From 62b9997afb850843f8fa52c66c3320f0f969d400 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 11 Oct 2022 18:07:46 +0200
Subject: [PATCH] tpm2-util: split out code that derives "good" TPM2 banks into
 an strv from pcrphase and generalize it in tpm2-util.c

That way we can reuse it later from different places.

(cherry picked from commit e4481cc512f48d423115b10d4ae1c8e1381ff84b)

Related: RHEL-16182
---
 src/boot/pcrphase.c    | 28 ++++++---------------------
 src/shared/tpm2-util.c | 43 ++++++++++++++++++++++++++++++++++++++++++
 src/shared/tpm2-util.h |  1 +
 3 files changed, 50 insertions(+), 22 deletions(-)

diff --git a/src/boot/pcrphase.c b/src/boot/pcrphase.c
index 8e91e80e22..6e3a564f35 100644
--- a/src/boot/pcrphase.c
+++ b/src/boot/pcrphase.c
@@ -123,35 +123,19 @@ static int parse_argv(int argc, char *argv[]) {
 }
 
 static int determine_banks(struct tpm2_context *c) {
-        _cleanup_free_ TPMI_ALG_HASH *algs = NULL;
-        int n_algs, r;
+        _cleanup_strv_free_ char **l = NULL;
+        int r;
 
         assert(c);
 
         if (!strv_isempty(arg_banks)) /* Explicitly configured? Then use that */
                 return 0;
 
-        n_algs = tpm2_get_good_pcr_banks(c->esys_context, UINT32_C(1) << TPM_PCR_INDEX_KERNEL_IMAGE, &algs);
-        if (n_algs <= 0)
-                return n_algs;
-
-        for (int i = 0; i < n_algs; i++) {
-                const EVP_MD *implementation;
-                const char *salg;
-
-                salg = tpm2_pcr_bank_to_string(algs[i]);
-                if (!salg)
-                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unknown PCR algorithm, can't measure.");
-
-                implementation = EVP_get_digestbyname(salg);
-                if (!implementation)
-                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unsupported PCR algorithm, can't measure.");
-
-                r = strv_extend(&arg_banks, EVP_MD_name(implementation));
-                if (r < 0)
-                        return log_oom();
-        }
+        r = tpm2_get_good_pcr_banks_strv(c->esys_context, UINT32_C(1) << TPM_PCR_INDEX_KERNEL_IMAGE, &l);
+        if (r < 0)
+                return r;
 
+        strv_free_and_replace(arg_banks, l);
         return 0;
 }
 
diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index 8171b3e9e9..45ece9d1a6 100644
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -730,6 +730,49 @@ int tpm2_get_good_pcr_banks(
         return 0;
 }
 
+int tpm2_get_good_pcr_banks_strv(
+                ESYS_CONTEXT *c,
+                uint32_t pcr_mask,
+                char ***ret) {
+
+        _cleanup_free_ TPMI_ALG_HASH *algs = NULL;
+        _cleanup_strv_free_ char **l = NULL;
+        int n_algs;
+
+        assert(c);
+        assert(ret);
+
+        n_algs = tpm2_get_good_pcr_banks(c, pcr_mask, &algs);
+        if (n_algs < 0)
+                return n_algs;
+
+        for (int i = 0; i < n_algs; i++) {
+                _cleanup_free_ char *n = NULL;
+                const EVP_MD *implementation;
+                const char *salg;
+
+                salg = tpm2_pcr_bank_to_string(algs[i]);
+                if (!salg)
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unknown PCR algorithm, can't measure.");
+
+                implementation = EVP_get_digestbyname(salg);
+                if (!implementation)
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "TPM2 operates with unsupported PCR algorithm, can't measure.");
+
+                n = strdup(ASSERT_PTR(EVP_MD_name(implementation)));
+                if (!n)
+                        return log_oom();
+
+                ascii_strlower(n); /* OpenSSL uses uppercase digest names, we prefer them lower case. */
+
+                if (strv_consume(&l, TAKE_PTR(n)) < 0)
+                        return log_oom();
+        }
+
+        *ret = TAKE_PTR(l);
+        return 0;
+}
+
 static void hash_pin(const char *pin, size_t len, TPM2B_AUTH *auth) {
         struct sha256_ctx hash;
 
diff --git a/src/shared/tpm2-util.h b/src/shared/tpm2-util.h
index c240335ae6..6d83281be0 100644
--- a/src/shared/tpm2-util.h
+++ b/src/shared/tpm2-util.h
@@ -68,6 +68,7 @@ static inline void Esys_Freep(void *p) {
 }
 
 int tpm2_get_good_pcr_banks(ESYS_CONTEXT *c, uint32_t pcr_mask, TPMI_ALG_HASH **ret_banks);
+int tpm2_get_good_pcr_banks_strv(ESYS_CONTEXT *c, uint32_t pcr_mask, char ***ret);
 
 #else
 struct tpm2_context;