
-#define NAMES "ES256", "ES384", "ES512"
+#define NAMES "ES256", "ES384", "ES512", "ES256K"
 
 typedef struct {
     jose_io_t io;
@@ -137,6 +137,19 @@ alg2crv(const char *alg)
     case 0: return "P-256";
     case 1: return "P-384";
     case 2: return "P-521";
+    case 3: return "secp256k1";
+    default: return NULL;
+    }
+}
+
+static const char *
+alg2hash(const char *alg)
+{
+    switch (str2enum(alg, NAMES, NULL)) {
+    case 0: return "S256";
+    case 1: return "S384";
+    case 2: return "S512";
+    case 3: return "S256";
     default: return NULL;
     }
 }
@@ -200,10 +213,11 @@ alg_sign_sug(const jose_hook_alg_t *alg, jose_cfg_t *cfg, const json_t *jwk)
     if (!type || strcmp(type, "EC") != 0)
         return NULL;
 
-    switch (str2enum(curv, "P-256", "P-384", "P-521", NULL)) {
+    switch (str2enum(curv, "P-256", "P-384", "P-521", "secp256k1", NULL)) {
     case 0: return "ES256";
     case 1: return "ES384";
     case 2: return "ES512";
+    case 3: return "ES256K";
     default: return NULL;
     }
 }
@@ -216,7 +230,7 @@ alg_sign_sig(const jose_hook_alg_t *alg, jose_cfg_t *cfg, json_t *jws,
     jose_io_auto_t *io = NULL;
     io_t *i = NULL;
 
-    halg = jose_hook_alg_find(JOSE_HOOK_ALG_KIND_HASH, &alg->name[1]);
+    halg = jose_hook_alg_find(JOSE_HOOK_ALG_KIND_HASH, alg2hash(alg->name));
     if (!halg)
         return NULL;
 
@@ -248,7 +262,7 @@ alg_sign_ver(const jose_hook_alg_t *alg, jose_cfg_t *cfg, const json_t *jws,
     jose_io_auto_t *io = NULL;
     io_t *i = NULL;
 
-    halg = jose_hook_alg_find(JOSE_HOOK_ALG_KIND_HASH, &alg->name[1]);
+    halg = jose_hook_alg_find(JOSE_HOOK_ALG_KIND_HASH, alg2hash(alg->name));
     if (!halg)
         return NULL;
 
@@ -302,6 +316,13 @@ constructor(void)
           .sign.sug = alg_sign_sug,
           .sign.sig = alg_sign_sig,
           .sign.ver = alg_sign_ver },
+        { .kind = JOSE_HOOK_ALG_KIND_SIGN,
+          .name = "ES256K",
+          .sign.sprm = "sign",
+          .sign.vprm = "verify",
+          .sign.sug = alg_sign_sug,
+          .sign.sig = alg_sign_sig,
+          .sign.ver = alg_sign_ver },
         {}
     };
 
diff --git a/lib/openssl/jwk.c b/lib/openssl/jwk.c
index 8fc1dd73..1e8f3118 100644
--- a/lib/openssl/jwk.c
+++ b/lib/openssl/jwk.c
@@ -169,6 +169,7 @@ jose_openssl_jwk_from_EC_POINT(jose_cfg_t *cfg, const EC_GROUP *grp,
     case NID_X9_62_prime256v1: crv = "P-256"; break;
     case NID_secp384r1: crv = "P-384"; break;
     case NID_secp521r1: crv = "P-521"; break;
+    case NID_secp256k1: crv = "secp256k1"; break;
     default: return NULL;
     }
 
@@ -366,10 +367,11 @@ jose_openssl_jwk_to_EC_KEY(jose_cfg_t *cfg, const json_t *jwk)
     if (strcmp(kty, "EC") != 0)
         return NULL;
 
-    switch (str2enum(crv, "P-256", "P-384", "P-521", NULL)) {
+    switch (str2enum(crv, "P-256", "P-384", "P-521", "secp256k1", NULL)) {
     case 0: nid = NID_X9_62_prime256v1; break;
     case 1: nid = NID_secp384r1; break;
     case 2: nid = NID_secp521r1; break;
+    case 3: nid = NID_secp256k1; break;
     default: return NULL;
     }
 
diff --git a/tests/jose-jwk-gen b/tests/jose-jwk-gen
index 364ba22c..063fd4e1 100755
--- a/tests/jose-jwk-gen
+++ b/tests/jose-jwk-gen
@@ -17,6 +17,7 @@ done
 jose jwk gen -i '{ "kty": "EC", "crv": "P-256" }'
 jose jwk gen -i '{ "kty": "EC", "crv": "P-384" }'
 jose jwk gen -i '{ "kty": "EC", "crv": "P-521" }'
+jose jwk gen -i '{ "kty": "EC", "crv": "secp256k1" }'
 
 jose jwk gen -i '{ "kty": "RSA", "bits": 3072 }'
 ! jose jwk gen -i '{ "kty": "RSA", "bits": 3072, "e": 257 }'