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buffer: Create ssh_buffer_validate_length()

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This functions allows if a given length can be obtained from the buffer.

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Andreas Schneider
2017-02-23 16:22:04 +01:00
parent 5f202d7ffa
commit 34bdc1ca78
2 changed files with 23 additions and 3 deletions
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2
include/libssh/buffer.h
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@@ -48,6 +48,8 @@ int ssh_buffer_add_u16(ssh_buffer buffer, uint16_t data);
int ssh_buffer_add_u32(ssh_buffer buffer, uint32_t data); int ssh_buffer_add_u32(ssh_buffer buffer, uint32_t data);
int ssh_buffer_add_u64(ssh_buffer buffer, uint64_t data); int ssh_buffer_add_u64(ssh_buffer buffer, uint64_t data);
int ssh_buffer_validate_length(struct ssh_buffer_struct *buffer, size_t len);
int ssh_buffer_pack_va(struct ssh_buffer_struct *buffer, int ssh_buffer_pack_va(struct ssh_buffer_struct *buffer,
const char *format, const char *format,
int argc, int argc,

22
src/buffer.c
View File

@@ -526,7 +526,7 @@ uint32_t ssh_buffer_get_data(struct ssh_buffer_struct *buffer, void *data, uint3
* Check for a integer overflow first, then check if not enough data is in * Check for a integer overflow first, then check if not enough data is in
* the buffer. * the buffer.
*/ */
if (buffer->pos + len < len || buffer->pos + len > buffer->used) { if (!ssh_buffer_validate_length(buffer, len)) {
return 0; return 0;
} }
memcpy(data,buffer->data+buffer->pos,len); memcpy(data,buffer->data+buffer->pos,len);
@@ -580,6 +580,24 @@ int ssh_buffer_get_u64(struct ssh_buffer_struct *buffer, uint64_t *data){
return ssh_buffer_get_data(buffer,data,sizeof(uint64_t)); return ssh_buffer_get_data(buffer,data,sizeof(uint64_t));
} }
/**
* @brief Valdiates that the given length can be obtained from the buffer.
*
* @param[in] buffer The buffer to read from.
*
* @param[in] len The length to be checked.
*
* @return SSH_OK if the length is valid, SSH_ERROR otherwise.
*/
int ssh_buffer_validate_length(struct ssh_buffer_struct *buffer, size_t len)
{
if (buffer->pos + len < len || buffer->pos + len > buffer->used) {
return SSH_ERROR;
}
return SSH_OK;
}
/** /**
* @internal * @internal
* *
@@ -599,7 +617,7 @@ struct ssh_string_struct *ssh_buffer_get_ssh_string(struct ssh_buffer_struct *bu
} }
hostlen = ntohl(stringlen); hostlen = ntohl(stringlen);
/* verify if there is enough space in buffer to get it */ /* verify if there is enough space in buffer to get it */
if (buffer->pos + hostlen < hostlen || buffer->pos + hostlen > buffer->used) { if (!ssh_buffer_validate_length(buffer, hostlen) {
return NULL; /* it is indeed */ return NULL; /* it is indeed */
} }
str = ssh_string_new(hostlen); str = ssh_string_new(hostlen);