150 lines
5.0 KiB
Diff
150 lines
5.0 KiB
Diff
From 3d651a6e234bed4c4d4865a56c5fa47dab89a5a6 Mon Sep 17 00:00:00 2001
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From: Greg Hudson <ghudson@mit.edu>
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Date: Mon, 26 Mar 2018 11:12:39 -0400
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Subject: [PATCH] Implement k5_buf_init_dynamic_zap
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Add a variant of dynamic k5buf objects which zeroes memory when
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reallocating or freeing the buffer.
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(cherry picked from commit 8ee8246c14702dc03b02e31b9fb5b7c2bb674bfb)
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---
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src/include/k5-buf.h | 6 ++-
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src/util/support/k5buf.c | 41 +++++++++++++++----
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src/util/support/libkrb5support-fixed.exports | 1 +
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3 files changed, 39 insertions(+), 9 deletions(-)
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diff --git a/src/include/k5-buf.h b/src/include/k5-buf.h
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index 1223916a6..48e2a7d53 100644
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--- a/src/include/k5-buf.h
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+++ b/src/include/k5-buf.h
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@@ -45,7 +45,7 @@
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*/
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/* Buffer type values */
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-enum k5buftype { K5BUF_ERROR, K5BUF_FIXED, K5BUF_DYNAMIC };
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+enum k5buftype { K5BUF_ERROR, K5BUF_FIXED, K5BUF_DYNAMIC, K5BUF_DYNAMIC_ZAP };
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struct k5buf {
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enum k5buftype buftype;
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@@ -63,6 +63,10 @@ void k5_buf_init_fixed(struct k5buf *buf, char *data, size_t space);
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/* Initialize a k5buf using an internally allocated dynamic buffer. */
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void k5_buf_init_dynamic(struct k5buf *buf);
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+/* Initialize a k5buf using an internally allocated dynamic buffer, zeroing
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+ * memory when reallocating or freeing. */
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+void k5_buf_init_dynamic_zap(struct k5buf *buf);
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+
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/* Add a C string to BUF. */
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void k5_buf_add(struct k5buf *buf, const char *data);
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diff --git a/src/util/support/k5buf.c b/src/util/support/k5buf.c
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index 35978f238..b2b5e5b67 100644
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--- a/src/util/support/k5buf.c
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+++ b/src/util/support/k5buf.c
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@@ -37,7 +37,7 @@
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/*
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* Structure invariants:
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*
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- * buftype is K5BUF_FIXED, K5BUF_DYNAMIC, or K5BUF_ERROR
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+ * buftype is K5BUF_FIXED, K5BUF_DYNAMIC, K5BUF_DYNAMIC_ZAP, or K5BUF_ERROR
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* if buftype is K5BUF_ERROR, the other fields are NULL or 0
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* if buftype is not K5BUF_ERROR:
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* space > 0
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@@ -77,22 +77,35 @@ ensure_space(struct k5buf *buf, size_t len)
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return 1;
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if (buf->buftype == K5BUF_FIXED) /* Can't resize a fixed buffer. */
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goto error_exit;
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- assert(buf->buftype == K5BUF_DYNAMIC);
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+ assert(buf->buftype == K5BUF_DYNAMIC || buf->buftype == K5BUF_DYNAMIC_ZAP);
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new_space = buf->space * 2;
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while (new_space - buf->len - 1 < len) {
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if (new_space > SIZE_MAX / 2)
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goto error_exit;
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new_space *= 2;
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}
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- new_data = realloc(buf->data, new_space);
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- if (new_data == NULL)
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- goto error_exit;
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+ if (buf->buftype == K5BUF_DYNAMIC_ZAP) {
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+ /* realloc() could leave behind a partial copy of sensitive data. */
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+ new_data = malloc(new_space);
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+ if (new_data == NULL)
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+ goto error_exit;
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+ memcpy(new_data, buf->data, buf->len);
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+ new_data[buf->len] = '\0';
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+ zap(buf->data, buf->len);
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+ free(buf->data);
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+ } else {
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+ new_data = realloc(buf->data, new_space);
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+ if (new_data == NULL)
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+ goto error_exit;
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+ }
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buf->data = new_data;
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buf->space = new_space;
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return 1;
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error_exit:
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- if (buf->buftype == K5BUF_DYNAMIC)
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+ if (buf->buftype == K5BUF_DYNAMIC_ZAP)
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+ zap(buf->data, buf->len);
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+ if (buf->buftype == K5BUF_DYNAMIC_ZAP || buf->buftype == K5BUF_DYNAMIC)
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free(buf->data);
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set_error(buf);
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return 0;
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@@ -123,6 +136,14 @@ k5_buf_init_dynamic(struct k5buf *buf)
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*endptr(buf) = '\0';
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}
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+void
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+k5_buf_init_dynamic_zap(struct k5buf *buf)
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+{
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+ k5_buf_init_dynamic(buf);
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+ if (buf->buftype == K5BUF_DYNAMIC)
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+ buf->buftype = K5BUF_DYNAMIC_ZAP;
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+}
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+
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void
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k5_buf_add(struct k5buf *buf, const char *data)
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{
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@@ -163,7 +184,7 @@ k5_buf_add_vfmt(struct k5buf *buf, const char *fmt, va_list ap)
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}
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/* Optimistically format the data directly into the dynamic buffer. */
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- assert(buf->buftype == K5BUF_DYNAMIC);
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+ assert(buf->buftype == K5BUF_DYNAMIC || buf->buftype == K5BUF_DYNAMIC_ZAP);
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va_copy(apcopy, ap);
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r = vsnprintf(endptr(buf), remaining, fmt, apcopy);
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va_end(apcopy);
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@@ -197,6 +218,8 @@ k5_buf_add_vfmt(struct k5buf *buf, const char *fmt, va_list ap)
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memcpy(endptr(buf), tmp, r + 1);
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buf->len += r;
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}
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+ if (buf->buftype == K5BUF_DYNAMIC_ZAP)
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+ zap(tmp, strlen(tmp));
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free(tmp);
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}
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@@ -241,7 +264,9 @@ k5_buf_free(struct k5buf *buf)
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{
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if (buf->buftype == K5BUF_ERROR)
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return;
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- assert(buf->buftype == K5BUF_DYNAMIC);
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+ assert(buf->buftype == K5BUF_DYNAMIC || buf->buftype == K5BUF_DYNAMIC_ZAP);
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+ if (buf->buftype == K5BUF_DYNAMIC_ZAP)
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+ zap(buf->data, buf->len);
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free(buf->data);
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set_error(buf);
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}
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diff --git a/src/util/support/libkrb5support-fixed.exports b/src/util/support/libkrb5support-fixed.exports
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index cb9bf0826..a5e2ade04 100644
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--- a/src/util/support/libkrb5support-fixed.exports
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+++ b/src/util/support/libkrb5support-fixed.exports
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@@ -3,6 +3,7 @@ k5_base64_encode
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k5_bcmp
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k5_buf_init_fixed
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k5_buf_init_dynamic
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+k5_buf_init_dynamic_zap
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k5_buf_add
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k5_buf_add_len
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k5_buf_add_fmt
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