Correctly handle network input

Add a parameter to git_pkt_parse_line to tell it how much data you
have in your buffer. If the buffer is too short, it returns an error
saying so. Adapt the git transport to use this and fix the offset
calculation.

Add the GIT_ESHORTBUFFER error code.

1 files changed, 57 insertions, 41 deletions

diff --git a/src/pkt.c b/src/pkt.c
index f77bc304..17edf320 100644
--- a/src/pkt.c
+++ b/src/pkt.c
@@ -30,6 +30,10 @@
 #include "common.h"
 #include "util.h"
 
+#include <ctype.h>
+
+#define PKT_LEN_SIZE 4
+
 static int flush_pkt(git_pkt **out)
 {
 	git_pkt *pkt;
@@ -50,8 +54,7 @@ static int flush_pkt(git_pkt **out)
 int ref_pkt(git_pkt **out, const char *line, size_t len)
 {
 	git_pkt_ref *pkt;
-	int error;
-	size_t name_len;
+	int error, has_caps = 0;
 
 	pkt = git__malloc(sizeof(git_pkt_ref));
 	if (pkt == NULL)
@@ -75,30 +78,22 @@ int ref_pkt(git_pkt **out, const char *line, size_t len)
 	line += GIT_OID_HEXSZ + 1;
 	len -= (GIT_OID_HEXSZ + 1);
 
-	name_len = min(strlen(line), len);
-	if (line[name_len - 1] == '\n')
-		--name_len;
+	if (strlen(line) < len)
+		has_caps = 1;
+
+	if (line[len - 1] == '\n')
+		--len;
 
-	pkt->head.name = git__strndup(line, name_len);
+	pkt->head.name = git__malloc(len + 1);
 	if (pkt->head.name == NULL) {
 		error = GIT_ENOMEM;
 		goto out;
 	}
+	memcpy(pkt->head.name, line, len);
+	pkt->head.name[len] = '\0';
 
-	/* Try to get the capabilities */
-	line += name_len + 1; /* + \0 */
-	len -= (name_len + 1);
-	if (line[len - 1] == '\n')
-		--len;
-
-	if (len > 0) { /* capatilities */
-		pkt->capabilities = git__malloc(len);
-		if (pkt->capabilities == NULL) {
-			error = GIT_ENOMEM;
-			goto out;
-		}
-
-		memcpy(pkt->capabilities, line, len);
+	if (has_caps) {
+		pkt->capabilities = strchr(pkt->head.name, '\0') + 1;
 	}
 
 out:
@@ -110,6 +105,29 @@ out:
 	return error;
 }
 
+static unsigned int parse_len(const char *line)
+{
+	char num[PKT_LEN_SIZE + 1];
+	int i, error;
+	long len;
+	const char *num_end;
+
+	memcpy(num, line, PKT_LEN_SIZE);
+	num[PKT_LEN_SIZE] = '\0';
+
+	for (i = 0; i < PKT_LEN_SIZE; ++i) {
+		if (!isxdigit(num[i]))
+			return GIT_ENOTNUM;
+	}
+
+	error = git__strtol32(&len, num, &num_end, 16);
+	if (error < GIT_SUCCESS) {
+		return error;
+	}
+
+	return (unsigned int) len;
+}
+
 /*
  * As per the documentation, the syntax is:
  *
@@ -123,35 +141,34 @@ out:
  * in ASCII hexadecimal (including itself)
  */
 
-int git_pkt_parse_line(git_pkt **head, const char *line, const char **out)
+int git_pkt_parse_line(git_pkt **head, const char *line, const char **out, unsigned int bufflen)
 {
 	int error = GIT_SUCCESS;
-	long int len;
-	const int num_len = 4;
-	char *num;
-	const char *num_end;
+	unsigned int len;
 
-	num = git__strndup(line, num_len);
-	if (num == NULL)
-		return GIT_ENOMEM;
+	/* Not even enough for the length */
+	if (bufflen > 0 && bufflen < PKT_LEN_SIZE)
+		return GIT_ESHORTBUFFER;
 
-	error = git__strtol32(&len, num, &num_end, 16);
-	if (error < GIT_SUCCESS) {
-		free(num);
+	error = parse_len(line);
+	if (error < GIT_SUCCESS)
 		return git__throw(error, "Failed to parse pkt length");
-	}
-	if (num_end - num != num_len) {
-		free(num);
-		return git__throw(GIT_EOBJCORRUPTED, "Wrong pkt length");
-	}
-	free(num);
 
-	line += num_len;
+	len = error;
+
+	/*
+	 * If we were given a buffer length, then make sure there is
+	 * enough in the buffer to satisfy this line
+	 */
+	if (bufflen > 0 && bufflen < len)
+		return GIT_ESHORTBUFFER;
+
+	line += PKT_LEN_SIZE;
 	/*
 	 * TODO: How do we deal with empty lines? Try again? with the next
 	 * line?
 	 */
-	if (len == 4) {
+	if (len == PKT_LEN_SIZE) {
 		*out = line;
 		return GIT_SUCCESS;
 	}
@@ -161,7 +178,7 @@ int git_pkt_parse_line(git_pkt **head, const char *line, const char **out)
 		return flush_pkt(head);
 	}
 
-	len -= num_len; /* the length includes the space for the length */
+	len -= PKT_LEN_SIZE; /* the encoded length includes its own size */
 
 	/*
 	 * For now, we're just going to assume we're parsing references
@@ -177,7 +194,6 @@ void git_pkt_free(git_pkt *pkt)
 {
 	if(pkt->type == GIT_PKT_REF) {
 		git_pkt_ref *p = (git_pkt_ref *) pkt;
-		free(p->capabilities);
 		free(p->head.name);
 	}