From 03d5348f4954acddd22367da64d8292587fbb3fa Mon Sep 17 00:00:00 2001
From: Damien Goutte-Gattat <dgouttegattat@incenp.org>
Date: Sat, 12 Jan 2019 20:04:40 +0000
Subject: [PATCH] Implement encryption only.

Allow the use of -E option to specify a recipient to encrypt the
message to. If several -E options are used, the message will be
encrypted to all specified recipients.
---
 src/fmail.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 113 insertions(+), 8 deletions(-)

diff --git a/src/fmail.c b/src/fmail.c
index 7156b02..757a019 100644
--- a/src/fmail.c
+++ b/src/fmail.c
@@ -114,6 +114,8 @@ typedef struct fmail_ctx
 {
     const char    **attachments;
     size_t          att_count;
+    const char    **recipients;
+    size_t          rcp_count;
     const char     *footer;
     magic_t         magic_ctx;
     gpgme_ctx_t     crypto_ctx;
@@ -300,7 +302,7 @@ process_text_body(fmail_ctx_t *ctx, FILE *out)
 
 
 
-/* Signing stuff. */
+/* Crypto stuff. */
 
 gpgme_ctx_t
 initialize_gpgme(void)
@@ -402,6 +404,99 @@ sign_stream(gpgme_ctx_t ctx, FILE *in, FILE *out)
     gpgme_data_release(gout);
 }
 
+static gpgme_key_t *
+get_recipient_keys(gpgme_ctx_t ctx, const char **recipients, size_t nr)
+{
+    gpgme_key_t *keys, key;
+    gpgme_error_t gerr;
+    int i, j;
+
+    keys = NULL;
+
+    for ( i = j = gerr = 0; i < nr && ! gerr ; i++ ) {
+        gerr = gpgme_op_keylist_start (ctx, recipients[i], 0);
+        while ( ! gerr ) {
+            gerr = gpgme_op_keylist_next (ctx, &key);
+            if ( gerr )
+                break;
+
+            if ( j % 10 == 0 )
+                keys = xrealloc(keys, j + 10);
+            keys[j++] = key;
+        }
+        if ( gpgme_err_code(gerr) == GPG_ERR_EOF )
+            gerr = 0;
+    }
+    if ( gerr != 0 && gpgme_err_code(gerr) != GPG_ERR_EOF)
+        errx(EXIT_FAILURE, "cannot get recipient keys: %s", gpgme_strerror(gerr));
+
+    /* GpgME expects a NULL-terminated array of keys. */
+    if ( j % 10 == 0 )
+        keys = xrealloc(keys, j + 1);
+    keys[j++] = NULL;
+
+    return keys;
+}
+
+static void
+encrypt_stream(gpgme_ctx_t  ctx,
+               FILE        *in,
+               FILE        *out,
+               const char **recipients,
+               size_t       nr)
+{
+    gpgme_data_t gin, gout;
+    gpgme_key_t *keys, *key;
+    gpgme_error_t gerr;
+    char boundary[32], buffer[512];
+    int n;
+
+    keys = get_recipient_keys(ctx, recipients, nr);
+    gpgme_data_new_from_stream(&gin, in);
+    gpgme_data_new(&gout);
+
+    gerr = gpgme_op_encrypt(ctx, keys, 0, gin, gout);
+    if ( gerr != GPG_ERR_NO_ERROR )
+        errx(EXIT_FAILURE, "encrypting failed: %s", gpgme_strerror(gerr));
+
+    generate_boundary(boundary, sizeof(boundary));
+    fprintf(out, "Content-Type: multipart/encrypted;\r\n"
+                 "  boundary=\"%s\";\r\n"
+                 "  protocol=\"application/pgp-encrypted\r\n"
+                 "\r\n"
+                 "--%s\r\n"
+                 "Content-Type: application/pgp-encrypted\r\n"
+                 "\r\n"
+                 "Version: 1\r\n"
+                 "\r\n"
+                 "--%s\r\n"
+                 "Content-Type: application/octet-stream\r\n"
+                 "\r\n",
+                 boundary, boundary, boundary);
+
+    gpgme_data_seek(gout, 0, SEEK_SET);
+    while ( (n = gpgme_data_read(gout, buffer, sizeof(buffer))) > 0 ) {
+        int i = 0;
+
+        while ( i < n ) {
+            if ( buffer[i] == '\n' )
+                fputc('\r', out);
+            fputc(buffer[i], out);
+
+            i += 1;
+        }
+    }
+
+    fprintf(out, "\r\n--%s--\r\n", boundary);
+
+    gpgme_data_release(gin);
+    gpgme_data_release(gout);
+
+    for ( key = keys; *key != NULL; key++ )
+        gpgme_key_release(*key);
+    free(keys);
+}
+
 
 
 /* Attachments stuff. */
@@ -535,7 +630,7 @@ main(int argc, char *argv[])
     char c, with_useragent, with_date;
     string_buffer_t *headers;
     fmail_ctx_t ctx;
-    int do_sign, do_encrypt;
+    int do_sign;
 
     struct option options[] = {
         { "help",       0, NULL, 'h' },
@@ -559,13 +654,15 @@ main(int argc, char *argv[])
     setlocale(LC_ALL, "");
     srand(time(NULL));
 
-    with_useragent = with_date = do_sign = do_encrypt = 0;
+    with_useragent = with_date = do_sign = 0;
 
     headers = sb_new(0);
     ctx.crypto_ctx = NULL;
     ctx.magic_ctx = initialize_magic();
     ctx.attachments = NULL;
     ctx.att_count = 0;
+    ctx.recipients = NULL;
+    ctx.rcp_count = 0;
     ctx.footer = NULL;
     ctx.input = stdin;
 
@@ -589,7 +686,9 @@ main(int argc, char *argv[])
             break;
 
         case 'E':
-            do_encrypt = 1;
+            if ( ctx.rcp_count % 10 == 0 )
+                ctx.recipients = xrealloc(ctx.recipients, ctx.rcp_count + 10);
+            ctx.recipients[ctx.rcp_count++] = optarg;
             break;
 
         case 'a':
@@ -636,9 +735,9 @@ main(int argc, char *argv[])
         }
     }
 
-    if ( do_sign && do_encrypt )
+    if ( do_sign && ctx.rcp_count )
         errx(EXIT_FAILURE, "encrypt and sign is not currently supported");
-    if ( do_sign || do_encrypt )
+    if ( do_sign || ctx.rcp_count )
         ctx.crypto_ctx = initialize_gpgme();
 
     /* Generate automatic headers */
@@ -657,12 +756,15 @@ main(int argc, char *argv[])
     /* Write all headers. */
     fprintf(stdout, "%s", sb_get(headers));
 
-    if ( do_sign ) {
+    if ( do_sign || ctx.rcp_count ) {
         FILE *tmp = tmpfile();
 
         process_text_body(&ctx, tmp);
         fseek(tmp, 0, SEEK_SET);
-        sign_stream(ctx.crypto_ctx, tmp, stdout);
+        if ( do_sign )
+            sign_stream(ctx.crypto_ctx, tmp, stdout);
+        else
+            encrypt_stream(ctx.crypto_ctx, tmp, stdout, ctx.recipients, ctx.rcp_count);
 
         fclose(tmp);
         gpgme_release(ctx.crypto_ctx);
@@ -675,6 +777,9 @@ main(int argc, char *argv[])
     if ( ctx.attachments )
         free(ctx.attachments);
 
+    if ( ctx.recipients )
+        free(ctx.recipients);
+
     magic_close(ctx.magic_ctx);
 
     return EXIT_SUCCESS;