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-rw-r--r--g10/decrypt-data.c173
1 files changed, 77 insertions, 96 deletions
diff --git a/g10/decrypt-data.c b/g10/decrypt-data.c
index 0b0051af7..b00f2bce1 100644
--- a/g10/decrypt-data.c
+++ b/g10/decrypt-data.c
@@ -192,6 +192,28 @@ aead_set_ad (decode_filter_ctx_t dfx, int final)
}
+/* Helper to check the 16 byte tag in TAGBUF. The FINAL flag is only
+ * for debug messages. */
+static gpg_error_t
+aead_checktag (decode_filter_ctx_t dfx, int final, const void *tagbuf)
+{
+ gpg_error_t err;
+
+ if (DBG_FILTER)
+ log_printhex (tagbuf, 16, "tag:");
+ err = gcry_cipher_checktag (dfx->cipher_hd, tagbuf, 16);
+ if (err)
+ {
+ log_error ("gcry_cipher_checktag%s failed: %s\n",
+ final? " (final)":"", gpg_strerror (err));
+ return err;
+ }
+ if (DBG_FILTER)
+ log_debug ("%stag is valid\n", final?"final ":"");
+ return 0;
+}
+
+
/****************
* Decrypt the data, specified by ED with the key DEK.
*/
@@ -531,6 +553,49 @@ decrypt_data (ctrl_t ctrl, void *procctx, PKT_encrypted *ed, DEK *dek)
}
+/* Fill BUFFER with up to NBYTES-OFFSET from STREAM utilizing
+ * information from the context DFX. Returns the new offset which is
+ * the number of bytes read plus the original offset. On EOF the
+ * respective flag in DFX is set. */
+static size_t
+fill_buffer (decode_filter_ctx_t dfx, iobuf_t stream,
+ byte *buffer, size_t nbytes, size_t offset)
+{
+ size_t nread = offset;
+ int c;
+
+ if (dfx->partial)
+ {
+ for (; nread < nbytes; nread++ )
+ {
+ if ((c = iobuf_get (stream)) == -1)
+ {
+ dfx->eof_seen = 1; /* Normal EOF. */
+ break;
+ }
+ buffer[nread] = c;
+ }
+ }
+ else
+ {
+ for (; nread < nbytes && dfx->length; nread++, dfx->length--)
+ {
+ c = iobuf_get (stream);
+ if (c == -1)
+ {
+ dfx->eof_seen = 3; /* Premature EOF. */
+ break;
+ }
+ buffer[nread] = c;
+ }
+ if (!dfx->length)
+ dfx->eof_seen = 1; /* Normal EOF. */
+ }
+
+ return nread;
+}
+
+
/* The core of the AEAD decryption. This is the underflow function of
* the aead_decode_filter. */
static gpg_error_t
@@ -542,7 +607,6 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
size_t off = 0; /* The offset into the buffer. */
size_t len; /* The current number of bytes in BUF+OFF. */
int last_chunk_done = 0; /* Flag that we processed the last chunk. */
- int c;
log_assert (size > 48); /* Our code requires at least this size. */
@@ -560,39 +624,12 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
* chunksize. After the last data byte from the last chunk 32 more
* bytes are expected for the last chunk's tag and the following
* final chunk's tag. To detect the EOF we need to try reading at least
- * one further byte; however we try to ready 16 extra bytes to avoid
+ * one further byte; however we try to read 16 extra bytes to avoid
* single byte reads in some lower layers. The outcome is that we
* have up to 48 extra extra octets which we will later put into the
* holdback buffer for the next invocation (which handles the EOF
* case). */
- if (dfx->partial)
- {
- for (; len < size; len++ )
- {
- if ((c = iobuf_get (a)) == -1)
- {
- dfx->eof_seen = 1; /* Normal EOF. */
- break;
- }
- buf[len] = c;
- }
- }
- else
- {
- for (; len < size && dfx->length; len++, dfx->length--)
- {
- c = iobuf_get (a);
- if (c == -1)
- {
- dfx->eof_seen = 3; /* Premature EOF. */
- break;
- }
- buf[len] = c;
- }
- if (!dfx->length)
- dfx->eof_seen = 1; /* Normal EOF. */
- }
-
+ len = fill_buffer (dfx, a, buf, size, len);
if (len < 32)
{
/* Not enough data for the last two tags. */
@@ -673,47 +710,19 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
err = gpg_error (GPG_ERR_TRUNCATED);
goto leave;
}
- len = 0;
last_chunk_done = 1;
}
else
{
- len = dfx->holdbacklen;
- if (dfx->partial)
- {
- for (; len < 48; len++ )
- {
- if ((c = iobuf_get (a)) == -1)
- {
- dfx->eof_seen = 1; /* Normal EOF. */
- break;
- }
- dfx->holdback[len] = c;
- }
- }
- else
- {
- for (; len < 48 && dfx->length; len++, dfx->length--)
- {
- c = iobuf_get (a);
- if (c == -1)
- {
- dfx->eof_seen = 3; /* Premature EOF. */
- break;
- }
- dfx->holdback[len] = c;
- }
- if (!dfx->length)
- dfx->eof_seen = 1; /* Normal EOF. */
- }
- if (len < 32)
+ len = 0;
+ dfx->holdbacklen = fill_buffer (dfx, a, dfx->holdback, 48,
+ dfx->holdbacklen);
+ if (dfx->holdbacklen < 32)
{
/* Not enough data for the last two tags. */
err = gpg_error (GPG_ERR_TRUNCATED);
goto leave;
}
- dfx->holdbacklen = len;
- len = 0;
}
}
else /* We already have the full tag. */
@@ -723,18 +732,9 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
memmove (buf + off, buf + off + 16, len - 16);
len -= 16;
}
- if (DBG_CRYPTO)
- log_printhex (tagbuf, 16, "tag:");
- err = gcry_cipher_checktag (dfx->cipher_hd, tagbuf, 16);
+ err = aead_checktag (dfx, 0, tagbuf);
if (err)
- {
- if (DBG_FILTER)
- log_debug ("gcry_cipher_checktag failed (1): %s\n",
- gpg_strerror (err));
- goto leave;
- }
- if (DBG_FILTER)
- log_debug ("tag is valid\n");
+ goto leave;
/* Prepare a new chunk. */
if (!last_chunk_done)
@@ -783,18 +783,9 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
if (!last_chunk_done)
{
log_assert (dfx->holdbacklen >= 32);
-
- if (DBG_FILTER)
- log_printhex (dfx->holdback, 16, "tag:");
- err = gcry_cipher_checktag (dfx->cipher_hd, dfx->holdback, 16);
+ err = aead_checktag (dfx, 0, dfx->holdback);
if (err)
- {
- log_error ("gcry_cipher_checktag failed (2): %s\n",
- gpg_strerror (err));
- goto leave;
- }
- if (DBG_FILTER)
- log_debug ("tag is valid\n");
+ goto leave;
}
/* Check the final chunk. */
@@ -815,19 +806,9 @@ aead_underflow (decode_filter_ctx_t dfx, iobuf_t a, byte *buf, size_t *ret_len)
gpg_strerror (err));
goto leave;
}
- if (DBG_CRYPTO)
- log_printhex (dfx->holdback+(last_chunk_done?0:16), 16, "tag:");
- err = gcry_cipher_checktag (dfx->cipher_hd,
- dfx->holdback+(last_chunk_done?0:16), 16);
+ err = aead_checktag (dfx, 1, dfx->holdback+(last_chunk_done?0:16));
if (err)
- {
- if (DBG_FILTER)
- log_debug ("gcry_cipher_checktag failed (final): %s\n",
- gpg_strerror (err));
- goto leave;
- }
- if (DBG_FILTER)
- log_debug ("final tag is valid\n");
+ goto leave;
err = gpg_error (GPG_ERR_EOF);
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-04-27 18:47:46 +0000