From e624cc132af462641b19db3762a58a5776047890 Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Thu, 2 Jul 2020 14:00:48 -0400
Subject: [PATCH] configure: can gpgme can verify signatures when decrypting
 with a session key?

If https://dev.gnupg.org/T3464 is unresolved in the version of gpgme
we are testing against, then we should know about it, because it
affects the behavior of notmuch.

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
---
 configure | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 2e01034b..2caa08c8 100755
--- a/configure
+++ b/configure
@@ -620,6 +620,78 @@ EOF
     if [ -n "$TEMP_GPG" -a -d "$TEMP_GPG" ]; then
         rm -rf "$TEMP_GPG"
     fi
+
+    # see https://dev.gnupg.org/T3464
+    # there are problems verifying signatures when decrypting with session keys with GPGME 1.13.0 and 1.13.1
+    printf "Checking signature verification when decrypting using session keys... "
+
+    cat > _verify_sig_with_session_key.c <<EOF
+#include <stdio.h>
+#include <gmime/gmime.h>
+
+int main () {
+    GError *error = NULL;
+    GMimeParser *parser = NULL;
+    GMimeMultipartEncrypted *body = NULL;
+    GMimeDecryptResult *result = NULL;
+    GMimeSignatureList *sig_list = NULL;
+    GMimeSignature *sig = NULL;
+    GMimeObject *output = NULL;
+    GMimeSignatureStatus status;
+    int len;
+
+    g_mime_init ();
+    parser = g_mime_parser_new ();
+    g_mime_parser_init_with_stream (parser, g_mime_stream_file_open("$srcdir/test/corpora/crypto/encrypted-signed.eml", "r", &error));
+    if (error) return !! fprintf (stderr, "failed to instantiate parser with test/corpora/pkcs7/smime-onepart-signed.eml\n");
+
+    body = GMIME_MULTIPART_ENCRYPTED(g_mime_message_get_mime_part (g_mime_parser_construct_message (parser, NULL)));
+    if (body == NULL) return !!	fprintf (stderr, "did not find a multipart/encrypted message\n");
+
+    output = g_mime_multipart_encrypted_decrypt (body, GMIME_DECRYPT_NONE, "9:13607E4217515A70EC8DF9DBC16C5327B94577561D98AD1246FA8756659C7899", &result, &error);
+    if (error || output == NULL) return !! fprintf (stderr, "decrypt failed\n");
+
+    sig_list = g_mime_decrypt_result_get_signatures (result);
+    if (sig_list == NULL) return !! fprintf (stderr, "sig_list is NULL\n");
+
+    if (sig_list == NULL) return !! fprintf (stderr, "no GMimeSignatureList found\n");
+    len = g_mime_signature_list_length (sig_list);
+    if (len != 1) return !! fprintf (stderr, "expected 1 signature, got %d\n", len);
+    sig = g_mime_signature_list_get_signature (sig_list, 0);
+    if (sig == NULL) return !! fprintf (stderr, "no GMimeSignature found at position 0\n");
+    status = g_mime_signature_get_status (sig);
+    if (status & GMIME_SIGNATURE_STATUS_KEY_MISSING) return !! fprintf (stderr, "signature status contains KEY_MISSING (see https://dev.gnupg.org/T3464)\n");
+
+    return 0;
+}
+EOF
+    if ! TEMP_GPG=$(mktemp -d "${TMPDIR:-/tmp}/notmuch.XXXXXX"); then
+        printf 'No.\nCould not make tempdir for testing signature verification when decrypting with session keys.\n'
+        errors=$((errors + 1))
+    elif ${CC} ${CFLAGS} ${gmime_cflags} _verify_sig_with_session_key.c ${gmime_ldflags} -o _verify_sig_with_session_key \
+            && GNUPGHOME=${TEMP_GPG} gpg --batch --quiet --import < "$srcdir"/test/gnupg-secret-key.asc \
+            && rm -f ${TEMP_GPG}/private-keys-v1.d/*.key
+    then
+        if GNUPGHOME=${TEMP_GPG} ./_verify_sig_with_session_key; then
+            gmime_verify_with_session_key=1
+            printf "Yes.\n"
+        else
+            gmime_verify_with_session_key=0
+            printf "No.\n"
+            cat <<EOF
+*** Error: GMime fails to verify signatures when decrypting with a session key.
+
+This is most likely due to a buggy version of GPGME, which should be fixed in 1.13.2 or later.
+See https://dev.gnupg.org/T3464 for more details.
+EOF
+        fi
+    else
+        printf 'No.\nFailed to set up gpg for testing signature verification while decrypting with a session key.\n'
+        errors=$((errors + 1))
+    fi
+    if [ -n "$TEMP_GPG" -a -d "$TEMP_GPG" ]; then
+        rm -rf "$TEMP_GPG"
+    fi
 else
     have_gmime=0
     printf "No.\n"
@@ -1144,7 +1216,8 @@ for flag in -Wmissing-declarations; do
 done
 printf "\n\t%s\n" "${WARN_CFLAGS}"
 
-rm -f minimal minimal.c _time_t.c _libversion.c _libversion _libversion.sh _check_session_keys.c _check_session_keys _check_x509_validity.c _check_x509_validity
+rm -f minimal minimal.c _time_t.c _libversion.c _libversion _libversion.sh _check_session_keys.c _check_session_keys _check_x509_validity.c _check_x509_validity \
+   _verify_sig_with_session_key.c _verify_sig_with_session_key
 
 # construct the Makefile.config
 cat > Makefile.config <<EOF
@@ -1438,6 +1511,9 @@ NOTMUCH_DEFAULT_XAPIAN_BACKEND=${default_xapian_backend}
 # Whether GMime can verify X.509 certificate validity
 NOTMUCH_GMIME_X509_CERT_VALIDITY=${gmime_x509_cert_validity}
 
+# Whether GMime can verify signatures when decrypting with a session key:
+NOTMUCH_GMIME_VERIFY_WITH_SESSION_KEY=${gmime_verify_with_session_key}
+
 # do we have man pages?
 NOTMUCH_HAVE_MAN=$((have_sphinx))