From: Stefan Eissing <stefan@eissing.org>
Date: Wed, 22 Oct 2025 13:04:53 +0000 (+0200)
Subject: smtp: fix EOB handling
X-Git-Tag: rc-8_17_0-3~49
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=a330117bb05f6b68f066a748177bfba13c4da35b;p=thirdparty%2Fcurl.git

smtp: fix EOB handling

SMTP automatically appends a \n.\n to an upload if there is not already
one at the end of the input. The implementation had a bug where this did
not happen, depending on read size and buffering.

Change test 900 to reproduce the failure. The bug only happened for mail
body input of known length, where EOS was known on the last chunk read.
Change test 900 to use an input file and make it large enough.

Fixes #18798
Closes #19193
Reported-by: madoe on github
---

diff --git a/lib/smtp.c b/lib/smtp.c
index 30f8535765..3d4f36364b 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -1927,6 +1927,7 @@ struct cr_eob_ctx {
   size_t eob;       /* Number of bytes of the EOB (End Of Body) that
                        have been received so far */
   BIT(read_eos);  /* we read an EOS from the next reader */
+  BIT(processed_eos);  /* we read and processed an EOS */
   BIT(eos);       /* we have returned an EOS */
 };
 
@@ -1967,6 +1968,8 @@ static CURLcode cr_eob_read(struct Curl_easy *data,
   if(!ctx->read_eos && Curl_bufq_is_empty(&ctx->buf)) {
     /* Get more and convert it when needed */
     result = Curl_creader_read(data, reader->next, buf, blen, &nread, &eos);
+    CURL_TRC_SMTP(data, "cr_eob_read, next_read(len=%zu) -> %d, %zu eos=%d",
+                  blen, result, nread, eos);
     if(result)
       return result;
 
@@ -2010,31 +2013,34 @@ static CURLcode cr_eob_read(struct Curl_easy *data,
           return result;
       }
     }
+  }
 
-    if(ctx->read_eos) {
-      /* if we last matched a CRLF or if the data was empty, add ".\r\n"
-       * to end the body. If we sent something and it did not end with "\r\n",
-       * add "\r\n.\r\n" to end the body */
-      const char *eob = SMTP_EOB;
-      switch(ctx->n_eob) {
-        case 2:
-          /* seen a CRLF at the end, just add the remainder */
-          eob = &SMTP_EOB[2];
-          break;
-        case 3:
-          /* ended with '\r\n.', we should escape the last '.' */
-          eob = "." SMTP_EOB;
-          break;
-        default:
-          break;
-      }
-      result = Curl_bufq_cwrite(&ctx->buf, eob, strlen(eob), &n);
-      if(result)
-        return result;
+  *peos = FALSE;
+
+  if(ctx->read_eos && !ctx->processed_eos) {
+    /* if we last matched a CRLF or if the data was empty, add ".\r\n"
+     * to end the body. If we sent something and it did not end with "\r\n",
+     * add "\r\n.\r\n" to end the body */
+    const char *eob = SMTP_EOB;
+    CURL_TRC_SMTP(data, "auto-ending mail body with '\\r\\n.\\r\\n'");
+    switch(ctx->n_eob) {
+      case 2:
+        /* seen a CRLF at the end, just add the remainder */
+        eob = &SMTP_EOB[2];
+        break;
+      case 3:
+        /* ended with '\r\n.', we should escape the last '.' */
+        eob = "." SMTP_EOB;
+        break;
+      default:
+        break;
     }
+    result = Curl_bufq_cwrite(&ctx->buf, eob, strlen(eob), &n);
+    if(result)
+      return result;
+    ctx->processed_eos = TRUE;
   }
 
-  *peos = FALSE;
   if(!Curl_bufq_is_empty(&ctx->buf)) {
     result = Curl_bufq_cread(&ctx->buf, buf, blen, pnread);
   }
@@ -2043,6 +2049,7 @@ static CURLcode cr_eob_read(struct Curl_easy *data,
 
   if(ctx->read_eos && Curl_bufq_is_empty(&ctx->buf)) {
     /* no more data, read all, done. */
+    CURL_TRC_SMTP(data, "mail body complete, returning EOS");
     ctx->eos = TRUE;
   }
   *peos = ctx->eos;
diff --git a/tests/data/test900 b/tests/data/test900
index 371544b765..f3aae4b631 100644
--- a/tests/data/test900
+++ b/tests/data/test900
@@ -19,14 +19,16 @@ smtp
 <name>
 SMTP
 </name>
-<stdin>
+<file name="%LOGDIR/mail%TESTNUMBER">
 From: different
 To: another
 
 body
-</stdin>
+%repeat[6553 x 0123456789]%
+</file>
+
 <command>
-smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER --mail-rcpt recipient@example.com --mail-from sender@example.com -T -
+smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER --mail-rcpt recipient@example.com --mail-from sender@example.com -T %LOGDIR/mail%TESTNUMBER
 </command>
 </client>
 
@@ -45,6 +47,8 @@ From: different
 To: another
 
 body
+%repeat[6553 x 0123456789]%
+
 .
 </upload>
 </verify>